Combination of a Bioceramic Scaffold and Simvastatin Nanoparticles as a Synthetic Alternative to Autologous Bone Grafting

The fragile nature of porous bioceramic substitutes cannot match the toughness of bone, which limits the use of these materials in clinical load-bearing applications. Statins can enhance bone healing, but it could show rhabdomyolysis/inflammatory response after overdosing. In this study, the drug-containing bone grafts were developed from poly(lactic acid-co-glycolic acid)-polyethylene glycol (PLGA-PEG) nanoparticles encapsulating simvastatin (SIM) (SIM-PP NPs) loaded within an appropriately mechanical bioceramic scaffold (BC). The combination bone graft provides dual functions of osteoconduction and osteoinduction. The mechanical properties of the bioceramic are enhanced mainly based on the admixture of a combustible reverse-negative thermoresponsive hydrogel (poly(N-isopropylacrylamide base). We showed that SIM-PP NPs can increase the activity of alkaline phosphatase and osteogenic differentiation of bone marrow stem cells. To verify the bone-healing efficacy of this drug-containing bone grafts, a nonunion radial endochondral ossification bone defect rabbit model (N = 3/group) and a nonunion calvarial intramembranous defect Sprague Dawley (SD) rat model (N = 5/group) were used. The results indicated that SIM-PP NPs combined with BC can improve the healing of nonunion bone defects of the radial bone and calvarial bone. Therefore, the BC containing SIM-PP NPs may be appropriate for clinical use as a synthetic alternative to autologous bone grafting that can overcome the problem of determining the clinical dosage of simvastatin drugs to promote bone healing.

Reshapable polymeric hydrogel for controlled soft-tissue expansion: In vitro and in vivo evaluation

Tissue expansion is the process by which extra skin is generated using a device that applies pressure from underneath the skin. Over the course of weeks to months, stretching by this pressure creates a flap of extra tissue that can be used to cover a defect area or enclose a permanent implant. Conventional tissue expanders require a silicone shell inflated either by external injections of saline solution or air, or by internal osmotic pressure generated by a hydrophilic polymer. In this study, a shell-free tissue expander comprised only of a chemically cross-linked biocompatible polymeric hydrogel is developed. The cross-linked network of hydrophilic polymer provides for intrinsically controlled swelling in the absence of an external membrane. The new type of hydrogel expanders were characterized in vitro as well as in vivo using a rat-skin animal model. It was found that increasing the hydrophobic polyester content in the hydrogel reduced the swelling velocity to a rate and volume that eliminate the danger of premature swelling rupturing the sutured area. Additionally, increasing the crosslinking density resulted in enough mechanical strength of the hydrogel to allow for complete post-swelling removal, without the hydrogel cracking or crumbling. No systemic toxicity was noted with the expanders and histology showed the material to be highly biocompatible. These expanders have an advantage of tissue expansion without requiring an external silicone membrane, and thus, they can be cut or reshaped at the time of implantation for applications in small or physically constrained regions of the body.

Novel Injectable and In situ Curable Glycolide/Lactide Based Biodegradable Polymer Resins and Composites

Novel in situ polymerizable liquid three-arm biodegradable oligomeric polyesters based upon glycolic acid (GA), L-lactic acid (LLA), and their copolymers are synthesized and characterized. Injectable and in situ curable polymer neat resins and their composites formulated with bioabsorbable beta-tricalcium phosphate are prepared at room temperature using photo- and redox-initiation systems, respectively. The cured neat resins show the initial compressive yield strength (YCS, MPa), modulus (M, MPa), ultimate compressive strength (UCS, MPa), and toughness (T, kN mm), ranging from 4.0 to 20.1, 201.5 to 730.2, 82.7 to 310.5, and 1.02 to 3.93. The cured composites show the initial YCS, M, UCS and T, ranging from 27.7 to 56.4, 1440 to 4870, 81.6 to 158.9, and 0.94 to 1.97. Increasing GA/LLA ratio increases all the initial compressive strengths of both neat resins and composites. Increasing filler content increases YCS and M but decreases UCS and T. A diametral tensile strength test shows the same trend as a compressive strength test. There seems to be an optimal flexural strength for the composite at the filler content around 43%. An increasing molar ratio increases curing time but decreases the degree of conversion (DC). An increasing filler content increases curing time but decreases exotherm and DC. During the course of degradation, all the materials show a burst degradation behavior within 24 h, followed by an increase in CS. The poly(glycolic acid) neat resin completely loses its strength at around Day 45. The composites completely lose their strengths at different time intervals, depending on their molar ratio and filler content. The degradation rate is found to be molar ratio and filler-content dependent.

Poly(lactide-co-glycolide) microspheres for MRI-monitored delivery of sorafenib in a rabbit VX2 model

Transcatheter arterial embolization and chemoembolization are standard locoregional therapies for hepatocellular carcinoma (HCC). However, these can result in tumor hypoxia, thus promoting tumor angiogenesis. The anti-angiogenic agent sorafenib is hypothesized to improve outcomes; however, oral administration limits patient tolerance. Therefore, the purpose of this study was to fabricate poly(lactide-co-glycolide) microspheres for local sorafenib delivery to tumors during liver-directed embolotherapies. Iron oxide nanoparticles (IONP) were co-encapsulated for magnetic resonance imaging (MRI) of microsphere delivery. Microspheres were fabricated using a double emulsion/solvent evaporation method and characterized for size, sorafenib and IONP content, and MRI properties. MRI was performed before and after intra-arterial microsphere infusions in a rabbit VX2 liver tumor model. The microspheres were 13 microns in diameter with 8.8% and 0.89% (w/w) sorafenib and IONP, respectively. 21% and 28% of the loaded sorafenib and IONP, respectively, released within 72 h. Rabbit VX2 studies demonstrated that sorafenib microspheres normalized VEGFR 2 activity and decreased microvessel density. Quantitative MRI enabled in vivo visualization of intra-hepatic microsphere distributions. These methods should avoid systemic toxicities, with MRI permitting follow-up confirmation of microsphere delivery to the targeted liver tumors.

CREDVW-Linked Polymeric Micelles As a Targeting Gene Transfer Vector for Selective Transfection and Proliferation of Endothelial Cells

Nowadays, gene transfer technology has been widely used to promote endothelialization of artificial vascular grafts. However, the lack of gene vectors with low cytotoxicity and targeting function still remains a pressing challenge. Herein, polyethylenimine (PEI, 1.8 kDa or 10 kDa) was conjugated to an amphiphilic and biodegradable diblock copolymer poly(ethylene glycol)-b-poly(lactide-co-glycolide) (mPEG-b-PLGA) to prepare mPEG-b-PLGA-g-PEI copolymers with the aim to develop gene vectors with low cytotoxicity while high transfection efficiency. The micelles were prepared from mPEG-b-PLGA-g-PEI copolymers by self-assembly method. Furthermore, Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide was linked to micelle surface to enable the micelles with special recognition for endothelial cells (ECs). In addition, pEGFP-ZNF580 plasmids were condensed into these CREDVW-linked micelles to enhance the proliferation of ECs. These CREDVW-linked micelle/pEGFP-ZNF580 complexes exhibited low cytotoxicity by MTT assay. The cell transfection results demonstrated that pEGFP-ZNF580 could be transferred into ECs efficiently by these micelles. The results of Western blot analysis showed that the relative ZNF580 protein level in transfected ECs increased to 76.9%. The rapid migration of transfected ECs can be verified by wound healing assay. These results indicated that CREDVW-linked micelles could be a suitable gene transfer vector with low cytotoxicity and high transfection efficiency, which has great potential for rapid endothelialization of artificial blood vessels.

Pitfalls of operative management of secondary post-tonsillectomy haemorrhage--a case report

INTRODUCTION

The authors present a potential complication associated with the surgical management of post-tonsillectomy haemorrhage using absorbable cellulose haemostatic dressings. The article discusses the deficiencies of our current understanding of how best to manage this common and potentially life-threatening ENT emergency.

CASE REPORT

A 40-year-old man presented to Accident-and-Emergency with a post-tonsillectomy haemorrhage on the 7th postoperative day. The bleeding was managed surgically, with suturing of the faucial pillars incorporating a piece of Surgicel into the closure. Two days later the patient experienced an episode of partial airway obstruction, due to a piece of dislodged haemostatic material, owing to failure of the closure. The techniques used in the operative management of post-tonsillectomy bleeding are not formally evaluated or discussed in the current literature, and in some cases are unreliable or even potentially hazardous. Further discussion, research, and formulation of a more stepwise approach would be of considerable benefit.

Synthesis and evaluation of γ-lactam analogs of PGE₂ as EP4 and EP2/EP4 agonists

To identify topically effective EP4 agonists and EP2/EP4 dual agonists with excellent subtype selectivity, further optimization of the 16-phenyl ω-chain moiety of the γ-lactam 5-thia prostaglandin E analog and the 2-mercaptothiazole-4-carboxylic acid analog were undertaken. Rat in vivo evaluation of these newly identified compounds as their poly (lactide-co-glycolide) microsphere formulation, from which sustained release of the test compound is possible, led us to discover compounds that showed efficacy in a rat bone fracture healing model after its topical administration without serious influence on blood pressure and heart rate. A structure-activity relationship study is also presented.

Comparison of Surgisis, AlloDerm, and Vicryl Woven Mesh grafts for abdominal wall defect repair in an animal model

BACKGROUND

Surgisis and AlloDerm, two biosynthetic materials, have been previously used with success in abdominal wall repairs in the setting of contaminated fields. Historically, Vicryl Woven Mesh, a synthetic material, has also been used in such settings as a temporary bridge for abdominal wall reconstruction. This study compares Surgisis and AlloDerm with Vicryl Woven Mesh with respect to tensile strength, collagen remodeling, and neovascularization using a rat hernia model.

METHODS

A prospective randomized trial of 54 Sprague-Dawley rats were assigned to the Surgisis, AlloDerm, or Vicryl Woven Mesh group with baseline, 30-day, and 60-day end points. A 1.5-cm x 5.0-cm defect was created in the right abdominis rectus muscle and repaired with an underlay bridge graft using the different treatment materials. Tensile strength was measured using an Instron tensiometer. Histologic specimens were evaluated for neovascularization, collagen deposition, and collagen organization at the 30- and 60-day time points.

RESULTS

Surgisis had significantly greater tensile strength compared to Vicryl Woven Mesh at the baseline time point (0.142 vs. 0.091 MPa, p < 0.05). There were no differences between groups tensile strength at 30 or 60 days postoperatively. The Vicryl Woven Mesh and AlloDerm groups showed increases in tensile strength at 30 days postoperatively versus baseline (p < 0.05). Vicryl Woven Mesh, Surgisis, and AlloDerm all showed increases in tensile strength at 60 days postoperatively compared to 30 days postoperatively and at baseline (p < 0.05). Surgisis and AlloDerm had significantly greater (p < 0.05) amounts of collagen deposition and organization at 30 and 60 days compared to Vicryl Woven Mesh. There was no significant difference between AlloDerm and Surgisis with respect to collagen deposition and organization. Surgisis and AlloDerm showed a significantly greater amount (p < 0.05) of neovascularization than Vicryl Woven Mesh at both time points. In addition, Surgisis had a significantly greater amount (p < 0.05) of neovascularization than AlloDerm at both 30 and 60 days.

CONCLUSION

Surgisis has increased baseline tensile strength compared to Vicryl Woven Mesh. Tensile strength in Vicryl Woven Mesh is equal to biosynthetic grafts after tissue incorporation. Biosynthetic grafts showed superior collagen deposition and organization. Surgisis mesh showed increased neovascularization over both AlloDerm and Vicryl Woven Mesh.

Effects of poloxamer 188 on the characteristics of poly(lactide-co-glycolide) nanoparticles

We tested the effects of poloxamer 188 on the preparation and characteristics of poly(lactice-co-glycolide) (PLGA) nanoparticles containing all-trans retinoic acid (ATRA). Spherical nanoparticles incorporated ATRA were prepared by an emulsification-diffusion method increasing concentrations of poloxamer 188 decreased nanoparticle size. The endothermic peak of ATRA at 183 degrees C disappeared in the nanoparticles and X-ray diffraction measurements showed the disappearance of characteristics of ATRA suggesting the change of the crystallinity of ATRA in the nanoparticles to an amorphous state. ATRA release in vitro increased as the concentration of poloxamer increased. The mean residence time of ATRA-loaded nanoparticles after the administration of a single intravenous dose to rats was longer than that of the sodium ATRA solution. The anti-cancer activity of ATRA-loaded nanoparticles in the human leukemia-60 cell line was similar to free ATRA. Thus, PLGA/poloxamer nanoparticles can provide a sustained release preparation of ATRA.

An injectable scaffold: rhBMP-2-loaded poly(lactide-co-glycolide)/hydroxyapatite composite microspheres

Poly(lactide-co-glycolide)/hydroxyapatite(50/50) (PLGA/HA(50/50)) composite microspheres were fabricated and treated with a mixture of 0.25M NaOH aqueous solution and ethanol (v/v=1/1) at 37 degrees C. The properties of untreated and treated PLGA/HA(50/50) composite microspheres were determined and compared. The results showed that the surface roughness, HA content and hydrophilicity of the treated PLGA/HA(50/50) composite microspheres increased with treatment time. However, the treatment time should be kept within 2h in order to maintain the shape of the PLGA/HA(50/50) microspheres. At the same time, a degradation study showed that both the untreated and treated microspheres degraded gradually with time, with the treated microspheres degrading faster in the first 4 weeks. The rhBMP-2-loaded PLGA/HA(50/50) composite microspheres were prepared by solution dipping treated PLGA/HA(50/50) composite microspheres. Mouse OCT-1 osteoblast-like cells were cultured on the untreated, treated and rhBMP-2-loaded PLGA/HA(50/50) composite microspheres and the cell affinity of the various microspheres was assessed and compared. It was found that the surface-treated PLGA/HA(50/50) composite microspheres clearly promoted osteoblast attachment, proliferation and alkaline phosphatase activity. It was considered that the hydrophilicity, osteoconductivity and surface roughness were increased by the increase in the HA component, which facilitated cell growth. Moreover, the rhBMP-2 loaded on the treated PLGA/HA(50/50) composite microspheres could be slowly released and further enhanced osteoblast differentiation. The good cell affinity and enhanced osteogenic potential of the rhBMP-2-loaded PLGA/HA composite microspheres indicate that they could be used as an injectable scaffold.

Efficacy of antimicrobial coating suture coated polyglactin 910 with tricosan (Vicryl plus) compared with polyglactin 910 (Vicryl) in reduced surgical site infection of appendicitis, double blind randomized control trial, preliminary safety report

OBJECTIVE

To evaluate the efficacy and safety of new antibacterial suture (Vicryl Plus) compared with a traditional braided suture (Vicryl) in a clinical study. The primary goal was to study effectiveness on reduced surgical site infection in an appendectomy operation. The authors' secondary goal was to analyze the safety and physical properties of Vicryl plus.

MATERIAL AND METHOD

This was a prospective, randomized, controlled, double blind, comparative, single-center study. After appendectomy was done, the patients were randomized in two groups: Vicryl Plus and Vicryl to selected suture for suturing the abdominal sheath. The surgical site infection was evaluated for 30 days, 6 months, and 1 year. The surgeons and attending doctor were blind to the type of suture. This is the primary report of the first 100 patients.

RESULTS

There was no difference in demographic and preoperative clinical in both groups. Although there was no statistical difference in the surgical site infection of Vicryl and Vicryl Plus (8 and 10%, p = 0.05), one case of deep surgical site infection was detected in the Vicryl group. No complications and no difference in related suture materials were detected.

CONCLUSION

Coated polyglactin 910 with tricosan (Vicryl Plus) is safe and satisfactory in surgical practice. Surgical site infection of appendectomy seemed too to be comparable between coated polyglactin 910 with tricosan (Vicryl Plus) and traditional polyglactin 910 (Vicryl) group.

Innovative management of anal fistula by the use of the anal fistula plug: hype or help?

Impressed by the initial success rates of 80% of the anal fistula plug for the closure of cryptoglandular and Crohn's associated anorectal fistulas, preliminary results from centers world-wide showed a healing rates between 24% and 88%. When compared to traditional flap repair for closing high anorectal fistulas, impairement of continence may be decreased using the plug procedure. Analyzing the different experiences of the plug procedure ranging from promising to disappointing results, a variety of issues such as bowel preparation, treatment of fistula tract, closure of the internal opening, and postoperative management have to be considered. Furthermore, the ''ideal'' indication has still to be defined. At the moment, all results which have been published only provide short-term results, and the question whether the plug procedure is appropriate and effective in Crohn's disease cannot be answered definitely. Finally, the question how to proceed in patients with plug dislodgement or failure remains unclear. In general, the introduction of the plug has accelerated a ''new'' discussion on the optimal treatment of complex fistulas. Further analysis is needed to explain the definite role of this innovative technique in comparison to traditional surgical techniques.

Study of the efficacy of coated Vicryl plus antibacterial suture in an animal model of orthopedic surgery

PURPOSE

To evaluate the efficacy in vitro and in vivo of a new antibacterial suture, polyglactin 910 suture with triclosan, compared with a traditional braided suture, polyglactin (Vicryl), in a validated animal model of orthopedic infection. Our primary goal was to compare the microbiologic effectiveness of the two sutures. The secondary goal was to evaluate histopathologic signs of an inflammatory response.

METHODS

We used 20 Sprague-Dawley rats. Samples of Staphylococcus epidermidis were diluted to a 0.5 McFarland concentration (100,000 colony-forming units/mL). A surgical steel suture was placed in the spinous process of the rats, and the deep zone of the incision was contaminated bilaterally. Wounds were closed with one of the sutures. After 16 days, the animals were sacrificed, and the surgical wounds were reopened, with cultures being performed of both the zone adjacent to the implant and the deep region of the wound. We also studied the histopathologic features of the tissue adjacent to the implant.

RESULTS

No clinical signs of infection were observed. The culture of the zone adjacent to the implant was positive in nine animals in the polyglactin group vs. three in the polyglactin 910 with triclosan group (p = 0.005). Culture of the deep zone of the wound was positive in ten animals in the polyglactin group vs. six in the polyglactin 910 with triclosan group (p = 0.03). We found predominant polymorphonuclear neutrophil populations in four samples in the polyglactin group vs. two in the polyglactin 910 with triclosan group.

CONCLUSIONS

Under simulated conditions of severe intraoperative contamination, the antibacterial suture reduced the number of positive cultures after surgery by 66.6%. Judging from the available clinical information, its use might contribute to reducing the number of infected implants by 25.8%. Human studies are needed to determine the clinical implications of these results.

A modified process for preparing cationic polylactide-co-glycolide microparticles with adsorbed DNA

We have previously shown that cationic polylactide-co-glycolide (PLG) microparticles can be effectively used to adsorb DNA and generate potent immune responses in vivo. We now describe a modified and easier process containing a single lyophilization step to prepare these cationic PLG microparticles with adsorbed DNA. Cationic PLG microparticle formulations with adsorbed DNA were prepared using a modified solvent evaporation technique. Formulations with a fixed CTAB content and DNA load were prepared. The loading efficiency and 24h DNA release was evaluated for each formulation and compared to the earlier method of preparation. Select formulations were tested in vivo. The modified cationic PLG microparticle preparation method with a single lyophilization step, showed comparable physico-chemical behaviour to the two lyophilization steps process and induced comparable immune. The modified process with a single lyophilization step is a more practical process and can be utlized to prepare cationic PLG microparticles with adsorbed DNA on a large scale.

Preparation of vancomycin microparticles: Importance of preparation parameters

The aim of the present work was to prepare microparticles containing vancomycin for intraocular injection. The primary objective was to guarantee continuous release and keep an intracameral drug concentration above the minimal inhibitory limit for at least 24h, needed in endophthalmitis prophylaxis after cataract surgery. Poly(lactide-co-glycolide) microparticles were prepared using the double emulsion (water-in-oil-in-water) solvent extraction/evaporation method. The influence of preparation parameters on the final microparticles properties was explored in an attempt to control particle sizes, stability, encapsulation rate and vancomycin release profile. Satisfying release profile and stability were obtained, independently of the process. Sizes and encapsulation rate were controlled using an experimental design. Final obtained properties demonstrated that the fabricated particles are suitable for the prophylactic intraocular use in cataract surgery. Further in vitro and in vivo experiments will be conducted to assess efficiency of the entrapped antibacterial and then validate its potential usefulness in prophylaxis.

Hepatitis C virus polyprotein vaccine formulations capable of inducing broad antibody and cellular immune responses

Although approximately 3 % of the world's population is infected with Hepatitis C virus (HCV), there is no prophylactic vaccine available. This study reports the design, cloning and purification of a single polyprotein comprising the HCV core protein and non-structural proteins NS3, NS4a, NS4b, NS5a and NS5b. The immunogenicity of this polyprotein, which was formulated in alum, oil-in-water emulsion MF59 or poly(dl-lactide co-glycolide) in the presence or absence of CpG adjuvant, was then determined in a murine model for induction of B- and T-cell responses. The addition of adjuvants or a delivery system to the HCV polyprotein enhanced serum antibody and T-cell proliferative responses, as well as IFN-gamma responses, by CD4+ T cells. The antibody responses were mainly against the NS3 and NS5 components of the polyprotein and relatively poor responses were elicited against NS4 and the core components. IFN-gamma responses, however, were induced against all of the individual components of the polyprotein. These data suggest that the HCV polyprotein delivered with adjuvants induces broad B- and T-cell responses and could be a vaccine candidate against HCV.

Uptake characteristics of NGR-coupled stealth PEI/pDNA nanoparticles loaded with PLGA-PEG-PLGA tri-block copolymer for targeted delivery to human monocyte-derived dendritic cells

We have investigated the in vitro uptake, toxicity, phenotypic consequences and transfection efficiency of a stealth NGR/PEG/PDBA-coupled-SHA-PEI/pDNA targeting polyplex loaded with PLGA-PEG-PLGA tri-block copolymer in human monocyte-derived dendritic cells (DCs). Modification with PEG effectively shielded and reduced non-specific phagocytosis by immature DCs to approximately 20%. Coupling the NGR cell-specific peptide to the PEGylated polyplex (NGR/PEG/PDBA-SHA-PEI/pDNA) however resulted in specific and enhanced phagocytosis in DCs without any observable toxicity at the optimum concentration of 0.25% of the copolymer. DNase treatment had no effect on DNA integrity in the encapsulated polyplex. Confocal microscopy confirmed intracellular localization of the targeting NGR/PEG/PDBA-SHA-PEI/pDNA microparticles, resulting in more enhanced uptake of the radiolabeled plasmid DNA and approximately 5- and 10-fold increase over the control tri-block Pluronic F68 copolymer and the non-targeting polyplex, respectively. More importantly, phagocytosis of the targeting microparticles neither altered the functionality of immature DCs nor the phenotypic expression of DC-specific cell surface molecules, CD80, CD86, CD40 and CD54 (ICAM-1), suggesting that uptake of the targeting microparticles by themselves did not induce DC maturation. Taken together, these results suggest that PLGA-PEG-PLGA encapsulation of this stealth targeting polyplex has no negative effects on key properties of immature DCs and should pave the way for targeting DCs for vaccination purposes.

Oral poly(lactide-co-glycolide) nanoparticle based antituberculosis drug delivery: toxicological and chemotherapeutic implications

The present study reports on the detailed toxicological and chemotherapeutic evaluation of antituberculosis drug loaded nanoparticles in mice. A single oral dose administration of poly(lactide-co-glycolide) (PLG, a synthetic polymer) nanoparticles containing rifampicin+isoniazid+pyrazinamide+ethambutol could maintain drug levels in various tissues for 9-10 days and did not elicit any adverse response even when administered at several fold higher than the recommended therapeutic dose. However, dosing with conventional free drugs at the equivalent higher doses was lethal. Despite multiple oral dosing with the formulation at every 10th day, no toxicity was observed on the completion of subacute (28 days) or chronic (90 days) toxicity studies based on survival, gross pathology, histopathology, blood biochemistry and hematology. In mice harboring a high mycobacterial load (mimicking human tuberculosis), two independent chemotherapeutic regimens, i.e. 5 doses of PLG nanoparticles encapsulating (rifampicin+isoniazid+pyrazinamide+ethambutol) administered 10 days apart, or 2 doses of the 4-drug formulation followed by 3 doses of 2-drug formulation (rifampicin+isoniazid) resulted in undetectable bacilli. Further, the efficacy was comparable to 46 daily doses of oral free drugs. Therefore, the experimental evidence suggests that PLG nanoparticle-based antituberculosis drug delivery system is safe and well suited for prolonged and intermittent oral chemotherapy.

A biodegradable delivery system for antibiotics and recombinant human bone morphogenetic protein-2: A potential treatment for infected bone defects

To produce an osteogenic and bacteriocidal biomaterial for the treatment of infected nonunions or bone defects, a synthetic degradable block copolymer of poly-D,L-lactic acid segments with randomly inserted p-dioxanone and polyethylene glycol (PLA-DX-PEG) segments was mixed with recombinant human BMP-2 (rhBMP-2) and antibiotics at high concentration. We then examined the in vitro elution profile of an antibiotic (teicoplanin) from the polymer, the effects of antibiotics on the bone-inducing capacity of rhBMP-2 or on ectopic new bone formation induced by the rhBMP, and the ability of the polymer to repair bone in a rat cranial defect model. Approximately 40% of teicoplanin was released within the first 24 h, with the remaining amount released steadily over 21 days with no loss of antibacterial activity. The polymer had disappeared by degradation in the phosphate buffered saline (pH 7.4) at the end of the incubation period. The in vivo performance of pellets with antibiotics and rhBMP-2 revealed no significant change in bone yield within the ossicles after 3 weeks. Also, antibiotics had no inhibitory effect on the ability of rhBMP2 to repair cranial defects. Indeed, when the defect was filled by a polymer disc loaded with rhBMP-2 with or without teicoplanin, the defect was repaired by new bone, and normal anatomy was restored within 6 weeks. In conclusion, the PLA/DX/PEG polymer appears to work as effectively for antibiotics as it does for rhBMP-2. Additionally, the biological activity of rhBMP-2 was retained irrespective of the presence of antibiotics.

Peptide-derivatized biodegradable nanoparticles able to cross the blood-brain barrier

Injectable nanoparticulate drug carriers (Np) able to cross the blood-brain barrier (BBB) have important potential applications for the treatment of diseases that affect the central nervous system (CNS). With the aim to create a system able to address Np to the CNS, we synthesized conjugates between a biodegradable copolymer, poly(D,L-lactide-co-glycolide) (PLGA), and five short peptides, by means of an amidic linkage. These peptides, that are similar to synthetic opioid peptides, were synthesized in turn by means of Fmoc solid-phase peptide synthesis. The new five modified copolymers thus obtained turned out to be valuable starting material for the preparation of Np; these were made fluorescent, in order to allow their localization after their administration, by inclusion of a fluorescent probe. The Np thus prepared were characterized (morphology, size and z-potential) and were shown to possess the peptidic moieties on their surface, as evidenced by ESCA spectroscopy. Then, their ability to cross the BBB was assessed by the in vivo Rat Brain Perfusion Technique and, in one case, by means of a systemic administration (rat femoral vein injection). Fluorescent and confocal microscopy studies showed that while PLGA Np are unable to cross the BBB, for the first time these solid Np surface-modified with peptides were shown to be able to cross the BBB.

Biodistribution properties of nanoparticles based on mixtures of PLGA with PLGA–PEG diblock copolymers

The basic characteristics and the biodistribution properties of nanoparticles prepared from mixtures of poly(lactide-co-glycolide) (PLGA) with poly(lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) copolymers were investigated. A PLGA(45)-PEG(5) copolymer of relatively low PEG content and a PLGA(5)-PEG(5) copolymer of relatively high PEG content were included in the study. Increasing the PLGA-PEG content of the PLGA/PLGA-PEG mixture, or when PLGA(45)-PEG(5) was replaced by PLGA(5)-PEG(5), a decrease in the size of the nanoparticles and an increase in the rate of PEG loss from the nanoparticles were observed. The blood residence of the PLGA/PLGA(45)-PEG(5) nanoparticles increased as their PLGA-PEG content was increased, reaching maximum blood longevity at 100% PLGA(45)-PEG(5). On the contrary, the blood residence of PLGA/PLGA(5)-PEG(5) nanoparticles exhibited a plateau maximum in the range of 80-100% PLGA(5)-PEG(5). At PLGA-PEG proportions lower than 80%, the PLGA/PLGA(45)-PEG(5) nanoparticles exhibited lower blood residence than the PLGA/PLGA(5)-PEG(5) nanoparticles, whereas at PLGA-PEG proportions higher than 80%, the PLGA/PLGA(45)-PEG(5) nanoparticles exhibited higher blood residence than the PLGA/PLGA(5)-PEG(5) nanoparticles. These findings indicate that apart from the surface PEG content, the biodistribution properties of the PLGA/PLGA-PEG nanoparticles are also influenced by the size of the nanoparticles and the rate of PEG loss from the nanoparticles.

Development of a CTL vaccine for Her-2/neu using peptide-microspheres and adjuvants

With the ultimate goal of developing a therapeutic cancer vaccine, we encapsulated the Her-2/neu peptide p369-377 in poly(lactide-co-glycolide) microspheres. This formulation was found to effectively elicit CD8+ cytotoxic T cell (CTL) responses in an HLA-A*0201 transgenic mouse model. In contrast, immunization with either peptide alone or peptide formulated in incomplete Freund's adjuvant (IFA) failed to elicit such CTL responses. Responses induced by the peptide-microsphere formulation were found to peak at approximately 6 weeks post-immunization, and were enhanced by delivering increased doses of peptide and with repeated administrations over time. Co-administration of the peptide-microspheres with adjuvants, including granulocyte-macrophage colony stimulating factor, MPL adjuvant and select synthetic Toll-Like Receptor 4 ligands, the aminoalkyl glucosaminide-4 phosphates, significantly augmented CTL responses. These studies provide important guidance for the design of human clinical trials of microsphere vaccines in terms of optimal peptide-microsphere formulation, vaccination regimen, vaccine dose, and adjuvant selection.

Triblock copolymers: synthesis, characterization, and delivery of a model protein

The purpose of this study was to synthesize and characterize biodegradable and thermosensitive triblock copolymers for delivering protein at controlled rate in biologically active form for longer duration of time. A series of thermosensitive triblock copolymers with different block lengths (PLGA-PEG-PLGA) were synthesized by ring-opening polymerization of d,l-lactide and glycolide with polyethylene glycol (PEG) in the presence of stannous octoate. Compositions and molecular weight of triblock copolymers were characterized by 1H NMR spectrometry and gel permeation chromatography, respectively. A single test-tube inverting method was employed to determine the sol-gel transition temperature. Lysozyme was used as a model protein. Lysozyme solution formulation was prepared with different triblock copolymers for in vitro release. Lysozyme concentration and its biological activity in the released sample were determined using a standard MicroBCA method and bacterial cell lysis method, respectively. The effects of varying block lengths and concentrations of copolymers on the in vitro release of lysozyme were evaluated. The release profiles from formulations showed a higher initial release followed by slower release up to 4 weeks. Increasing the block lengths of copolymers decreased burst release of lysozyme from 41.2+/-5.4% to 16.1+/-3.9%. Increasing copolymer concentrations decreased the drug release. Lysozyme in the 4 weeks released samples retained most of its biological activity (>80%). It is feasible to deliver protein in biologically active form for longer duration by varying block lengths and concentrations of triblock copolymers.

Intraoperative 125I Vicryl mesh brachytherapy after sublobar resection for high-risk stage I nonsmall cell lung cancer

PURPOSE

To assess the feasibility and outcomes of (125)I Vicryl mesh brachytherapy after sublobar resection in stage I non small cell lung cancer (NSCLC) patients with poor pulmonary function.

METHODS AND MATERIALS

Between January 1997 and July 2004, patients with poor cardiopulmonary reserve who had stage IA and IB (T1-2 N0 M0) NSCLC and a forced expiratory volume in 1s (FEV(1)) of > micro=0.6L were considered for limited surgical resection either by an open or video-assisted thoracoscopic procedure and for a subsequent (125)I Vicryl mesh brachytherapy implant. Mediastinal and hilar lymph node staging was performed routinely in all patients. After clear margins were obtained grossly and on frozen section, a single-plane (125)I implant was designed to encompass a plane consisting of the staple line and a 2-cm margin of surrounding visceral pleura. The implant was introduced through the surgical incision and sutured to the visceral pleura. A prescribed dose of 100-120 y was delivered to a volume within 0.5 cm rom the plane of the implant. Follow-up orthogonal films or CTs were obtained for dosimetric analysis. Kaplan-Meier analyses were used to estimate the local control, locoregional control, and overall survival rates.

RESULTS

Of the 110 patients, 65 had stage IA and 45 had stage IB NSCLC. The mean preoperative FEV(1) was 47% of the predicted volume. With a median follow-up of 11 months (range 1-68 months), there were four recurrences within the radiation volume. The estimated 5-year local (in-field) control, locoregional control, and overall survival rates were 90%, 61%, and 18%, respectively.

CONCLUSION

Vicryl mesh brachytherapy after sublobar resection for high-risk stage I NSCLC patients is a feasible procedure, which results in an excellent local (in-field) control rate.

Modulation of allergic responses in mice by using biodegradable poly(lactide-co-glycolide) microspheres

BACKGROUND

Biodegradable poly(lactide- co -glycolide) (PLGA) microspheres are a promising carrier for vaccine delivery capable of maturing antigen-presenting cells to stimulate T-cell-mediated immune responses. However, the potential of microspheres to downregulate an allergic response in vivo is unknown.

OBJECTIVE

The aim of this study was to determine whether microspheres could potentiate DNA vaccination against allergy and to evaluate the immunomodulatory properties of microspheres alone.

METHODS

Mice were treated prophylactically with DNA-loaded plain PLGA microspheres before sensitization with phospholipase A2 (PLA2), the major allergen of bee venom. PLA2-specific IgG1, IgG2a, IgE in serum were measured for 8.5 months, and splenocyte proliferative responses and cytokine profiles were determined. Protection against anaphylaxis was evaluated after injection of an otherwise lethal dose of PLA2.

RESULTS

Phospholipase A2-specific IgG1 and IgG2a production turned out to be 2 times higher using cationic microspheres compared with anionic microspheres, but was not influenced by the presence of DNA. In contrast, reduction in IgE production and T-cell hyporesponsiveness were observed with all microsphere formulations. Recall challenge with PLA2 triggered combined expression of both IL-4 and IFN-gamma, together with sustained expression of IL-10 that can explain the protective effect against anaphylaxis.

CONCLUSION

Our data suggest a dual mechanism that does initially rely on a TH2 to TH1 immune deviation and then on IL-10-mediated suppression. This is the first physiological demonstration that plain PLGA microspheres can induce tolerance in mice for as long as 6 months postsensitization.

Incorporation and controlled release of a hydrophilic antibiotic using poly(lactide-co-glycolide)-based electrospun nanofibrous scaffolds

The successful incorporation and sustained release of a hydrophilic antibiotic drug (Mefoxin, cefoxitin sodium) from electrospun poly(lactide-co-glycolide) (PLGA)-based nanofibrous scaffolds without the loss of structure and bioactivity was demonstrated. The morphology and density of the electrospun scaffold was found to be dependent on the drug concentration, which could be attributed to the effect of ionic salt on the electrospinning process. The drug release behavior from the electrospun scaffolds and its antimicrobial effects on Staphylococcus aureus cultures were also investigated. In all tested scaffolds, the maximum dosage of drug was released after 1 h of incubation in water at 37 degrees C. The usage of the amphiphilic block copolymer (PEG-b-PLA) reduced the cumulative amount of the released drug at earlier time points and prolonged the drug release rate at longer times (up to a 1-week period). The antibiotic drug released from these electrospun scaffolds was effective in their ability to inhibit Staphylococcus aureus growth (>90%). The combination of mechanical barriers based on non-woven nanofibrous biodegradable scaffolds and their capability for local delivery of antibiotics increases their desired utility in biomedical applications, particularly in the prevention of post-surgical adhesions and infections.

Biodegradable Triblock Copolymer of PLGA-PEG-PLGA Enhances Gene Transfection Efficiency

PURPOSE

A tri-block copolymer of PLGA-PEG-PLGA was used as an excipient to enhance the gene transfection efficiency of various cationic polymeric carriers.

METHODS

Luciferase plasmid DNA was complexed with polyethylenimine for gene transfection. Various concentrations of PLGA-PEG-PLGA copolymer up to 0.5% were added in the transfection medium to explore whether the copolymer increased the level of gene expression. Pluronic F68 was used as a control. Various polyplexes and different cell lines were used to verify the effect of the triblock copolymer on gene transfection. The cellular uptake extent of radiolabeled plasmid was quantitatively determined as a function of PLGA-PEG-PLGA concentration.

RESULTS

PLGA-PEG-PLGA copolymer significantly enhanced gene transfection efficiency at a concentration as low as 0.25% (w/v), which was more effective than Pluronic F68 at the same concentration range. The additive effect of the triblock copolymer in the transfection medium was clearly observed for various cationic polyplexes and cell lines, although the gene expression extents largely depended on polymers and cell lines used. Five- to 10-fold increment of gene transfection levels were attained in the presence of the PLGA-PEG-PLGA tri-block copolymer. The enhanced gene transfection efficiency was attributed to the increased cellular uptake of PEI/DNA complexes in the presence of the PLGA-PEG-PLGA tri-block copolymer.

CONCLUSIONS

Biodegradable PLGA-PEG-PLGA tri-block copolymer that facilitates the endocytic process can be used as a novel additive in non-viral gene transfection.

Loading of tetanus toxoid to biodegradable nanoparticles from branched poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide) nanoparticles by protein adsorption: a mechanistic study

PURPOSE

Mucosal delivery of vaccine-loaded nanoparticles (NP) is an attractive proposition from an immunologic perspective. Although numerous NP preparation methods are known, sufficient antigen loading of NP remains a challenge. The aim of this study was to evaluate adsorptive loading of NP with a negatively charged surface structure using tetanus toxoid (TT) as a model vaccine.

METHODS

Blank NP, consisting of poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide), as well as poly(lactide-co-glycolide) NP were prepared by a solvent displacement technique. The use of polymers with different degrees of substitution resulted in NP with different negative surfaces charges. Adsorption of TT to NP was performed varying to NP surface properties, protein equilibrium concentration, and loading conditions.

RESULTS

The protein adsorption was controlled by NP surface properties, and maximum TT adsorption occurred at highly negatively charged NP surfaces. Results from isothermal titration calorimetry and zeta-potential measurement suggest an adsorption process governed by electrostatic interactions. The adsorption followed the Langmuir isotherm in the concentration ranges studied. TT withstood this gentle loading procedure in a nonaggregated, enzyme-linked immunoabsorbant assay-active form.

CONCLUSION

The results demonstrate that negatively charged NP consisting of poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide) are suitable for adsorptive loading with TT and may have potential for mucosal vaccination.

The inhibitory effect of octreotide on experimental colorectal carcinogenesis

PURPOSE

This study was conducted to investigate the effect of octreotide on colorectal carcinogenesis by administering octreotide either alone or combined with polyglactin, which is a well-known suture material, on chemically induced colorectal cancer development in rats.

METHODS

A total of 72 rats were divided into six groups. Two groups were subjected to a colotomy and repair using polyglactin. Another two groups underwent a sham procedure. The fifth group received octreotide alone and the sixth group served as a control. Both groups of rats in the polyglactin and sham groups received octreotide additionally. Methylnitrosourea was administered rectally to all the animals at a dose of 4 mg/kg per week for 20 weeks to induce carcinogenesis. Octreotide was injected twice a day at a total daily dose of 100 microg/kg. The thymidine labeling index was used to assess the synthesis phase fraction in order to measure the cell proliferation rate.

RESULTS

The mean number of tumors per rat was significantly higher in the polyglactin group than in both the sham and control groups. It was significantly lower in the octreotide and polyglactin + octreotide groups than in the control and polyglactin groups, respectively. All the animals in the octreotide group had one tumor, while 66.6% of the control group had multiple tumors. The number of multiple tumors was significantly lower in the polyglactin + octreotide and sham + octreotide groups than in the polyglactin and sham groups, respectively. The mean tumor size in the octreotide group was significantly smaller than in the control group, whereas it was larger in the polyglactin group in comparison with the sham and control groups. It was also reduced in the polyglactin + octreotide group in comparison with the polyglactin group. The thymidine labeling index was significantly higher in the polyglactin group compared with both the sham and control groups, whereas it was lower in the octreotide group in comparison with the control group. The addition of octreotide administration to the polyglactin usage and the sham procedure significantly decreased the thymidine labeling indexes.

CONCLUSION

These results indicate that octreotide reduces the frequency of tumor occurrence and has an inhibitory effect on its development in chemically induced experimental colorectal cancer. Octreotide can also reduce the enhancing effect of polyglactin on colorectal carcinogenesis when it is combined with polyglactin.

In vivo study of hot compressing molded 50:50 poly (DL-lactide-co-glycolide) antibiotic beads in rabbits

The authors investigated poly (DL-lactide-co-glycolide) beads as an antibiotic delivery system in vivo for the treatment of various surgical infections. In this study, the copolymer 50:50 poly (DL-lactide):co-glycolide was mixed with vancomycin powder and hot compressing molded at 55 degrees C to form 8 mm in diameter biodegradable antibiotic beads. The antibiotic beads were implanted in the distal femoral cavities of rabbits for in vivo investigation. The local concentration of vancomycin was well above the breakpoint sensitivity concentration (the antibiotic concentration at the transition point between bacterial killing and resistance to the antibiotic) for 56 days. The release was most marked during the first day. The diameters of the sample inhibition zone ranged from 8 to 18 mm, and the relative activity of vancomycin ranged from 9.1% to 100%. Only low systemic blood levels of vancomycin were measured after beads implantation. There was no increase in the concentration of blood urea nitrogen and serum creatinine after the implantation. Histological observations showed that the bead materials were biodegradable, resorbed slowly, and did not cause a significant host reaction. This study offers a biodegradable delivery system of antibiotics to treat various surgical infections.

Surgically implantable long-term antipsychotic delivery systems for the treatment of schizophrenia

Non-adherence with medication remains a major correctable cause for poor outcome in schizophrenia. We describe a surgically implantable preparation of haloperidol with the aim that patients will have superior outcomes with improved medication adherence from implants. In contrast to depot formulations, implantable pellets could last many months, providing symptomatic improvement for periods of time never before possible. Additionally, in the event of unacceptable side effects, implants could be removed, offering a degree of reversibility not available with depot formulations. A surgically-implantable formulation of haloperidol has been created using biodegradable polymers. Implants have been characterized for in-vitro kinetics, as well as in-vivo bioactivity in rodents. Haloperidol implants demonstrate steady release of drug for 5 months. Animals treated with haloperidol implants display increased striatal D2 receptor expression as well as increased apomorphine stimulated locomotion. Surgically-implantable formulations are a viable approach to provide long-term delivery of antipsychotic medications to patients with psychotic disorders.

Sol-gel transition temperature of PLGA-g-PEG aqueous solutions

Aqueous solutions of poly(DL-lactic acid-co-glycolic acid)-g-poly(ethylene glycol) copolymers exhibited sol-to-gel transition with increasing temperature. Further increase in temperature makes the system flow and form a sol phase again. Subcutaneous injection of a copolymer aqueous solution (0.5 mL) resulted in a formation of a hydrogel depot by temperature-sensitive sol-to-gel transition in a rat model. The reliable determination and control of sol-to-gel transition temperatures are the most important issues for this kind of sol-gel reversible hydrogel. The sol-to-gel transition temperature determined by the test tube inverting method, falling ball method, and dynamic mechanical analysis coincided within 1-2 degrees C. Fine tuning of the sol-to-gel transition temperature was achieved by varying the ionic strength of the polymer solutions and by mixing two polymer aqueous solutions with different sol-to-gel transition temperatures. The sol-to-gel transition temperature of polymer mixture aqueous solutions was well described by an empirical equation of miscible blends, indicating miscibility of the two polymer systems in water on the molecular level.

Protective immune responses elicited in mice by immunization with formulations of poly(lactide-co-glycolide) microparticles

Parenteral administration of microparticle encapsulated DNA elicits immune responses to the encoded antigens. Experiments were performed to test whether the addition of certain lipophilic agents to such formulations enhanced the activity of a beta-galactosidase (beta-gal) DNA vaccine. Addition of either taurocholic acid (TA) or monomethoxy polyethylene-glycol-distearoylphosphatidylehanolamine (PEG-DSPE) increased the efficiency of DNA encapsulation. Immunization of mice with encapsulated DNA formulations containing either compound significantly increased the number of antibody positive responders over that achieved with non-lipid containing particles. Moreover, responding animals demonstrated trends towards higher antibody titers and increased T cell responses. Tumor protection against the CT26.CL25 tumor cell line was demonstrated with lipid and non-lipid containing formulations. These results are the first demonstration of protection obtained by parenteral administration of PLG encapsulated DNA vaccines.

Polymeric system for dual growth factor delivery

The development of tissues and organs is typically driven by the action of a number of growth factors. However, efforts to regenerate tissues (e.g., bone, blood vessels) typically rely on the delivery of single factors, and this may partially explain the limited clinical utility of many current approaches. One constraint on delivering appropriate combinations of factors is a lack of delivery vehicles that allow for a localized and controlled delivery of more than a single factor. We report a new polymeric system that allows for the tissue-specific delivery of two or more growth factors, with controlled dose and rate of delivery. The utility of this system was investigated in the context of therapeutic angiogenesis. We now demonstrate that dual delivery of vascular endothelial growth factor (VEGF)-165 and platelet-derived growth factor (PDGF)-BB, each with distinct kinetics, from a single, structural polymer scaffold results in the rapid formation of a mature vascular network. This is the first report of a vehicle capable of delivery of multiple angiogenic factors with distinct kinetics, and these results clearly indicate the importance of multiple growth factor action in tissue regeneration and engineering.

Microparticles for intranasal immunization

Of the several routes available for mucosal immunization, the nasal route is particularly attractive because of ease of administration and the induction of potent immune responses, particularly in the respiratory and genitourinary tracts. However, adjuvants and delivery systems are required to enhance immune responses following nasal immunization. This review focuses on the use of microparticles as adjuvants and delivery systems for protein and DNA vaccines for nasal immunization. In particular we discuss our own work on poly(lactide co-glycolide) (PLG) microparticles with entrapped protein or adsorbed DNA as a vaccine delivery system. The possible mechanisms involved in the enhancement of immune responses through the use of DNA adsorbed onto PLG microparticles are also discussed.

Effects of inner water volume on the peculiar surface morphology of microspheres fabricated by double emulsion technique

Poly(D,L-lactide-co-glycolide) (PLG, 65:35) was used to encapsulate bovine serum albumin (BSA) using a water-in-oil-in-water (W/O/W) double emulsion solvent extraction technique. To investigate the effects of an inner water/oil ratio on microsphere characteristics, microspheres were fabricated using four different formulations with a fixed oil volume of 12ml and the inner aqueous phase volume of 0.2ml, 0.3 ml, 0.4ml or 0.5 ml, respectively. Spherical microspheres were obtained after collection by filtration for formulations employing any of the four different inner water/oil ratios. However, microspheres with smaller inner water volumes tend to collapse after vacuum drying. The surface of the formulation with a higher inner water/oil ratio was shown to possess many more pores than that of the formulations with lower inner water/oil ratios. These pores may facilitate the water withdrawal during vacuum drying. Furthermore, microspheres with the lowest inner water/oil ratio (1/60) had higher initial burst release due to its larger surface area. However, microspheres with the highest inner water volume yield a faster release profile of BSA due to interconnected voids within microspheres and more pores on the surface. Therefore, the inner water/oil ratio is a crucial factor in the W/O/W double emulsion technique affecting the morphology and release kinetics of the resulting microspheres.

Encapsulation in biodegradable microparticles enhances serum antibody response to parenterally-delivered beta-amyloid in mice

Poly(lactide-co-glycolide) (PLG) microspheres were tested as a parenteral delivery system for human beta-amyloid (1-42) (Abeta), a potential immunotherapeutic undergoing assessment in Phase 1 studies for Alzheimer's disease (AD). Abeta was successfully encapsulated in PLG microspheres of average sizes of 3 or 15 microm diameter. Swiss Webster (SW) mice were injected by the sub-cutaneous (s.c.) or intra-peritoneal (i.p.) routes with 3-33 microg Abeta. Abeta-PLG microparticles (3 microm) induced dose-dependent antibody responses, which were maximal at 33 microg Abeta, while Abeta in phosphate-buffered saline (PBS) produced weak antibody responses at the same doses by both routes. Significantly increased antibody responses were seen for both small and large particle formulations given by the i.p. route in comparison to the s.c route. It was previously reported that passive immunisation with Abeta-specific antibodies cleared amyloid plaques in a mouse model of AD (Bard F, Cannon C, Barbour R, et al. Peripherally administered antibodies against amyloid beta-peptide enter the nervous system and reduce pathology in a mouse model of Alzheimer disease. Nature Med 2000;6:916-19), an indication that induction of serum antibody is a prerequisite for efficacy.

Effect of dose on the biodistribution and pharmacokinetics of PLGA and PLGA-mPEG nanoparticles

The effect of nanoparticle dose on the biodistribution and pharmacokinetics of conventional PLGA and stealth poly(Lactide-co-glycolide)-monomethoxypoly(ethyleneglycol) (PLGA-mPEG) nanoparticles was investigated. The precipitation-solvent diffusion method was used to prepare PLGA and PLGA-mPEG nanoparticles labeled with 125I-cholesterylaniline. These were administered intravenously (i.v.) in mice and at predetermined time intervals the animals were sacrificed and their tissues were excised and assayed for radioactivity. Within the dose range applied in this study, blood clearance and mononuclear phagocyte system (MPS) uptake of the PLGA nanoparticles depended on dose whereas they were independent of dose in the case of the PLGA-mPEG nanoparticles. Increasing the dose, decreased the rates of blood clearance and MPS uptake of the PLGA nanoparticles, indicating a certain degree of MPS saturation at higher doses of PLGA nanoparticles. The dose affected the distribution of PLGA nanoparticles between blood and MPS (liver) but it did not affect the nanoparticle levels in the other tissues. Within the range of doses applied here, the PLGA nanoparticles followed non-linear and dose-dependent pharmacokinetics whereas the PLGA-mPEG nanoparticles followed linear and dose-independent pharmacokinetics. In addition to the prolonged blood residence, the dosage-independence of the pharmacokinetics of the PLGA-mPEG nanoparticles would provide further advantages for their application in controlled drug delivery and in drug targeting.

Poly(lactide-co-glycolide)/hydroxyapatite delivery of BMP-2-producing cells: a regional gene therapy approach to bone regeneration

Currently, functional treatment of fracture non-unions and bone loss remains a significant challenge in the field of orthopaedic surgery. Tissue engineering of bone has emerged as a new treatment alternative in bone repair and regeneration. Our approach is to combine a polymeric matrix with a cellular vehicle for delivery of bone morphogenetic protein-2 (BMP-2), constructed through retroviral gene transfer. The objective of this study is to develop an osteoinductive, tissue-engineered bone replacement system by culturing BMP-2-producing cells on an osteoconductive, biodegradable, polymeric-ceramic matrix. The hypothesis is that retroviral gene transfer can be used effectively in combination with a biodegradable matrix to promote bone formation. First, we examined the in vitro attachment and growth of transfected BMP-producing cells on a PLAGA-HA scaffold. Second, the bioactivity of the produced BMP in vitro was evaluated using a mouse model. It was found that the polymer-ceramic scaffold supported BMP-2 production, allowing the attachment and growth of retroviral transfected, BMP-2-producing cells. In vivo, the scaffold successfully functioned as a delivery vehicle for bioactive BMP-2, as it induced heterotopic bone formation in a SCID mouse model.

Biodegradable polymers for ocular drug delivery

A variety of ocular drug delivery systems, including a controlled release of the drug, drug targeting, and penetration enhancement of the drug, have been investigated. Biodegradable polymers have been widely used as the drug carrier for controlled-release systems. Biodegradable polymers release the drug as they themselves degrade and are finally absorbed within the body. Several ocular drug delivery systems using different kinds of biodegradable polymers have been studied. In this article, we describe the fundamental mechanisms of drug delivery systems, polymer erosion and drug release, and then review those systems using the most popular biodegradable polymers, poly(lactic acid) and poly(lactic-glycolic acid).

PEGylated PLGA nanoparticles as protein carriers: synthesis, preparation and biodistribution in rats

The aim of the present work was to assess the merits of PEGylated poly(lactic-co-glycolic acid) (PEG-PLGA) nanoparticles as protein and peptide drugs (PPD) carriers. PEG-PLGA copolymer, which could be used to prepare the stealth nanoparticles or long-circulating nanoparticles, was synthesized with methoxypolyethyleneglycol (MePEG) and PLGA. The structure of PEG-PLGA was confirmed with (1)H NMR and Fourier transform infrared (FTIR) spectrum, and molecular weight was determined by gel permeation chromatography (GPC). Bovine serum albumin (BSA), chosen as model protein, was encapsulated within the stealth nanoparticles with the double emulsion method. The particles were characterized in terms of size, zeta potential and in vitro release of the protein. The biological fate of the BSA-loaded nanoparticles following intravenous administration was determined over 24 h in rats. The experimental results showed that PEG-PLGA could be obtained by ring-opening polymerization of lactide and glycolide in the presence of MePEG. (1)H NMR and FTIR spectrum were consistent with the structure of PEG-PLGA copolymer. Molecular weight determined by GPC was 50800. The stealth nanoparticles loading BSA could be prepared by the double emulsion technique. The entrapment efficiency was 48.6%, particle size about 200 nm and zeta potential -16.1 mV. BSA release from the stealth nanoparticles showed an initial burst release and then sustained release. PEG-PLGA nanoparticles could extend half-life of BSA from 13.6 min of loaded in PLGA nanoparticles to 4.5 h and obviously change the protein biodistribution in rats compared with that of PLGA nanoparticles. Thus, PEG-PLGA nanoparticles could be an effective carrier for PPD delivery.

Biodegradable polymeric micelles composed of doxorubicin conjugated PLGA-PEG block copolymer

Biodegradable polymeric micelles containing doxorubicin in the core region were prepared from a di-block copolymer composed of doxorubicin-conjugated poly(DL-lactic-co-glycolic acid) (PLGA) and polyethyleneglycol (PEG). The di-block copolymer of PLGA-PEG was first synthesized and the primary amino group of doxorubicin was then conjugated to the terminal hydroxyl group of PLGA, which had been pre-activated using p-nitrophenyl chloroformate. The resulting polymeric micelles in aqueous solution were characterized by measurement of size, drug loading, and critical micelle concentration. The micelles containing chemically-conjugated doxorubicin exhibited a more sustained release profile than PEG-PLGA micelles containing physically-entrapped doxorubicin. The cytotoxic activity of the micelles against HepG2 cells was greater than free doxorubicin, suggesting that the micelles containing conjugated doxorubicin were more effectively taken up cellularly, by an endocytosis mechanism rather than by passive diffusion. Confocal microscopic observation and flow cytometry analysis supported the enhanced cellular uptake of the micelles.

Technological considerations related to the up-scaling of protein microencapsulation by spray-drying

Research and development of therapeutics and vaccines based on biodegradable polymers are intensive and one of the most promising fields in controlled drug delivery. However, new applications necessitate successful technology transfer and industrial scale-ups. In an endeavour to produce clinical samples of a single-administration tetanus vaccine based on poly(lactide-co-glycolide) microspheres, we report on technological parameters that are of importance in the up-scaling of the spray-drying process. The results show that an up-scaling of the encapsulation of protein vaccines or drug by spray-drying is feasible, but that additives, the type of polymer solvent, the polymer concentration, the w/o ratio and the product collection method influence process and product quality.

Drug release from biodegradable injectable thermosensitive hydrogel of PEG-PLGA-PEG triblock copolymers

An aqueous solution of newly developed low-molecular-weight PEG-PLGA-PEG triblock copolymers with a specific composition is a free flowing sol at room temperature but becomes a gel at body temperature. Two model drugs, ketoprofen and spironolatone, which have different hydrophobicities, were released from the PEG-PLGA-PEG triblock copolymer hydrogel formed in situ by injecting the solutions into a 37 degrees C aqueous environment. Ketoprofen (a model hydrophilic drug) was released over 2 weeks with a first-order release profile, while spironolactone (a model hydrophobic drug) was released over 2 months with an S-shaped release profile. The release profiles were simulated by models considering degradation and diffusion, and were better described by a model assuming a core-shell structure of the gel.

Stabilization of proteins encapsulated in injectable poly (lactide- co-glycolide)

Controlled release from biodegradable polymers is a novel approach to replace daily painful injections of protein drugs. A major obstacle to development of these polymers is the need to retain the structure and biological activity of encapsulated proteins during months of incubation under physiological conditions. We encapsulated bovine serum albumin (BSA) in injectable poly(DL-lactide- co-glycolide) (PLGA) 50/50 cylindrical implants and determined the mechanism of BSA instability. Simulations of the polymer microclimate revealed that moisture and acidic pH (<3) triggered unfolding of encapsulated BSA, resulting in peptide bond hydrolysis and noncovalent aggregation. To neutralize the acids liberated by the biodegradable lactic/glycolic acid-based polyester, we coincorporated into the polymer an antacid, Mg(OH)2, which increased microclimate pH and prevented BSA structural losses and aggregation for over one month. We successfully applied this stabilization approach in both cylinder- and microsphere-injectable configurations and for delivery of angiogenic basic fibroblast growth factor and bone-regenerating bone morphogenetic protein-2.

Evaluation of biodegradable ampicillin anhydrate microcapsules for local treatment of experimental staphylococcal osteomyelitis

Successful treatment of chronic osteomyelitis requires sustained high concentrations of antibiotics locally within the infected bone. The efficacy of biodegradable (poly-DL-lactide-co-glycolide) microspheres containing 30.7% ampicillin anhydrate for the local treatment of experimental staphylococcal osteomyelitis was evaluated in rabbits. In the initial experiment, antibiotic therapy was initiated immediately following injection of Staphylococcus aureus into the proximal tibial metaphysis. A single intramedullary injection of microencapsulated ampicillin (100 mg) prevented osteomyelitis in all seven animals tested and was as effective as a two-week course of parenteral ampicillin administration. When antibiotic therapy was delayed for seven days, osteomyelitis developed in four of eight animals treated locally with microencapsulated ampicillin and in six of eight animals that received parenteral ampicillin therapy. When antibiotic therapy was delayed for seven days and was preceded by debridement, all ten animals treated locally with microencapsulated ampicillin had sterile bone cultures. In contrast, seven of ten animals treated locally with unencapsulated ampicillin powder developed osteomyelitis. Biodegradable antibiotic-loaded microspheres may be of clinical benefit for the local treatment of chronic osteomyelitis.

Pharmaceutical manipulation of leuprorelin acetate to improve clinical performance

Leuprorelin acetate, a highly potent luteinizing hormone releasing hormone agonist, was originally launched in the USA to be administered once daily by self-injection for the treatment of metastatic prostatic cancer. A once-monthly intramuscularly or subcutaneously injectable depot form of leuprorelin acetate has, subsequently, been developed. Biodegradable copoly(DL-lactic acid/glycolic acid) was chosen as the release-controlling polymer and the microcapsules containing leuprorelin acetate were prepared by an in-water drying method. Results of studies in rats showed that a copolymer with a molecular weight of 14,000 and a lactic acid/glycolic acid ratio of 75/25 had the most satisfactory releasing properties. Microcapsules given once monthly reduced serum testosterone levels in rats, dogs and man. In clinical studies, the depot preparation effectively reduced the dose of leuprorelin acetate required to up to one-eighth of that needed when injected daily. A sophisticated manufacturing system has now been developed and a very reliable controlled-release product is now available that has many advantages.

[Protection of sutures of the injured esophagus using polyglactin 910 (Vicryl) mesh]

Dehiscence of suture after operative treatment of esophageal rupture is a quite frequent and dangerous complication. Several methods of reinforcement of suture with autologus material have been suggested of which the use of a pleura flap was the most successful one. After experimental investigations in the Department of Surgery of the University Hospital of Münster the securing of suture was performed by using Polyglactin 910 (Vicryl) meshgrafts. In 8 patients where the mesh grafts were used, a secondary leakage could be avoided. Considering our experiences, securing of suture by the use of Polyglactin 910 mesh-grafts is a recommendable method.

Clinical evaluation of an improved injectable microcapsule contraceptive system

Pharmacokinetics and pharmacodynamics of a long-acting injectable microcapsule, poly(DL-lactide-co-glycolide), delivery system were tested in 10 women. Two doses (75 or 100 mg of norethindrone) were administered by intramuscular injection. Treatment suppressed ovarian function and inhibited ovulation for 3 months in all subjects. Levels of norethindrone in subjects who received the 100 mg dose were proportionately higher than those in subjects who received the 75 mg dose. Subsequent to the injection, there was a rapid rise in the serum levels of norethindrone followed by a gradual decline until 8 to 10 weeks. Between 10 and 20 weeks after treatment, there was a secondary rise and fall in the serum levels of norethindrone. Treatment caused suppression of the endometrium for 3 months, and, except for spotting and irregular menstrual cycles, there were no adverse side effects. Treatment had no significant effect on serum lipids.