Asymmetrical flow field-flow fractionation for the analysis of PEG-asparaginase

Asymmetric flow field-flow fractionation as a multifunctional technique for the characterization of polymeric nanocarriers

The importance of polymeric nanocarriers in the field of drug delivery is ever-increasing, and the accurate characterization of their properties is paramount to understand and predict their behavior. Asymmetric flow field-flow fractionation (AF4) is a fractionation technique that has gained considerable attention for its gentle separation conditions, broad working range, and versatility. AF4 can be hyphenated to a plurality of concentration and size detectors, thus permitting the analysis of the multifunctionality of nanomaterials. Despite this potential, the practical information that can be retrieved by AF4 and its possible applications are still rather unfamiliar to the pharmaceutical scientist. This review was conceived as a primer that clearly states the "do's and don'ts" about AF4 applied to the characterization of polymeric nanocarriers. Aside from size characterization, AF4 can be beneficial during formulation optimization, for drug loading and drug release determination and for the study of interactions among biomaterials. It will focus mainly on the advances made in the last 5 years, as well as indicating the problematics on the consensus, which have not been reached yet. Methodological recommendations for several case studies will be also included.

Bacillus sonorensis L. Asparaginase: Cloning, Expression in E. coli and Characterization

L-asparaginases (L-ASNases; EC 3.5.1.1) are aminohydrolases that catalyze the hydrolysis of L-asparagine (L-Asn) to L-aspartic acid and ammonia, resulting in the death of acute lymphoblastic leukemic cells and other blood cancer cells. In this study, Bacillus sonorensis (accession number MK523484) uncharacterized L-ASNase gene (accession number MN562875) was isolated by polymerase chain reaction (PCR), cloned into pET28a (+) vector, and expressed in Escherichia coli as a cytosolic protein. The recombinant enzyme was purified by affinity chromatography at 23.79-fold and 49.37% recovery. Denaturing polyacrylamide gel (10%) analysis of the purified enzyme resulted in a single protein band at 36 kDa that immunoreacted strongly with 6His-tag monoclonal antibody. The purified enzyme exhibited optimal activity at 45 °C and pH 7.0 and retained 92% and 85% of its initial activity after incubation for 60 min at 37 °C and 45 °C, respectively. The purified enzyme exhibited substrate specificity toward L-asparagine and low glutaminase activity (15.72%) toward L-glutamine at a concentration of 10 mM. The Km and Vmax values were 2.004 mM and 3723 µmol min^1-, respectively.