Silk-Silk Composite Foams for Surgical Packing, Liquid Absorption, and Drug Delivery

Degradable hemostatic materials such as gelatin foam are widely used as middle ear packing materials to support tympanic membrane grafts; while safe and biocompatible, such materials have limited mechanical stability when wet. Here, we demonstrate the fabrication of silk-silk composite foams by mixing microfibrillated silk with a low molecular weight silk solution glue to produce water-stable and highly porous foams that retain their structure when wet. The foams exhibited excellent (over 2000%) water absorption, more than 5 times higher than Gelfoam, a commercial hemostatic packing material, and hence higher loading of antibiotics such as ciprofloxacin. Moreover, unlike Gelfoam, ciprofloxacin could be encapsulated into the composite foams during fabrication to produce a dried, off-the-shelf, drug-eluting packing material. This enabled sustained drug release for over 16 days. The addition of microfibers significantly improved shape retention after annealing: samples containing at least a 1:1 mix of silk solution to microfibers showed no shrinkage after annealing, while control foams made from just silk solution shrank by at least 25%. These hybrid foams have immense potential for use as dual-function factor-concentrating hemostatic materials with drug delivery capacity for middle ear packing.