Untitled

Abstract

The process of microencapsulation of proteins by double emulsion/evaporation in a matrix of polylactide (PLA) can be divided into three successive steps: first, an aqueous solution of the active compound is emulsified into an organic solution of the hydrophobic coating polymer; second, this primary water-in-oil emulsion (w/o) is dispersed in water with formation of a double water-oil-water emulsion (w/o/w); third, the organic solvent is removed with formation of solid microparticles. This paper focuses on the effect of primary emulsion stability on the morphology and properties of polylactide microparticles loaded with bovine serum albumin (BSA) used as model drug. Depending on the stability of the primary emulsion, the internal structure of microparticles can be changed from a multivesicular to a matrix-like structure. Similarly, the average porosity can be controlled in a range from a few tenths of a micron to ca. 20 to 30 microns. This morphology control could find potential applications not only for the controlled drug delivery but also for the production of microporous particles intended for some specific applications, such as cell culture supports and chromatographic matrices. Although, the interplay of several processing parameters (polymer precipitation rate, polymer coprecipitation with interfacial compounds such as protein or surfactant, stirring rate...) may not be disregarded, this study also indicated that a high loading of a hydrophilic drug can only be expected from a stable primary emulsion. When the stability of the primary emulsion is such as to prevent formation of macropores (> 10 microns), the total pore volume is close to that of the originally dispersed aqueous drug solution.

Inhaled sildenafil as an alternative to oral sildenafil in the treatment of pulmonary arterial hypertension (PAH)

“…3A). As we have discussed previously [21, 23], PEI, a polycation, may have increased the drug entrapment efficiency by increasing the stability of IAP [37] and by interacting with negatively charged sildenafil [38]. …”

Síntese e caracterização de copolímeros do tipo ABA para encapsulação de hemoglobina bovina

“…Consequentemente, o valor de EE% pode ser afetado pelos seguintes fatores: estabilidade da emulsão w/o e w/o/w; taxa de remoção de solvente; interações entre polímeros, componente ativo, solventes e aditivos e, tamanho de partícula. 38,40,41 Além disso, esses fatores são influenciados pela natureza hidrofílica/hidrofóbica dos materiais utilizados para a preparação de microesferas.…”

Polímeros sintéticos biodegradáveis: matérias-primas e métodos de produção de micropartículas para uso em drug delivery e liberação controlada

“…Estas podem consistir em emulsões simples -do tipo O/A [34,35] ou O/O [36,37] ou em emulsões múltiplas do tipo A/O/A [38][39][40] . A primeira etapa do processo consiste na obtenção da emulsão, na qual uma das fases é constituída por uma solução de um polímero de natureza hidrófobica num solvente adequado.…”