Methods for performing surface-mediated protein delivery into living cells, and fabricating protein-transfected cell cluster arrays are provided. The method comprises providing a protein-containing mixture; depositing said protein-containing mixture onto a surface at defined locations; affixing the protein-containing mixture to the surface as microspots; and plating cells onto the surface in sufficient density and under conditions for the proteins to be delivered into the cells. The protein-containing mixture comprises any suitable amino acid sequence, including peptides, proteins, protein-domains, antibodies, or protein-nucleic acid conjugates, etc., with a carrier reagent. Protein-transfected cell arrays may be used for rapid and direct, screening of protein or enzymatic functions or any given intracellular protein interaction in the natural environment of a living cell, as well as for high-throughput screening of other biological and chemical analytes, which affect the functions of these proteins.