Hybrid electro-optical stimulation of the rat sciatic nerve induces force generation in the plantarflexor muscles.

Objective. Optical methods of neural activation are becoming important tools for the study and treatment of neurological disorders. Infrared nerve stimulation (INS) is an optical technique exhibiting spatially precise activation in the native neural system.

Femtosecond plasma mediated laser ablation has advantages over mechanical osteotomy of cranial bone.

Background: Although mechanical osteotomies are frequently made on the craniofacial skeleton, collateral thermal, and mechanical trauma to adjacent bone tissue causes cell death and may delay healing. The present study evaluated the use of plasma-mediated laser ablation using a femtosecond laser to circumvent thermal damage and improve bone regeneration.

Methods: Critical-size circular calvarial defects were created with a trephine drill bit or with a Ti:Sapphire femtosecond pulsed laser.

A handheld laser scanning confocal reflectance imaging-confocal Raman microspectroscopy system.

Confocal reflectance microscopy and confocal Raman spectroscopy have shown potential for non-destructive analysis of samples at micron-scale resolutions. Current studies utilizing these techniques often employ large bench-top microscopes, and are not suited for use outside of laboratory settings. We have developed a microscope which combines laser scanning confocal reflectance imaging and confocal Raman spectroscopy into a compact handheld probe that is capable of high-resolution imaging and spectroscopy in a variety of settings.

Comparing an optical parametric oscillator (OPO) as a viable alternative for mid-infrared tissue ablation with a free electron laser (FEL).

Beneficial medical laser ablation removes material efficiently with minimal collateral damage. A Mark-III free electron laser (FEL), at a wavelength of 6.45 μm has demonstrated minimal damage and high ablation yield in ocular and neural tissues.

Pulse duration determines levels of Hsp70 induction in tissues following laser irradiation.

Induction of heat shock protein (Hsp) expression correlates with cytoprotection, reduced tissue damage, and accelerated healing in animal models. Since Hsps are transcriptionally activated in response to stress, they can act as stress indicators in burn injury or surgical procedures that produce heat and thermal change. A fast in vivo readout for induction of Hsp transcription in tissues would allow for the study of these proteins as therapeutic effect mediators and reporters of thermal stress∕damage.

Image-guided genomic analysis of tissue response to laser-induced thermal stress.

The cytoprotective response to thermal injury is characterized by transcriptional activation of "heat shock proteins" (hsp) and proinflammatory proteins. Expression of these proteins may predict cellular survival. Microarray analyses were performed to identify spatially distinct gene expression patterns responding to thermal injury.

Microarray analysis of cellular thermotolerance.

Background And Objectives: Previously, we have shown that a 43°C pretreatment can provide thermotolerance to a following, more severe, thermal stress at 45°C. Using cells that lack the Hsp70 gene, we have also shown that there is still some thermotolerance in the absence of HSP70 protein. The purpose of this study was to determine which genes play a role in thermotolerance by measuring viability and proliferation of the cells at 2 days after heating.

Fiber-optic probes enable cancer detection with FTIR spectroscopy.

Fourier transform infrared spectroscopy (FTIR) reveals biochemical 'fingerprints' and has found disease patterns in excised human tissues. Fiber-optic probes have been developed for FTIR in living systems, allowing for cancer detection. There are challenges to making in vivo FTIR a reality, which are being addressed through hardware advances, determining key wavelengths and tissue preparation.

FTIR microspectroscopy for improved prostate cancer diagnosis.

Accurate diagnosis and prognosis is essential for cancer management but is subject to sampling and inter-observer error. In a recent study, Baker et al. compared Fourier transform infrared (FTIR) microspectroscopy with histological pathology to evaluate prostate tissue for disease severity.

Laser-induced disruption of systemically administered liposomes for targeted drug delivery.

Liposomal formulations of drugs have been shown to enhance drug efficacy by prolonging circulation time, increasing local concentration and reducing off-target effects. Controlled release from these formulations would increase their utility, and hyperthermia has been explored as a stimulus for targeted delivery of encapsulated drugs. Use of lasers as a thermal source could provide improved control over the release of the drug from the liposomes with minimal collateral tissue damage.

Use of an endoscope-compatible probe to detect colonic dysplasia with Fourier transform infrared spectroscopy.

Fourier transform infrared (FTIR) spectroscopy is sensitive to the molecular composition of tissue and has the potential to identify premalignant tissue (dysplasia) as an adjunct to endoscopy. We demonstrate collection of mid-infrared absorption spectra with a silver halide (AgCl(0.4)Br(0.

Role of HSP70 in cellular thermotolerance.

Background And Objective: Thermal pretreatment has been shown to condition tissue to a more severe secondary heat stress. In this research we examined the particular contribution of heat shock protein 70 (HSP70) in thermal preconditioning.

Study Design/materials And Methods: For optimization of preshock exposures, a bioluminescent Hsp70-luciferase reporter system in NIH3T3 cells tracked the activation of the Hsp70 gene.

In-vivo optical imaging of hsp70 expression to assess collateral tissue damage associated with infrared laser ablation of skin.

Laser surgical ablation is achieved by selecting laser parameters that remove confined volumes of target tissue and cause minimal collateral damage. Previous studies have measured the effects of wavelength on ablation, but neglected to measure the cellular impact of ablation on cells outside the lethal zone. In this study, we use optical imaging in addition to conventional assessment techniques to evaluate lethal and sublethal collateral damage after ablative surgery with a free-electron laser (FEL).

In vivo analysis of heat-shock-protein-70 induction following pulsed laser irradiation in a transgenic reporter mouse.

Induction of heat shock protein (Hsp) expression appears to correlate with a cytoprotective effect in cultured cells and with improved healing of damaged tissues in animal models and in humans. This family of proteins can also serve as indicators of thermal stress in cases of burn injury or surgical procedures that produce heat. Thus, a rapid in vivo readout for induction of Hsp transcription would facilitate studies of Hsp genes and their encoded proteins as mediators of therapeutic effects and as reporters of thermal damage to tissues.

Accelerated bone repair after plasma laser corticotomies.

Objective: To reveal, on a cellular and molecular level, how skeletal regeneration of a corticotomy is enhanced when using laser-plasma mediated ablation compared with conventional mechanical tissue removal.

Summary Background Data: Osteotomies are well-known for their most detrimental side effect: thermal damage. This thermal and mechanical trauma to adjacent bone tissue can result in the untoward consequences of cell death and eventually in a delay in healing.

Mid infrared optical parametric oscillator (OPO) as a viable alternative to tissue ablation with the free electron laser (FEL).

Background And Objectives: Investigations with a Mark-III free electron laser, tuned to 6.45 microm in wavelength have demonstrated minimal collateral damage and high ablation yield in ocular and neural tissues. While the use of mid-IR light produced by the free electron laser (FEL) has shown much promise for surgical applications, further advances are limited due the high costs of its use.

Effect of optical tissue clearing on spatial resolution and sensitivity of bioluminescence imaging.

In vivo bioluminescence imaging (BLI) is a powerful method of in vivo molecular imaging based on the use of optically active luciferase reporter genes. Although this method provides superior sensitivity relative to other in vivo imaging methods, spatial resolution is poor due to light scattering. The objective of this study was to use hyperosmotic agents to reduce the scattering coefficient and hence improve spatial resolution of the BLI method.

The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: biological effects.

Previous studies have shown that changing the pulse structure of the free electron laser (FEL) from 1 to 200 ps and thus reducing the peak irradiance of the micropulse by 200 times had little or no effect on both the ablation threshold radiant exposure and the ablated crater depth for a defined radiant exposure. This study focuses on the ablation mechanism at 6.1 and 6.

The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: ablation metrics.

Pulsed mid-infrared (6.45 microm) radiation has been shown to cut soft tissue with minimal collateral damage (<40 microm); however, the mechanism of ablation has not been elucidated to date. The goal of this research was to examine the role of the unique pulse structure of the Vanderbilt Mark-III free-electron laser (FEL) and its role in the efficient ablation of soft tissue with minimal collateral damage.

Assessment of cellular response to thermal laser injury through bioluminescence imaging of heat shock protein 70.

Assessment of laser-induced tissue damage is not complete without an investigation into the resulting cellular and molecular changes. In the past, tissue damage was quantified macroscopically by visual effects such as tissue mass removal, carbonization and melting. Microscopically, assessment of tissue damage has been typically limited to histological analysis of excised tissue samples.

Delivery of midinfrared (6 to 7-microm) laser radiation in a liquid environment using infrared-transmitting optical fibers.

Ablation at wavelengths near lambda = 6.45 microm results in tissue ablation with minimal collateral damage (< 40 microm) yet yields a high ablation rate that is useful for human surgery. However, delivery of this wavelength has been limited to that in air and thus to applications in which the target tissue can be readily exposed.