INSTITUTE OF PHYSICS PUBLISHING NANOTECHNOLOGY Nanotechnology 15 (2004) 383–389 PII: S0957-4484(04)71143-5 ViriChip: a solid phase assay for detection and identification of viruses by atomic force microscopy Saju R Nettikadan 1,4 , James C Johnson 1,3 , Srikanth G Vengasandra 1 , James Muys 1 and Eric Henderson 1,2 1 BioForce Nanosciences Incorporated, 2901 South Loop Drive, Suite 3400, Ames, IA 50010, USA 2 Iowa State University, Department of GDCB, Ames, IA 50011, USA 3 Des Moines University, Department of Microbiology, Des Moines, IA 50312, USA E-mail: snettikadan@bioforcenano.com Received 24 October 2003 Published 19 January 2004 Online at stacks.iop.org/Nano/15/383 (DOI: 10.1088/0957-4484/15/3/027) Abstract Bionanotechnology can be viewed as the integration of tools and concepts in nanotechnology with the attributes of biomolecules. We report here on an atomic force microscopy–immunosensor assay (AFMIA) that couples AFM with solid phase affinity capture of biological entities for the rapid detection and identification of group B coxsackievirus particles. Virus identification is based on type-specific immunocapture and the morphological properties of the captured viruses as obtained by the AFM. Representatives of the six group B coxsackieviruses have been specifically captured from 1 μl volumes of clarified cell lysates, body fluids and environmental samples. Concentration and kinetic profiles for capture indicate that detection is possible at 10 3 TCID 50 μl -1 and the dynamic range of the assay spans three logs. The results demonstrate that the melding of a nanotechnological tool (AFM) with biotechnology (solid phase immunocapture of virus particles) can create a clinically relevant platform, useful for the detection and identification of enterovirus particles in a variety of samples. 1. Introduction The detection of a pathogen’s antigen by immunoassay, or genomic fragments by polymerase chain reaction (PCR) procedures in clinical and other samples is taken to indicate the presence of the infectious agent. However, without other data such as infectivity studies or electron microscopic analysis, it cannot be concluded that pathogens are present in the samples. For example, Chlamydia trachomatis DNA is present in urine of humans for up to two weeks after the infectious agent has been cleared by antibiotic treatment [1]. Viral RNA of measles may be found in brain tissue years after the paramyxovirus has been cleared from extra-neural sites [2, 3]. Post-polio syndrome has been associated with the finding of viral nucleic acids but no infectious virus particles [4]. In occult type 4 Author to whom any correspondence should be addressed. B hepatitis infections, wherein infectious virus and genomic materials can be detected, surface antigens of the hepadnavirus may not be detected in blood [5]. Methods are needed for the direct visualization of virus particles in virus detection assays. Currently, the only standard methods by which viral particles are directly detected are scanning and transmission electron microscopy (EM), with or without immune enhancement [6]. These methods have led to the discovery of a number of new viruses including the Norwalk-like caliciviruses and the rotaviruses that cause human gastroenteritis [7–10]. However, EM procedures remain somewhat cumbersome, time consuming and dependent upon expensive equipment. Furthermore, staining and metal coatings destroy the biological function of the particles and often prevent further analyses of the material by immunological or genomic (PCR) means. Despite these 0957-4484/04/030383+07$30.00 © 2004 IOP Publishing Ltd Printed in the UK 383