Preparation of double-encapsulated microcapsules for mitigating drug loss and extending release

Design and evaluation of niacin microspheres

Present study aims to prepare and evaluate niacin microspheres. Niacin-ethyl cellulose microspheres were prepared by water-in-oil-in-oil double emulsion solvent diffusion method. Spherical, free flowing microspheres having an entrapment efficiency of 72% were obtained. The effect of polymer-drug ratio, surfactant concentration for secondary emulsion process and stirring speed of emulsification process were evaluated with respect to entrapment efficiency, in vitro drug release behavior and particle size. FT-IR and DSC analyses confirmed the absence of drug-polymer interaction. The in vitro release profile could be altered significantly by changing various processing and formulation parameters to give a controlled release of drug from the microspheres. The percentage yield was 85%, particle size range was 405 to 560 μm. The drug release was controlled for 10 h. The in vitro release profiles from optimized formulations were applied on various kinetic models. The best fit with the highest correlation coefficient was observed in Higuchi model, indicating diffusion controlled principle. The in vitro release profiles of optimized formulation was studied and compared with commercially available niacin extended release formulation.

Multilayer microcapsules as anti-cancer drug delivery vehicle: deposition, Sustained release, and in vitro bioactivity

A drug delivery system based on spontaneous deposition of soluble, low-molecular-weight therapeutic agents has been developed for the purpose of sustaining drug release. Layer-by-layer assembly of oppositely charged polyelectrolytes onto melamine formaldehyde (MF) colloidal particles, followed by removal of the cores at low pH has yielded intact hollow microcapsules having the ability to induce deposition of various water-soluble substances. Dynamic observation by confocal laser scanning microscopy provided direct evidence of such deposition. Dependence of loading rate on molecular weight was investigated. Efficient loading of an anti-cancer drug, daunorubicin (DNR), was confirmed by transmission electron microscopy (TEM). Its release was quantified by fluorometry. The results indicated that loading, and subsequent release, could be tuned by factors such as feeding concentrations, temperature, and salt concentrations. The intrinsic mechanism of loading and release was discussed taking into account the interaction between the drugs and the poly(styrene sulfonate)/MF complex existing in the hollow capsules. With culture of the HL-60 cell line, a kind of human leukemia cell, the presence of DNR-loaded capsules was seen to steadily decrease the cyto-viability. Fluorescence intensity averaged from inside the circles as a function of incubation time.

Binding of 3-isobutyl-1-methylxanthine into copolymers of N-isopropylacrylamide

Linear and crosslinked copolymers based on N-isopropylacrylamide, NIPAAm, containing aromatic esters, have been synthesised. Vinyl benzoate and cinnamoyloxyethyl methacrylate have been used as aromatic comonomers. Certain aromatic esters are known of their capability to form molecular complexes with xanthines and thus, the purpose was to build up thermally responsive copolymers which specifically bind certain xanthines in aqueous solutions and release those under an influence of an environmental stimulus. The solutions of the linear copolymers have been studied in water in the presence of 3-isobutyl-1-methylxanthine, IBMX, as a function of drug concentration and temperature. The synthesised linear copolymers exhibited sensitivity to IBMX concentration in aqueous solutions above and below LCST, observed by viscosimetry and dynamic light scattering. The results are indicative of complex formation between the copolymers and IBMX. The crosslinked copolymers showed an increased IBMX binding capacity with an increasing amount of aromatic ester groups in the polymer network. IBMX release rates from the crosslinked gels were slowed down by the increasing degree of aromatic substitution, especially above LCST.