Evaluation of polyelectrolyte and emulsion covalent crosslink of chitosan for producing mesalasine loaded submicron particles

This study evaluates various techniques for producing mesalamine (5ASA)-loaded particles employing chitosan as a biopolymer: (1) the polyelectrolyte complexation of chitosan with phthalate hypromelose (HP), (2) the chemical crosslinking of chitosan with genipin and (3) the water-in-oil emulsion method associated with chemical crosslinking with genipin. Systems were characterized by dynamic light scattering, zeta potential (ζ), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and a drug release profile. Method (1) was efficiently produced unloaded nanoparticles (491 nm, PdI=0.26 and ζ = 23.2), but the conditions for chitosan and HP cross-linking enhanced the precipitation of 5ASA. Method (2) caused the degradation of the drug. Method 3 produced sub-micron and microparticles, thereby varying the agitation method; 3 h magnetic agitation resulted in 2692 nm, Pdi = 0.6 and ζ = 46, while Ultra-Turrax, 5 min produced submicron particles (537 nm, PdI = 0.6). The percentage yield was approximately 50%, which is very satisfactory considering the impossibility of encapsulating 5ASA using other methods. FTIR showed the covalent interaction of chitosan and genipin. The drug release was rapid in acidic fluid, but in neutral pH a slower release was obtained in the initial stage, followed by rapid release, which may ensure the controlled release of 5ASA in the colon.

A novel approach in mucoadhesive drug delivery system to improve zidovudine intestinal permeability

ABSTRACT Zidovudine (AZT) mucoadhesive solid dispersions (SD) were prepared using a sodium starch glycolate (SSG) and hypromellose phthalate (HPMCP) mixtures as carrier to enhance the intestinal permeability and bioavailability of zidovudine. SDs were prepared using the co-precipitation method followed by solvent evaporation and characterized according to their physicochemical properties such as particle size, crystallinity, thermal behavior, and liquid uptake ability. In vitro drug dissolution, mucoadhesiveness and AZT intestinal permeability were also determined. Thermal behavior and X-ray diffraction patterns demonstrated the amorphous state of AZT in SD systems. The HPMCP polymer restricted the liquid uptake ability in the acid medium; however, this property significantly increased with higher pH values. SDs allowed drug dissolution to occur in a controlled manner. HPMCP decreased the dissolution rates in the acid medium. The mucoadhesiveness of SDs was demonstrated and the permeability of AZT carried in solid dispersions was significantly improved. The effect of the SD carrier polymers on blocking efflux pump can be an important approach to improve the bioavailability of AZT.

Avaliação da pectina fosfatada aplicada na formação de filmes isolados: material candidato a novos sistemas para liberação modificada de fármacos / Phosphated pectin application in the development of films for drug delivery systems: evaluation of permeability properties and swelling

Pectina fosfatada (Pect-TMFT) juntamente com o α-Gluco-oligossacarídeo (Bioecolians®) foram incorporados à dispersão aquosa de polimetacrilato (Eudragit® RS 30 D) para obtenção de filmes isolados pelo processo "casting" (50 ºC) em placa de Teflon®. A Pect-TMFT e o Bioecolians® foram adicionados à dispersão de Eudragit® RS 30 D nas concentrações: 90: 05: 05, 80: 10: 10 e 70: 20: 10 (4 por cento p/v). Citrato de trietila (TEC) foi utilizado como plastificante (20 por cento da massa do polimetacrilato). As dispersões propostas apresentaram habilidades filmogênicas. Os filmes isolados foram caracterizados pela determinação da permeabilidade ao vapor d'água (TVA), pelo índice de intumescimento (Ii por cento) em fluidos de simulação gástrica (FSG) e intestinal (FSI) e por microscopia eletrônica de varredura (MEV). O aumento do polissacarídeo modificado e do Bioecolians® nos filmes favoreceram a permeabilidade ao vapor d'água e o grau de hidratação quando em FSI (pH= 6,8). Dessa forma, o filme 70: 20: 10, poderá impedir a liberação prematura do fármaco em regiões superiores do TGI quando aplicado como revestimento de sistemas sólidos orais. Além disso, a presença da Pect-TMFT e do Bioecolians®, poderá favorecer a degradação específica da película por enzimas produzidas pela microflora colônica, possibilitando uma cinética de liberação modificada de fármacos apesar das variações inter-individuais de pH que possam existir.

Phosphated pectin (Pect-TMFT) together with α-gluco-oligossacaride (Bioecolians®) were incorporated into aqueous dispersion of polymethacrylate (Eudragit® RS 30 D) to obtain free films by the casting process (50ºC) in Teflon® plate. Pect-TMFT and Bioecolians® were added into dispersions of Eudragit ® RS 30 D at different rates: 90:05:05, 80:10:10 and 70:20:10 (4 percent p/v). Triethyl citrate (TEC) was used as plasticizer (20 percent of mass of the polymethacrylate). The proposed dispersions showed film formation ability. The free films were characterized by the determination of water vapour transmission (WVT), by the swelling index (Ii percent) in fluids of gastric simulation (FGS) and intestinal (FIS) and by scanning electron microscopy (SEM). The increase of modified polysaccharide and Bioecolians® in the films favored their permeability to the water vapour and their hydration degree when in FIS (pH = 6.8). In that way, the obtained film in the concentration 70:20:10, can prevent the premature release of the drug in the up GIT when applied to develop oral solid systems coating. Besides, the presence of Pect-TMFT and Bioecolians® can contribute to the specific membrane degradation by colonic microflora enzymes, making possible a modified release kinetics of drugs even with the existence of inter-individual variations of pH.