Metformin hydrochloride (MetHCl) is a drug extensively used to treat diabetes mellitus Type 2. However, its high hydrophilicity drastically reduces its metabolic absorption. Consequently, high drug concentrations should be taken by patients to achieve the desired therapeutical efficiency, causing several side effects. The present study proposes the development of a MetHCl sustained release biopolymeric system composed of poly(L-lactic acid) (PLLA) and carboxymethyl cellulose (CMC) as a strategy to minimize the problems aforementioned. The PLLA-CMC microparticles were produced by the double emulsion-solvent evaporation technique using two distinct emulsifiers in the first emulsion (Span 80 and Tween 80). The microparticles were characterized by ultraviolet-visible spectrophotometry, scanning electron microscopy with field emission gun, thermogravimetric analyses, and differential scanning calorimetry (DSC). Additionally, in vitro drug release assays were performed. The results demonstrated that the emulsion stability and encapsulation efficiency increased in a dependent fashion way with the CMC concentration. DSC findings showed that the choice of the emulsifier of the first emulsion influences the polymer particle's crystallinity and, consequently, the releasing behavior of the drug. The in vitro studies revealed that the encapsulation of MetHCl in PLLA-CMC microparticles is a promising sustained release system compatible with a zero-order kinetic mechanism.

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