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

弹性蛋白是动物组织和胶原蛋白的重要组成部分。弹性蛋白分子是由交联网络的共价边界形成的，它们的网络可以像橡皮筋一样拉伸和回弹。这种弹性符合皮肤、血管和肺部的弹性，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)等疏水氨基酸残基组成，它们的氨基酸重复形式(GVGVP)n存在于动物体内。当温度升高时，它们在被称为浊点(CP)的特定温度以上折叠和组装，形成了II型β-转角的螺旋结构。利用这些疏水氨基酸残基，Urry等人合成了独特的热响应多肽：Poly[(GVGVP)_&lt；251&gt；]。利用大肠杆菌重组DNA技术，这些多肽表现出了显著的生物相容性。利用这些温敏性多肽，利用弹性蛋白模型多肽的温敏聚集、聚[(GVGVP)_&lt；251&gt；]和伽马射线交联制备纳米颗粒。采用“慢加热”、“快速加热”和“热休克”三种不同的加热方法对多肽进行聚集，并通过伽马射线交联得到稳定的纳米颗粒。结果，只有“热休克”过程才能得到直径小于约150 nm且尺寸分布较窄的稳定纳米颗粒。圆二色谱表明，这种多肽通过“热休克”过程在浊点(CP)以上的温度下形成了II型β转角结构，并保持了这种结构在交联型纳米粒子中，这表明这种结构对于产生稳定的交联型粒子至关重要。

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.