Monitoring thermal,structural properties,methotrexate release and biological activity from biocompatible spray-dried microparticles

Boron phosphates (BPs) with different acidities were prepared by regulating the calcination temperatures for the reaction products of boric acid and phosphoric acid. The crystal structure, morphology, surface acidity, and thermal stability were characterized by X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), chemical absorbed apparatus, and thermogravimetric analysis (TG). The effects of BPs on the combustion behavior and catalyzing the carbonization of bisphenol-A epoxy resin (EP) were investigated by the limiting oxygen index (LOI) and cone calorimetry test. Upon loading 5 mass% BP prepared at 300 °C, the LOI value of the EP/BP composites increased to 29.6%, and moreover, the peak heat release rate and average specific extinction area decreased by 43 and 25%, respectively. A possible catalyzing carbonization mechanism was explored by TG coupled with Fourier transform infrared spectroscopy (TG–FTIR), TG, FTIR, SEM, Raman spectroscopy (Raman), and XPS. The results demonstrated that BP catalyzed EP to degrade at relatively low temperature, and the yield, compactness, and graphitization degree of the char residue were obviously enhanced with an increase in the ratio of Brønsted and Lewis acid sites (B/L value) and the total surface acid sites on the BP surface. Therefore, the catalyzing carbonization flame retardancy of the EP/BP composites can be improved through regulating the surface acidity of BP.     

Structural and thermal properties of spray-dried methotrexate-loaded biodegradable microparticles

Drug–polymer interactions, structural properties, thermal behavior, and stability of biodegradable microparticles are fundamental aspects in the developing of new polymeric drug delivery systems. In this study, poly (d,l-lactide-co-glycolide) (PLGA) microparticles containing methotrexate (MTX) were successfully obtained by spray drying. Scanning electronic microscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction (XRD), and drug-loading efficiency were used to investigate the effect of drug–polymer ratio and its interactions, in a new MTX-loaded PLGA spray-dried microparticles. High levels of encapsulation efficiency (about 90 %) and a prevalent spherical shape were identified for different drug–polymer ratios used (9, 18, and 27 % m/m). The thermal analyses (DSC and TG) and XRD indicate that MTX is homogeneously distributed in the polymeric matrix, with a prevalent amorphous state in a stable molecular dispersion. Therefore, a correlation between drug content and the structural-thermal properties of drug-loaded PLGA microparticles was established using the thermal analysis data. The biodegradable microparticle leads to an increment of thermal stability of MTX, confirming that spray drying is an efficient process for obtaining MTX-loaded PLGA microparticles.     

Compatibility study between chitosan and pharmaceutical excipients used in solid dosage forms

Microcrystalline cellulose is an excipient widely used in solid dosage forms as adsorbent, suspending agent, diluent, and disintegrant, depending on the percentage employed in the formulation. The structural similarity between cellulose and chitosan and the ecological advantage in the manufacturing process of chitosan have justified and reinforced the study of this polysaccharide as a novel pharmaceutical excipient. Nevertheless, it still does not appear to be present as constituent in any marketed medicine due to the absence of regulatory hurdles to standardize its physicochemical and functional specifications as well as its compatibility with other formulation ingredients. The physical compatibilities between chitosan and the most excipients used in solid dosage forms, such as diluents (microcrystalline cellulose, starch, lactose monohydrate, dicalcium phosphate dihydrate, and calcium carbonate), disintegrants (sodium starch glycolate, and croscarmellose sodium), and glidants (magnesium stearate, talc, sodium lauryl sulfate, and colloidal silicon dioxide), were studied by thermal analysis and FT-IR. In order to facilitate the IR spectra interpretations, an ad hoc algorithm was used to generate theoretical spectra to be compared with the respective experimental ones. Chitosan proved to be physically compatible with microcrystalline cellulose, starch, lactose, sodium starch glycolate, croscarmellose sodium, talc, colloidal silicon dioxide, and sodium lauryl sulfate. Moreover, chitosan raises the thermal stability of cellulose from 310 to 330 °C. Once the amino groups of chitosan were able to form coordination complexes with divalent cations of dicalcium phosphate dihydrate, calcium carbonate, and magnesium stearate, they were considered incompatible with chitosan.