Depth profiling of mammalian cells by photoacoustic spectroscopy: localization of ligands

Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements

In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.

Photo-formation of gold nanoparticles: photoacoustic studies on solid monoliths of Au(III)-chitosan-silica aerogels

Photo-formation of gold nanoparticles in the solid monoliths of Au(III)-chitosan-silica aerogels with different Au/NH(2) molar ratios has been investigated using photoacoustic spectroscopy. Upon exposing to 320 nm UV light, a new absorption feature in the visible region around 525 nm could be seen due to the surface plasmon resonance of gold particles that are generated as a result of UV-induced reduction of Au(III) to Au(0). The plasmon band becomes stronger and shows saturation effects upon increasing the UV exposure time. A blue shift of about 7 nm is also noticed on exposing the sample (Au/NH(2)=1/5) for 6h, indicating a slight decrease in the nanoparticle size due to light-induced annealing with increasing the UV exposure time. The PA signals monitored as a function of chopping frequency show omega(-1) dependence, implying the thermally thin character of Au(III)-chitosan-silica aerogels.

Laser-induced bubbles in living cells

BACKGROUND AND OBJECTIVES

Laser-activated micro- and nano-bubbles (LAB) in cells may be used as universal and sensitive non-toxic probes for measuring functional properties of individual cells.

STUDY DESIGN/MATERIALS AND METHODS

Such bubbles can be detected and imaged by microscopy and flow cytometry. LABs in living blood and tumor cells were induced by pulsed (532 nm, 10 nanoseconds) laser radiation and detected by the thermal lens optical method.

RESULTS

Registered lifetime and maximal diameter of the studied LABs varied within the ranges of 0.02-10 microseconds and 0.44-100 microm, respectively. LAB parameters, thresholds and probabilities, were found to depend upon the physiological state of cells. Specificity and sensitivity of LAB cytometry were increased due to the use of light-absorbing nanoparticles conjugated to specific monoclonal antibodies.

CONCLUSIONS

LAB were found to be the universal phenomena that can be used for sensitive and non-invasive monitoring of any individual cell, intact or nanoparticle-treated.

Using the linearization approach for synchronizing the phase of photoacoustic reference and sample data

Linearization of photoacoustic spectra is a technique that allows for detection of surface layers and the compensation of saturation effects in photoacoustic spectra by combining amplitude and phase information. The objective of this report is a thorough description of the linearization procedure. The influence of interferogram rotation on the real and imaginary parts of the complex Fourier transformation and on spectral phase angles is shown. The possibility of using the linearization approach to correct for phase differences between reference and sample data is discussed. The method can be used to calculate phase spectra from photoacoustic spectra taken with rapid scan spectrometers.