Injectable systems gelation

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. 

Gel Solution Behavior During Injection, Gel solution behavior during the period a solution is being injected is of interest because it relates to gel placement in the porous medium. It has been shown that, at least for some systems, gelation time during flow in a porous medium is not the same as gelation time measured in a beaker or viscometer. I08,ii3-ii6 ... 

The oranges were washed, chopped in a meat mincer and homogenised by a Fryma mill. Water (0.6 volumes) were added before the slurry was heat treated by steam injection at 100°C for 2 minutes. The enzyme treatment was carried out for 1 hour at 40°C with 10 lU/g slurry of PME and 25 pg enzyme protein/g slurry of the other enzymes for each of the enzymes. The gelated orange slurry were treated at 85°C for 3 minutes to inactivate the enzymes before the strength of the gel was measured by a SMS TeJrture Analyser TA-XT2 (Stable Micro Systems, XT. RA Dimensions, Operations Manual versions) by compression analysis using a flat cylinder (20 mm dia.) with a speed of 2 mm/s. The force to provide a 20% compression was recorded. 

Cationic polyacrylamide may be used in the initial treatment stages to promote rapid polymer adsorption (201). Adjustment of the pH may allow deeper penetration of the fluids in an aluminate crosslinking system prior to gelation (202). A process involving injection of alternate slugs of stoichiometrically equivalent amounts of partially hydrolyzed polyacrylamide and Al O ) has been evaluated in the laboratory permeability of sana packs were reduced by more than 96% (203). Mixtures of Al(IIl) and Zr(IV) have also been evaluated as partially hydrolyzed polyacrylamide crosslinkers (204). 

An analysis of the temperature distribution in a mold (Fig. 4.54) at the final moment of filling for two reactive systems with different values of G shows that the temperature along the central line increases monotonically downstream (at distance x) from the inlet nozzle. At high values of the gelation criterion, the temperature at locations close to the injection nozzle is maximum near the mold wall. Moving down stream, the position of the temperature maximum shifts to the center, except at the frontal zone. Here the temperature is nearly constant, because the major part of the... 

Sharifi, S. et al, 2009. Injectable in situ forming drug delivery system based on poly (e-caprolactone fumarate) for tamoxifen citrate delivery gelation characteristics, in vitro drug release and anti-cancer evaluation. Acta Biomaterialia, 5(6), 1966-1978. 

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