The encapsulation of ribozymes in biodegradable polymeric matrices

Toward the development of partially biodegradable and injectable thermoresponsive hydrogels for potential biomedical applications

A series of hydrogels containing a biodegradable dextran (Dex) chain grafted with a hydrophobic poly(-caprolactone)-2-hydroxylethyl methacrylate (PCL-HEMA) chain and a thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) chain were synthesized. The molecular weight of PCL-HEMA was determined by gel permeation chromatography, and the inner morphology of the hydrogel was observed by scanning electron microscopy. The release profiles from the hydrogels were investigated using bovine serum albumen as a model drug. It was found that the release behavior could be adjusted by varying the composition of the hydrogel. In vitro cytotoxicity studies of the hydrogels showed that the copolymer Dex-PCL-HEMA/PNIPAAm exhibited low cytotoxicity. The in vivo degradation and histological studies demonstrated that the hydrogels had good biocompatibility and were promising for use as an injectable polymeric scaffold for tissue engineering applications.

Biodegradable microspheres of ketorolac tromethamine for parenteral administration

Ketorolac tromethamine loaded microspheres were prepared using two different polyesters, namely poly (lactic acid) and poly (glycolic acid) by solvent evaporation technique. The morphology of microspheres was analysed by scanning electron microscopy. In vitro release profiles of these microspheres were studied in phosphate buffered saline pH 7.4. The release kinetics of ketorolac tromethamine from the microspheres was evaluated by fitting the release data to the zero-order, Higuchi and korsemeyer-peppas equations. All microspheres showed initial burst release, followed by fickian diffusion of drug through microspheres. These microspheres were formulated as parenterals to have controlled release system.

Magnetic poly epsilon-caprolactone nanoparticles containing Fe3O4 and gemcitabine enhance anti-tumor effect in pancreatic cancer xenograft mouse model

We prepared magnetic (Fe(3)O(4)) poly epsilon-caprolactone (PCL) nanoparticles (mean diameter 164 +/- 3 nm) containing an anticancer drug (gemcitabine) using emulsion-diffusion method in order to develop more efficient drug delivery for cancer treatment. Nanoparticles were smooth, well individualized and homogeneous in size. The values of magnetizations for the magnetic PCL nanoparticles were observed around 10.2 emu/g at 2000 Oe magnetic field intensity and showed super-paramagnetic property. In case of the drug, the drug loading contents was 18.6% and entrapment efficiency was 52.2%. The anti-tumor effects caused by these particles were examined using nude mice bearing subcutaneous human pancreatic adenocarcinoma cells (HPAC) in vivo. We divided that these mice were randomly assigned to one of five treatment groups for experimental contrast. The antitumor effect was showed with 15-fold higher dose when compared to free gemcitabine. From the result, the magnetic PCL nanoparticles may provide a therapeutic benefit by delivering drugs efficiently to magnetically targeted tumor tissues, thus achieving safe and successful anti-tumor effects with low toxicity.

Enzymatic biodegradable micro-reactors for therapeutic applications

Poly(epsilon-caprolactone) is a well known biocompatible polymer, widely used as drug immobilization systems. In this work poly(epsilon-caprolactone) microparticles with average size between 5 and 25 microm have been prepared by O/W emulsion evaporation method. Inside the microparticles, we have encapsulated Glucose Oxidase with the aim of preparing micro-reactors for enzymatic therapy. These microparticles were structurally characterized and its enzymatic activity analyzed in order to improve the enzyme entrapment. Thus, at the optimum synthesis conditions the enzyme entrapped in the microparticles showed an enzymatic activity of (29.9 +/- 2.1)% comparing with the same amount of free enzyme. Moreover the microparticles maintained a (70.4 +/- 3.2)% of their initial enzymatic activity after placing them in buffer solution for two weeks.

Gene targeting by ribozyme against TNF-alpha mRNA inhibits autoimmune arthritis

Ribozymes are catalytic RNA that bind and cleave specific regions of target RNA. Therefore, protein synthesis by the target RNA may be specifically inhibited by ribozymes. In this study, we have investigated if ribozymes possess therapeutic activity on inflammatory processes in vivo, as judged from effects on an arthritis model. A hammerhead ribozyme against TNF-alpha was designed and its catalytic activity in vitro was verified. The ribozyme was employed in vivo without any delivery system, as the plasmid-based ribozyme was taken up adequately by various tissues in mice by intravenous injection. The ability of the ribozyme to regulate the development of collagen-induced arthritis (CIA), a model largely dependent on TNF-alpha, was investigated. Systemic administration of the ribozyme to mice immunized with collagen type II in CFA significantly reduced the development of CIA. No effect was observed with a catalytically inactive variant of the ribozyme. Furthermore, the ribozyme efficiently blocked cartilage and bone destruction in the joints and ameliorated established CIA. These data demonstrate for the first time that gene targeting by a ribozyme to inactivate TNF-alpha in vivo is highly efficient in suppressing autoimmune arthritis, thus providing proof of concept that it may be used as therapeutic tool for TNF-alpha-dependent chronic inflammatory disorders.

Poly-epsilon-caprolactone microspheres and nanospheres: an overview

Poly-epsilon-caprolactone (PCL) is a biodegradable, biocompatible and semicrystalline polymer having a very low glass transition temperature. Due to its slow degradation, PCL is ideally suitable for long-term delivery extending over a period of more than one year. This has led to its application in the preparation of different delivery systems in the form of microspheres, nanospheres and implants. Various categories of drugs have been encapsulated in PCL for targeted drug delivery and for controlled drug release. Microspheres of PCL either alone or of PCL copolymers have been prepared to obtain the drug release characteristics. This article reviews the advancements made in PCL-based microspheres and nanospheres with special reference to the method of preparation of these and their suitability in developing effective delivery systems.

Engineering of RNase P ribozyme for gene-targeting applications

Ribonuclease P (RNase P) is a ubiquitous ribonucleoprotein complex responsible for the biosynthesis of tRNA. This enzyme from Escherichia coli contains a catalytic RNA subunit (M1 ribozyme) and a protein subunit (C5 cofactor). M1 ribozyme cleaves an RNA helix that resembles the acceptor stem and T-stem structure of its natural tRNA substrate. When covalently linked with a guide sequence, M1 RNA can be engineered into a sequence-specific endonuclease, M1GS ribozyme, which can cleave any target RNA sequences that base pair with the guide sequence. Recent studies indicate that M1GS ribozymes efficiently cleave the mRNAs of herpes simplex virus 1, human cytomegalovirus, and cancer causing BCR-ABL proteins in vitro and effectively inhibit the expression of these mRNAs in cultured cells. Moreover, RNase P ribozyme variants that are more active than the wild type M1 RNA can be generated using in vitro selection procedures and the selected variants are also more effective in inhibiting gene expression in cultured cells. These results demonstrate that engineered RNase P ribozymes represent a novel class of promising gene-targeting agents for applications in both basic research and clinical therapy. This review discusses the principle underlying M1GS-mediated gene inactivation and methodologies involved in effective M1GS construction, expression in vivo and emerging prospects of this technology for gene therapy.

Biodegradable microspheres for protein delivery

In a very short time, since their emergence, the field of controlled delivery of proteins has grown immensely. Because of their relatively large size, they have low transdermal bioavailabilities. Oral bioavailability is generally poor since they are poorly absorbed and easily degraded by proteolytic enzymes in the gastrointestinal tract. Ocular and nasal delivery is also unfavorable due to degradation by enzymes present in eye tissues and nasal mucosa. Thus parenteral delivery is currently most demanding and suitable for delivery of such molecules. In systemic delivery of proteins, biodegradable microspheres as parenteral depot formulation occupy an important place because of several aspects like protection of sensitive proteins from degradation, prolonged or modified release, pulsatile release patterns. The main objective in developing controlled release protein injectables is avoidance of regular invasive doses which in turn provide patient compliance, comfort as well as control over blood levels. This review presents the outstanding contributions in field of biodegradable microspheres as protein delivery systems, their methods of preparation, drug release, stability, interaction with immune system and regulatory considerations.