Oligochitosan and human serum albumin: Focus on compatibility, protein stability, and antibacterial activity in...

Antimicrobial activity of chitosan in protein media was found only in acidic media, but not in alkaline ones so far in spite of a peculiar interest to the application of chitosan in isotonic protein solution and physiological fluids, containing human serum albumin (HSA). The key goal of this study was to develop chitosan derivatives, in particular those that would not only have antimicrobial activity at physiological level of HSA concentration in solution, but also would not cause changes in the native structure of HSA. As a result, it was shown that N-reacetylated oligochitosan (ROCHI) with molecular weight of about 10 kDa possessed bacteriostatic activity (MIC 0.025÷0.05%) in 0.16÷5.0% isotonic HSA solution with pH 7.4. Turbidimetric titration and dynamic light scattering methods confirmed the absence of complexation and mutual compatibility of HSA with ROCHIs, having a molecular weight of ~10 kDa and DA ranged from 16 to 35%, at ROCHI/HSA weight ratios of q ≤ 0.12 in the medium. The remaining thermal stability and native structure of HSA at q ≤ 0.2 were confirmed by differential scanning calorimetry, circular dichroism and fluorescence emission spectroscopy. The finding could expand the scope of oligochitosan application in complex protein mixtures and physiological fluids.