A method mixes a first component, a second component, and a buffer material. The first component includes an electrophilic polymer material comprising poly(ethylene glycol) having a functionality of at least three. The second component includes a nucleophilic material comprising a natural or synthetic protein at a concentration of about 25% or less that, when mixed with the first component within a reaction pH range, cross-links with the first component to form a non-liquid, three-dimensional barrier. The buffer material includes tris-hydroxymethylaminomethane having a pH within the reaction pH range. The method applies the mixture to adhere to a tissue region.