polymeric nano particle
by
Md.imran ansari
1. Introduction
Ø The word nanoparticle was comes from the Greek word ‘nano’ (symbol=n).The s.i. unit is ‘nm’ (1nm=10-9).
Ø The nanoparticles are solid, colloidal particles ranging 10-1000nm in size.
Ø Tt consists of macromolecular materials in which the active ingrediants (drug or biologically active material) is dissolved, entrapped or absorbed or attached.
Ø The nanoparticles are subnanosized colloidal structure composed of synthetic or semisynthetic polymers.
Ø The polymeric nanoparticles can carry drug or proteinaceous substances that is antigen.these bioactives are entrapped in the polymer matrix as particulate enmesh or solid solution or may be bound to the particle surface by physical adsprption or chemically.
1.1.Historical Prospectives
Ø Nanoparticles are generally considered an invention of modern science; they actually have a very long history. Nanoparticles were used by Artisans as far back as the 9th century in Mesopotamia for generating a glittering effect on the surface of pots. . These nanoparticles were created by the artisans by adding copper and silver salts and oxides together with vinegar, ochre and clay, on the surface of previously-glazed pottery. Ø
Depending on the process used for their preparation, two types of nanoparticles can be obtained.
. A.Nanospheres B.Nanocapsules
Ø Nanospheres have a matrix type structure in which a drug is dispersed, where as nanocapsules exhibits a membrane wall structure with an oily core containing the drug.
Ø As nanoparticulate system have a very high surface area, drug may also be absorbed on their surface.
Ø Nanoparticles are made of artificial or natural polymers; the use of these polymers is often restricted by their bioacceptability.
2. Types of nanoparticles
Ø Nanosized Particles
Ø Polymeric Nanoparticle
Ø Solid-Lipid Nanoparticle
Ø Nanpcrystal
Ø Nanolipid Carriers
Ø Nanoconstruct
Ø Nanoplexes
Ø Nano Coposite
Ø Nano Enclusion Compound
Ø Metallic Nanoparticle
Ø Nano Emulsion and Nano Suspension
Ø Flurescent Nanoparticle
Ø Nanochelates
Ø Nano Eggs
Ø Nano Agglomerates
3. Factors Affecting the Clearance and Biodistribution of Polymeric nanoparticles
The main factors are-
Tissue defects
Stealth properties
Targeting and the Size of the nanoparticles are major factors affecting the biodistribution and Clearance of Polymeric nanoparticles
Effect of core
Effect of surface functionality and charge
Effect of active targeting
Nanoparticle (NP) drug delivery systems (5−250 nm) have the potential to improve current disease therapies because of their ability to overcome multiple biological barriers and releasing a therapeutic load in the optimal dosage range. Rapid clearance of circulating nanoparticles during systemic delivery is a critical issue for these systems and has made it necessary to understand the factors affecting particle biodistribution and blood circulation half-life.
In this review, we discuss the factors which can influence nanoparticle blood residence time and organ specific accumulation. These factors include interactions with biological barriers and tunable nanoparticle parameters, such as composition, size, core properties, surface modifications (pegylation and surface charge), and finally, targeting ligand functionalization. All these factors have been shown to substantially affect the biodistribution and blood circulation half-life of circulating nanoparticles by reducing the level of nonspecific uptake, delaying opsonization, and increasing the extent of tissue specific accumulation.
Nanoparticles have drawn increasing interest from every branch of medicine for their ability to deliver drugs in the optimum dosage range, often resulting in increased therapeutic efficacy of the drug, weakened side effects and improved patient compliance.
Blood circulation residence, maximal tolerated dose (MTD), and selectivity are the most important factors for achieving a high therapeutical index and corresponding clinical success. Polymeric nanoparticles are defined by their morphology and polymer composition in the core and corona. The therapeutic load is typically conjugated to the surface of the nanoparticle, or encapsulated and protected inside the core. The delivery systems can be designed to provide either controlled release or a triggered release of the therapeutic molecule. The nanoparticle surface can then be functionalized by various methods to form the corona. Surface functionalization can be utilized to increase residence time in the blood, reduce nonspecific distribution, and, in some cases, target tissues or specific cell surface antigens with a targeting ligand (peptide, aptamer, antibody/antibody fragment, small molecule).
For instance, it is well established that hydrophilic polymers, most notably poly (ethylene glycol) (PEG), can be grafted, conjugated, or absorbed to the surface of nanoparticles to form the corona, which provides steric stabilization and confers “stealth” properties such as prevention of protein absorption.
Surface functionalization can address the major limiting factor for long-circulating nanoparticle systems, which is protein absorption. Proteins adsorbed on the surface of the nanoparticle promote opsonization, leading to aggregation and rapid clearance from the bloodstream. The resultant rapid clearance is due to phagocytosis by the mononuclear phagocyte system (MPS) in the liver and splenic filtration. Typically, the majority of opsonized particles are cleared by a receptor-mediated mechanism in fewer than a few minutes due to the high concentration of phagocytic cells in the liver and spleen, or they are excreted. Thus, over the past 20 years, numerous approaches to improving nanoparticle blood residence and accumulation in specific tissues for the treatment of disease have been developed.
Overcoming Biological Barriers: Effect of Physiological Defects:-
Numerous biological barriers exist to protect the human body from invasion by foreign particles. These barriers include cellular and humoral arms of the immune system as well as mucosal barriers among others. These barriers must be overcome in order for nanoparticles to reach their target (Figure 2). Due to their unique size, and amenability to surface functionalization to incorporate the desired characteristics, nanoparticles are particularly well suited to overcoming these barriers. This is especially true in the case of abnormal neovascularization. Blood vessels are responsible for delivering molecules, nutrients, and oxygen to organs throughout the body. Endothelia composing the blood vessels have been classified as continuous, fenestrated, or discontinuous, depending on the morphological features of the endothelium. The continuous endothelium morphology appears in arteries, vessels, and the lungs In contrast, fenestrated endothelium appears in glands, digestive mucosa, and kidney. Discontinuous endothelium is a characteristic of the liver (fenestrea of 50−100 nm) and bone marrow. Endothelial cells from the blood vessels are able to respond to the physiological environment, resulting in angiogenic activity. Angiogenesis is well-characterized for cancers as well as ocular and inflammatory diseases, with antiangiogenesis compounds commonly used for therapy. Angiogenesis during tumor growth results in defective hypervasculature and a deficient lymphatic drainage system, which has given rise to the concept of passive targeting of nanoparticles to tumors through the “enhanced permeability and retention” (EPR) effect. The EPR is a unique feature which allows macromolecules or drug delivery nanoparticles (cutoff size of >400 nm) to preferentially accumulate and diffuse in tumor tissues. Long-circulating drug delivery nanoparticles are able to extravasate into tumor tissues, accumulate, and release the therapeutic drug locally in the extracellular area. Similarly, abnormal neovascularization or angiogenesis as well as enhanced vascular permeability are major causes of many ocular disorders, including age-related macular degeneration (AMD), retinopathy of prematurity (ROP), ischemic retinal vein occlusions, and diabetic retinopathy (DR), causing irreversible vision loss. In ocular disorders, the angiogenic process appears to be due to a stimulus response for retinal neovascularization. The stimulus can be tissue hypoxia, inflammatory cell infiltration, increased local concentration of cytokines (VEGF, PDGF, FGF5 TNF, IGF etc.). The result is the formation of new vessels, which disrupt the organizational structure of the neural retina or break through the inner limiting membranes into the vitreous Many other disorders are also characterized by angiogenesis or vasculature defects such as obesity asthma diabetes, and multiple sclerosis The development of new imaging systems and medical knowledge about physiological defects is leading to novel therapeutic approaches using nanoparticle drug delivery systems. It is now well accepted that nanoparticles are suitable for crossing biological barriers through tissue diffusion, extravasation, and escape from hepatic filtration. 3.1. Effect of Size
On the basis of physiological parameters such as hepatic filtration, tissue extravasation, tissue diffusion, and kidney excretion, it is clear that, along with surface composition, particle size is a key factor in the biodistribution of long-circulating nanoparticles and achieving therapeutic efficacy (Figure 2). In one study, in vivo biodistribution results of polystyrene nanoparticles with consistent composition and varying particle sizes of 50 and 500 nm showed higher levels of agglomeration of the larger nanoparticles in the liver. It was suggested that the mechanism of hepatic uptake was mediated by surface absorption of proteins leading to opsonization. However, the effect of temperature (37 °C vs 4 °C) on hepatic elimination showed unexpectedly faster uptake of the 50 nm polystyrene nanoparticles at the lower temperature. Similarly, the size of the nanoparticle was shown to have a substantial effect on the protein absorption. Small (<100 nm), medium (100−200 nm), and large (>200 nm) pegylated PHDCA nanoparticles incubated with serum protein for 2 h showed a significant correlation between particle size and protein absorption.Protein absorption on small nanoparticles (80 nm) was quantified (6%) and compared to the same nanoparticle formulation with a larger size (171 and 243 nm, 23 and 34%, respectively). The effect of protein absorption on different sized nanoparticles was also confirmed with the analysis of nanoparticle uptake by murine macrophages and blood clearance kinetics. Blood clearance of the smaller nanoparticles was twice as slow as with the larger nanoparticle formulations. More importantly, the amount of drug encapsulated (TNF-α) in nanoparticles that accumulated in the tumor within 24 h was twice that of the larger nanoparticle formulation. In summary, it has been consistently shown that pegylated nanoparticles smaller than 100 nm have reduced plasma protein adsorption on their surface and also have reduced hepatic filtration. Further, these small pegylated nanoparticles have a long blood residence time and a high rate of extravasation into permeable tissues, demonstrating the importance of tunable particle size and surface composition for achieving effective, targeted delivery
3.2. Effect of the Core
On the basis of physiological parameters such as hepatic filtration, tissue extravasation, tissue diffusion, and kidney excretion, it is clear that, along with surface composition, particle size is a key factor in the biodistribution of long-circulating nanoparticles and achieving therapeutic efficacy (Figure 2). In one study, in vivo biodistribution results of polystyrene nanoparticles with consistent composition and varying particle sizes of 50 and 500 nm showed higher levels of agglomeration of the larger nanoparticles in the liver. It was suggested that the mechanism of hepatic uptake was mediated by surface absorption of proteins leading to opsonization. However, the effect of temperature (37 °C vs 4 °C) on hepatic elimination showed unexpectedly faster uptake of the 50 nm polystyrene nanoparticles at the lower temperature. Similarly, the size of the nanoparticle was shown to have a substantial effect on the protein absorption. Small (<100 nm), medium (100−200 nm), and large (>200 nm) pegylated PHDCA nanoparticles incubated with serum protein for 2 h showed a significant correlation between particle size and protein absorption.Protein absorption on small nanoparticles (80 nm) was quantified (6%) and compared to the same nanoparticle formulation with a larger size (171 and 243 nm, 23 and 34%, respectively). The effect of protein absorption on different sized nanoparticles was also confirmed with the analysis of nanoparticle uptake by murine macrophages and blood clearance kinetics. Blood clearance of the smaller nanoparticles was twice as slow as with the larger nanoparticle formulations. More importantly, the amount of drug encapsulated (TNF-α) in nanoparticles that accumulated in the tumor within 24 h was twice that of the larger nanoparticle formulation. In summary, it has been consistently shown that pegylated nanoparticles smaller than 100 nm have reduced plasma protein adsorption on their surface and also have reduced hepatic filtration. Further, these small pegylated nanoparticles have a long blood residence time and a high rate of extravasation into permeable tissues, demonstrating the importance of tunable particle size and surface composition for achieving effective, targeted delivery. 3.3Effect of Surface Functionality and Charge
It has been established that the physicochemical characteristics of a polymeric nanoparticle such as surface charge and functional groups can affect its uptake by the cells of the phagocytic system. It was previously shown that polystyrene microparticles with a primary amine at the surface underwent significantly more phagocytosis as compared to microparticles having sulfate, hydroxyl, and carboxyl groups. Therefore, it is well accepted that positively charged nanoparticles have a higher rate of cell uptake compared to neutral or negatively charged formulations. Nanoparticles carrying a positively charged surface are also expected to have a high nonspecific internalization rate and short blood circulation half-life. Nanoshells having a negative surface charge have shown a marked reduction in the rate of uptake. The ζ potential for nanoshells with BSA absorbed on the surface of the nanoparticle was characterized by a shift to a more negative value. However, the BSA absorption did not promote a higher rate of cell uptaketer in controlling the developmen Thus; surface functionality is another critical parame t of long-circulating nanoparticles.
3.4 Effect of Active Targeting
Active targeting of nanoparticles involves the conjugation of targeting ligands to the surface of nanoparticles. These ligands can include antibodies, engineered antibody fragments, proteins, peptides, small molecules, and aptamers. The active targeting mechanism takes advantage of highly specific interactions between the targeting ligand and certain tissues or cells within the body to promote the accumulation of nanoparticles. In the case of weak binding ligands, low affinity can be offset by increased avidity through the surface functionalization of multiple molecules or multivalent designs and has been shown to be a valid approach. There are several examples of FDA-approved antibodies in clinical practice today, including Rituxan (target, CD20-positive B-cells for the treatment of non-Hodgkin’s lymphoma and rheumatoid arthritis), Herceptin (target, HER-2-overexpressing breast cancer cells), Erbitux [target, epidermal growth factor receptor (EGFR) for the treatment of colorectal cancer], Iressa (target, EGFR for the treatment of non-small cell lung cancer and metastatic breast cancer), and Avastin [target, vascular epidermal growth factor (VEGF) for the treatment of metastatic colorectal, non-small lung, and breast cancers]. While the progress with monoclocal antibodies has been encouraging, they have not been shown to be curative. Currently, drug delivery carriers are being functionalized with proteins, including antibodies or antibody fragments and various other targeting ligands, with the goal of both delivering a high therapeutic dose and delivering this high therapeutic dose to specific tissues or cells. Conjugation approaches for controlling the amount of targeting proteins on the surface of the nanoparticles have been developed to increase specificity and binding affinity. Research using proteins for targeting applications has led to a better understanding of the effect of stability and size of the ligand for successful targeting and clinical development. Cyclodextran-based nanoparticles containing transferrin targeting ligand (NP size of 
70 nm) showed enhanced intracellular accumulation in a human tumor xenograft mouse model the discovery of new peptide targeting domains provides the advantage of being able to utilize small synthetic molecules for active targeting. One such example is peptides which are relatively stable compared to antibodies and are also less likely to be immunogenic. Similarly, small molecules can be very attractive for use as targeting ligands, and small molecules such as folic acid or sugar molecules have been extensively used. For example, cell surface membrane lectins have been shown to be overexpressed on the surface of numerous cancer cells and are able to specifically internalize sugar molecules (lactose, galactose, and mannose).Similarly, nucleic acid aptamers are able to fold into unique structures capable of binding to specific targets with high affinity and specificity. Conclusion
The exact role of each of the proteins adsorbed on the surface of the nanoparticles in the clearance and biodistribution is still not clear besides their role in opsonization and enhanced hepatic uptake. It is generally assumed that the rapid uptake of injected nanoparticles is triggered by receptor-mediated mechanisms of absorbed proteins from the blood (opsonins) onto their surface and complement activation. However, it is not clear if a specific type, a combination of proteins, or even the protein conformation is the most important factor for a high rate of phagocytotic uptake. The efficacy of the PEG “brush” in altering the biodistribution of nanoparticles has been clearly demonstrated, and in vivo studies showed a drastic increase in blood circulation time with an increase in PEG surface density. Recently, targeted nanoparticles funtionalized with ligands that have high affinity and specificity have been shown to efficiently accumulate in specific tissues and dramatically increase the therapeutic efficacy of long-circulating nanoparticle drug delivery systems. Natural and synthetic polymers are now in preclinical and clinical phases for drug delivery. More importantly, targeted and nontargeted polymeric nanoparticles are now in the preclinical and clinical phases and confirm the great promise of the past 20 years of research and lessons learned from the failure of some clinical studies to increase the therapeutic index of drugs approved for clinical use.
4. Polymer used for preparation of nanoparticles
There are two polymers generally use in nanoparticle preparation
4.1. Natural hydrophilic polymer
4.2. Synthetic hydrophobic polymer
4.1. Natural hydrophilic polymer
Natural hydrophilic polymers are conveniently classified as protein and polysaccharide.
Various protein and polysaccharides used for the preparation of nanoparticles.
Protein-gelatin, albumin, lectins, legumin, vicilin etc.
Polysaccharide-alginate, dextran, chitosan, agarose, etc.
Note:-
Alginate based delivery systems for oral and ophthalamic administration have been aproved
In contrast, dextran, albumin, and gelatin which are though acceptable materials for parentral administration.
Disadvantage:-the polymer of natural origin suffer some disadvantage are-
Batch to batch variation
Conditional biodegradability
Antigenicity
Parentral administration of polymeric nanoparticle gets compromised mainly due to antigenicity.
4.2. Synthetic hydrophobic polymer
Most of them are typically hydrophobic in nature
The polymers are either pre-polymerised or synthesized before (first group) or during the (second group) process of nanoparticle preparation.
The polymer from the ester class polylactic acid and polylacticglycolic acid copolymer are representative of the first group along with poly caprolactoneand already been approved for humen use.
The second group is represented by poly (alkylcyanoacrylate), which have received the greatest attention as polymeric nanoparticle system but gathered number of controversies due to the toxicity of the corresponding alkylcyanoacrylate monomers.
Various synthetic polymers used for the preparation of nanoparticles
Pre-polymerised-poly (E-caprolactone), poly (lactic acid), poly (lactide-co-glycolide), polystyrene
Polymerised in process -poly (isobutylcyanoacrylate), poly (butylcyanoacrylate), poly (hexylcyanoacrylate), polymethyl (methacrylat)
Reason behind the formation of polymeric nanoparticle
Ø Administration of therapeutic agents has been limited by multiple factors such as low solubility, stability, and rapid clearance, the result is a short circulation half life and low efficacy, making frequent administration necessory. Additionally, there can be significant side-effect in non-diseased tissues that adsorbe therapeutic agent.
Ø These issues have led to the development of various targeting strategies aimed at increasing therapeutic index including monoclonal antibodiesand immunoconjugates.In addition to these strategies, it has been shown that polymer-drugconjugates can substantially improve the blood residence time and weaken side-effect.
Ø Many polymers have been investigated, including HPMA (N-(2-hydroxypropyl) methacrylamide, dextran and polyglutamate.
Ø HPMAand polyglutamate drug conjugates represent 35% of all the polymeric drug delivery system in clinical development. Thus, the main impact of polymeric conjugates has been to improve the pharmacokinetics parameters of drugs already in clinical use.
Ø These polymeric nanocarriers must be non-toxic, non-immunogenic and carry sufficient amount of drug and release the drug at the optimal dose.
5. Method of preparation
5.1. Amphiphilic macromolecules cross linking
5.1.1 Heat cross linking
5.1.2Chemical cross linking
5.2. Polymerization based method
5.2.1. Polymerization of monomers in-situ
5.2.2. Emulsion (micellar) polymerization
5.2.3. Dispersion polymerization
5.2.4. Interfacial condensation polymerization
5.2.5. Interfacial compexation
5.3. Polymer precipitation method
5.3.1. Solvent extraction/evaporation
5.3.2. Solvent displacement (nano precipitation)
5.3.3. Salting out
5.1. Preparation by cross-linking of amphiphilic macromolecules
Polymeric nanoparticle can be prepared from amphiphilic macromolecules, proteins and polysaccharide (which have affinity for aqueous and lipid solvents)
Macromolecular cross linking in water in oil (W/O) emulsion
Cross-linking in w/o emulsion
The cross linking method is exhaustively used for the nano-encapsulation of drugs.
The method involves the emulsification of bovin serum albumin (BSA)/human serum albumin (HAS) or protein aqueous solution in oil using high pressure homogenization or high frequency sonicatio 
The water in oil emulsion formed 
Then poured in to preheated oil (temp.above 100˚c)
Suspension in preheated oil maintained above (100˚c) is held stirred for a specific time in order to denature and aggregate the protein content of aq.pool completely 
Evaporate the water
Proteinaceous subnanoscopic particle are formed Formed particles are washed with an organic solvent to remove any adherent or absorbed oi and subsequently collected by centrifugation Polymers used for the preparation of nanoparticle
Polymer Used Technique Candidate Drug
1. Hydrophilic
Eg: albumin and heat denaturation and cross linking in hydrophilic
Gelatin w/o emulsion
desolvation and cross linking in aq. hydrophilic and
Medium protein affinity
Alginate, chitosan cross-linking in aq.medium hydrophilic and
Protein affinity
Dextran polymer precipitation in an hydrophilic
Organic solvent
2. Hydrophobic
Eg: poly (alkylcyanoacrylate) emulsion polymerization hydrophilic
interfacial o/w polymerization hydrophobic
3. Polyesters: eg
Poly lactic acid solvent extraction/evaporation hydrophilic and hydrophobic
, polylactide-co-glycolide solvent displacement soluble in polar solvent
Poly (E-caprolactone) salting out soluble in polar solvent
5.2. Preparation of PNP using polymerization based method
5.2.1. Polymerization of monomer in-situ
Preparation of polymeric nanoparticles mainly discusses in-situ emulsion technique.
Polymers used for nanospheres preparation include poly (methylmethacrylate), poly (acrylamide),
Poly (butylcyanoacrylate), n, n-methylene-bis-acryl-amide etc.
Two different approaches are generally adapted for the preparation of nanospheres using insitu polymerisation technique
5.2.1.1. Method in which the monomer to be polymerise is emulsified in a non solvent phase (emultion polymerisation)
5.2.1.2. Method in which the monomer is dissolved in a solvent that is non solvent for resulting polymer (dispersion polymerisation)
5.2.2. Emulsion polymerisation
Two different mechanism were proposed for the emulsion polymerisation process and they include
5.2.2.1. Micellar nucleation and polymerisation
5.2.2.2. Homogenous nucleation and polymerisation
Micellar nucleation and polymerisation
Step 1-swollen monomer micelles at the site of nucleation and polymerisation
The monomer is emulsified in the non solvent phase with the help of surfactant molecule 
Formation of monomer swollen micelle and stabilise monomer dropletSwollen micelle exhibit sizes in the nanometric range and thus has a much larger surface area in comparision to monomer droplet
Step 2-
The polymerisation reaction proceeds through nucleation and propagation stage in the presence of chemical or physical initiator
The energy provide by the initiator creates free reactive monomers in the continuous phase which then collide with surrounding unreactive monomer and initiate the polymerisation chain reaction
Being slightly soluble in the sorrounding phase the monomer mollecules reach the micelle by diffusion from the monomer droplet through the continuous phase thus allowing the polymerisation to progress within the micelles therefore in this case the monomer droplet essentially act as monomer reservoir.
Preparation of poly alkylcyanoacrylate (paca) nanoparticles using emulsion polymerization
Poly nanosphere poly nanocapsule
**for lipophilic drug:-
Mixture of polar solvent =methanol/acetone
Oil=benzylbenzoate, coconut oil
Lipophilicsurfactant=lecithin
5.2.3. Dispersion polymerization
The term emulsion polymerization is used when the monomer is emulsified in an immiscible (non-solvent) phase by means of surfactant.
In case of dispersion polymerization however, the monomer instead of being emulsified, is dissolved in an aq.medium which acts as a precipitant for subsequent formed polymer.
Polymerization based method essentially involves in-situ controlled polymerization of appropriate monomer where drug may be added to monomeric phase or may be added to the formed polymeric nanoparticulate dispersion for adsorptive loading.
The monomer is introduced in to the dispersion medium (phase) of an emulsion or an inverse emulsion in to non-solvent based polymeric solution.
Polymerization is initiated by adding a catalyst and proceeds with nucleation phase followed by a growth phase (propagation).
On the other hand, in the case of dispersion polymerization, the nucleation is directally induced in the aq.monomer solution and the persence of stabilizers or surfactant is not absolutely necessary for the formation of stable nanospheres.
5.2.4. Interfacial polymerization
In this method, the preformed polymer phase is finally transformed to an embryonic sheath.
A polymer that eventually becomes core of nanoparticle and drug molecules to be loaded are dissolved in a volatile solvent.
The solution is then poured in to a non-solvent for both polymer and core phase.
The polymer phase is separated as a coacervate phase at o/w interface.
The resultant mixture instantaneously turns milky owing to the formation of nanocapsules.
The solvent is subsequently removed undervacuum
The size of nanocapsules ranges from 30-300nm and drug loading efficiency depends on drug solubility in core phase.
Core dispersed in polymer
Phase (O/W emulsion) Add non-solvent, which precipitate out polymer
From either of phases and solvent is
Subsequently removed under vacuum
Polymeric nanocapsules
(30-300nm)
5.2.5. Interfacial complexatio
The method is based on the process of microencapsulation. In the case of polymeric nanoparticle preparation, aq. Polyelectrolyte solution is carefully dissolved in reverse micelles in an apolar bulk phase with the help of an appropriate surface active agent.subsequently, competing polyelectrolyte is added to the bulk which allows a layer of insoluble polyelectrolyte complex to coacervate at the interface.
5.3. Nanoparticle preparation using polymer precipitation method
In this method, hydrophobic polymer (dextran, mainly polyesters) orhydrophobic drug is dissolved in a particular organic solvent followed by its dispersion in a continuous aq.phase in which the polymer is insoluble.
The external phase also contains the stabilizers.
Depending upon solvent miscibility techniques they are designated as solvent extraction/evaporation method
The polymer precipitation occurs as a consequence of the solvent extraction or evaporation.
Stirred properly
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Then dispersion in a continuous phase in which polymer is insoluble
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5.3.1. Solvent extraction/evaporation method
Sonication/homogenizatio
O/W emulsion Solvent extraction/evaporation
Polymeric nanoparticle is formed
This method involves the formation of a conventional o/w emulsion between a partially water miscible solvent containing the polymer, drug, and an aq.phase containing stabilizer.
The subsequent removal of solvent (solvent evaporation method) with high speed /pressure homogenization.
The homogenizer breaks the initial coarse emulsion in nanodroplets (nanofluidizatio) yielding nanospheres with a narrow size distribution.
Double emulsion solvent evaporation method
Sonication/homogenization
W/O emulsion stabilized at 4®c
Add aqueous phase with stabilizer (polyvinylalcohol)
W/O/W emulsion
Solvent extraction/solvent evaporation
Polymeric nanoparticle is formed
Aqueous phase Distilled water, poloxamer 188 |
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Organic phase Solvent, polymer, drug |
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5.3.2. Solvent displacement or nano precipitation
Magnetic stirring
Polymeric nanospheres
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Aqueous phase Distilled water, poloxamer 188 |
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Organic phase Polar solvent, oil, polymer, drug |
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Magnetic stirring Polymeric nanospheres
Polymeric nanosphere is formed
5.3.3. Salting out method
This technique is suitable for drug and polymers that are soluble in polar solvent.
In this technique, the miscibility of both phases is prevented by the saturation of the external aq. Phase with polyvinylalcohol.
The precipitation of the polymer occurs when a sufficient amount of water is added to the external phase to allow coplete diffusion of the acetone from internal phase in to aq. Phase.
Aqueous phase Distilled water, polyvinylalcohol, Magnesiumchloride |
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Organic phase Organic solvent, drug, polymer |
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Mechanical stirring
O/W emulsion
Add distilled water (precipitation occurs)
Polymeric nanoparticles is formed
6. Evaluation and characterization parameter of polymeric nanoparticle
6.1. Size and morphology
The particle size is one of the most important parameters of polymeric nanoparticles.
There are two techniques generally used to determine the particle size distribution of polymeric nanoparticle
Photon correlation spectroscopy (pcs)
Electron microscopy
The scanning electrone microscopy (SEM), transmission electron microscopy (TEM) and freeze-fracture techniques are used.
6.2. Density
The density of polymeric nanoparticles is determined with helium or air using a gas pycnometer.
The value obtained with air and with helium is much more pronounced due to the specific surface area and porosity of the structure.
6.3. Surface charge and electrophoretic mobility
The nature and intensity of the surface charge of polymeric nanoparticle is very important as it determines their interaction with the biological environment as well as their electrostatic interaction with bioactives compounds.
The surface charge of colloidal particles could be measured by electrophoretic mobility.
Generally the electrophoretic mobility of polymeric nanoparticle is determined in phosphate saline buffer (pH=7.4) and human serum.
Phosphate buffer solution (pH=7.4) relatively reduce the absolute charge value due to ionic interaction of buffer components with the charged surface of polymeric nanoparticle
6.4. Surface hydrophobicity
The surface hydrophobicity of polymeric nanoparticle has an important influence on the interaction of colloidal particles with the biological environment (eg.protein adsorption and cell adhesion)
The hydrophobicity and hydrophilicity collctively determine the bio-fate of nanoparticles and their content.
The hydrophobicity regulates the extent and type of hydrophobic interactions of nanoparticulates with blood component.
Several methods including –
-Hydrophobic interaction chromatgraphy
-Two phase partition
-Adsorption of hydrophobic fluorescent or radiolabelled probes
-Contact angle measurement
6.5. Specific surface
The specific surface area of freeze –dried polymeric nanoparticle is generally determined by the help of sorptometer
The equation given below can be used in the calculation of specific surface area.
A=specific surface area, σ=density, d=diameter of the particle
6.6. Molecular weight measurements of nanoparticle -molecular weight of the polymer and its distribution in the matrix can be evaluated by gel permeation chromatography (GPC) using a refractive index detector.
6.7. Nanoparticle recovery and drug incorporation
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Concentration of drug in polymeric nanoparticle %Nanoparticles recovery = x100 or drug content Concentration of polymeric nanoparticle |
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6.8. In vitro release
In vitro release profile can be determined using standard dialysis, diffusin cell or recently introduced modified ultrafiltration technique.
In vitro drug release from the polymeric nanoparticles can be evaluated in phosphate buffer utilizing double chamber diffusion cells on a shaker stand
A millipore hydrophilic low-protein binding membrane is placed between the two chambers.
The donar chamber is filled with polymeric nanoparticulate suspension and the receiver chamber with plain buffer.
The receiver compartment is assayed at different time intervals for the released drug using standard procedure.
Magenheim and co-workers, 1993 used a modified ultrafiltration technique to determine in vitro release behaviour of the PnP suspension.
The PnP suspension is added directly in to a stirred ultrafiltration cell containing buffer.
At different time interval aliquots of the dissolution medium are filtered through the ultrafiltration membrane using less than two bars positive nitrogen pressure and assayed for the released drug using standard procedures.
7. Application of polymeric nanoparticles
7.1. Cancer therapy-
Material used-: poly (alkylcyanoacrylate)
Purpose-: targeting, reduced toxicity, enhanced uptake of antitumour agents, improve in-vitro and in-vivo stability.
7.2. Intracellular targeting-
Material used-: poly (alkylcyanoacrylate), polyesters with anti-parasitic or antiviral agent.
Purpose-: target reticuloendothelial system for intracellular infection.
7.3. Prolonged systemic circulation-
Material used-: polyesters with adsorbed polyethylene glycolor pluronic or derivatized polymer.
Purpose-: prolonged systemic drug effect, avoid uptake by the reticuloendothelial system.
7.4. Vaccine adjuvant-
Material used-: poly (methylmethacrylate) nanoparticle with vaccine (oral and intramuscular immunization).
Purpose-: enhances immune response, alternate acceptable adjuvant.
7.5. Peroral adsorption-
Material used-: poly (methylmethacrylate) nanoparticle with protein and therapeutic agent.
Purpose-: enhanced bioavailability, protection from gastrointestinal enzymes.
7.6. Ocular delivery-
Material used-: poly (methylmethacrylate) nanoparticle with steroids, anti-inflammatory agents, anti-bacterial agentfor glucoma.
Purpose-: improve retention of drug/reduced wash out.
7.7. DNA delivery-
Material used-: DNA-gelatin nanoparticles, DNA-chitosan nanoparticle, PDNA-poly (DL-lactide-co-glycolide) nanoparticles.
Purpose-: enhanced delivery and significantly higher expression levels.
7.8. Oligonucleotide delivery-
Material used-: alginate nanoparticle, poly (D, L) lactic acid nanoparticle.
Purpose-: enhanced delivery of oligonucleotides.
7.9. Other application-
Material used-: poly (alkylcyanoacrylate) nanoparticle with peptides.
Purpose-: crosses blood –brain barriers.
Material used-: poly (alkylcyanoacrylate) nanoparticle for transdermal application.
Purpose-: improve absorption and permeation.
Material used-: nanoparticles with adsorbed enzymes.
Purpose-: enzyme immunoassay.
Material used-: nanoparticles with radioactive or contrast agent.
Purpose-: radio-imaging.
Other than pharmaceutical uses
· Waterborne paint
· Adhesive
· Coating
· Redispersible latices
· Powder coatings
· Pressure sensitive adhesives
· Hot melts
· Biotechnology
· Biomedical products
· Drug delivery
· Medical diagnostics
· Problem solving
· Electronics
· Magnetics
· Optoelectronics
8.Patent and marketed product
Clinical Status of Polymeric Drug Delivery Nanoparticles under Development
| composition (trade name) | status | particle size (nm) | circulation half-life | relative tissue accumulation of the drug | maximum tolerated dose (MTD) | efficacy |
| methoxy-PEG-poly(d,l-lactide)Taxol (Genexol-PM) | Phase II | 30−60 nm | paclitaxel, 12 h (human) | Genexol-PM vs Taxol: 2× more in liver, spleen, heart, and tumor (mice) | 390 mg/m2administered intravenously for 3 h every 3 weeks (human) | 75% of metastatic breast cancer patient showed 2 years overall survival |
| HPMA-DACH palatinate (ProLindac, previously AP5346) | Phase II | 6−15 nm | DACH-platinum, 70 h (human) | | 640 mg/m2 (initial cycle); repeated cycles of therapy were not assessed (human) | |
| PEG-arginine deaminase (Hepacid, previously ADI-SS PEG 20000 MW) | Phase I/II | | arginine deaminase, 7 days (human | | 640 units/m2 once a week (MTD > maximum feasible dose by intravenous (iv) administration) | double median survival time of patients with metastatic melanoma; 47% response rate in HCC patients (n = 19) |
| PEG-camptothecin (Prothecan) | Phase I/II | | camptothecin, 40 h (human) | camptothecin % ID/g of tissue 24 h postinjection: 3.7% in tumor, 4.41% in blood, 2.32% in liver (mice) | 7000 mg/m2administered in 1 h iv infusions every 3 weeks (human) | |
| Pluronic-doxorubicin (SP1049C) | Phase II | 25 nm | doxorubicin, 3 h (human) | enhanced AUC in tumor (50.8 vs 30.1) and brain (9.2 vs 5.6) compared with free doxorubicin (mice) | 70 mg/m2administered intravenously every 3 weeks for a maximum of six cycles (human) | three patients over 21 showed responses to treatment |
| polycyclodextrin camptothecin (IT-101) | Phase I | 40 nm | camptothecin, 38 h (mice)71 | camptothecin % ID/g of tissue: tumor = 1.3%; liver = 1.9% (24 h) (mice) | | preliminary data is reported to show stable disease rate in patients with solid tumor |
| polyglutamate camptothecin (CT-2106) | Phase I/II | | camptothecin, 44−63 h (human) | | 25 mg/m2administered by iv infusion weekly every 3 of 4 weeks (human) | less toxicity than free dru |
| polyglutamate paclitaxel (Xyotax) | Phase III | | paclitaxel, 100 h (human) | paclitaxel % ID/g of tissue: tumor = 2.2%; spleen = 16%; liver = 8% (mice) | for an iv administration, 233 mg/m2 for patients on a two-dose weekly schedule and 177 mg/m2 on a three-dose weekly schedule (human) | response rate of 10% for 99 patients and a median time to disease progression of 2 months |
| dextran-doxorubicin (AD-70) | Phase I | | doxorubicin, 3−12 h (human) | |
20 mg/m2(human) | discontinued due to severe hepatotoxicity limiting the dose at 20 mg/m2 |
| dextran-camptothecin (DE-310) | Phase I/II | | camptothecin, 300−400 h (human) | | 9 mg/m2 given once every 4 weeks (human) | no new major toxicity compared to drug beside hepatotoxicity reported as reversible |
| HPMA-paclitaxel (PNU166945) | Phase I | | paclitaxel, 3−12 h (huma | | 196 mg/m2(human) | discontinued due to severe neurotoxicity |
| HPMA-doxorubicin (PK1) | Phase II | | doxorubicin, 93 h (human) | | 320 mg/m2(human) | hepatic toxicity at doses > 120 mg/m2; two partial and two minor responses over 36 patient |
| PEG-aspartic acid-doxorubicin (NK911) | Phase I | 30−50 nm | doxorubicin, 1.6−4.7 h (human) |
| 67 mg/m2, plasma clearance 400-fold higher than Doxil (human) | no severe toxicity; Phase II clinical trial for pancreatic cancer |
| HPMA-doxorubicin with galactosamine (PK2)
| Phase I | 8.4 nm | biphasic clearance with half-lives of 2.9 and 26.7 h when 120 mg/m2administered by 24 h infusion (human) | enhanced accumulation in liver, hepatoma, and metastatic hepatoma compared with nontargeted HPMA-doxorubicin (human
| 160 mg/m2 with administration by iv infusion over 1 h every 3 weeks (human) | of 18 patients, three responded to treatment, with two in partial remission for >26 and >47 month |
9. Recent development in polymeric nanoparticle
9.1 Recent Developments in Polymeric Nanoparticle Engineering and Their Applications in experimental and Clinical Oncology
Promising results have come from attempts to direct drugs, nucleic acids and diagnostic agents to tumours by using polymeric nanoparticles. Such carriers are versatile; their encapsulation capacity, drug release profile, and biological performance vary with their chemical makeup, morphology, and size. Polymeric nanoparticles may therefore be engineered for therapeutic and diagnostic purposes in accordance with the type, developmental stage and location of the cancer as well as the required route of administration. This article examines recent developments in design and engineering of polymeric nanoparticles and related platforms to include supramolecular systems such as nanocapsules and nanoparticlebased hydrogels, and assesses their potential diagnostic and therapeutic applications in experimental and clinical oncology.
9.2 Nanotechnology has the potential to revolutionize cancer diagnosis and therapy.
Advances in protein engineering and materials science have contributed to novel nanoscale targeting approaches that may bring new hope to cancer patients. Several therapeutic nanocarriers have been approved for clinical use. However, to date, there are only a few clinically approved nanocarriers that incorporate molecules to selectively bind and target cancer cells. This review examines some of the approved formulations and discusses the challenges in translating basic research to the clinic. We detail the arsenal of nanocarriers and molecules available for selective tumour targeting, and emphasize the challenges in cancer treatment.
9.3 Layer-by-Layer Growth of Polymer/Nanoparticle Films Containing Monolayer-Protected Gold Clusters:-
Multilayer films of nanoparticles were grown in a systematic and controlled manner layer-by-layer by alternating exposures of suitably functionalized substrates (glass, Au) to either poly(allylamine) and carboxylic acid-functionalized nanoparticles or to poly(styrene sulfonate) and arylamine-functionalized nanoparticles. Electrostatic interactions comprise the dominant film growth factors. The rate of multilayer film growth depends on the polymer solution pH and other details of the solution exposures. Growth was followed by spectrophotometry of the Au nanoparticle cores, voltammetry of the Au core double layer charging, and film mass (quartz crystal microbalance). The first example is reported of quantized double layer charging of the Au cores in a layer-by-layer film that is composed of monolayer-protected clusters and a polyelectrolyte.
9.4 Recent developments in ophthalmic drug delivery
Recent research efforts in ophthalmic drug delivery have mainly focused on systems in which drugs may be administered in the form of eye-drops. As a result of these efforts, significant advancements have been made in the following areas: in situ-forming gels, oil-in-water emulsions, colloidal drug delivery systems (liposomes and nanoparticles) and microparticulates. Protein and peptide delivery, posterior drug delivery and non-aqueous vehicles are three new areas of interest in ophthalmic drug delivery, and this review will discuss recent progress and specific development issues relating to these drug delivery systems
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