The in-vitro and in-vivo characterization of PLGA:L-PLA microspheres containing dexamethasone sodium phosphate

Direct drug milling in organic PLGA solution facilitates the encapsulation of nanosized drug into PLGA microparticles

The objective of this study was to prepare poly(lactide-co-glycolide) (PLGA) microparticles loaded with nanosized drug by combining non-aqueous wet bead milling and microencapsulation. 200-300 nm dexamethasone, hydrocortisone and dexamethasone sodium phosphate nanosuspensions were successfully prepared by wet bead milling the drug in dichloromethane using PLGA as a stabilizer. PLGA microparticles loaded with nanosized drugs were then prepared by a solid-in-oil-in-water (S/O/W) solvent evaporation method or solid-in-oil-in-oil (S/O/O) organic phase separation method. The microparticles were characterized by laser diffraction (LD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and in vitro drug release. The nanosized drugs were homogeneously distributed within the microparticle matrix and remained crystalline, however, with a decrease in crystallinity. High drug encapsulation efficiencies >80 % were achieved at theoretical drug loadings between 5 and 30 %. Drug release profiles could be controlled by varying PLGA grades/blends, microparticle size and drug loadings. Quasi-linear release profiles without the PLGA-typical slow release phase were achieved with PLGA encapsulated nanosized drug.

Design and Characterization of Dexamethasone Loaded Microsponges for the Management of Ulcerative Colitis

Ulcerative colitis is an inflammatory condition with ulcerations throughout the colon. The existing remedies have some limitations such as drug inactivation, poor absorption, and adverse reactions. The present study aimed to design novel microsponge formulations to enhance remission of the dexamethasone (as a model pharmaceutical ingredient) in the colon. Microsponges were prepared by using the quasi-emulsion technique. The optimal formulation was selected by applying the design of experiments approach which used methylcellulose (MC) (0.75-2%, w/w), polyvinylalcohol (PVA)(0.5-1%, w/w), and tween 80 (TW80) (1.5-2.5%, w/w). The critical quality attributes were selected as particle size and entrapment efficiency. The particle size and encapsulation efficiency were found as 140.38 ± 9.2 µm and 77.96 ± 3.4 %. After the optimization; morphological, thermal, and physicochemical characterization studies were performed. Ultimately, the optimal formulation was investigated by using the acetic acid-induced ulcerative colitis model in rats. The physicochemical characterization studies confirmed that the formulation components were compatible with each other. The in vitro release mechanisms were fitted to First order kinetics at pH 1.2 (R²:0.9563), and Korsmeyer-Peppas kinetics at pH 4.5 (R²: 0.9877), and pH 6.8 (R²: 0.9706). The medicated microsponges exhibited remarkable recovery compared to the control group of the in vivo ulcerative colitis model (p<0.05). It could be concluded that microsponges were evaluated as a promising alternative drug delivery system for the management of ulcerative colitis.

Inhibition of the p‑SPAK/p‑NKCC1 signaling pathway protects the blood‑brain barrier and reduces neuronal apoptosis in a rat model of surgical brain injury

Surgical brain injury (SBI) can disrupt the function of the blood‑brain barrier (BBB), leading to brain edema and neurological dysfunction. Thus, protecting the BBB and mitigating cerebral edema are key factors in improving the neurological function and prognosis of patients with SBI. The inhibition of WNK lysine deficient protein kinase/STE20/SPS1‑related proline/alanine‑rich kinase (SPAK) signaling ameliorates cerebral edema, and this signaling pathway regulates the phosphorylation of the downstream Na⁺‑K⁺‑Cl^‑ cotransporter 1 (NKCC1). Therefore, the purpose of the present study was to investigate the role of SPAK in SBI‑induced cerebral edema and to determine whether the SPAK/NKCC1 signaling pathway was involved in SBI via regulating phosphorylation. An SBI model was established in male Sprague‑Dawley rats, and the effects of SPAK on the regulation of the NKCC1 signaling pathway on BBB permeability and nerve cell apoptosis by western blotting analysis, immunofluorescence staining, TUNEL staining, Fluoro‑Jade C staining, and brain edema and nervous system scores. The results demonstrated that, compared with those in the sham group, phosphorylated (p)‑SPAK and p‑NKCC1 protein expression levels were significantly increased in the SBI model group. After inhibiting p‑SPAK, the expression level of p‑NKCC1, neuronal apoptosis and BBB permeability were significantly reduced in SBI model rats. Taken together, these findings suggested that SBI‑induced increases in p‑SPAK and p‑NKCC1 expression exacerbated post‑traumatic neural and BBB damage, which may be mediated via the ion‑transport‑induced regulation of cell edema.

Dexamethasone-loaded β-cyclodextrin for osteogenic induction of mesenchymal stem/progenitor cells and bone regeneration

Dexamethasone (DEX) is a glucocorticoid commonly used as an in vitro osteogenic inducer of mesenchymal stem/progenitor cells (abbreviated MSCs). However, several studies investigating the effects of glucocorticoids on bone regeneration through systemic injections have demonstrated negative impacts of the drugs at high concentration on the healing of hard tissues. These contrasting evidences suggest that application of glucocorticoids should be limited to low dosages but at the same time a long enough treatment period is preferred, which prompted us to evaluate the effects of different local release systems of DEX on MSC differentiation and bone repair. Two types of DEX-loaded β-cyclodextrin (CD) complexes, including CD/DEX and CD/AD-DEX, were fabricated via host-guest interactions and characterized by FTIR, 1H-NMR, MS-ESI, and UV-vis. The results demonstrated that these CD-based assemblies released DEX in differentiated profiles, with CD/DEX releasing significantly faster than CD/AD-DEX. Although CD/DEX were slightly more powerful than CD/AD-DEX in inducing rat bone marrow MSCs (rBMSCs) into osteogenic lineage in vitro, CD/AD-DEX was advantageous over CD/DEX in accelerating bone regeneration over a time period of 4 weeks in a rat tibia defect model. The results suggest that DEX-loaded assemblies via host-guest interactions are flexible in modulating DEX release patterns and have great potential in bone tissue engineering.

Improvement of side-effects and treatment on the experimental colitis in mice of a resin microcapsule-loading hydrocortisone sodium succinate

CONTEXT

Extensive or long-time use of corticosteroids often causes many toxic side-effects. The ion exchange resins and the coating material, Eudragit, can be used in combination to form a new oral delivery system to deliver corticosteroids.

OBJECTIVES

The resin microcapsule (DRM) composed by Amberlite 717 and Eudragit S100 was used to target hydrocortisone (HC) to the colon in order to improve its treatment effect on ulcerative colitis (UC) and reduce its toxic side-effects.

METHODS

Hydrocortisone sodium succinate (HSS) was sequentially encapsulated in Amberlite 717 and Eudragit S100 to prepare the HSS-loaded resin microcapsule (HSS-DRM). The scanning electron microscopy (SEM) was employed to investigate the morphology and structure of HSS-DRM. The in vitro release and in vivo studies of pharmacokinetics and intestinal drug residues in rat were used to study the colon-targeting of HSS-DRM. The mouse induced by 2,4,6-trinitrobenzenesulfonic acid was used to study the treatment of HSS-DRM on experimental colitis.

RESULTS

SEM study showed good morphology and structure of HSS-DRM. In the in vitro release study, > 80% of HSS was released in the colon environment (pH 7.4). The in vivo studies showed good colon-targeting of HSS-DRM (T_max= 0.97 h, C_max= 118.28 µg/mL of HSS; T_max = 2.16 h, C_max = 64.47 µg/mL of HSS-DRM). Moreover, the HSS-DRM could reduce adverse reactions induced by HSS and had good therapeutic effects on the experimental colitis.

CONCLUSIONS

The resin microcapsule system has good colon-targeting and can be used in the development of colon-targeting preparations.

Investigation of the colon-targeting, improvement on the side-effects and therapy on the experimental colitis in mouse of a resin microcapsule loading dexamethasone sodium phosphate

CONTEXT

Dexamethasone is the major drug in the treatment of ulcerative colitis (UC). However, the extensive or long-time use of dexamethasone causes many toxic side-effects. Ion exchange resins react with external-ions through their own functional groups and Eudragit S occurs degradation when pH > 7. These features make them suitable for oral delivery system.

OBJECTIVE

Resin microcapsule (DRM) composed by 717 anion exchange resin and Eudragit S100 was used to target dexamethasone to the colon to improve its treatment effect on UC and reduce its toxic side-effects.

RESULTS

Dexamethasone sodium phosphate (DXSP) was sequentially encapsulated in 717 anion-exchange resin and Eudragit S100 to prepare the DXSP-loaded resin microcapsule (DXSP-DRM). The in vitro release study and in vivo study of pharmacokinetics and the intestinal drug residues in rat demonstrated the good colon-targeting of DXSP-DRM. Moreover, the DXSP-DRM can reduce the toxic side-effects induced by DXSP and have good therapeutic effects on colitis mouse induced by 2,4,6-trinitrobenzenesulfonic acid.

DISCUSSION

Dexamethasone can be targeted to the colon by DRM, thereby enhancing its treatment effect and reducing its toxic side effects.

CONCLUSION

The resin microcapsule system has good colon-targeting and can be used in the development of colon-targeted preparations.

Extrusion printed polymer structures: a facile and versatile approach to tailored drug delivery platforms

A novel extrusion printing system was used to create drug delivery structures wherein dexamethasone-21-phosphate disodium salt (Dex21P) was encapsulated within a biodegradable polymer (PLGA) and water soluble poly(vinyl alcohol) (PVA) configurations. The ability to control the drug release profile through the spatial distribution of drug within the printed 3-dimensional structures is demonstrated. The fabricated configurations were characterised by optical microscopy and SEM to evaluate surface morphology. The results clearly demonstrate the successful encapsulation of dexamethasone within a laminated PLGA:PVA structure. The resulting drug release profiles from the structures show a two stage release profile with distinctly different release rates and minimal initial burst release observed. Dexamethasone release was monitored over a 4-month period. This approach clearly demonstrates that the extrusion printing technique provides a facile and versatile approach to fabrication of novel drug delivery platforms.

Incorporation, Release, and Effectiveness of Dexamethasone in Poly(Lactic-Co-Glycolic Acid) Nanoparticles for Inner Ear Drug Delivery

Poly (D,L-lactide-co-glycolide) (PLGA) particles have been widely used as drug delivery carriers for a variety of payloads. Three forms of dexamethasone (DEX), namely, acetate, base, and phosphate, were incorporated into a PLGA matrix. First, we compared the drug loading efficiency and release kinetics of drug-loaded PLGA particles. Dexamethasone acetate (DEX-Ac) loaded particles exhibited a higher loading efficiency and a more linear release profile of drug as compared with the other forms of DEX particles. Also, we coincorporated oleic acid-coated superparamagnetic iron oxide nanoparticles (SPION) with DEX-Ac into PLGA submicron particles. No differences in size, zeta potential, drug loading, or release kinetics were found between particles prepared with and without SPION. Additionally, particles were applied to an in vitro cochlear, organotypic culture. DEX-Ac PLGA nanoparticles showed a protective effect against 4-hydroxynonenal induced hair cell damage. These results suggest a promising method for inner ear magnetic targeted treatment.

Physicochemical properties of extruded and non-extruded liposomes containing the hydrophobic drug dexamethasone

The physicochemical and release properties of non-extruded 'multilamellar' and small sonicated and extruded 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes containing hydrophobic drug dexamethasone were investigated. Non-extruded liposomes had similar diameter, however dexamethasone encapsulation decreased with increase in lipid chain length. Dexamethasone destabilized the liposome membranes as indicated by decrease in enthalpy and increase in the peak width of the main transition. Based on calorimetric analysis, it appeared that dexamethasone and cholesterol were heterogeneously distributed in the non-extruded liposomes. Sonication and extrusion reduced the diameter (DSPC>DPPC>DMPC) and decreased drug encapsulation (approximately 50%). Cholesterol incorporation decreased drug encapsulation in both extruded and non-extruded DMPC liposomes which appeared to be due to structural similarities between cholesterol and dexamethasone. Incorporation of dexamethasone and cholesterol in the same DMPC liposomes caused a marked perturbation in the phase transition. Dexamethasone release from extruded liposomes was fast, while non-extruded liposomes showed slower release. Release was fastest from DMPC liposomes and slowest from liposomes of high phase transition lipid DSPC. Incorporation of cholesterol did not decrease release from DMPC liposomes. These results indicated that change in the physicochemical properties and the phase transition behavior of liposomes, due to processing as well as incorporation of hydrophobic drug dexamethasone, changed their release properties.

Dexamethasone-loaded scaffolds prepared by supercritical-assisted phase inversion

The aim of this study was to evaluate the possibility of preparing dexamethasone-loaded starch-based porous matrices in a one-step process. Supercritical phase inversion technique was used to prepare composite scaffolds of dexamethasone and a polymeric blend of starch and poly(l-lactic acid) (SPLA) for tissue engineering purposes. Dexamethasone is used in osteogenic media to direct the differentiation of stem cells towards the osteogenic lineage. Samples with different drug concentrations (5-15 wt.% polymer) were prepared at 200bar and 55 degrees C. The presence of dexamethasone did not affect the porosity or interconnectivity of the polymeric matrices. Water uptake and degradation studies were also performed on SPLA scaffolds. We conclude that SPLA matrices prepared by supercritical phase inversion have a swelling degree of nearly 90% and the material presents a weight loss of approximately 25% after 21days in solution. Furthermore, in vitro drug release studies were carried out and the results show that a sustained release of dexamethasone was achieved over 21days. The fitting of the power law to the experimental data demonstrated that drug release is governed by an anomalous transport, i.e., both the drug diffusion and the swelling of the matrix influence the release of dexamethasone out of the scaffold. The kinetic constant was also determined. This study reports the feasibility of using supercritical fluid technology to process in one step a porous matrix loaded with a pharmaceutical agent for tissue engineering purposes.

Enhancing growth and proliferation of human gingival fibroblasts on chitosan grafted poly (epsilon-caprolactone) films is influenced by nano-roughness chitosan surfaces

The bioactivity of poly (epsilon-caprolactone) (PCL) films is improved by grafting chitosan (CS) surfaces with various values of nano-roughness on PCL surfaces. To examine the effects of the design, growing human gingival fibroblasts (HGFs) on the films was conducted. Various values of nano-rough CS surfaces were cast using nano-rough PCL molds that had been fabricated using a solvent-etched technique. The features of nano-CS/PCL surfaces were characterized using an atomic force microscope (AFM) to observe the topography and to determine the value of centerline average roughness of a surface, R(a). The R(a) values of the nano-CS/PCL films were 36.8 +/- 1.6, 100.0 +/- 3.0, and 148 +/- 7.0 nm, while that of the smooth CS/PCL film was 12.5 +/- 1.6 nm. The growth and proliferation of HGFs on the films are elucidated by fluorescent staining and analyzed by MTT viability assay following three and 7 days of culture. The viability assay of the cells reveals that the growth rates of HGFs on both CS/PCL and nano-CS/PCL films significantly exceed (95% or more; P < 0.001) those of PCL on both days, demonstrating the improvement of the bioactivity of PCL films by grafting CS. Additionally, the growth rates and proliferations of HGFs on nano-CS/PCL films of roughness 100 and 148 nm markedly exceed (15% or more; P < 0.001) those on 36.8 nm nano-CS/PCL and CS/PCL films, after both periods of culturing, indicating that the high nano-roughness CS surfaces further enhance the growth rate of HGFs. In conclusion, markedly improving the bioactivity of PCL films by grafting CS is demonstrated. Moreover, high nano-roughness of nano-CS/PCL films can further accelerate the growth and proliferation of HGFs compared with those of CS/PCL films. This work presents a new concept for designing biomaterials in tissue engineering.

Effect of poly(lactide-co-glycolide) molecular weight on the release of dexamethasone sodium phosphate from microparticles

The objective of this study was to investigate the effect of poly(lactide-co-glycolide) (PLGA) molecular weight (Resomer RG 502H, RG 503H, and RG 504H) on the release behavior of dexamethasone sodium phosphate-loaded microparticles. The microparticles were prepared by three modifications of the solvent evaporation method (O/W-cosolvent, O/W-dispersion, and W/O/W-methods). The encapsulation efficiency of microparticles prepared by the cosolvent- and W/O/W-methods increased from approximately 50% to >90% upon addition of NaCl to the external aqueous phase, while the dispersion method resulted in lower encapsulation efficiencies. The release of dexamethasone sodium phosphate from PLGA microparticles (>50 microm) was biphasic. The initial burst release correlated well with the porosity of the microparticles, both of which increased with increasing polymer molecular weight (RG 504H > 503H > 502H). The burst was also dependent on the method of preparation and was in the order of dispersion method > WOW method > consolvent method. In contrast to the higher molecular weight PLGA microparticles, the release from RG 502H microparticles prepared by cosolvent method was not affected by volume of organic solvent (1.5-3.0 ml) and drug loading (4-13%). An initial burst of approximately 10% followed by a 5-week sustained release phase was obtained. Microparticles with a size <50 microm released in a triphasic manner; an initial burst was followed by a slow release phase and then by a second burst.

Polymeric nanoparticles for siRNA delivery and gene silencing

Gene silencing using small interfering RNA (siRNA) has several potential therapeutic applications. In the present study, we investigated nanoparticles formulated using the biodegradable polymer, poly(d,l-lactide-co-glycolide) (PLGA) for siRNA delivery. A cationic polymer, polyethylenimine (PEI), was incorporated in the PLGA matrix to improve siRNA encapsulation in PLGA nanoparticles. PLGA-PEI nanoparticles were formulated using double emulsion-solvent evaporation technique and characterized for siRNA encapsulation and in vitro release. The effectiveness of siRNA-loaded PLGA-PEI nanoparticles in silencing a model gene, fire-fly luciferase, was investigated in cell culture. Presence of PEI in PLGA nanoparticle matrix increased siRNA encapsulation by about 2-fold and also improved the siRNA release profile. PLGA-PEI nanoparticles carrying luciferase-targeted siRNA enabled effective silencing of the gene in cells stably expressing luciferase as well as in cells that could be induced to overexpress the gene. Quantitative studies indicated that presence of PEI in PLGA nanoparticles resulted in 2-fold higher cellular uptake of nanoparticles while fluorescence microscopy studies showed that PLGA-PEI nanoparticles delivered the encapsulated siRNA in the cellular cytoplasm; both higher uptake and greater cytosolic delivery could have contributed to the gene silencing effectiveness of PLGA-PEI nanoparticles. Serum stability and lack of cytotoxicity further add to the potential of PLGA-PEI nanoparticles in gene silencing-based therapeutic applications.

Atorvastatin efficiency after traumatic brain injury in rats

BACKGROUND

The neuroprotective effects of statins possibly depend on their pleiotropic effect such as antioxidative and anti-inflammatory properties. In this study, we have evaluated the efficiency of atorvastatin on brain edema, lipid peroxidation, and ultrastructural changes in TBI animal model.

METHODS

Modified Feeney method has been used for the trauma model in rats. Only craniectomy for group A and trauma after craniectomy for group B was the procedure for animals. For the trauma, rods weighing 24 g were dropped on a foot plate just over the dura. Atorvastatin (1 mg/kg, IP) was administered to the animals in group C after craniectomy and trauma; but on the other hand, animals in group D received only 0.5 mL PEG as the vehicle. Brains were harvested 24 hours after the trauma for the assays of wet-dry weight, lipid peroxidation level, and ultrastructural investigations. Lipid peroxidation levels, TEM, and UNGS were the investigated parameters. The statistical comparisons between the groups were investigated by 1-way ANOVA and post hoc analysis by Duncan and Dunnett T3 test within the groups at the significance level P = .05.

RESULTS

Trauma increased water contents of the brain tissues and lipid peroxidation levels in groups B and D. When compared with the results of group B (brain edema, 84.694% +/- 1.510%; lipid peroxidation, 74.932 +/- 2.491 nmol/g tissue), atorvastatin (1 mg/kg) significantly decreased brain edema (77.362% +/- 1.448%), lipid peroxidation level (58.335 +/- 3.980 nmol/g tissue), and UNGS scores in group C (P < 0.05).

CONCLUSION

In this descriptive study, the remarkable improvements of atorvastatin on brain edema, lipid peroxidation, and ultrastructural investigations encouraged us for a further dose optimization study.

Polymer-surfactant nanoparticles for sustained release of water-soluble drugs

Poor drug encapsulation efficiency and rapid release of the encapsulated drug limit the use of nanoparticles in biomedical applications involving water-soluble drugs. We have developed a novel polymer-surfactant nanoparticle formulation, using the anionic surfactant Aerosol OT (AOT) and polysaccharide polymer alginate, for sustained release of water-soluble drugs. Particle size of nanoparticles, as determined by atomic force microscopy and transmission electron microscopy, was in the range of 40-70 nm. Weakly basic molecules like methylene blue, doxorubicin, rhodamine, verapamil, and clonidine could be encapsulated efficiently in AOT-alginate nanoparticles. In vitro release studies with basic drug molecules indicate that nanoparticles released 60-70% of the encapsulated drug over 4 weeks, with near zero-order release during the first 15 days. Studies with anionic drug molecules demonstrate poorer drug encapsulation efficiency and more rapid drug release than those observed with basic drugs. Further studies investigating the effect of sodium concentration in the release medium and the charge of the drug suggest that calcium-sodium exchange between nanoparticle matrix and release medium and electrostatic interaction between drug and nanoparticle matrix are important determinants of drug release. In conclusion, we have formulated a novel surfactant-polymer drug delivery carrier demonstrating sustained release of water-soluble drugs.

Methods to assess in vitro drug release from injectable polymeric particulate systems

This review provides a compilation of the methods used to study real-time (37 degrees C) drug release from parenteral microparticulate drug delivery systems administered via the subcutaneous or intramuscular route. Current methods fall into three broad categories, viz., sample and separate, flow-through cell, and dialysis techniques. The principle of the specific method employed along with the advantages and disadvantages are described. With the "sample and separate" technique, drug-loaded microparticles are introduced into a vessel, and release is monitored over time by analysis of supernatant or drug remaining in the microspheres. In the "flow-through cell" technique, media is continuously circulated through a column containing drug-loaded microparticles followed by analysis of the eluent. The "dialysis" method achieves a physical separation of the drug-loaded microparticles from the release media by use of a membrane, which allows for sampling without interference of the microspheres. With all these methods, the setup and sampling techniques seem to influence in vitro release; the results are discussed in detail, and criteria to aid in selection of a method are stated. Attempts to establish in vitro-in vivo correlation for these injectable dosage forms are also discussed. It would be prudent to have an in vitro test method for microparticles that satisfies compendial and regulatory requirements, is user friendly, robust, and reproducible, and can be used for quality-control purposes at real-time and elevated temperatures.

Poly (e-caprolactone) Grafted With Nano-structured Chitosan Enhances Growth of Human Dermal Fibroblasts

Polyester films are modified with their bioactivity for tissue engineering by grafting a nano-structured bioactive material, nano-structured chitosan (nano-CS), on a model polymer, poly (epsilon-caprolactone) (PCL). The nano-CS was duplicated using a solvent-etched PCL mold and then grafted onto PCL using a selected solvent. The structure of the nano-CS/PCL surface was characterized using an atomic force microscope to observe the topography and determine the roughness. The centerline average roughness, Ra, of the surface of the nano-CS/PCL film is 106.0+/-4.0 nm whereas that of the surface of the CS-grafted PCL film (CS/PCL) is 3.6+/-0.4 nm. The latter is therefore very smooth. CS is known to swell following hydration, so the Ra values were determined again after immersion for 12 h in phosphate buffered saline. Although the centerline average roughness of the nano-CS/PCL was lower, it still markedly exceeded that of the CS/PCL film. Cells grown on nano-CS/PCL, CS/PCL, nano-structured PCL (nano-PCL), and PCL films were observed by fluorescent staining and analyzed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) viability assay following 3 and 7 days of culture, to evaluate the effects of the design on the growth of fibroblasts. The viability assay of the cells reveals that the growth rate of cells on both CS/PCL and nano-CS/PCL films significantly exceeds (P<0.001) those of PCL and nano-PCL films on both cultural days. Additionally, the growth rate and proliferation of fibroblasts on nano-CS/PCL films significantly exceed (P<0.001) those on CS/PCL films after both periods of culturing, suggesting that the bioactive surface following a nano-structured treatment promotes the growth rate of cells. However, nano-PCL films do not have the same effects as nano-CS/PCL films do. In conclusion, a novel biomaterial, nano-CS/PCL, is developed by grafting a nano-structured bioactive surface, CS, onto the PCL surface to promote the the growth rate of fibroblasts. This work elucidates a new concept for designing films or scaffolds for tissue engineering-the grafting of nano-structured bioactive biomaterials to the films or scaffolds to promote the growth of cells.

In vitro characterization of vascular endothelial growth factor and dexamethasone releasing hydrogels for implantable probe coatings

Anti-fouling hydrogel coatings, copolymers of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidinone, and polyethylene glycol, were investigated for the purpose of improving biosensor biocompatibility. These coatings were modified to incorporate poly(lactide-co-glycolide) (PLGA) microspheres in order to release dexamethasone (DX) and/or vascular endothelial growth factor (VEGF). DX and VEGF release kinetics from microspheres, hydrogels, and microspheres embedded in hydrogels were determined in 2-week and 1-month studies. Overall, monolithic, non-degradable hydrogel drug release had an initial burst followed by release at a significantly lower amount. Microsphere drug release kinetics exhibited an initial burst followed by sustained release for 1 month. Embedding microspheres in hydrogels resulted in attenuated drug delivery. VEGF release from embedded microspheres, 1.1+/-0.3 ng, was negligible compared to release from hydrogels, 197+/-33 ng. After the initial burst from DX-loaded hydrogels, DX release from embedded microspheres was similar to that of hydrogels. The total DX release from hydrogels, 155+/-35 microg, was greater than that of embedded microspheres, 60+/-6 microg. From this study, hydrogel sensor coatings should be prepared incorporating VEGF in the hydrogel and DX either in the hydrogel or in DX microspheres embedded in the hydrogel.

Polymer microspheres for controlled drug release

Polymer microspheres can be employed to deliver medication in a rate-controlled and sometimes targeted manner. Medication is released from a microsphere by drug leaching from the polymer or by degradation of the polymer matrix. Since the rate of drug release is controlled by these two factors, it is important to understand the physical and chemical properties of the releasing medium. This review presents the methods used in the preparation of microspheres from monomers or from linear polymers and discusses the physio-chemical properties that affect the formation, structure, and morphology of the spheres. Topics including the effects of molecular weight, blended spheres, crystallinity, drug distribution, porosity, and sphere size are discussed in relation to the characteristics of the release process. Added control over release profiles can be obtained by the employment of core-shell systems and pH-sensitive spheres; the enhancements presented by such systems are discussed through literature examples.

Drug delivery to Brain by Microparticulate Systems

The site specific delivery of chemotherapeutic agents allows maximum concentration of an agent at a desired body site. This area specific drug delivery decreases the unwanted systemic distribution and decreases toxicity of the administered drugs. Blood-Brain Barrier (BBB) is considered to be an obstacle in delivering large number of drugs to brain. The endothelial cells forming the tubular capillaries in the brain are cemented together by intercellular tight junctions. In this way, the BBB has an important role in providing a stable extracellular environment in the central nervous system. Lack of fenestrations, very few pinocytotic vesicles, and more mitochondria are other differences of the brain capillaries which play important role in transport of drugs to brain (Fig.1). The purpose of this paper is to summarise the methods for BBB permeability modifications and to focus on various examples in delivering drugs, especially neuroncology and neuroactive drugs, to brain by microparticulate systems.

Molecular release from a polymeric microreservoir device: Influence of chemistry, polymer swelling, and loading on device performance

A polymeric microreservoir device for controlled-release drug delivery relies on the degradation of thin poly(lactic-co-glycolic acid) membranes that seal each reservoir to achieve pulsatile drug delivery. In vitro release studies in which the swelling of the reservoir membranes was measured indicate a correlation between the release times of various radiolabeled molecules from the devices and the time at which the maximum membrane swelling was observed. Varying the chemistry (lipophilicity/hydrophilicity) or molecular weight of the molecules loaded into the devices did not appear to affect the degree of membrane swelling that was observed, or the time at which the molecules were released from the devices. The amount of drug that was loaded into the reservoirs also did not appear to affect the observed release time of the drug from the device, a significant departure from the behavior of many matrix-type polymeric drug delivery systems.

Dexamethasone-releasing biodegradable polymer scaffolds fabricated by a gas-foaming/salt-leaching method

Dexamethasone, a steroidal anti-inflammatory drug, was incorporated into porous biodegradable polymer scaffolds for sustained release. The slowly released dexamethasone from the degrading scaffolds was hypothesized to locally modulate the proliferation and differentiation of various cells. Dexamethasone containing porous poly(D,L-lactic-co-glycolic acid) (PLGA) scaffolds were fabricated by a gas-foaming/salt-leaching method. Dexamethasone was loaded within the polymer phase of the PLGA scaffold in a molecularly dissolved state. The loading efficiency of dexamethasone varied from 57% to 65% depending on the initial loading amount. Dexamethasone was slowly released out in a controlled manner for over 30 days without showing an initial burst release. Release amount and duration could be adjusted by controlling the initial loading amount within the scaffolds. Released dexamethasone from the scaffolds drastically suppressed the proliferations of lymphocytes and smooth muscle cells in vitro. This study suggests that dexamethasone-releasing PLGA scaffolds could be potentially used either as an anti-inflammatory porous prosthetic device or as a temporal biodegradable stent for reducing intimal hyperplasia in restenosis.