Synthesis and characterization of a novel in situ forming gel based on hydrogel dispersions

This report describes the synthesis and characterization of hydrogel dispersions for the potential use as an in situ gel-forming wound sealant. A series of polyacrylamide (PAAm) particles (solid content 5-10 wt %) were prepared by dispersion polymerization of acrylamide (AAm) in a solvent mixture of ethanol/water (90/10 w/w). These particles are characterized by the presence of a "core" [ethylene glycol dimethacrylate (EGDMA) crosslinked PAAm] surrounded by a "shell" [acetoacetoxyethyl methacrylate (AAEMA) or 2-aminoethylmethacrylate-containing PAAm, named as AAEMA-xPAAm and NH(2)-xPAAm, respectively; x represents "crosslinked"]. Two "2-in-1" working systems were prepared: (1) AAEMA-xPAAm mixed with NH(2)-xPAAm and (2) AAEMA-xPAAm mixed with 1,6-diaminohexane [AAEMA:NH(2) (1:1 mol/mol in (1) and (2)]. These systems appeared to possess essential characteristics for their potential use as wound sealants. For example, at 37 degrees C (and/or room temperature), both systems (1) and (2) formed transparent films, within 2 min upon applying them to a substrate; a rapid, concomitant crosslinking reaction occurred between AAEMA and -NH(2) on their outer "shells," knitting the EGDMA-crosslinked PAAm micro-"gel" together into a macro one. In contrast to other reported wound sealants, which are in either solution form or powder form, the advantages of hydrogel dispersion-based sealant may include ease of application (sprayable due to its low viscosity), species encapsulation and protection, and so forth. To our best knowledge, this is the first report on designing a wound sealant based on micro-particle dispersions.