Abstract: A composition is provided which comprises a protein or peptide containing lysines, wherein at least one of the lysines and/or the N-terminal amino group of the protein or peptide, such as casein, .beta.-lactoglobulin, powdered milk or whey, is modified by contact with an aromatic acid anhydride compound, such as trimellitic anhydride, trimellitic anhydride chloride or 3-hydroxyphthalic anhydride. Additionally a composition is provided wherein a protein or peptide containing arginines is modified by an arginine modifying agent containing at least one carboxyl group, such as p-carboxyphenylglyoxal. The compositions are capable of binding to CD4 cell receptors, such as the HIV-1 or HIV-2 binding site on CD4 cell receptors. The compositions are thus useful for the prevention of HIV-1 or HIV-2 infection, especially by local administration.

Abstract: An improved spacer material for improving the biocompatibility of a biomaterial and a method for making it in which a polyalkylimine is covalently attached to an aminated substrate and combined with a crosslinking agent which is at least difunctional in aldehyde groups. The polyalkylimine can be for example, polyethyleneimine and the crosslinking agent can be, for example, glutaraldehyde. Preferably, the crosslinking agent is applied in dilute solution and at a pH suitable to accomplish light crosslinking of the polyalkylimine and also provide aldehyde linkages at the interface between the biomolecule and the spacer.