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Swelling nanocomposite hydrogels mechanical properties and cell surface desorption from the gel slice

Author: WangTao
Tutor: TongZhen
School: South China University of Technology
Course: Materials Science
Keywords: Nanocomposite Hydrogels Semi-IPN Cell culture Rapid desorption cell sheets Fluorescence
CLC: O631.3
Type: PhD thesis
Year: 2011
Downloads: 203
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Abstract

This work is mainly from the poly-N-isopropylacrylamide (PNIPAm) - Lithium diatomaceous earth Laponite nanocomposite hydrogel (NC gel) formation of equilibrium swelling gel under large strain and mechanical properties of the gel surface Cell culture and cell sheet automatic desorption and other aspects of high toughness NC gel more systematic study. Study basic idea is: With fluorescent probes investigated monomer N-isopropyl acrylamide (NIPAm) molecules and Laponite particles and tracks to explore the interaction between NC gel formation process; through uniaxial compressive and tensile study NC gel swelling in water balance large strain mechanical behavior of the gel also investigated in different solvents or swelling behavior in solution; through the introduction of biocompatible component NC gel promotes cell proliferation and desorption in the surface of the gel . The main content of the work and the results are as follows: 1. Using the fluorescent probe pyrene (pyrene), pyrene methyl amine hydrochloride (PyMA · HCl) and naphthalene methylamine (1-NpMA) on NIPAm monomer Laponite film layer conducted a systematic study of the adsorption. And by increasing the ionic strength we centrifugation, that the dispersion in the Laponite XLS, most fluorescent probe PyMA · HCl can be adsorbed on the Laponite XLS sheet. Using excimer fluorescence probe, anisotropy ratio and non-radiative energy transfer and other methods proved NIPAm molecules in aqueous dispersion of Laponite is adsorbed onto Laponite XLS sheet layer. 2 NC fluorescence probe to track formation of the gel. NIPAm concentration of monomer in the polymerization reaction liquid occurs during a sudden drop in transmittance after a few minutes there are different degrees of recovery, and the fluorescence spectrum of the reaction solution before and after mutation transmittance greater change, fluorescence spectra excimer relative peak intensity transmittance mutations increased significantly. Inferred from the fluorescent spectra, polymerization of the polymer chains adsorbed on the Laponite sheet around occupy some space on the sheet, so that the adsorption layers on the Laponite fluorescent molecules are squeezed close, thereby forming excimer fluorescence thereof. We hypothesized that the gel polymerization process NC transmittance change and changes in the fluorescence spectra of a certain link, which is know NC gel crosslinked structure provides an experimental method. 3 through compression and tensile test preparation and study of a new equilibrium swelling of PNIPAm NC gel mechanical behavior under large strain. Successful use of Mooney-Rivlin equation for uniaxial compression stress - strain curve fitting; also observed that there is significant stress NC gel hardening phenomenon, this phenomenon is as Laponite content increases strengthened, and the gel after swelling weakened, the compression process does not destroy the gel appears. Swollen gel at 200% elongation, and even up to 450%, while the traditional chemical crosslinking hydrogel elongation rate of about 100%, indicating that even in the swollen gel after the NC has a higher elongation . Using the Mooney-Rivlin equation can not be a good fit uniaxial tensile test results, we introduce by an upper-convected Maxwell (UCM) model and a parallel Gent strain hardening model from the new model, which can be a good plan combined tensile and compression test results. By examining the NC gel compression - recovery and stretching - recovery behavior and found that NC gel deformation recovery process lag phenomenon, and the lag with Laponite content increased with the increase, the gel after swelling hysteresis weakened. NC hysteresis loop as Laponite gel content also shows the increase of the fracture energy with Laponite gel content increases. Equilibrium swelling gel repeatedly stretched - recovery experiments showed swollen gel can withstand repeated stress without breaking, which its muscle in an artificial cartilage or artificial materials such as repeated application of force possible. NC gel by calculating the effective network chain density, we found that the swelling of the gel NC crosslinked network is only the initial expansion of the gel cross-linked network during swelling is not damaged. Prepared just calculated for each gel slice Laponite adsorbed on the number of the effective network chain about 165, and basically does not vary with the concentration of Laponite is changed, indicating that the gel in the NC Laponite XLS as polyfunctional crosslinking points. 4 The effects of non-ionic and ionic gel PNIPAm NC PNIPAm / sodium acrylate (SA) NC gel type organic solvent or aqueous organic solvent in the swelling behavior and the mechanical properties after swelling. The results showed that two kinds of gel in a non-polar solvent of n-hexane can be stably stored, does not swell or shrink, mechanical strength basically unchanged. PNIPAm NC gel in aqueous ethanol with the increase of ethanol concentration, showing the contraction of the first secondary swelling of the swelling. Appeared in the aqueous acetone solution and broken phenomenon. PNIPAm / SA NC ionic aqueous ethanol gel swelling phenomenon does not appear in the second, the ethanol concentration is low, the swelling ratio with the increase of concentration of SA; but in the ethanol concentration is high, the swelling ratio as SA content increases. PNIPAm / SA NC gel also appeared in aqueous acetone dissolved or broken phenomenon. These results are different from the NC gel solution provide a reference. 5 Preparation of ultra stretch temperature-sensitive alginate-PNIPAm NC semi-IPN hydrogels, the introduction of hydrophilic natural polysaccharide alginate later, NC gel still has excellent stretchability and ultra-phase transition temperature is lower than 37 oC. We chose fibroblasts (L929), human lung cancer cells (A549) and cervical cancer cells (HeLa) in the semi-IPN gel surface were cultured NC, found that the addition of alginate gel surface in favor of cell proliferation. L929 cells in the semi-IPN gel surface NC cells proliferate and form into a slice, by replacing the culture medium can achieve lower gel cell sheet automatic temperature desorption. We found that cell sheets in alginate concentration 0.2 w / v% of the semi-IPN NC gel surface has a faster desorption rate, cell sheets can be complete within 15 min desorption. NC through an atomic force microscope gel gel surface roughness surface morphology found desorption rate associated with the cell sheet, alginic acid molecule is added to change the surface roughness caused by the gel, the gel surface roughness with appropriate beneficial water molecules in the cell between the surface sheet and gel permeation, and promote desorption cell sheet. After desorption cell sheets can continue to develop and proliferate, indicating that cell sheet has excellent cell activity, may be used for tissue engineering or other biomedical fields.

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