Photothermal (PT) technique was applied to the detection of laser-induced local thermal effects around absorbing nanoparticles into cells. The experiments demonstrated the capability of this technique for studying the threshold and the dynamic of thermal events around even a single particle in a broad temperature range, including monitoring of microbubble dynamic. PT technique shows promise for optimizing cancer-cell killing by incorporation of gold nanoparticles into the cells (selective “nanophotothermolysis”), as verified by electron microscopy and conventional viability tests.

para-nitroaniline isomers (ONA, MNA, and PNA, respectively) were investigated with surface-enhanced infrared absorption (SEIRA) and surface-enhanced Raman spectroscopy (SERS) via adsorption of the individual isomers on vacuum-deposited silver films and on silver powders of varying physical dimensions using temperature-programmed desorption (TPD). PNA exhibited a strong SERS signal, whereas the ONA and MNA isomers showed more moderate enhancement. Only the MNA isomer exhibited SEIRA. Varying the polarity of the deposition solvent changed the MNA adsorbate orientation and the degree of vibrational enhancement. Solvent experiments with MNA were the first to show SEIRA enhancement of the -NH 2 symmetric and antisymmetric stretch modes. TPD and vibrational experiments show evidence for nitroaniline intermolecular hydrogen bonding on 100-µm silver powder while suggesting stronger nitroaniline adsorption to 100-nm silver powder. Resonance effects, adsorbate geometries, and hydrogen-bonding variations combined with changes in the strength of adsorption explain the differences in SEIRA versus SERS enhancement of the individual isomers, solvent effects, and desorption characteristics.

In vivo flow cytometry using vessels as natural tubes with native cell flows has revolutionized the study of rare circulating tumor cells in a complex blood background. However, the presence of many blood cells in the detection volume makes it difficult to count each cell in this volume. We introduce method for manipulation of circulating cells in vivo with the use of gradient acoustic forces induced by ultrasound and photoacoustic waves. In a murine model, we demonstrated cell trapping, redirecting and focusing in blood and lymph flow into a tight stream, noninvasive wall-free transportation of blood, and the potential for photoacoustic detection of sickle cells without labeling and of leukocytes targeted by functionalized nanoparticles. Integration of cell focusing with intravital imaging methods may provide a versatile biological tool for single-cell analysis in circulation, with a focus on in vivo needleless blood tests, and preclinical studies of human diseases in animal models.