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PubMedDate not supplied

Gamma-sterilization-induced radicals in biodegradable drug delivery systems.

Electron paramagnetic resonance (EPR) spectroscopy (1.2 and 9.25 GHz, 25 degrees C) was used to characterize free radicals in gamma-ray sterilized biodegradable polymers of the type which are in clinical use. Free radicals were detected in all irradiated polymer samples. The temperature of irradiation (25 degrees C vs dry ice temperature) had only a minor influence on the yield of radicals and the shape of the EPR spectra. In contrast, the composition of the polymers and the drugs incorporated in them did strongly influence the amount of radiation-induced free radicals and their reactivity. In general, polymers with high melting points and crystallinity had the highest yields of radicals observable at room temperature. We were able to use the free radicals induced by the usual sterilization procedures to follow the penetration of water and the degradation of the polymers in vitro and in vivo. The ability of in vivo EPR to follow drug delivery noninvasively and continuously in vivo, using the free radicals induced in the usual sterilization process indicates that this approach could be applied immediately for the characterization of these drug delivery systems in experimental animals and in the near future should be able to be used in human subjects.

Animals↗
PubMed2003

Chitin/PLGA blend microspheres as a biodegradable drug delivery system: a new delivery system for protein.

Novel chitin/PLGAs and chitin/PLA based microspheres were developed for the delivery of protein. These biodegradable microspheres were prepared by polymers blending and wet phase-inversion methods. The parameters such as selected non-solvents, temperature of water and ratio of polylactide to polyglycolide were adjusted to improve thermodynamic compatibility of individual polymer (chitin and PLGAs or chitin/PLA), which affects the hydration and degradation properties of the blend microspheres. Triphasic pattern of drug release model is observed from the release of protein from the chitin/PLGAs and chitin/PLA microspheres: the initially fast release (the first phase), the following slow release (the second phase) and the second burst release (the third phase). Formulations of the blends, which are based on the balance among the hydration rate of the chitin phase and degradation of chitin/PLA and PLGA phase, can lead to a controllable release of bovine serum albumin (BSA). In conclusion, such a chitin/PLGA 50/50 microsphere is novel and interesting, and may be used as a protein delivery system.

Absorbable Implants↗
PubMed1981

Biodegradable drug delivery systems based on aliphatic polyesters: application to contraceptives and narcotic antagonists.

The classes of polymer which form the basis of different types of drug delivery systems are discussed, and the relationships between the chemical structure of the polymer and its permeability, morphology, biodegradability, and mechanical properties are considered, using polyesters as specific examples. Studies of the permeability and biodegradability of poly epsilon-caprolactone), poly(DL-lactic acid), and various copolymers are described and used to illustrate how these properties may be varied by the choice of polymer structure. An induction period prior to bioerosion of these polymers, coupled with high permeability, permits their use as reservoir devices (capsules) which exhibit constant, diffusion-controlled drug release rates and which erode after the drug is exhausted. The applications of this approach to the long term delivery (1 year) of levonorgestrel, a contraceptive agent, and the short term delivery (1-2 months) of naltrexone, a narcotic antagonist, are described.

Animals↗
PubMed1998

Progesterone-loaded chitosan microspheres: a long acting biodegradable controlled delivery system.

Smooth, highly spherical, crosslinked chitosan microspheres in the size range of 45-300 microns loaded with progesterone were prepared by glutaraldehyde crosslinking of an aqueous acetic acid dispersion of chitosan containing progesterone in a non-aqueous dispersion medium consisting of liquid paraffin and petroleum ether stabilized using sorbitan sesquioleate. In vitro release of the drug into phosphate buffer at 37 degrees C was determined as a function of crosslinking density of the microspheres and particle size. The extent of drug release had a remarkable dependence on the crosslinking density of the microspheres, the highly crosslinked spheres releasing only around 35% of the incorporated steroid in 40 days compared to 70% from spheres lightly crosslinked. Determination of the in vivo bioavailability of the steroid from microsphere formulation by intramuscular injection in rabbits showed that a plasma concentration of 1 to 2 ng/ml was maintained up to 5 months without a high 'burst effect'. Data obtained suggest that the crosslinked chitosan microspheres would be an interesting system for long term delivery of steroids.

Animals↗
PubMedDate not supplied

Pluronic F127-based ocular delivery system containing biodegradable polyisobutylcyanoacrylate nanocapsules of pilocarpine.

The objectives of our study were to prepare a biodegradable polyisobutylcyanoacrylate (PIBCA) colloidal particulate system of pilocarpine, to incorporate it into a Pluronic F127(PF127)-based gel delivery system, and to evaluate its ability to prolong the release of pilocarpine. Polyisobutylcyanoacrylate nanocapsules (PIBCA-NC) of pilocarpine were prepared by interfacial polymerization. Physicochemical characterization of the colloidal dispersion of PIBCA-NC of pilocarpine was performed by measuring drug loading, particle size analysis, and scanning electron microscopy. Results indicated that approximately 13.5% of pilocarpine was loaded onto the PIBCA-NC, the nanocapsules ranged from 370 to 460 nm, the distribution was narrow, and there was no significant effect of stirring speed on particle size. The PIBCA-NC dispersion of 1% pilocarpine alone (I) and after incorporation into the Pluronic F127 gel delivery system (II) were compared against 1% pilocarpine incorporated into a PF127 gel containing 5% methylcellulose (PF127MC) alone (III) by measuring the miotic response in the albino rabbit eye. Statistical analysis indicated a rank-order for both the duration and intensity of miosis of II > III >> I, with all differences being significant (p < 0.05). Thus, it appears that II increases the contact time of pilocarpine with the absorbing tissue in the eye, thereby improving ocular bioavailability. The PIBCA-NC of pilocarpine dispersed in the PF127MC gel delivery system has considerable potential for achieving a prolonged delivery for such drugs as pilocarpine and other more hydrophobic drugs.

Algorithms↗
PubMed2006

Polymer-based biodegradable drug delivery systems in pain management.

Pain is an unpleasant sensory experience commonly produced by damage to bodily tissues and it is one of the most significant public health problems, because 21.5% of the world population is estimated to suffer from pain. It results in a total loss of more than 165 billion US dollars each year in the United States alone. Pain reflects a mixture of various pathophysiologic, psychologic, and genetic contributions. When undertreated, pain usually results in serious immune and metabolic upset. Therefore, it requires wide understanding and intensive effort for a better management. Currently, pain control is limited by the modest efficiency of the used drugs, the serious side effects of these drugs, and the inefficacy of conventional drug administration. By the introduction of the technology of biodegradable controlled-release devices into clinical practice, pain control not only benefits from these novel methods for a better delivery of various drugs, but the side effects of the drugs are reduced because use of the devices improves patient compliance. Biodegradable controlled-release devices are polymer-based devices that are designed to deliver drugs locally in a predesigned manner. Recently, there was a high interest in developing these devices for the delivery of different drugs used for pain control. This paper first highlights the dimensions and basics of the problem of pain. Then, it presents an overview of the biodegradable polymers that are used in drug delivery systems and summarizes the studies carried out on these systems in the field of pain management. We refer to our experience in developing a device for multimodal drug delivery, including the use of nanotechnology. Future perspectives are also presented.

Absorbable Implants↗
PubMed1999

Development of a biodegradable antibiotic delivery system.

Antibiotic beads have been used as a drug delivery system 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 five types of biodegradable antibiotic beads. The beads were placed in 1 mL of phosphate buffered saline and incubated at 37 degrees C. The phosphate buffered saline was changed daily, and the removed buffer solutions were stored at -70 degrees C until the antibiotic concentration in each sample was determined by high performance liquid chromatography system assay. The concentration of vancomycin in each sample was well above the breakpoint sensitivity concentration (the antibiotic concentration at the transition point between bacterial killing and resistance to the antibiotic) for more than 32 days. The release was most marked during the first 48 hours. All copolymer 50:50 poly(DI lactide):co-glycolide biodegradable beads released high concentrations of the antibiotics in vitro for the time needed to treat bone infections (4 to 6 weeks). The diameter of the sample inhibition zone ranged from 6.5 mm to 10 mm, and the relative activity of vancomycin ranged from 12.5% to 100%. Copolymers with low heat of formation temperatures are required for making a controlled release system to prevent antibiotic decomposition, which occurs when using the hot compressing molded method. The rate and duration of release from the antibiotic beads can be adjusted by varying the diameter of the beads. This offers a convenient method to adjust the release rate to meet the specific antibiotic requirements for different patients.

Absorbable Implants↗
PubMed1990

Growth and differentiation factors: role in bone induction and potential application in craniofacial surgery.

Repair of craniofacial bone often requires autogenous or allogeneic bone. Natural materials deliver bone-inducing substances to wound beds and provide scaffolding for osteoconduction, but not without risk of morbidity. We are developing a synthetic material consisting of proteins which stimulate bone repair encased within a moldable, biodegradable delivery system. The stages of bone induction include chemoattraction of stem cells, proliferation and differentiation of these cells to competent chondrocytes and osteoblasts, angiogenesis, mineralization, and remodeling. Bovine osteogenin induces bone formation in soft tissue in rats, and accelerates bone repair in cranial defects. The protein has been purified and partially sequenced. Growth factors may augment the inductive effects of osteogenin by attracting preosteoblasts, accelerating their proliferation, and stimulating angiogenesis. A composite material of osteogenin and growth factors released from a biodegradable delivery system in a time-dependent fashion is proposed to decrease the necessity for autogenous and allogeneic bone implants.

Bone Morphogenetic Protein 3↗
PubMedDate not supplied

Biodegradable drug delivery system for the treatment of bone infection and repair.

A drug delivery system (DDS) which provides a sustained release of antibiotics at the focal site either singly, or in combination with a bone stimulating factor could both eliminate infection and increase the number of potentially healthy osteogenic cells. In this study, we address the use of a degradable gelatin DDS, for the combined release of therapeutic levels of both gentamicin and growth hormone (GH). An initial bolus release was observed during the first 24 h followed by a reduced, but sustained, release for both drugs up to 14 days. Bioactivity of gentamicin was demonstrated by growth inhibition of Staphylococcus aureus for over 96 h with a mean zone of inhibition of 29.4 mm (+/-0.19) for the time period studied. Furthermore, GH was shown to have a direct effect on primary human osteoblast-like (HOB) cells, stimulating proliferation and enhancing their differentiation. Site-specific drug delivery offers the advantage of localizing a drug directly at the target site, thus minimizing systemic effects. The results of this study suggest that gelatin is a good DDS for the combined release of drugs. In addition, gelatin is both biocompatible and biodegradable, thus making it a promising DDS for the management of acute and chronic bone and tissue infection such as osteomyelitis.

Journal Article↗
PubMed1997

Porous-coated titanium implant impregnated with a biodegradable protein delivery system.

Tissue ingrowth into porous-coated orthopedic and dental implants is commonly used as a means to achieve long-term fixation of these prostheses. However, the degree of tissue ingrowth is often inadequate and inconsistent. If the pores of these implants are impregnated with a controlled drug release system delivering relevant growth factors, then it might be possible to stimulate more tissue ingrowth. The present study introduces such a system based on biodegradable polymers and investigates its protein release profile and polymer degradation characteristics. Porous coated titanium implants were impregnated with a mixture of a 50%-50% polylactic acid-polyglycolic acid copolymer and a model protein, soybean trypsin inhibitor. Control implants contained only the polymer and no protein. The implants were subjected to hydrolytic degradation in phosphate buffered saline at 37 degrees C for periods of 3, 6, and 11 weeks. The protein release and the mass and molecular weight of the polymer were monitored. The results indicate that the protein is released in three distinct phases and the polymer loses almost all its mass and molecular weight by 11 weeks. There was a significant difference in the polymer degradation characteristics between the control and test implants, which might be the result of some complex polymer-protein interactions.

Biocompatible Materials↗
PubMed1996

In vitro release of new quinolones from biodegradable systems: a comparative study.

A new biodegradable delivery system based on low molecular weight poly(lactic acid) has been formulated, with potential application in the sustained antibiotic release against bone infection. The in vitro release of two new quinolones (ofloxacin and ciprofloxacin) from the biodegradable matrix showed that the delivery of ofloxacin from the matrix lasted fifty-six days, whereas that of ciprofloxacin lasted fifty-one days. In both cases, release is controlled by the drug diffusion and the matrix degradation, the latter being the most critical factor. The obtained concentration levels are well above the Minimum Inhibitory Concentration (MIC) against the major causative bacteria of osteomyelitis. This fact in combination with the good reproducibility of measurements indicated that the system studied could be of value for the preparation of implantable controlled release systems for treatment of diseases in the bone system.

Anti-Infective Agents↗
PubMed2000

Biodegradable progesterone microsphere delivery system for osteoporosis therapy.

The purpose of this study was to formulate and characterize a controlled-release biodegradable delivery system of progesterone for the treatment or prevention of osteoporosis. Microspheres of progesterone were formulated using copolymers of poly(glycolic acid-co-dl-lactic acid) (PGLA 50/50 and PGLA 15/85) and poly(L-lactic acid) (L-PLA) of similar molecular weight by the emulsion solvent evaporation technique. The effects of process variables, such as volume fraction, polyvinyl alcohol (PVA) concentration, polymer composition, and stir speed during preparation, on the yield, encapsulation efficiency (EEF), particle size distribution, in vitro release profiles of progesterone, and surface morphology of progesterone microspheres were investigated. Increasing the volume fraction from 9% to 22% increased the EEF without significantly increasing the yield; however, the rate of progesterone release from the microspheres decreased. Increasing the PVA concentration from 1% to 5% had no significant influence on the EEF, but the rate of progesterone release from microspheres increased. Polymer composition had no significant effect on the EEF, but had a significant effect on the particle size distribution, surface morphology, and release rate of progesterone from the microspheres. Stir speed did not have a significant influence on the EEF; however, stir speed influenced particle size distribution and the rate of progesterone release from microspheres of the same sieve-size range. The results suggest that controlled release of progesterone is possible by varying the different process variables, and that PGLA 50/50 provided the slowest release of progesterone. This should provide a means of delivering progesterone for months for the treatment or prevention of osteoporosis in postmenopausal women.

Antimicrobial Cationic Peptides↗
PubMed2001

In vivo-in vitro study of biodegradable methadone delivery systems.

Three one-week controlled-release methadone formulations: polylactic acid microspheres (F-PLA) and poly(lactide-co-glycolide) microspheres (F-PLGA) with 24 and 30% methadone content, respectively, and an implant of 50:50 poly(lactide-co-glycolide): methadone, were evaluated in vitro and in vivo. The implant released the total amount of methadone in vitro while microsphere formulations released the methadone incompletely, 63% from F-PLA and 85% from F-PLGA in a week. Methadone release in vivo was estimated by deconvolution, F-PLGA giving a bioavailability >99% (methadone was totally released in 48h), while the estimated bioavailability of F-PLA was lower than expected. The bioavailability of the implant by deconvolution was around 60%, but absence of methadone in the implant indicated its complete release. These differences are due to an increase in methadone clearance after 72 h of the in vivo experimental period had passed, disturbing a good in vivo-in vitro correlation. A linear correlation between in vitro methadone release and in vivo release calculated from the amount of drug remaining within the implant, was found until the drug was completely released.

Animals↗
PubMed2004

In vitro tobramycin elution analysis from a novel beta-tricalcium phosphate-silicate-xerogel biodegradable drug-delivery system.

This in vitro research analyzed local tobramycin elution characteristics from a novel, biodegradable drug delivery system, consisting of a beta-TCP bone substitute, VITOSS trade mark, encapsulated with silicate xerogel prepared by the sol-gel process. Tobramycin elution from silicate-xerogel-encapsulated VITOSS was compared directly with non-silicate-xerogel-encapsulated VITOSS to assess whether xerogels are effective in delivering greater tobramycin quantities in a controllable, sustained manner crucial for microbial inhibition. Tobramycin elution characteristics indicate an initial release maximum during the first 24 h that diminishes gradually several days after impregnation. The copious tobramycin quantity eluted from the VITOSS/silicate-xerogel systems is attributed to various factors: the intrinsic ultraporosity and hydrophilicity of VITOSS, the ability of tobramycin to completely dissolve in aqueous media, tobramycin complexation with highly polar SO(4) (2-) salts that further assist dissolution, and ionic exchanges between VITOSS and the environment. Silicate-xerogel-encapsulated VITOSS eluted 60.65 and 61.31% of impregnated tobramycin, whereas non-silicate-xerogel-encapsulated VITOSS eluted approximately one-third less impregnated tobramycin, at 21.53 and 23.60%. These results suggest that silicate xerogel optimizes tobramycin elution because of its apparent biodegradability. This mechanism occurs through xerogel superficial acidic sites undergoing exchanges with various ions present in the leaching buffer. Tobramycin elution kinetics were evaluated, and demonstrate that first-order elution rate constants are considerably less when silicate xerogels are employed, following a more uniform exponential decay-type mechanism, thus bolstering controlled release. Overall, tobramycin elution rates adhere to linear-type Higuchi release profiles. Elution rate constants are initially first order, and taper into zero-order elution kinetics in the latter stages of release. Because VITOSS and silicate xerogel are completely biodegradable, essentially all impregnated tobramycin will be delivered to the surgical site after implantation.

Anti-Bacterial Agents↗
PubMed1989

Biodegradable microspheres: vaccine delivery system for oral immunization.

The potential of biocompatible and biodegradable microspheres as a controlled release oral vaccine delivery system has been examined. Orally-administered 1-10 micron microspheres composed of poly (DL-lactide-co-glycolide) were specifically taken up into the Peyer's patch lymphoid tissue of the gut, where those greater than or equal to 5 micron remained for up to 35 days. Microspheres less than 5 micron disseminated within macrophages to the mesenteric lymph nodes and spleen. In contrast to soluble staphylococcal enterotoxin B toxoid, oral immunization with enterotoxoid in microspheres induced circulating toxin-specific antibodies and a concurrent secretory IgA anti-toxin response in saliva and gut fluid.

Administration, Oral↗
PubMed2005

In vitro evaluation of drug release from self micro-emulsifying drug delivery systems using a biodegradable homolipid from Capra hircus.

Self micro-emulsifying drug delivery systems (SMEDDS) are specialized form of delivery systems in which drugs are encapsulated in a lipid base with or without a pharmaceutically acceptable surfactant. In this work, SMEDDS were formulated with a biodegradable homolipid from Capra hircus and Tween 65, and contained lipophilic drug-piroxicam, hydrophilic drug-chlorpheniramine maleate and hydrolipophilic drug-metronidazole. The SMEDDS formulated were evaluated for their drug release and drug content. The drug release studies were conducted in simulated gastric fluid (SGF), simulated intestinal fluid (SIF), and distilled water, representing different pH values. Particle size of the SMEDDS was determined by light microscopy. The results of this study indicated that drug release was affected by the particle size of the SMEDDS. It was found that piroxicam release from the SMEDDS formulated with homolipids from Capra hircus was highest in SIF compared to the other drugs. This method of drug delivery could prove to be a versatile and reliable alternative to conventional drug delivery approaches.

Adipose Tissue↗
PubMed1996

Periodontal pocket treatment in beagle dogs using subgingival doxycycline from a biodegradable system. I. Initial clinical responses.

The present study evaluated the clinical response of periodontal pockets in beagle dogs after treatment with a biodegradable delivery system containing 10% doxycycline hyclate (ABDS-D). Eight adult, female beagle dogs had generalized, severe periodontitis with plaque and calculus-laden pockets. In each animal, 3 teeth with multiple pocket sites > or = 4 mm (mean depth = 6.0 mm) associated with attachment loss (mean = 5.4 mm) and which bled on probing (mean score = 2.5) were treated with a single application of either ABDS-D (experimental group) or the delivery system alone without the doxycycline (control group). Residual polymer was removed at day 7. Bioassay of doxycycline in gingival crevicular fluid associated with presence of ABDS-D gave mean levels of bioactivity of approximately 250 micrograms/ml. Levels of bioactive doxycycline were detected for approximately 7 days after ABDS-D removal. Periodontal maintenance consisted of thrice-weekly toothbrushing the treated sites. Clinical responses were evaluated at 2 weeks, and at bi-weekly intervals thereafter for 4 months. Analyses of the data from the control group showed that there was only slight clinical improvement. In contrast, in the experimental group, bleeding on probing and probing depths were significantly reduced from baseline at all post-treatment time points. At 1 month, mean probing depth reduction was 2.4 mm and this was maintained at 4 months (mean reduction = 2.5 mm). These probing depth reductions occurred primarily through gain of clinical attachment which was 2.0 mm at 4 months. Bleeding had been virtually eliminated (mean = 0.2). It was concluded that, for the beagle dogs with severely infected periodontal pockets in this study, treatment with subgingival doxycycline using the delivery system resulted in substantial improvement in periodontal health.

Administration, Topical↗