Miniaturization applied to analysis of nucleic acids in heterogeneous tissues

Despite huge efforts in sample analysis, the measurement of marker nucleic acids within tissues remains largely nonquantitative. Gene analyses have benefited from sensitivity gains through in vitro gene amplification, including PCR. However, whilst these processes are intrinsically suited to highly reproducible, accurate and precise gene measurement, the term semiquantitative analysis is still commonly used, suggesting that other fundamental limitations preclude a generic quantitative basis to gene analysis. The most poorly defined aspect of gene analysis relates to the sample itself. The amount of cells and, particularly, cell subtype composition are rarely annotated before analysis; indeed, they are often extrapolated after analysis. To advance our understanding of pathogenesis, assay formats will benefit from resembling the dimensions of the cell, to assist in the analysis of cellular components of tissue complexes. This review is partly a perspective on how current miniaturization technologies, in association with molecular biology, microfluidics and surface chemistries, may evolve from the parts of a paradigm to enable the unambiguous quantitative analysis of complex biologic matter.