There has been a great interest in application of nanoparticles as biomaterials for delivery of therapeutic molecules such as drugs and genes, and for tissue engineering. In particular, biopolymers are suitable materials as nanoparticles for clinical application due to their versatile traits, including biocompatibility, biodegradability and low immunogenicity. Biopolymers are polymers that are produced from living organisms, which are classified in three groups: polysaccharides, proteins and nucleic acids. It is important to control particle size, charge, morphology of surface and release rate of loaded molecules to use biopolymer-based nanoparticles as drug/gene delivery carriers. To obtain a nano-carrier for therapeutic purposes, a variety of materials and preparation process has been attempted. This review focuses on fabrication of biocompatible nanoparticles consisting of biopolymers such as protein (silk, collagen, gelatin, β-casein, zein and albumin), protein-mimicked polypeptides and polysaccharides (chitosan, alginate, pullulan, starch and heparin). The effects of the nature of the materials and the fabrication process on the characteristics of the nanoparticles are described. In addition, their application as delivery carriers of therapeutic drugs and genes and biomaterials for tissue engineering are also reviewed.
A new synthesis technique that produces homogeneous oligopeptides that are essential for the formation of self-assembled structures is described. In contrast with endopeptidases, exopeptidases, which catalyze the cleavage of terminal peptide bonds, can potentially prevent unexpected hydrolysis during aminolysis. This is the first report on exopeptidase-catalyzed oligopeptide synthesis. Oligo(L-leucine) was synthesized using the exopeptidase carboxypeptidase Y (CPDY), which also prevented enzymatic hydrolysis. A high yield of oligo(L-leucine) with a narrow polydispersity (PDI) was obtained by limiting polypeptide cleavage during aminolysis. The reaction conditions, such as the temperature, pH, CPDY and substrate concentrations, were optimized to produce the best yields, molecular weights and PDI of the oligomers. Hydrophobic L-leucine methyl ester and L-isoleucine methyl ester were found to be the appropriate substrates for CPDY-catalyzed oligomerization; however, no oligomers were obtained using hydrophilic amino-acid esters. Oligomer yields were also affected by the amino-acid ester groups. Remarkably, the PDI of the oligomers was as low as 1.0, regardless of the reaction conditions and types of substrates used. Thus, exopeptidase-catalyzed oligomerization may become an alternative route for the current endopeptide-catalyzed oligomerization of peptides.
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