Preparation, Characterization and Optimization of Chitosan Nanoparticles as Carrier for Immobilization of Thermophilic Recombinant Esterase
(713-721) Journal of Macromolecular Science Part A - Pure and Applied Chemistry 48 #9 (2011)
Abstract
İlgü, Turan and Mohamed obtained  thermophilic esterase enzyme using recombinant DNA technology and purified applying one-step His-Select HF nickel affinity gel. The synthesis of chitosan was achieved from chitin by deacetylation process and degree of deacetylation was calculated as 89% by elemental analysis.  Chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions.  The morphology of chitosan nanoparticles was spherical and the nanospheres’ average diameter was 75.3 nm.  The purified recombinant esterase was immobilized efficiently by physical adsorption onto chitosan nanoparticles and effects of various immobilization conditions were investigated in details to develope highly cost-effective esterase as a biocatalyst to be utilized in biotechnological purposes. The optimal conditions of immobilization were determined as follows; 1.0 mg/mL of recombinant esterase was immobilized on 1.5 mg chitosan nanoparticles for 30 min at 60°C, pH 7.0 under 100 rpm stirring speed. Under optimized conditions, immobilized recombinant esterase activity yield was 88.5%. (RDC 8/2/2011)

Chitosan–polycaprolactone microspheres as carriers for delivering glial cell line-derived neurotrophic factor
(925-932) Reactive and Functional Polymers 71 #9 (2011)
Wu et al, China, synthesized chitosan–polycaprolactone (CH–PCL) copolymers with brush-like chain structures.  Some CH–PCLs with a PCL content less than 50 wt% were used to build glial cell line-derived neurotrophic factor (GDNF)-loaded microspheres via an emulsification method using genipin as a cross-linker.  The resulting microspheres were spherical with a smooth surface and a diameter less than 40 μm; however, their loading efficiency could be higher than 80% if crosslinked properly.  These microspheres had various swelling characteristics in lysozyme-containing PBS, which mainly depended on the PCL content, and they did not exhibit significant degradation up to 3 weeks.  It is found that the PCL content in the CH–PCLs predominantly governed GDNF releases from some optimal microspheres and that the amount of cross-linker imposed limited impacts on the release behavior.  Release kinetics revealed that GDNF release from microspheres was controlled by anomalous mechanisms involving Fickian diffusion and case-II transport.  Some microspheres with an initial loading ratio of approximately 5-ng GDNF to 1.0-mg dry microsphere had sustained GDNF release upon addition of a simulant in vivo medium; an approximate linear rate of release was observed, which lasted over 4 weeks, was controllable and did not involve a significant burst release.  (RDC 8/4/2011)