The present invention relates to a method of producing a solid carrier, to which at least one affinity-reagent is coupled that binds specifically to a target molecule, comprising the steps of (i) coupling at least one affinity-reagent to a solid carrier, (ii) overlaying the affinity-reagent-coupled carrier obtained in (i) by incubation with a composition comprising heparin and/or a functional derivative thereof, and (iii) overlaying the affinity-reagent-coupled carrier by incubation with a composition comprising stabilising excipients, wherein steps (ii) and (iii) are carried out subsequently or simultaneously and subsequently to step (i). The invention further relates to a solid carrier comprising (i) at least one affinity-reagent, wherein the at least one affinity-reagent is coupled to the solid carrier, (ii) an overlay comprising heparin and/or a functional derivative thereof, and (ii) an overlay comprising stabilising excipients. In addition, the invention relates to the use of the carrier of the invention or of the carrier produced by the method of the invention to specifically bind and enrich a target molecule or a target cell which carries a biological target molecule on its surface from a liquid sample. Further, the invention relates to the use of the carrier of the invention or of the carrier produced by the method of the invention to specifically induce a biological response in a target cell. Furthermore, the invention relates to an ex-vivo or in-vitro method for specifically binding and enriching a target cell out of a liquid sample comprising contacting the liquid sample with the carrier of the invention or the carrier produced by the method of the invention, wherein the contacting is effected by inducing the liquid sample to flow over the surface of the carrier to which the at least one affinity-reagent is coupled, and wherein the target cell carries a biological target molecule on its surface to which the at least one affinity-reagent specifically bind
