to the epstein barr nuclear antigen ebna as analyte monoclonal antibodies atcc hb 8742 or hb 8746 that immunoreact with human apolipoprotein b 100 as analyte or monoclonal antibodies atcc hb 9200 or hb 9201 that immunoreact with human apolipoprotein a i as analyte as are described in u s pat no 4 828 986 whose disclosures are incorporated by reference and the several deposited monoclonal antibodies listed at column 13 of u s pat no 5 281 710 and their listed binding partners as analyte which disclosures are incorporated by reference electrochemical etching of si can generate a thin approximately 1 10 u03bcm layer of porous si on the silicon substrate with cavities of about 10 nm to about 200 nm in diameter providing a large surface area for biomolecular interaction inside the porous si layer the porous films are uniform and sufficiently transparent to display fabry perot fringes in their optical reflection spectrum more particularly a porous si substrate is prepared by an electrochemical etch of a polished 100 oriented p type silicon b doped 3 ohm cm resistivity wafer the etching solution is prepared by adding an equal volume of pure ethanol to an aqueous solution of hf 48 by weight.