In situ gelation

Huang, C-G. Green, D.W. Willhite, G.P. "An Experimental Study of the In-Situ Gelation of Chromium(+3)-Polyacrylamide Polymer in Porous Media", SPE/DOE paper 12638, 1984 SPE/DOE Fourth Symposium on Enhanced Oil Recovery, Tulsa, April 15-18. 

Chitosan can form 3D scaffold that are too weak to be useful in tissue engineering. Hence, inclusion in the chitosan matrix and/or grafting onto chitosan of other substances such as collagen, other biopolymers, or hydroxyapatite has been achieved to improve the mechanical properties of the scaffold and to mimic the nanostructure of the tissue for a better cell adhesion/infiltration and/or to provide thermosensitivity for in situ gelation. 

Jeong B, Bae YH, Kim SW. In situ gelation of PEG-PLGA-PEG triblock copolymer aqueous solutions and degradation thereof. J Biomed Mater Res 2000 50 171-177. 

Chemical gelation. Many of the original polymers developed for in situ gelation relied upon a chemical reaction in which monomers polymerize... 

Key words biodegradability, sol-gel transition, thermosensitivity, hydrogel, block copolymer, in-situ gelation, drug debvery system. 

Brona et al [18] have tested the relationship between alginate concentration, scaffold stiffness and viscoelastic behavior mimics that of the NP. The effect of variations in scaffold stiffness had been investigated on the expression of ECM molecules specific to NP. The sample discs were prepared of various concentrations of alginate (1 6%) by two different methods i.e. diffusion and in situ gelation. They found that the alginate can mimic the viscoelastic properties of the NP and capable of preserving the biosynthetic phenotype of NP cells. 

In situ gelation is the basis of injectable systems that eliminate the need for surgical procedures and offers the advantage of the ability to form any desired implant shape. 

Scheme 27 Synthesis of di- (193-195) and triurea (196-198) gelators exhibiting in situ gelation at room temperature...

Polymer In Situ Gels. Dmg encapsulation for injectable gels could be carried out by simple mixing of the dmg into the polymer gel. To obtain sustained release, it is desirable that the polsrmer gel should acquire some viscosity upon injection into the body. Such in situ gelation characteristics could be achieved by various mechanisms such as those described below ... 

Gan T, Zhang Y, Guan Y. In situ gelation of P(NIPAM-HEMA) microgel dispersion and its applications as injectable 3D cell scaffold. Biomacromolecules 2009 10 1410-1415. 

Bercea Maria, Morariu Simona, and Rusu Daniela. In situ gelation of aqueous solutions of entangled poly(vinyl alcohol). Soft Matter. 9 no. 4 (2013) 1244-1253. 

Davis, N. E., Ding, S., Forster, R. E., Pinkas, D. M., and Barron, A. E. 2010. Modular enzymaticaUy cross-linked protein polymer hydrogels for in situ gelation. Biomaterials, 31 7288-97. 

Polymers also are used to improve volumetric sweep efficiency in reservoirs that are fractured or have considerable permeability variation. In this application, commonly called in-situ permeability modification, the polymer is crosslinked in situ to form a gel network. In-situ gelation reduces the permeability in the region contacted by the polymer. By selection of chemical systems, treatments... 

McCool, C.S., Green, D.W., and Willhite, G.P. Permeability Reduction Mechanisms Involved in In-Situ Gelation of a Polyacryla-mlde/Chromium(VI)/Thiourea System in Porous Media, SPERE (Feb, 1991) 77-83. 

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