Authors: N. Dwivedii, M.A. Arunagirinathan, S. Sharma, J. Bellare
Affilation: Indian Institute of Technology Bombay, India
Pages: 770 - 773
Keywords: nanoparticle-protein interactions
Silica-insulin nanocomposite (SINC) and ferrite coated SINC (FeSINC) prepared by polyelectrolytic condensation of silica precursor on insulin were studied to control the glucose level. Silica precursor which has a negative charge binds to insulin that is polycationic at pH 2 thereby forming nanoparticles of silica insulin nanocomposite. Silica nanosphere obtained in the presence of soft template is well known1. It is established that silica coating is chemically inert, biocompatible, hydrophilic and inexpensive. Proteins find more stable environment upon encapsulation in a silica host2, because of polymeric silica frame that grows around the macromolecule which protects insulin from denaturation. SINC was prepared by the formation of silica layer over insulin using tetra ethyl ortho silicate (TEOS) by acid- base catalysed polymerization at room temperature by modified Stober’s process in the presence of ethanol. FeSINC nanoparticles were prepared by co-precipitation of both ferric and ferrous salts above the bovine insulin loaded silica nanoparticle. The nanoparticles of SINC (Fig. 2) and FeSINC (Fig. 3) were 100-200 nm while the silica nanoparticles in the absence of insulin (Fig. 1) were less than 50 nm as observed under TEM. The increase in particle size of these silica nanocomposites can be attributed to the fusion of particles due to polyelectrolytic condensation of silica on insulin in SINC and FeSINC. The insulin encapsulation efficiency was 50 % and 20 % for SINC and FeSINC respectively as quantified through HPLC. The presence of ferrite coating in FeSINC was identified from ESR and electron dense regions in electron micrograph (Fig. 3). In addition, the intermolecular interactions between ferrite, silica and insulin in these nanocomposites were studied by FTIR. The chemical stability of insulin encapsulated in the SINC and FeSINC was confirmed from disulfide and amide stretching spectral characteristic of insulin by Confocal Micro Raman spectroscopy3. Subcutaneous study of SINC and FeSINC in Wistar rats indicated that FeSINC was biologically active in reducing the glucose level as compared to standard bovine insulin (Fig. 4). Presence of stable outer silica layer in these nanocomposites prevents complete release of entrapped insulin thus decreasing the availability of insulin for glucose reduction. Since the ferrite particles enhance the absorption via transferrin receptors present in gut and proceeds through portal vein to liver, the target delivery of FeSINC can be studied for oral delivery of insulin.