Controllable self-annealing microgel particles for biomedical applications

Abstract

A microporous gel system for certain applications, including biomedical applications, includes an aqueous solution containing plurality of microgel particles including a biodegradable crosslinker. In some aspects, the microgel particles act as gel building blocks that anneal to one another to form a covalently-stabilized scaffold of microgel particles having interstitial spaces therein. In certain aspects, annealing of the microgel particles occurs after exposure to an annealing agent that is endogenously present or exogenously added. In some embodiments, annealing of the microgel particles requires the presence of an initiator such as exposure to light. In particular embodiments, the chemical and physical properties of the gel building blocks can be controlled to allow downstream control of the resulting assembled scaffold. In one or more embodiments, cells are able to quickly infiltrate the interstitial spaces of the assembled scaffold.

1 - 66 . (canceled) 
     
     
         67 . A method of providing a covalently-stabilized scaffold in living mammalian tissue, comprising:
 a) delivering to the living mammalian tissue a flowable solution comprising a plurality of spherical microgel particles without delivering cells to the living mammalian tissue, wherein the spherical microgel particles comprise a hydrogel material having a polymer backbone comprising poly(ethylene glycol) (PEG) pre-modified with an RGD peptide, K peptide, Q peptide, and a matrix metalloprotease (MMP)-degradable cross-linker; and   b) annealing the spherical microgel particles using activated Factor XIII to crosslink a portion of the spherical microgel particles directly to adjacent spherical microgel particles to form the covalently-stabilized scaffold with interconnected pores, wherein the interconnected pores contain no crosslinked hydrogel therein and are large enough to accommodate penetration, migration, and growth of cells.   
     
     
         68 . The method of  claim 67 , wherein the interconnected pores comprise diameters ranging from 10 microns to 35 microns. 
     
     
         69 . The method of  claim 67 , wherein the spherical microgel particles comprise a hydrogel material having a shear storage modulus between 10 Pa to 1000 Pa. 
     
     
         70 . The method of  claim 67 , wherein annealing comprises forming the covalently stabilized scaffold with a void volume of about 26% to about 36%. 
     
     
         71 . The method of  claim 67 , wherein the spherical microgel particles have a diameter of 10 microns to 1000 microns when they are fully swollen. 
     
     
         72 . The method of  claim 67 , wherein the spherical microgel particles have a diameter of 30 microns to 150 microns when they are fully swollen. 
     
     
         73 . The method of claim  88 , wherein the polymer backbone comprises 4 arm PEG-vinyl sulfone. 
     
     
         74 . The method of  claim 73 , wherein the 4 arm PEG-vinyl sulfone is present at a concentration in a spherical microgel particle of 4.5% w/v to 5.5% w/v. 
     
     
         75 . The method of  claim 67 , wherein delivering comprises injecting the flowable solution into the living mammalian tissue from a syringe. 
     
     
         76 . The method of  claim 67 , wherein the concentration of K peptide and Q peptide in the spherical microgel particles is 10 μM to 500 μM. 
     
     
         77 . The method of  claim 67 , wherein the K peptide comprises a polypeptide sequence represented by SEQ ID NO. 1 and the Q peptide comprises a polypeptide sequence represented by SEQ ID NO. 2. 
     
     
         78 . The method of  claim 67 , wherein the spherical microgel particles have a coefficient of variation in diameter of less than 35%. 
     
     
         79 . The method of  claim 67 , wherein providing the covalently-stabilized scaffold comprises increasing the shear storage modulus of the covalently-stabilized scaffold. 
     
     
         80 . The method of  claim 73 , wherein an r-ratio of free cross-linker ends (—SH) to vinyl groups (—VS) on the PEG-vinyl sulfone comprises between 0.70 and 0.90. 
     
     
         81 . The method of  claim 67 , wherein annealing further comprises using activated Factor XIII to link a portion of the spherical microgel particles directly to one or more lysine or glutamine residues in adjacent living mammalian tissue to form the covalently-stabilized scaffold in the living mammalian tissue.