Fabrication of Nanoparticles by Gamma-ray crosslinking of thermosensitive polypeptides and analysis for controled release of drugs

弹性蛋白和胶原蛋白一样是动物组织中的重要成分。弹性蛋白分子由共价键连接的交联网络形成，其网络可以像橡皮筋一样伸缩。这种弹性符合弹性，如皮肤，血管和肺，需要这种弹性才能发挥作用[6]。弹性蛋白分子主要由甘氨酸（G）、丙氨酸（A）、脯氨酸（P）和缬氨酸（V）等疏水性氨基酸残基组成，其氨基酸重复序列为（GVGVP）n。在升高温度时，它们在称为浊点（CP）的特定温度以上折叠和组装，并形成II型β转角的螺旋结构。利用这些疏水氨基酸残基，Urry等利用大肠杆菌重组DNA技术合成了独特的温度响应性多肽：poly [（GVGVP）_<251>]，这些多肽表现出显著的生物相容性。利用这些热敏性多肽，利用弹性蛋白模型多肽的热敏性聚集;聚[（GVGVP）_<251>]和γ-射线交联制备纳米颗粒。三种不同的加热方法，“缓慢加热”，“快速加热”，和“热休克”，被应用于肽的聚集，并检查产生稳定的纳米颗粒通过γ-射线交联。结果，只有“热休克”程序产生稳定的纳米粒子的直径小于约。150 nm和窄的尺寸分布。CD光谱表明，该多肽在用“热休克”程序将温度升高到浊点（CP）以上时形成II型β-转角结构，并且将该结构保持在交联的纳米颗粒内，这表明该结构对于产生稳定的交联颗粒至关重要。

Elastin is an essential component in animal tissues as well as collagen. Elastin molecules are formed by covalent bounds of a cross-linked network and their network can stretch and recoil like rubber band. This elasticity conform a flexibility to such as skin, blood vessels, and lungs, need to this elasticity in order to function [6]. Elastin molecules are composed largely of hydrophobic amino acid residues, such as glycine (G) ,alanine (A) ,proline (P) and valine (V) and their amino acids repeat as (GVGVP)n exist in the animals. On raising the temperature, they folded and assembled above a specific temperature called cloud point (CP) and it formed helical structure of type II beta-turn. Using these hydrophobic amino acid residues, unique thermoresponsive polypeptides: poly [(GVGVP)_<251>]was synthesized by Urry, et al. using Escherichia coli recombinant DNA technology and these polypeptides exhibit a remarkable biocompatibility. Utilizing these thermosensitive polypeptides, Nanoparticles were prepared utilizing the thermosensitive aggregation of the elastin model polypeptides; poly[(GVGVP)_<251>]and gamma-ray crosslinking. Three different heating methods, "Slow heating", "Fast heating", and "Heat shock", were applied for the aggregation of the peptide and examined to yield stable nanoparticles by gamma-ray crosslinking. As a result, only "heat shock" procedure yielded stable nanoparticles with diameters of less than ca. 150 nm and a narrow size distribution. CD spectrometry showed that this polypeptide formed type II beta-turn structure on raising temperature above cloud point(CP)with the "heat shock" procedure and, kept the structure within the crosslinked nanoparticles, suggesting that this structure would be crucial to yield stable crosslinked particles.