Biodegradable polymeric nanoparticles based drug delivery systems

Enhanced immunomodulatory activity of gelatin-encapsulated Rubus coreanus Miquel nanoparticles

The aim of this work was to investigate the immunomodulatory activities of Rubus coreanus Miquel extract-loaded gelatin nanoparticles. The mean size of the produced nanoparticles was 143 ± 18 nm with a bandwidth of 76 nm in the size distribution and a maximum size of ~200 nm, which allows effective nanoparticle uptake by cells. Confocal imaging confirmed this, since the nanoparticles were internalized within 30 min and heterogeneously distributed throughout the cell. Zeta-potential measurements showed that from pH = 5 onwards, the nanoparticles were highly negatively charged, which prevents agglomeration to clusters by electrostatic repulsion. This was confirmed by TEM imaging, which showed a well dispersed colloidal solution. The encapsulation efficiency was nearly 60%, which is higher than for other components encapsulated in gelatin nanoparticles. Measurements of immune modulation in immune cells showed a significant effect by the crude extract, which was only topped by the nanoparticles containing the extract. Proliferation of B-, T- and NK cells was notably enhanced by Rubus coreanus-gelatin nanoparticles and in general ~2–3 times higher than control and on average ~2 times higher than ferulic acid. R. coreanus-gelatin nanoparticles induced cytokine secretion (IL-6 and TNF-α) from B- and T-cells on average at a ~2–3 times higher rate compared with the extract and ferulic acid. In vivo immunomodulatory activity in mice fed with R. coreanus-gelatin nanoparticles at 1 mL/g body weight showed a ~5 times higher antibody production compared to control, a ~1.3 times higher production compared to the extract only, and a ~1.6 times higher production compared to ferulic acid. Overall, our results suggest that gelatin nanoparticles represent an excellent transport vehicle for Rubus coreanus extract and extracts from other plants generally used in traditional Asian medicine. Such nanoparticles ensure a high local concentration that results in enhancement of immune cell activities, including proliferation, cytokine secretion, and antibody production.

Theranostic applications of nanomaterials in cancer: drug delivery, image-guided therapy, and multifunctional platforms

Successful cancer management depends on accurate diagnostics along with specific treatment protocols. Current diagnostic techniques need to be improved to provide earlier detection capabilities, and traditional chemotherapy approaches to cancer treatment are limited by lack of specificity and systemic toxicity. This review highlights advances in nanotechnology that have allowed the development of multifunctional platforms for cancer detection, therapy, and monitoring. Nanomaterials can be used as MRI, optical imaging, and photoacoustic imaging contrast agents. When used as drug carriers, nanoformulations can increase tumor exposure to therapeutic agents and result in improved treatment effects by prolonging circulation times, protecting entrapped drugs from degradation, and enhancing tumor uptake through the enhanced permeability and retention effect as well as receptor-mediated endocytosis. Multiple therapeutic agents such as chemotherapy, antiangiogenic, or gene therapy agents can be simultaneously delivered by nanocarriers to tumor sites to enhance the effectiveness of therapy. Additionally, imaging and therapy agents can be co-delivered to provide seamless integration of diagnostics, therapy, and follow-up, and different therapeutic modalities such as chemotherapy and hyperthermia can be co-administered to take advantage of synergistic effects. Liposomes, metallic nanoparticles, polymeric nanoparticles, dendrimers, carbon nanotubes, and quantum dots are examples of nanoformulations that can be used as multifunctional platforms for cancer theranostics. Nanomedicine approaches in cancer have great potential for clinically translatable advances that can positively impact the overall diagnostic and therapeutic process and result in enhanced quality of life for cancer patients. However, a concerted scientific effort is still necessary to fully explore long-term risks, effects, and precautions for safe human use.

Biodegradable nanoparticles are excellent vehicle for site directed in-vivo delivery of drugs and vaccines

Biodegradable nanoparticles (NPs) are gaining increased attention for their ability to serve as a viable carrier for site specific delivery of vaccines, genes, drugs and other biomolecules in the body. They offer enhanced biocompatibility, superior drug/vaccine encapsulation, and convenient release profiles for a number of drugs, vaccines and biomolecules to be used in a variety of applications in the field of medicine. In this manuscript, the methods of preparation of biodegradable NPs, different factors affecting optimal drug encapsulation, factors affecting drug release rates, various surface modifications of nanoparticles to enhance in-vivo circulation, distribution and multimodal functionalities along with the specific applications such as tumor targeting, oral delivery, and delivery of these particles to the central nervous system have been reviewed.

Anti-P-glycoprotein conjugated nanoparticles for targeting drug delivery in cancer treatment

Targeting therapeutics to specific sites can enhance the efficacy of drugs, reduce required doses as well as unwanted side effects. In this work, using the advantages of the specific affinity of an immobilized antibody to membrane P-gp in two different nanoparticle formulations were thus developed for targeted drug delivery to multi-drug resistant cervical carcinoma (KB-V1) cells. Further, this was compared to the human drug sensitive cervical carcinoma cell line (KB-3-1) cells. The two nanoparticle preparations were: NP1, anti-P-gp conjugated with poly (DL-lactic-coglycolic acid) (PLGA) nanoparticle and polyethylene glycol (PEG); NP2, anti-P-gp conjugated to a modified poloxamer on PLGA nanoparticles. The cellular uptake capacity of nanoparticles was confirmed by fluorescent microscopy. Comparing with each counterpart core particles, there was a higher fluorescence intensity of the targeted nanoparticles in KBV1 cells compared to KB-3-1 cells suggesting that the targeted nanoparticles were internalized into KB-V1 cells to a greater extent than KB-3-1 cell. The results had confirmed the specificity and the potential of the developed targeted delivery system for overcoming multi-drug resistance induced by overexpression of P-gp on the cell membrane.

Nanomedical system for nucleic acid drugs created with the biodegradable nanoparticle platform

Nanomedical applications of biodegradable poly(DL-lactide-co-glycolide) (PLGA) nanoparticles (NPs) developed are discussed in this review. A surface-functionalized PLGA NP platform for drug delivery was established to encapsulate a number of macromolecular drugs such as peptides and nucleic acids as well as low-molecular-weight drugs by the emulsion solvent diffusion method. The interaction of PLGA NPs with cells and tissues could be controlled by changing the surface properties of NPs, suggesting their potential utility for the intracellular drug delivery of nucleic acid-based drugs. Furthermore, orally administered NF-κB decoy oligonucleotide-loaded CS-PLGA NPs are also useful in treating experimental colitis. These approaches using surface-modified PLGA NPs could be able to open new possibilities for nucleic acid-based drug delivery via noninvasive administration method.

Nanocarriers: a tool to overcome biological barriers in siRNA delivery

INTRODUCTION

siRNA has poor in vivo stability and has a plasma half life of only a few minutes after intravenous administration. These problems can be overcome by conjugating/encapsulating siRNA with various nanosystems. Surface modifications of such nanosystems can further improve the cellular uptake of siRNA-nanosystems. In this review, the authors have highlighted the problems encountered in siRNA delivery, conjugation strategies and nanosystems for siRNA delivery and for improving their in vivo delivery performance.

AREAS COVERED

The authors briefly cover various problems encountered in siRNA delivery and discuss nanocarriers for overcoming these biological barriers.

EXPERT OPINION

siRNA binding and unpacking are important factors for optimizing the interactions between siRNA and nanosystems. Several crucial conjugation parameters, such as the conjugation site of siRNA, and the nature of molecules to be conjugated (charge, molecular weight and hydrophobicity), should be carefully considered for maximising delivery efficiency of siRNA conjugated nanosystems.

Polycaprolactone microspheres as carriers for dry powder inhalers: effect of surface coating on aerosolization of salbutamol sulfate

This study reports the factors controlling aerosolization of salbutamol sulfate (SS) from mixtures with polycaprolactone (PCL) microspheres fabricated using an emulsion technique with polyvinyl alcohol (PVA) as stabilizer. The fine particle fraction (FPF) of SS from PCL measured by a twin-stage impinger was unexpectedly found to be zero, although scanning electron microscopy showed that the drug coated the entire microsphere. Precoating the microspheres with magnesium stearate (MgSt) excipient solutions (1%-2%) significantly increased (p < 0.05, n = 5) the FPF of SS (11.4%-15.4%), whereas precoating with leucine had a similar effect (FPF = 11.3 ± 1.1%), but was independent of the solution concentration. The force of adhesion (by atomic force microscopy) between the PCL microspheres and SS was reduced from 301.4 ± 21.7 nN to 110.9 ± 30.5 nN and 121.8 ± 24.6 nN, (p < 0.05, n = 5) for 1% and 2% MgSt solutions, respectively, and to 148.1 ± 21.0 nN when coated with leucine. The presence of PVA on the PCL microspheres (detected by X-ray photoelectron spectroscopy) affected the detachment of SS due to strong adhesion between the two, presumably due to capillary forces acting between them. Precoating the microspheres with excipients increased the FPF significantly by reducing the drug-carrier adhesion.

Fabrication, modeling and characterization of multi-crosslinked methacrylate copolymeric nanoparticles for oral drug delivery

Nanotechnology remains the field to explore in the quest to enhance therapeutic efficacies of existing drugs. Fabrication of a methacrylate copolymer-lipid nanoparticulate (MCN) system was explored in this study for oral drug delivery of levodopa. The nanoparticles were fabricated employing multicrosslinking technology and characterized for particle size, zeta potential, morphology, structural modification, drug entrapment efficiency and in vitro drug release. Chemometric Computational (CC) modeling was conducted to deduce the mechanism of nanoparticle synthesis as well as to corroborate the experimental findings. The CC modeling deduced that the nanoparticles synthesis may have followed the mixed triangular formations or the mixed patterns. They were found to be hollow nanocapsules with a size ranging from 152 nm (methacrylate copolymer) to 321 nm (methacrylate copolymer blend) and a zeta potential range of 15.8–43.3 mV. The nanoparticles were directly compressible and it was found that the desired rate of drug release could be achieved by formulating the nanoparticles as a nanosuspension, and then directly compressing them into tablet matrices or incorporating the nanoparticles directly into polymer tablet matrices. However, sustained release of MCNs was achieved only when it was incorporated into a polymer matrix. The experimental results were well corroborated by the CC modeling. The developed technology may be potentially useful for the fabrication of multi-crosslinked polymer blend nanoparticles for oral drug delivery.

The use of micro- and nanospheres as functional components for bone tissue regeneration

During the last decade, the use of micro- and nanospheres as functional components for bone tissue regeneration has drawn increasing interest. Scaffolds comprising micro- and nanospheres display several advantages compared with traditional monolithic scaffolds that are related to (i) an improved control over sustained delivery of therapeutic agents, signaling biomolecules and even pluripotent stem cells, (ii) the introduction of spheres as stimulus-sensitive delivery vehicles for triggered release, (iii) the use of spheres to introduce porosity and/or improve the mechanical properties of bulk scaffolds by acting as porogen or reinforcement phase, (iv) the use of spheres as compartmentalized microreactors for dedicated biochemical processes, (v) the use of spheres as cell delivery vehicle, and, finally, (vi) the possibility of preparing injectable and/or moldable formulations to be applied by using minimally invasive surgery. This article focuses on recent developments with regard to the use of micro- and nanospheres for bone regeneration by categorizing micro-/nanospheres by material class (polymers, ceramics, and composites) as well as summarizing the main strategies that employ these spheres to improve the functionality of scaffolds for bone tissue engineering.

Poly-є-caprolactone based formulations for drug delivery and tissue engineering: A review

Biodegradable polymer based novel drug delivery systems have provided many avenues to improve therapeutic efficacy and pharmacokinetic parameters of medicinal entities. Among synthetic biodegradable polymer, poly-є-caprolactone (PCL) is a polymer with very low glass transition temperature and melting point. Owing to its amicable nature and tailorable properties it has been trialed in almost all novel drug delivery systems and tissue engineering application in use/investigated so far. This review aims to provide an up to date of drugs incorporated in different PCL based formulations, their purpose and brief outcomes. Demonstrated PCL formulations with or without drugs, intended for drug delivery and/or tissue engineering application such as microsphere, nanoparticles, scaffolds, films, fibers, micelles etc. are categorized based on method of preparation.

Biomedical exploitation of chitin and chitosan via mechano-chemical disassembly, electrospinning, dissolution in imidazolium ionic liquids, and supercritical drying

Recently developed technology permits to optimize simultaneously surface area, porosity, density, rigidity and surface morphology of chitin-derived materials of biomedical interest. Safe and ecofriendly disassembly of chitin has superseded the dangerous acid hydrolysis and provides higher yields and scaling-up possibilities: the chitosan nanofibrils are finding applications in reinforced bone scaffolds and composite dressings for dermal wounds. Electrospun chitosan nanofibers, in the form of biocompatible thin mats and non-wovens, are being actively studied: composites of gelatin + chitosan + polyurethane have been proposed for cardiac valves and for nerve conduits; fibers are also manufactured from electrospun particles that self-assemble during subsequent freeze-drying. Ionic liquids (salts of alkylated imidazolium) are suitable as non-aqueous solvents that permit desirable reactions to occur for drug delivery purposes. Gel drying with supercritical CO₂ leads to structures most similar to the extracellular matrix, even when the chitosan is crosslinked, or in combination with metal oxides of interest in orthopedics.

Induction of an in vitro reversible hypometabolism through chitosan-based nanoparticles

OBJECTIVE

Chitosan-based nanoparticles (NPs) were prepared to promote intracellular sustained delivery of the synthetic delta opioid D-Ala(2)-D-Leu(5)-enkephalin (DADLE), prolonging peptide activity and inducing a safe and reversible hypometabolic state.

MATERIALS AND METHODS

NPs were prepared by combining ionotropic gelation and ultrasonication treatment. NP uptake studies and the effects of encapsulated DADLE on HeLa cells proliferation were tested by transmission electron microscopy (TEM) analysis, by immuno-fluorescence and immuno-cytochemistry.

RESULTS

DADLE-loaded NPs are produced with suitable characteristics, a satisfactory process yield (55.4% ± 2.4%) and encapsulation efficiency (64.6% ± 2.1%). NPs are effective in inducing a hypometabolic stasis at a 10(-4) M DADLE concentration. Moreover, as seen from the immunofluorescence study, the effect persists through the recovery period (72 h). Indeed, NPs labelled by anti-enkephalin antibody inside cell nucleus reassert that the in vivo release of the peptide can be prolonged with respect to the case of free peptide supply.

CONCLUSION

The nanoparticulate drug delivery system described seems to be effective in inducing and prolonging a sort of hibernation-like state in the cells.

Microfluidic devices for modeling cell-cell and particle-cell interactions in the microvasculature

Cell-fluid and cell-cell interactions are critical components of many physiological and pathological conditions in the microvasculature. Similarly, particle-cell interactions play an important role in targeted delivery of therapeutics to tissue. Development of in vitro fluidic devices to mimic these microcirculatory processes has been a critical step forward in our understanding of the inflammatory process, developing of nano-particulate drug carriers, and developing realistic in vitro models of the microvasculature and its surrounding tissue. However, widely used parallel plate flow based devices and assays have a number of important limitations for studying the physiological conditions in vivo. In addition, these devices are resource hungry and time consuming for performing various assays. Recently developed, more realistic, microfluidic based devices have been able to overcome many of these limitations. In this review, an overview of the fluidic devices and their use in studying the effects of shear forces on cell-cell and cell-particle interactions is presented. In addition, use of mathematical models and computational fluid dynamics (CFD) based models for interpreting the complex flow patterns in the microvasculature is highlighted. Finally, the potential of 3D microfluidic devices and imaging for better representing in vivo conditions under which cell-cell and cell-particle interactions take place is discussed.

Mesoporous silica nanoparticles for bioadsorption, enzyme immobilisation, and delivery carriers

Mesoporous silica nanoparticles (MSNs) provide a non-invasive and biocompatible delivery platform for a broad range of applications in therapeutics, pharmaceuticals and diagnosis. The creation of smart, stimuli-responsive systems that respond to subtle changes in the local cellular environment are likely to yield long term solutions to many of the current drug/gene/DNA/RNA delivery problems. In addition, MSNs have proven to be promising supports for enzyme immobilisation, enabling the enzymes to retain their activity, affording them greater potential for wide applications in biocatalysis and energy. This review provides a comprehensive summary of the advances made in the last decade and a future outlook on possible applications of MSNs as nanocontainers for storage and delivery of biomolecules. We discuss some of the important factors affecting the adsorption and release of biomolecules in MSNs and review of the cytotoxicity aspects of such nanomaterials. The review also highlights some promising work on enzyme immobilisation using mesoporous silica nanoparticles.

Stem cell-biomaterial interactions for regenerative medicine

The synergism of stem cell biology and biomaterial technology promises to have a profound impact on stem-cell-based clinical applications for tissue regeneration. Biomaterials development is rapidly advancing to display properties that, in a precise and physiological fashion, could drive stem-cell fate both in vitro and in vivo. Thus, the design of novel materials is trying to recapitulate the molecular events involved in the production, clearance and interaction of molecules within tissue in pathologic conditions and regeneration of tissue/organs. In this review we will report on the challenges behind translating stem cell biology and biomaterial innovations into novel clinical therapeutic applications for tissue and organ replacements (graphical abstract).

Comparison of intracellular accumulation and cytotoxicity of free mTHPC and mTHPC-loaded PLGA nanoparticles in human colon carcinoma cells

The second generation photosensitizer mTHPC was approved by the European Medicines Agency (EMA) for the palliative treatment of advanced head and neck cancer in October 2001. It is known that mTHPC possesses a significant phototoxicity against a variety of human cancer cells in vitro but also exhibits dark toxicity and can cause adverse effects (especially skin photosensitization). Due to its poor water solubility, the administration of hydrophobic photosensitizer still presents several difficulties. To overcome the administration problems, the use of nanoparticles as drug carrier systems is much investigated. Nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) have been extensively studied as delivery systems into tumours due to their biocompatibility and biodegradability. The goal of this study was the comparison of free mTHPC and mTHPC-loaded PLGA nanoparticles concerning cytotoxicity and intracellular accumulation in human colon carcinoma cells (HT29). The nanoparticles delivered the photosensitizer to the colon carcinoma cells and enabled drug release without losing its activity. The cytotoxicity assays showed a time- and concentration-dependent decrease in cell proliferation and viability after illumination. However, first and foremost mTHPC lost its dark toxic effects using the PLGA nanoparticles as a drug carrier system. Therefore, PLGA nanoparticles are a promising drug carrier system for the hydrophobic photosensitizer mTHPC.

Size dependency of PLGA-nanoparticle uptake and antifungal activity against Aspergillus flavus

AIMS

Itraconazole and coumarin-6 loaded polylactic-co-glycolic acid-nanoparticles (PLGA-ITZ- and PLGA-C6-NPs) were synthesized and tested for fungal cell uptake and antifungal ability based on particle size.

MATERIALS & METHODS

PLGA-ITZ- and PLGA-C6-NPs were synthesized using an oil-in-water emulsion evaporation method. Fungal cell uptake and antifungal activity of the polymeric NPs was tested on Aspergillus flavus.

RESULTS

PLGA-C6-NPs of 203 nm associated with fungal cell surfaces and internalized efficiently, while 1206 nm NPs associated with cell surfaces were internalized less efficiently. Antifungal studies of PLGA-ITZ-NPs of 232, 630 and 1060 nm showed differences in inhibitory activity with 232 nm NPs showing superior activity at the lowest ITZ concentration of 0.003 mg/ml, followed by 630 and 1060 nm NPs. No differences in antifungal activity were observed at higher ITZ concentrations.

CONCLUSION

The PLGA-ITZ-NP system can increase bioavailability of ITZ by improving its aqueous dispersibility and efficiently delivering ITZ to fungal cells via endocytosis.

Anandamide-loaded nanoparticles: preparation and characterization

OBJECTIVE

Preparation and characterization of anandamide (N-arachidonoyl-ethanolamine, AEA) loaded polycaprolactone nanoparticles (PCL NP) as a research tool to clarify the presence of an AEA transporter in cell membranes and to avoid AEA plastic adsorption and instability.

MATERIALS AND METHODS

High performance liquid chromatography and light scattering were used to determine encapsulation efficiency, particle size, drug release, permeability and stability.

RESULTS

A high encapsulation efficiency 96.05 ± 1.77% and a particle size of 83.52 ± 21.38 nm were obtained. Nearly 40% of AEA remained in the NP after a 99.9% dilution and only 50% was released after 24 h at 37 °C with a 99% dilution. PCL NP prevented the adsorption of the drug to polypropylene or polystyrene, but not to acrylic multiwell plates. Drug permeability through artificial membranes was low (10⁻⁷ to 10⁻⁸ cm/s) and was affected by the presence of NP. NP increased AEA stability in suspension (drug half-life 431 h vs. 12 h) and freeze-dried with 5% sucrose.

CONCLUSION

This article presents the first study where stable AEA-loaded NP with high encapsulation efficiencies have been obtained.

Recent advances in leishmaniasis treatment

About 1.5 million new cases of cutaneous leishmaniasis and 500,000 new cases of visceral leishmaniasis occur each year around the world. For over half a century, the clinical forms of the disease have been treated almost exclusively with pentavalent antimonial compounds. In this review, we describe the arsenal available for treating Leishmania infections, as well as recent advances from research on plants and synthetic compounds as source drugs for treating the disease. We also review some new drug-delivery systems for the development of novel chemotherapeutics. We observe that the pharmaceutical industry should employ its modern technologies, which could lead to better use of plants and their extracts, as well as to the development of synthetic and semi-synthetic compounds. New studies have highlighted some biopharmaceutical technologies in the design of the delivery strategy, such as nanoparticles, liposomes, cochleates, and non-specific lipid transfer proteins. These observations serve as a basis to indicate novel routes for the development and design of effective anti-Leishmania drugs.

A fibrin gel loaded with chitosan nanoparticles for local delivery of rhEGF: preparation and in vitro release studies

Recombinant human epidermal growth factor (rhEGF) is known to stimulate cell proliferation and accelerate wound healing. Direct delivery of rhEGF at the wound site in a sustained and controllable way without loss of bioactivity would enhance its biological effects. The aim of this study was to prepare a novel local delivery system for the sustained and controllable release of rhEGF, a fibrin gel loaded with chitosan nanoparticles. First, rhEGF-loaded chitosan nanoparticles were prepared and characterized, and these showed an ability to protect rhEGF from proteolysis. The prepared nanoparticles were then incorporated into a fibrin gel matrix during polymerization. In vitro release studies showed that the fibrin gel loaded with rhEGF/chitosan nanoparticles could achieve a more sustained release of rhEGF than either chitosan nanoparticles or an unloaded fibrin gel. Additionally, the release rate could be controlled by altering the contents of fibrinogen and thrombin in this composite delivery system. The bioactivity of the released rhEGF was determined by assessing its ability to stimulate the proliferation of BALB/c 3T3 cells, and the results showed that rhEGF bioactivity was not affected during the preparation process and could be maintained for at least 7 days. This novel delivery system may have great potential applications in the local administration of rhEGF.

Bioconjugated PLGA-4-arm-PEG branched polymeric nanoparticles as novel tumor targeting carriers

In this study, we have developed a novel carrier, micelle-type bioconjugated PLGA-4-arm-PEG branched polymeric nanoparticles (NPs), for the detection and treatment of pancreatic cancer. These NPs contained 4-arm-PEG as corona, and PLGA as core, the particle surface was conjugated with cyclo(arginine-glycine-aspartate) (cRGD) as ligand for in vivo tumor targeting. The hydrodynamic size of the NPs was determined to be 150-180 nm and the critical micellar concentration (CMC) was estimated to be 10.5 mg l( - 1). Our in vitro study shows that these NPs by themselves had negligible cytotoxicity to human pancreatic cancer (Panc-1) and human glioblastoma (U87) cell lines. Near infrared (NIR) microscopy and flow cytometry demonstrated that the cRGD conjugated PLGA-4-arm-PEG polymeric NPs were taken up more efficiently by U87MG glioma cells, over-expressing the α(v)β(3) integrin, when compared with the non-targeted NPs. Whole body imaging showed that the cRGD conjugated PLGA-4-arm-PEG branched polymeric NPs had the highest accumulation in the pancreatic tumor site of mice at 48 h post-injection. Physical, hematological, and pathological assays indicated low in vivo toxicity of this NP formulation. These studies on the ability of these bioconjugated PLGA-4-arm-PEG polymeric NPs suggest that the prepared polymeric NPs may serve as a promising platform for detection and targeted drug delivery for pancreatic cancer.

Application of hydroxyapatite nanoparticles in development of an enhanced formulation for delivering sustained release of triamcinolone acetonide

We report an analysis of in vitro and in vivo drug release from an in situ formulation consisting of triamcinolone acetonide (TR) and poly(d,l-lactide-co-glycolide) (PLGA) and the additives glycofurol (GL) and hydroxyapatite nanoparticles (HA). We found that these additives enhanced drug release rate. We used the Taguchi method to predict optimum formulation variables to minimize the initial burst. This method decreased the burst rate from 8% to 1.3%. PLGA-HA acted as a strong buffer, thereby preventing tissue inflammation at the injection site caused by the acidic degradation products of PLGA. Characterization of the optimized formulation by a variety of techniques, including scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and Fourier transform near infrared spectroscopy, revealed that the crystalline structure of TR was converted to an amorphous form. Therefore, this hydrophobic agent can serve as an additive to modify drug release rates. Data generated by in vitro and in vivo experiments were in good agreement.

Influence of process and formulation parameters on the formation of submicron particles by solvent displacement and emulsification-diffusion methods critical comparison

Solvent displacement and emulsification-diffusion are the methods used most often for preparing biodegradable submicron particles. The major difference between them is the procedure, which results from the total or partial water miscibility of the organic solvents used. This review is devoted to a critical and a comparative analysis based on the mechanistic aspects of particle formation and reported data on the influence of operating conditions, polymers, stabilizing agents and solvents on the size and zeta-potential of particles. In addition, a systematic study was carried out experimentally in order to obtain experimental data not previously reported and compare the data pertaining to the different methods. Thus the discussion of the behaviors reported in the light of the results obtained from the literature takes into account a wide range of theoretical and practical information. This leads to discussion on the formation mechanism of the particles and provides criteria for selecting the adequate method and raw materials for satisfying specific objectives in submicron particle design.

Polysaccharide drug delivery systems based on pectin and chitosan

Chitosans and pectins are natural polysaccharides which show great potential in drug delivery systems. Chitosans are a family of strongly polycationic derivatives of poly-N-acetyl-D-glucosamine. This positive charge is very important in chitosan drug delivery systems as it plays a very important role in mucoadhesion (adhesion to the mucosal surface). Other chitosan based drug delivery systems involve complexation with ligands to form chitosan nanoparticles with can be used to encapsulate active compounds. Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions often described in simplified terms as the "smooth" and "hairy" regions respectively. Pectin HG regions consist of poly-glacturonic acid residues which can be partially methyl esterified. Pectins with a degree of methyl esterification (DM) > 50% are known as high methoxyl (HM) pectins and consequently low methoxyl (LM) pectins have a DM less than 50%. Low methoxyl pectins are of particular interest in drug delivery as they can form gels with calcium ion (Ca2+) which has potential applications especially in nasal formulations. In this chapter we will discuss the physicochemical properties of both chitosans and pectins and how these translate to current and potential drug delivery systems.

Nanomaterials: applications in cancer imaging and therapy

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics that are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multimodal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge, physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and to achieve active targeting. This is stimulating the development of a diverse range of nanometer-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

PLGA nanoparticles containing various anticancer agents and tumour delivery by EPR effect

As mortality due to cancer continues to rise, advances in nanotechnology have significantly become an effective approach for achieving efficient drug targeting to tumour tissues by circumventing all the shortcomings of conventional chemotherapy. During the past decade, the importance of polymeric drug-delivery systems in oncology has grown exponentially. In this context, poly(lactic-co-glycolic acid) (PLGA) is a widely used polymer for fabricating 'nanoparticles' because of biocompatibility, long-standing track record in biomedical applications and well-documented utility for sustained drug release, and hence has been the centre of focus for developing drug-loaded nanoparticles for cancer therapy. Such PLGA nanoparticles have also been used to develop proteins and peptides for nanomedicine, and nanovaccines, as well as a nanoparticle-based drug- and gene-delivery system for cancer therapy, and nanoantigens and growth factors. These drug-loaded nanoparticles extravasate through the tumour vasculature, delivering their payload into the cells by the enhanced permeability and retention (EPR) effect, thereby increasing their therapeutic effect. Ongoing research about drug-loaded nanoparticles and their delivery by the EPR effect to the tumour tissues has been elucidated in this review with clarity.