Poly(lactide-co-glycolide)-methoxy-poly(ethylene glycol) nanoparticles: drug loading and release properties

In this work, the drug loading and in vitro release properties of PLGA-mPEG nanoparticles were studied. Three methyl-xanthine derivatives differing significantly in aqueous solubility, i.e., caffeine, theophylline, and theobromine, were employed as model drugs. Two different PLGA-mPEG copolymer compositions, namely PLGA(40)mPEG(5) and PLGA(136)mPEG(5), were included in the study. The nanoparticles were prepared by a double emulsion technique. The drug release properties of the nanoparticles in phosphate buffered saline (PBS) and in human plasma were determined. An increase of the drug proportion in the feed led to increased drug loading. The composition of the PLGA-mPEG copolymer (PLGA/mPEG molar ratio) did not appear to affect drug loading and encapsulation. Caffeine exhibited higher loading in the nanoparticles than theobromine and this exhibited a little higher loading than theophylline. Solid-state solubility of the drug in PLGA-mPEG did not affect drug loading. Drug loading and encapsulation in the PLGA-mPEG nanoparticles appeared to be governed by the partition coefficient of the drug between the organic phase and the external aqueous phase employed in nanoparticle preparation. Relatively low loading and encapsulation values were obtained, suggesting that the physical entrapment of drugs in PLGA-mPEG nanoparticles could only be an option in the development of formulations of potent drugs. Only the release of the least water-soluble theobromine was efficiently sustained by its entrapment in the nanoparticles, indicating that the physical entrapment of drugs provides the means for the development of controlled-release PLGA-mPEG nanoparticulate formulations only in the case of drugs with low aqueous solubility.     

Cationic poly(lactide-co-glycolide) nanoparticles as efficient in vivo gene transfection agents

Poly(lactide-co-glycolide) (PLGA), a biocompatible and biodegradable polyester co-polymer of PLA and PGA, has been recognized for its ability to deliver genes. However, gene delivery by PLGA nanoparticles is limited by their negative charge and their poor transport through mucosal barriers. In this study, PLGA nanoparticles were surface modified with cationic chitosan in an effort to improve their gene delivery capability. PLGA nanoparticles were synthesized by emulsion-diffusion-evaporation technique using PVA-chitosan (PLGA1) or PVA-chitosan-PEG (PLGA2) blend as stabilizers. This method is reproducible and produces nanoparticles with hydrodynamic diameter <200 nm. The nanoparticles were characterized by zetasizer, photon correlation spectroscopy and atomic force microscopy. A549 epithelial cells were transfected in vitro with PLGA particles complexed with a reporter plasmid encoding green fluorescent protein. PLGA particles transferred EGFP gene, but were less efficient than the lipofectamine control. The nanoparticles were also tested for their ability to transport across the nasal mucosa in vivo in mice. The results show that both PLGA1 and PLGA2 facilitate gene delivery and expression in vivo with increased efficiency and without causing inflammation, as measured by IL-6. Together, these results indicate that chitosan-modified PLGA nanoparticles have greater potential as gene carriers.     

Poly(lactide-co-glycolide) encapsulated hydroxyapatite microspheres for sustained release of doxycycline

The purpose of this study was to prepare a poly(lactide-co-glycolide) (PLGA) encapsulated hydroxyapatite microspheres (HAP-MSs) as injectable depot for sustained delivery of Doxycycline (Doxy). Doxy loaded HAP-MSs (Doxy-HAP-MSs) were encapsulated with PLGA by solid-in-oil-in-water (S/O/W) emulsion-solvent evaporation technique, the effects of the PLGA used (various intrinsic viscosity and LA/GA ratio) and ratio of PLGA/HAP-MSs on the formation of Doxy-HAP-MSs and in vitro release of Doxy were studied. The results showed that sustained drug release without obvious burst was obtained by using PLGA encapsulated HAP-MSs as the carrier, also the drug release rate could be tailored by changing the ratio of PLGA/HAP-MSs, or PLGA of various intrinsic viscosities or LA/GA ratio. Lower ratio of PLGA/HAP-MSs corresponded faster Doxy release, e.g. for the microspheres of PLGA/HAP-MSs ratio of 8 and 0.25, the in vitro Doxy release percents at the end of 7days were about 23% and 76%, respectively. Higher hydrophilicity (higher ratio of GA to LA) and lower molecular weight of PLGA corresponded to higher Doxy release rates. For in vivo release study, PLGA encapsulated HAP-MSs were subcutaneously injected to the back of mice, and the results showed good correlation between the in vivo and in vitro drug release. Meanwhile, the plasma Doxy levels after subcutaneous administration of PLGA encapsulated Doxy-HAP-MSs were relatively lower and steady compared to that of the un-encapsulated microspheres. In conclusion, PLGA encapsulated HAP-MSs may be a potential vehicle for the sustained delivery of Doxy.     

Release of adriamycin from poly(lactide-co-glycolide)-polyethylene glycol nanoparticles

In order to develop a prolonged circulating drug carrier and to overcome p-glycoprotein-mediated multidrug resistance to adriamycin (ADR), which is a potent chemotherapeutic agent in the treatment of various cancers, poly(lactide-co-glycolide)-polyethylene glycol (PLGA-PEG) nanoparticles were prepared and characterized. ADR-loaded PLGA-PEG nanoparticles prepared by the emulsification-diffusion method were spherical and homogeneous with smooth surfaces when assessed by scanning electron microscopy. The nanoparticles were 200-230 nm in size and the encapsulation efficiency of ADR in the nanoparticles was 30 approximately 35%. The release of ADR from nanoparticles was extended compared to that from free ADR solution. After intravenous administration of adriamycin-loaded PLGA-PEG nanoparticles to rats, the plasma level of ADR from PLGA-PEG nanoparticle was extended until 24 hours and the mean residence time of ADR of nanoparticles was increased compared to that of ADR solution. And ADR-loaded nanoparticles showed a higher growth inhibitory effect than free ADR solution in an ADR resistant MCF-7 human breast carcinoma cell line. The prepared ADR-loaded PLGA-PEG nanoparticles can be used as a good delivery system for ADR.     

Preparation and evaluation of oleoyl-carboxymethy-chitosan (OCMCS) nanoparticles as oral protein carriers

Oleoyl-carboxymethy chitosan (OCMCS) nanoparticles based on chitosan with different molecular weights (50, 170 and 820 kDa) were prepared by self-assembled method. The nanoparticles had spherical shape, positive surface charges and the mean diameters were 157.4, 274.1 and 396.7 nm, respectively. FITC-labeled OCMCS nanoparticles were internalized via the intestinal mucosa and observed in liver, spleen, intestine and heart following oral deliverance to carps (Cyprinus carpio). Extracellular products (ECPs) of Aeromonas hydrophila as microbial antigen was efficiently loaded to form OCMCS–ECPs nanoparticles and shown to be sustained release in PBS. Significantly higher (P < 0.05) antigen-specific antibodies were detected in serum after orally immunized with OCMCS-ECPs nanoparticles than that immunized with ECPs alone and non-immunized in control group in carps. These results implied that amphiphilic modified chitosan nanoparticles had great potential to be applied as carriers for the oral administration of protein drugs.     

Potential of albumin nanoparticles as carriers for interferon gamma

Although interferon gamma (IFN-gamma has been extensively studied as a potent activator for macrophages and as a promising adjuvant in vaccines, its rapid biodegradation and clearance have severely limited its clinical efficacy. Our major objective in this work was to develop formulation conditions to get high association of the cytokine to albumin nanoparticles, without leading any conformational changes and subsequent loss of activity. To achieve this objective, two different formulations were prepared by either 1) incubation between the cytokine and the newly prepared nanoparticles (IFN-NPA) or 2) between the protein and IFN-gamma prior coacervation (IFN-NPB). Steady-state fluorescence emission spectra revealed that the environment of the tryptophan (Trp) residue was not affected by conditions of mechanical stress required for preparing nanoparticles. A bioassay for antiproliferative activity with Hela cells indicated that the cytokine, after their desorption from the surface of nanoparticles (IFN-NPA), fully retained its activity. It also indicated that the cytokine was principally associated with nanoparticles via electrostatic interactions and confirmed by desorption experiments carried out in media with different pH and ionic strength, with burst effect ranked in the order pH 5 > pH 7.4 > pH 8.5. Also, the adsorption of IFN-gamma onto these carriers was able to improve the priming effects of IFN-gamma on the nitric oxide production (NO) by RAW macrophages. On the contrary, when we incubated the cytokine with the albumin solution prior to the desolvation process for preparing nanoparticles (IFN-NPB), we obtained better encapsulation efficiencies (around 100%), but the cytokine was inactive: it was not detected by ELISA or bioassay in Hela cells and unable to stimulate NO production by macrophages.     

Effects of poly-(lactide-co-glycolide) nanoparticles on electrophysiological properties of enteroendocrine cells

PLGA nanoparticles are widely used to deliver pharmacological compounds and genes to a variety of cell types. Despite the fact that many of these cells types depend critically on ion channel activity to function normally, there have been no studies on the effect of nanoparticles on the ion channel activity. To this end, we have investigated the effect of nanoparticles on cholecystokinin (CCK)-releasing enteroendocrine cell (EEC) line STC-1. It has been shown that regulation of CCK release from STC-1 cells in response to food depends on the normal electrogenic properties of these cells, including the activity of voltage-gated calcium and potassium channels. Due to the importance of voltage-gated ion channels in the normal physiological responses of STC-1 cells, we performed electrophysiological (patch clamp) experiments to assess the effects of PLGA nanoparticles on the voltage-gated calcium and potassium channels. Whole-cell patch clamp recordings on STC-1 cells containing 100 nm nanoparticles show no macroscopic differences in calcium and potassium channel activity. Additional experiments determined that the activation, inactivation, and use-dependent inactivation of these voltage-gated ion channels did not have any significant effect of nanoparticles on these basic biophysical properties. Lastly, we have examined the effects of PLGA nanoparticles on stimulus-induced rise in intracellular calcium concentration in STC-1 cells, which is necessary for release of CCK. Our data demonstrate that the use of PLGA nanoparticles did not alter the electrophysiological properties of STC-1 cells and supports the use of PLGA nanoparticles as an attractive option for delivering pharmaceuticals/genes to cells of the digestive system that might eventually prove useful for reducing appetite/food intake and in treatment of various gastrointestinal illnesses.     

Poly(ethylene glycol) decorated poly(methylmethacrylate) nanoparticles for protein adsorption

Poly(ethylene glycol) decorated poly(methyl methacrylate) particles were synthesized by means of emulsion polymerization using poly(ethylene glycol) sorbitan monolaurate (Tween-20) as surfactant. PMMA/PEG particles presented mean diameter (195 ± 15) nm, indicating narrow size distribution. The adsorption behavior of bovine serum albumin (BSA) and concanavalin A (ConA) onto PMMA/PEG particles was investigated by means of spectrophotometry. Adsorption isotherms obtained for BSA onto PMMA/PEG particles fitted well sigmoidal function, which is typical for multilayer adsorption. Con A adsorbed irreversibly onto PMMA/PEG particles. The efficiency of ConA covered particles to induce dengue virus quick agglutination was evaluated.     

Poly(lactide-co-glycolide)/hydroxyapatite nanofibrous scaffolds fabricated by electrospinning for bone tissue engineering

Poly(lactide-co-glycolide) (PLGA) nanofibrous composite scaffolds having nano-hydroxyapatite particles (HAp) in the fibers were prepared by electrospinning of PLGA and HAp with an average diameter of 266.6 ± 7.3 nm. Microscopy and spectroscopy characterizations confirmed integration of the crystalline HAp in the scaffolds. Agglomerates gradually appeared and increased on the fiber surface along with increase of the HAp concentration. In vitro mineralization in a 5 × simulated body fluid (SBF) revealed that the PLGA/HAp nanofibrous scaffolds had a stronger biomineralization ability than the control PLGA scaffolds. Biological performance of the nanofibrous scaffolds of the control PLGA and PLGA with 5 wt% HAp (PLGA/5HAp) was assessed by in vitro culture of neonatal mouse calvaria-derived MC3T3-E1 osteoblasts. Both types of the scaffolds could support cell proliferation and showed sharp increase of viability until 7 days, but the cells cultured on the PLGA/5HAp nanofibers showed a more spreading morphology. Despite the similar level of the cell viability and cell number at each time interval, the alkaline phosphatase secretion was significantly enhanced on the PLGA/5HAp scaffolds, indicating the higher bioactivity of the as-prepared nano-HAp and the success of the present method for preparing biomimetic scaffold for bone regeneration.     

Development and In Vitro Evaluation of Surface Modified Poly(lactide-co-glycolide) Nanoparticles with Chitosan-4-Thiobutylamidine

ABSTRACT

The objective of this study was to develop a nanoparticulate drug delivery system based on the surface modification of poly(lactide-co-glycolide) (PLGA) nanoparticles with a thiolated chitosan. PLGA nanoparticles were prepared by the emulsification-solvent evaporation method. Immobilization of chitosan to the surface of PLGA nanoparticles via amide bonds was mediated by a carbodiimide. Thiol groups were covalently bound to the chitosan surface of particles by reaction with 2-iminothiolane. Obtained nanoparticles were characterized in vitro regarding size, zeta potential, thiol group content, stability at different pH values, mucoadhesion, and drug release. Results demonstrated that the surface modification of PLGA nanoparticles with thiolated chitosan (chitosan-TBA) leads to nanoparticles of a mean diameter of 889.5 ± 72 nm and positive zeta potential of + 24.74 mV. The modified nanoparticles contained 7.32 ± 0.24 μmol thiol groups per gram nanoparticles. The size of nanoparticles was strongly influenced by the pH of the surrounding medium, being 925.0 ± 76.3 nm at pH 2 and 577.8 ± 66.7 nm at pH 7.4. Thiolated nanoparticles showed a 3.3-fold prolonged residence time on the mucosa and an unchanged release profile in comparison to unmodified PLGA nanoparticles. These data suggest that surface modified chitosan-TBA conjugate PLGA nanoparticles have the potential to be used as mucoadhesive drug delivery system.     

Poly(vinyl alcohol) hydrogels as hydrophilic matrices for the release of lipophilic drugs loaded in PLGA nanoparticles

Poly(vinyl alcohol) (PVA) hydrogels prepared by a freeze-thawing procedure were evaluated as matrices for the release of water-insoluble drugs such as dexamethasone. As it is impossible to directly entrap a lipophilic drug into a hydrophilic matrix, a novel mechanism has been designed based on producing biodegradable nanoparticles loaded with the drug, that could then be entrapped into the hydrogels. Nanoparticles were prepared by a solvent evaporation technique using a biodegradable copolymer of poly(lactic acid)-poly(glycolic acid) (PLGA). The effects of several processing parameters on particle properties were investigated. The drug release from free nanoparticles was compared to that from the nanoparticles entrapped into the PVA matrices. It was observed that the release profile of the drug is not significantly affected by the PVA matrix. A correlation was found between the amount of drug released and the PVA concentration in the hydrogels: the percentage of drug released, as a function of time, decreased by increasing PVA concentration, indicating that PVA concentration can be used as a tool in modulating the release of the drug.     

Investigation of polymeric amphiphilic nanoparticles as antitumor drug carriers

In this paper, polymeric amphiphilic nanoparticles based on oleoyl–chitosan (OCH) with different degrees of substitution (DS, 5%, 11% and 27%) were prepared by Oil/Water emulsification method. Mean diameters of the nanoparticles were 327.4 nm, 255.3 nm and 192.6 nm, respectively. Doxorubicin (DOX) was efficiently loaded into OCH nanoparticles and provided a sustained released after a burst release in PBS. These nanoparticles showed no cytotoxicity to mouse embryo fibroblasts (MEF) and low hemolysis rates (<5%). The results of SDS-PAGE indicated that bovine calf serum (BCS) adsorption on OCH nanoparticles was inhibited by smaller particle size. Cellular uptake was evaluated by incubating fluorescence labeled OCH nanoparticles with human lung carcinoma cells (A549) and mouse macrophages (RAW264.7). Cellular uptake of OCH nanoparticles was time––and concentration––dependent. Finding the appropriate incubation time and concentration of OCH nanoparticles used as drug carriers might decrease phagocytic uptake, increase cancer cell uptake and ultimately improve therapeutic efficiency of antitumor therapeutic agents.     

Smart tetrazole-based antibacterial nanoparticles as multifunctional drug carriers for cancer combination therapy

Due to multidrug resistance of cancer tissues and immune-suppression of cancerous patients during chemotherapy in one hand and the use of tetrazole derivatives in medicine because of its anticancer, antifungal, and antiviral properties, on the other, we were encouraged to design novel smart antibacterial nanocomposites-based polymer of tetrazole as dual anticancer drug delivery systems. The structures of nanocomposites characterized by FTIR, ¹H NMR, FESEM-EDX, and TGA analyzes and antibacterial activity of smart carriers were evaluated by determination of minimum inhibitory concentration (MIC) values against some bacteria and fungi. Then, the pH-responsive manner of both nanocomposites was proved by checking their release profiles at pH of the physiological environment (pH 7.4) and pH of tumor tissues (mildly acidic). Finally, the potential antitumoral activity of these nanocomposite systems against MCF7 cell lines was evaluated by MTT assay and cell cycle studies. The results demonstrated that the novel developed nanocomposites not only meet our expectations about simultaneous release of two anticancer drugs according to the predicted profile but also showed antibacterial and anticancer properties in vitro experimental. Moreover, it was proved that these carriers have tremendous potential in multifunctional drug delivery in cancer therapy.     

Mucoadhesive nanostructured lipid carriers (NLCs) as potential carriers for improving oral delivery of curcumin

Purpose: To examine effects of polymer types on the mucoadhesive properties of polymer-coated nanostructured lipid carriers (NLCs).

Experiment: Curcumin-loaded NLCs were prepared using a warm microemulsion technique followed by coating particle surface with mucoadhesive polymers: polyethylene glycol400 (PEG400), polyvinyl alcohol (PVA), and chitosan (CS). The physicochemical properties and entrapment efficacy were examined. In vitro mucoadhesive studies were assessed by wash-off test. In addition, the stability of mucoadhesive NLCs in gastrointestinal fluids and the pattern of drug release were also investigated.

Findings: The obtained nanoparticles showed spherical shape with size ranging between 200?nm and 500?nm and zeta potential between ?37 and ?9?mV depending on the type of polymer coating. Up to 80% drug entrapment efficacy was observed. In vitro mucoadhesive studies revealed that PEG-NLCs and PVA-NLCs were adhered strongly to freshly porcine intestinal mucosa, more than 2-fold mucoadhesive compared to CS-NLCs and uncoated-NLCs. The particle size of all polymer-coated NLCs could be maintained in both simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) suggesting good physical stability in physiological fluid. In contrast, uncoated-NLCs showed particle aggregation in SGF. In vitro dissolution studies revealed a fast release characteristic.     

Poly(amino acid)-facilitated electrochemical growth of metal nanoparticles

Poly(amino acids) are natural chelating agents for various metal ions. Zinc ions were encapsulated in situ in a conductive polypyrrole film using polyglutamic acid as a localized complexing agent within the film. The subsequent electrochemical reduction of the metal ions to zero-valent metal leads to the formation of the nanoparticles. The electrochemical approach demonstrated in this report provides facile regeneration of the particles and also prevents aggregation of nanoparticles in the conductive polymeric film. The correlation of the amount of zinc with the thickness of the film indicates that the zinc resides largely in the outer layer of the film. TEM and EDS data show that the nanoparticles formed are composed of zinc and are 18 +/- 7 nm in diameter. The nanoparticle/ polymer composite was used to reduce halogenated organics, indicating its potential usefulness in remediation applications.     

Poly(vinylpyrrolidone) coated iron nanoparticles in polar aprotic solvent

Poly(vinylpyrrolidone) (PVP) coated iron nanoparticles which show well-defined core-shell structures have been successfully synthesized in a polar aprotic solvent. In this approach, PVP was employed not as capping agent, but as coating polymer directly applied to the metallic (iron) core nanoparticles. The morphologies, structures, compositions and magnetic properties of the products were investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), SQUID magnetometry and FTIR spectroscopy.     

Development and in vitro evaluation of surface modified poly(lactide-co-glycolide) nanoparticles with chitosan-4-thiobutylamidine

The objective of this study was to develop a nanoparticulate drug delivery system based on the surface modification of poly(lactide-co-glycolide) (PLGA) nanoparticles with a thiolated chitosan. PLGA nanoparticles were prepared by the emulsification-solvent evaporation method. Immobilization of chitosan to the surface of PLGA nanoparticles via amide bonds was mediated by a carbodiimide. Thiol groups were covalently bound to the chitosan surface of particles by reaction with 2-iminothiolane. Obtained nanoparticles were characterized in vitro regarding size, zeta potential, thiol group content, stability at different pH values, mucoadhesion, and drug release. Results demonstrated that the surface modification of PLGA nanoparticles with thiolated chitosan (chitosan-TBA) leads to nanoparticles of a mean diameter of 889.5 ± 72 nm and positive zeta potential of + 24.74 mV. The modified nanoparticles contained 7.32 ± 0.24 μmol thiol groups per gram nanoparticles. The size of nanoparticles was strongly influenced by the pH of the surrounding medium, being 925.0 ± 76.3 nm at pH 2 and 577.8 ± 66.7 nm at pH 7.4. Thiolated nanoparticles showed a 3.3-fold prolonged residence time on the mucosa and an unchanged release profile in comparison to unmodified PLGA nanoparticles. These data suggest that surface modified chitosan-TBA conjugate PLGA nanoparticles have the potential to be used as mucoadhesive drug delivery system.     

Poly(2-oxazoline)s as materials for biomedical applications

The conjunction of polymers and medicine enables the development of new materials that display novel features, opening new ways to administrate drugs, design implants and biosensors, to deliver pharmaceuticals impacting cancer treatment, regenerative medicine or gene therapy. Poly(2-oxazoline)s (POx) constitute a polymer class with exceptional properties for their use in a plethora of different biomedical applications and are proposed as a versatile platform for the development of new medicine. Herein, a global vision of POx as a platform for novel biomaterials is offered, by highlighting the recent advances and breakthroughs in this fascinating field.     

The release characteristics of a model protein from self-assembled succinimide-terminated poly(lactide-co-glycolide ethylene oxide fumarate) nanoparticles

Lactide-co-glycolide-based functionalized nanoparticles (NPs), because of their high surface areas for conjugation and biodegradability, are attractive as carriers for stabilization and sustained delivery of therapeutic agents and protein drugs. The objective of this work was to compare the release characteristics of model molecules encapsulated in NPs produced from poly(lactide-co-glycolide fumarate) (PLGF) macromer with those of model molecules conjugated to NPs produced from succinimide (NHS)-terminated PLGF-NHS macromer. Poly(lactide fumarate) (PLAF), PLGF and poly(lactide-co-ethylene oxide fumarate) (PLEOF) macromers were synthesized by condensation polymerization. The hydroxyl end-groups of PLAF and PLGF macromers were reacted with N,N(')-disuccinimidyl carbonate (DSC) to produce succinimide-terminated PLAF-NHS and PLGF-NHS macromers. The macromers were self-assembled by dialysis to form NPs. The amphiphilic PLEOF macromer was used as the surfactant to stabilize the NPs in the process of self-assembly. 1-(2-pyridylazo)-2-naphthol (PAN) was used as a model small molecule for encapsulation in PLAF or PLGF NPs and bovine serum albumin (BSA) was used as a model protein for conjugation to PLAF-NHS and PLGF-NHS NPs. The profile of release of the encapsulated PAN from PLAF and PLGF NPs was non-linear and consisted of a burst release followed by a period of sustained release. The release profile for BSA, conjugated to PLAF-NHS and PLGF-NHS NPs, was linear up to complete degradation of the NPs. PLGF and PLAF NPs degraded in 15 and 28 days, respectively, while PLGF-NHS and PLAF-NHS NPs degraded in 25 and 38 days, which demonstrated that the release was dominated by erosion of the matrix. PLAF-NHS and PLGF-NHS NPs are potentially useful as carriers for sustained in situ release of protein drugs.