Microencapsulation of protein into biodegradable matrix: a smart solution cross-linking technique.

Sustained-release albumin microspheres (MSs) can be obtained by chemically cross-linking albumin. However, a significant challenge is preventing the cross-linking of the active pharmaceutical (protein or small molecule) ingredient (API) with the MS matrix. To prevent cross-linking of the API with the albumin matrix, a smart "solution cross-linking-microencapsulation" method was developed which involves cross-linking albumin solution with glutaraldehyde first, neutralizing any excess glutaraldehyde with sodium bisulphite, followed by the addition of API and finally spray drying. Using lysozyme as model API, MS formulations FL1 and FL2 were prepared and characterized. Physicochemical characterization using FT-IR and bioactivity evaluation indicate that microencapsulated API did not undergo any significant change in its native structure and the bioactivity was preserved during the formulation processing. Preliminary immunogenicity potential of the cross-linked albumin matrix determined by in vivo studies did not show any significant increase in antigen-specific serum-IgG levels, implying safety and biocompatibility of the cross-linked albumin matrix.

Formulation and in vitro characterization of spray-dried antisense oligonucleotide to NF-kappaB encapsulated albumin microspheres.

The aim of this study was to formulate and characterize microspheres containing antisense oligonucleotide to NF-kappaB using bovine serum albumin as the polymer matrix. Microspheres were prepared by spray-drying technique with 5, 10 and 15% drug loading. Glutaraldehyde was used as a cross-linking agent. The particle sizes ranged from 3-5 microm. Microspheres were smooth and spherical in shape, as determined by scanning electron microscopy (SEM). The yield of microspheres ranged from 70-75% and the encapsulation efficiencies were found to be in the range of 59-60%, as determined by a novel HPLC method. Zeta potential of the microspheres ranged between -39 to -53 mV, thus indicating good suspension stability in water. In-vitro release studies performed using phosphate buffer saline demonstrated extended drug release up to 72 h. Kinetic model fitting showed high correlation with the Higuchi model, suggesting that the drug release was primarily diffusion controlled.

Oral delivery of gastro-resistant microencapsulated typhoid vaccine.

Oral vaccination has long been regarded as the best alternative to conventional parenteral vaccination considering practical, economical, and immunological aspects. The purpose of this study was to develop albumin-chitosan mixed matrix microsphere-filled coated capsule formulations of Typhoid Vi antigen and to determine whether it can induce antigen-specific mucosal and systemic immune responses on oral administration. Formulations with Typhoid Vi antigen were prepared and filled into hard gelatin capsules (size # 9) and enteric coated. Formulations were characterized and administered to Sprague-Dawley rats to evaluate the induction of immune response to the antigen. The results indicated that the particle size, zeta potential, swelling, and disintegration rates were optimal for the oral delivery of microencapsulated vaccines. In vivo studies displayed multifold increase of antigen-specific IgG and IgA levels 8 weeks after oral immunization. No statistically significant difference in the antigen-specific IgG and IgA levels were found between oral and parenteral injection groups 8 weeks after vaccination. On the basis of the results of the study, it can be concluded that the oral administration of Typhoid Vi antigen microspheres was successful in inducing antigen-specific systemic and mucosal immune response.

Oral delivery of low molecular weight heparin microspheres prepared using biodegradable polymer matrix system.

Parenteral route is preferred for low molecular weight heparin (LMWH) due to poor oral bioavailability. Biodegradable formulation components were evaluated for possible interactions between the physical mixtures using differential scanning calorimetry. LMWH and an absorption enhancer papain were encapsulated in bovine serum albumin matrix and four formulations were spray-dried (MS.1, MS.2, MS.3, MS.4). Formulations were evaluated for product yield, particle size, particle charge and encapsulation efficiency. In vitro release assessed in pH 7.2 phosphate buffer saline (PBS) revealed a burst release effect (60%) for all the formulations except MS.1. In vivo studies performed in male Sprague Dawley rats showed an enhancement in drug absorption for the MS.2 and MS.3 formulations because of papain action on paracellular tight junctions. A significant increase in LMWH oral bioavailability was demonstrated by MS.3 (21%), among the formulations encapsulated with papain.

Treatment of adjuvant arthritis using microencapsulated antisense NF-κB oligonucleotides.

Antisense oligonucleotides are promising new therapeutic agents used to selectively inhibit target genes such as Nuclear Factor Kappa B (NF-κB), an important transcription factor in the pathogenesis of inflammatory disease. The purpose of the present study was to evaluate microencapsulated antisense oligonucleotides specific to NF-κB for in vitro efficacy and treatment of adjuvant-induced arthritis in rats. Oligonucleotide-loaded albumin microspheres were prepared and characterized in terms of size, zeta potential, morphology and release pattern. This study reports significant NF-κB inhibition in vitro after treatment with microencapsulated antisense oligonucleotides. Furthermore, microencapsulated antisense NF-κB oligonucleotides were found to inhibit paw inflammation associated with rat adjuvant-induced arthritis in a dose-dependent manner. Taken together, the results presented in this work described albumin microspheres to be effective delivery vehicles for antisense NF-κB oligonucleotides and a potential treatment for inflammatory diseases.

Formulation and evaluation of albumin microspheres and its enteric coating using a spray-dryer.

This study optimized and evaluated the conditions for surface coating of microspheres using a spray-dryer. Four formulations of Bromophenol blue (BPB)-loaded albumin microspheres were prepared using a spray-dryer, cross-linked at different concentrations and time periods. One of the optimized formulations with the desired characteristics was selected for enteric coating with Eudragit L100-55. The procedure involved suspending BPB microspheres in polymer solution and spray-drying it. Four enteric coated formulations were prepared with different concentrations of microspheres in suspension (0.25 and 0.5%w/v) and polymer concentrations (0.25 and 0.5%w/v). Change in the mean particle size after coating was determined using a Laser Particle Counter. The surface coating technique employed did not significantly increase the particle size. Enteric coating efficiency was determined in simulated gastric fluid. Compared to the uncoated microspheres the cumulative amount of drug released from coated microspheres was significantly lower for 3 h, implying efficient surface coating.