In-vivo optical detection of intracellular cancer biomarkers using gold nanoparticles

Specific genotypes of human papillomavirus (HPV) are well correlated with cervical oncogenesis. The major transforming and immortalizing protein in high risk HPVs, namely HPV16, is E7 protein. E7 protein functions by deregulating the cell cycle and promoting S-phase reentry in differentiated keratinocytes. Currently, clinical diagnosis of cervical cancer is based on phenotypic changes observed in a screening Papanicolaou smear. Although screening has been effective in reducing the occurrence of cervical cancer, the low specificity of the Pap smear results in resources wasted on the evaluation of low-grade lesions not likely to progress to cervical cancer. Molecular characterization of active HPV infections using molecular specific contrast agents are combined with in-vivo optical imaging is proposed to be a cost-effective, non-invasive technique for the detection of cervical pre-cancers. Contrast is achieved by exploiting the peak absorbance and scattering shift in aggregated gold nanoparticles over isolated ones and molecular specificity is achieved via recognition moieties with high affinities for E7. Conjugates of gold nanoparticles and HPV16 anti-E7 antibodies are delivered into the nucleus of living cells and imaged with reflectance confocal microscopy. These contrast agents have been used to successfully enhance contrast in HPV16+ cervical cancer cells over HPV- cells by a factor of 2.5. Further characterization and development of these contrast agents will provide a robust, low cost screening tool for the detection of cervical pre-cancers.