Fabrication Of A System To Regulate The Cell Adhesion And Detachment In Molecular Level

Biological materials science, known as an important interdisciplinary subjectbetween two areas-materials science and life science that have mutual penetration of eachother, has made many breakthroughs and progresses in recent years due to thefundamental reason of the healthy needs of people and economical development, whichmake the fields in biocompatible materials, tissue engineering, nano-biomaterials,bio-mineralized materials and biomimetic smart materials become the research frontier ofbiological materials. This thesis mainly focus on the synthesis of artificial proteins andthermoresponsive polymers, which we use to fabricate a thermoresponsive system on thegold surface to regulate the cell adhesion and cell detachment in combination with theadvantages of both of the two materials. The main results are summarized as follows:Approaches of molecular biology are introduced to fabricate the plasmids and inducethe expression of artificial polypeptide Bcys, NcysA, and NcysARGD. These materials areperfectly biocompatible because they are produced through genetic engineering methodsand at the same time, they can be manipulated to add, remove or change the amino acid’sequence in molecular level by easily cloning different DNA sequences so as to connectother thermoresponsive or photoresponsive materials and get some complexcharacteristics. Meanwhile, molecular recognition between the pair of complementaryleucine zipper domains A and B, which heterodimerized through noncovalent, reversibleinteraction, indicated their application in fabrication of complicated system.A thermoresponsive polymer mPEG-PNIPAM-B, in which artificial protein B andPEG are fused, is created through RAFT polymerization reaction and other chemicalmodification methods, and the thermoresponsive effect do not disappear with the fusion ofB and PEG. The molecular structure of PNIPAM can be stretched and shrinked bylowering or raising the temperature in order to control the distance between B and PEG,which shows broad application aspects in intelligent control of cell culture.At last, we construct a kind of intelligent system that can dynamically and reversiblyregulate cell adhesion and detachment in molecular level by only changing thetemperature, This molecular design offers several advantages: the regulation is reversible and thermoresponsive; the ligand RGD remains immobilized during dynamic regulationso that cells are not exposed to the soluble form of the ligand that potentially hasdetrimental effects; the precision of the on/off states is assured by the molecular-leveluniformity of the ligand and PEG coimmobilized through leucine zipperheterodimerization. The method can be readily adapted for dynamic regulation of otherimmobilized bioactive ligands of interest.