Biophotonics is an exciting and fast-expanding frontier which involves the fusion of advanced photonics and biology. It has not only created many novel methodologies for biomedical research, but also achieved many significant results as an independent field. Thanks to femtosecond (fs) laser technologies, important progresses have been made regarding the manipulation, imaging, and engineering of biological samples ranging from single molecules to tissues in the last 20 years. The ultrashort pulses at near-infrared band provide many advantages: high nonlinear efficiency, low absorption by biological samples, high spatial and temporal resolution and confinement, and low phototoxicity. They are noninvasive and easy to control. Although the mechanism of how fs laser pulses interact with cells remains unclear, experimental results have shown that they could open up the cell membrane and hence made optical transfection and optical cell fusion possible. In this review, some of the seminal works on transfection and cell fusion by fs lasers are presented. The ideas behind and the experimental details will be described together with a highlight on their significances. Specifically, the thermal effect is analyzed based on multiphoton excitation and plasma formation in an aqueous environment to explain the nontoxic characteristic of fs laser irradiation. Last, some applications of fs laser induced transfection and cell-cell fusion with potential major impact in biomedical sciences are proposed.

Photometry was employed to study the optimum extraction conditions of anthraquinone derivatives from rhizomes of Rheum officinale Baill in this study. The influences of extraction solvents (chloroform, benzene, ethanol, methanol, and glycerol), acid, and extraction time on the extraction yield were discussed. The results indicate that, to the Rhubarb rhizomes powder with the average particle size 0.18 mm, the conditions of the extraction solvent composed by chloroform, glycerol, and sulfuric acid (20%) in the ratio of 4:1:1 (v : v), the weight of dried Rhubarb to the solvent volume in the ratio of 1:12 ew: vT, extraction time of 110 min, the anthraquinone derivatives extraction could achieve the best yield. And the antibacterial tests showed the raw extraction products had the MIC (minimal inhibitory concentration) of 20 μg=mL and 30 μg=mL to Staphylococcus aureus and Escherichia coli, respectively.

Sirtuins comprise a family of enzymes implicated in the determination of organismal lifespan in yeast and the nematode. Human sirtuin SIRT1 has been shown to deacetylate several proteins in a NADt-dependent manner. It is reported that SIRT1 regulates physiological processes including senescence, fat metabolism, glucose homeostasis, apoptosis, and neurodegeneration. In general, SIRT1 has initially been thought to represent an exclusive nuclear protein. However, depending on the cell lines and organisms examined, a partial or temporary cytoplasmic localization was observed in murine pancreatic beta cells and neonatal rat cardiomyocytes. Since SIRT1 deacetylates both histone and nonhistone-proteins, such as a number of transcription factors, changes in subcellular localization probably play a role in the regulation of its function. In the present studies, we investigated the subcellular localization of SIRT1 in response to growth factor deprivation in African green monkey SV40-transformed kidney fibroblast cells (COS-7). Using SIRT1-EGFP fluorescence reporter, we found that SIRT1 localized to nucleus in physiological conditions. We devised a model enabling cell senescence via growth factor deprivation and found that SIRT1 partially translocated to cytosol under the treatment, suggesting a reduced level of SIRT1 activity. We found PI3K/Akt pathway was involved in the inhibition of SIRT1's cytosolic translocation, because inhibition of these kinases significantly decreased the amount of SIRT1 maintained in nucleus. Taken together, we demonstrate that growth factor deprivation induces cytosolic translocation of SIRT1, which suggests a possible connection between cytoplasm-localized SIRT1 and the aging process and provides a new application of single molecule fluorescence imaging of the molecule events in living cells.

Optical magnetic twisting cytometry and traction force microscopy are two advanced cell mechanics research tools that employ optical methods to track the motion of microbeads that are either bound to the surface or embedded in the substrate underneath the cell. The former measures rheological properties of the cell such as cell stiffness, and the latter measures cell traction force dynamics. Here we describe the principles of these two cell mechanics research tools and an example of using them to study physical behaviors of the living cell in response to transient stretch or compression. We demonstrate that, when subjected to a stretch-unstretch manipulation, both the stiffness and traction force of adherent cells promptly reduced, and then gradually recover up to the level prior to the stretch. Immunofluorescent staining and Western blotting results indicate that the actin cytoskeleton of the cells underwent a corresponding disruption and reassembly process almost in step with the changes of cell mechanics. Interestingly, when subjected to compression, the cells did not show such particular behaviors. Taken together, we conclude that adherent cells are very sensitive to the transient stretch but not transient compression, and the stretch-induced cell response is due to the dynamics of actin polymerization.

Hemodynamic low-frequency (~0.1 Hz) spontaneous oscillations as detected in the brain by nearinfrared spectroscopy have potential applications in the study of brain activation, cerebral autoregulation, and functional connectivity. In this work, we have investigated the phase lag between oscillations of cerebral deoxy- and oxy-hemoglobin concentrations in the frequency range 0.05-0.10 Hz in a human subject during a mental workload task. We have obtained a measure of such phase lag using two different methods: (1) phase synchronization analysis as used in the theory of chaotic oscillators and (2) a novel cross-correlation phasor approach. The two methods yielded comparable initial results of a larger phase lag between low-frequency oscillations of deoxy- and oxyhemoglobin concentrations during mental workload with respect to a control, rest condition.

Epithelial cancer comprises more than 85% of human cancers. The detection and treatment at the early stage has been demonstrated to apparently improve patient survival. In this review, we summarize our recent research works on the diagnostic application of epithelial tissue based on multiphoton microscopy (MPM), including identification of the layered structures of esophagus, oral cavity, skin and bronchus tissues, establishment of the diagnostic features for distinguishing gastric normal tissue from cancerous tissue, linking collagen alteration and ectocervical epithelial tumor progression for evaluating epithelial tumor progression, and differentiating normal, inflammatory, and dysplastic ectocervical epithelial tissues. These results provide the groundwork for developing MPM into clinical multiphoton endoscopy.

We report on tests of combined positron emission tomography (PET) and fluorescence molecular tomography (FMT) imaging system for in vivo investigation on small animals. A nude mouse was inoculated with MD-MB-231 breast cancer cells which expressed red fluorescent protein (RFP). For FMT system, reflective illumination mode was adopted with full-angle data acquisition. [18F]-Fluorodeoxyglucose ([18F]-FDG) was used as radioactive tracer for PET. Both data were acquired simultaneously and then reconstructed separately before fusion. Fluorescent tomography results showed exactly where the tumor was located while PET results offered more metabolic information. Results confirmed feasibility for tumor detection and showed superiority to single modality imaging.

Understanding muscle hemodynamics using near-infrared spectroscopy is increasingly evident in the recent spinal disorders-related literature. However, none of these human studies addressed the issue of physiological limits for the lumbar muscle within the same participants during various exercise modes. The purpose of this study is to evaluate physiological limits for the lumbar muscle during dynamic and static endurance tests. On three separate days, 22 healthy men and women performed three endurance protocols (static prone trunk extension, arm cranking, and pushing- pulling) until volitional exhaustion. For each protocol, minimum and maximum oxygenation and blood volume responses from the right lumbar erector spinae were obtained using a continuous dual wavelength near-infrared spectroscopy (Micro-Runman, NIM Inc., PA, USA). Statistical analysis showed that greatest reduction in oxygenation (minimum) were obtained during dynamic exercises: pushing-pulling (2.1 times) and arm cranking (2.03 times) versus static test （P < 0.05）. Physiological change (calculated as the difference between maximum during recovery and minimum at the point of volitional exhaustion) during static test was lower [(66-75% for oxygenation) and (34-46% for blood volume)] than dynamic exercises （P < 0.05）. Contrary to the theory that sufficient occlusion of blood flow to the lumbar muscle is possible with static trunk extension, it was concluded that a dynamic protocol until volitional exhaustion might be a good alternative in establishing near-infrared spectroscopy-derived physiological limits to the lumbar muscle. Further research is essential to identify an optimal calibration procedure for establishing true hypoxic values for the human lumbar muscle.

Understanding the mechanisms of interaction between bone/bone marrow, circulatory system and nervous system is of great interest due to the potential clinical impact. In humans, the amount of knowledge in this domain remains relatively limited due to the extreme difficulty to monitor these tissues continuously, noninvasively and for long or repeated periods of time. A typical difficult task would be, for example, to continuously monitor bone/bone marrow blood perfusion, hemoglobin oxygen saturation or blood volume and study their dependence on the activity of the autonomic nervous system. In this review article, we want to show that nearinfrared light might be utilized to solve these problems in part. We hope that the present analysis will stimulate future studies in this domain, for which near-infrared light appears as the best available technology today.

We present a novel optical sensor to acquire simultaneously functional near-infrared imaging (fNIRI) and functional magnetic resonance imaging (fMRI) data with an improved handling and direct localization in the MRI compared to available sensors. Quantitative phantom and interference measurements showed that both methods can be combined without reciprocal adverse effects. The direct localization of the optical sensor on MR images acquired with a T1-weighted echo sequence simplifies the co-registration of NIRI and MRI data. In addition, the optical sensor is simple to attach, which is crucial for measurements on vulnerable subjects. The fNIRI and T2*- weighted fMRI data of a cerebral activation were simultaneously acquired proving the practicability of the setup.

A near-infrared (NIR) tomography system with spectrally-encoded sources in two wavelength bands was built to quantify the temporal oxyhemoglobin and deoxyhemoglobin contrast in breast tissue at a 20 Hz bandwidth. The system was integrated into a 3T magnetic resonance (MR) imaging system through a customized breast coil interface for simultaneous optical and MRI acquisition. In this configuration, the MR images provide breast tissue structural information for NIR spectroscopy of adipose and fibro-glandular tissue in breast. Spectral characterization performance of the NIR system was verified through dynamic phantom experiments. Normal human subjects were imaged with finger pulse oximeter (PO) plethysmogram synchronized to the NIR system to provide a frequency-locked reference. Both the raw data from the NIR system and the recovered absorption coefficients of the breast at two wavelengths showed the same frequency of about 1.3 Hz as the PO output. The frequency lock-in approach provided a practical platform for MR-localized recovery of small pulsatile variations of oxyhemoglobin and deoxyhemoglobin in the breast, which are related to the heartbeat and vascular resistance of the tissue.

Electrical stimulation of the mammalian neurohypophysial infundibular stalk evokes the entry of Nat and Ca2t into the neurosecretory terminals during the action potential. These events, in turn, increase intracellular Ca2t and activate NaK- and Ca-ATPases, prompting the mitochondria to increase oxidative phosphorylation which can be monitored by recording the changes in FAD and NADH fluorescence. This paper reflects our efforts to determine whether or not modulating the capacity of mitochondria to produce ATP, by changing the concentrations of two important substrates of the Krebs cycle of the nerve terminal mitochondria, pyruvate and glucose, has an effect on the intrinsic fluorescence changes triggered by action potential stimulation.

Most techniques for measuring tissue concentrations of drugs are invasive, time-consuming, and often require the removal of tissue or body fluids. Optical pharmacokinetics (OP) is a minimally invasive alternative giving an immediate result. Pulses of white light are directed at the tissue of interest using a fiber optic probe. Scattered light is detected by a second fiber immediately adjacent to the first in the same probe (separation 1.7 mm). Using the photosensitizer disulfonated aluminium phthalocyanine (AlS₂Pc), OP measurements were made in phantoms and on the mouth, stomach, colon, skin, and liver of normal rats 1 and 24 h after intravenous AlS₂Pc administration. AlS₂Pc concentration was determined by calculating the area under the curve (AUC) in the spectral region around the peak drug absorption or measuring the height of the peak. Spectral baseline interpolation removed the need for pre-drug, control optical measurements. OP measurements correlated well with values from alkali chemical extraction (CE) of the corresponding tissues, (R² 0.87-0.97). OP measurements in the mouth also correlated with CE of less accessible internal organs (R² 0.77-0.88). In phantoms, the lowest detectable concentration was 0.1 μg/g. In vivo, results were limited by the lower accuracy in the CE measurements but were almost certainly comparable. An incidental finding was a 12-15nm red shifted component in the spectra observed 1 h after drug administration, suggesting partitioning of the drug in different microenvironment compartments, which could prove to be of considerable interest in future studies. In conclusion, OP shows promise for real-time measurement of concentrations of drugs with suitable absorption peaks.

Britton Chance, an Olympic gold medalist in sailing (Helsinki, 1952), was also one of the best and most legendary sailors in science.Britton Chance was born in Wilkes-Barre, Pennsylvania, USA on July 24th, 1913. He received a B.S. degree in 1935, an M.S. in 1936 and a Ph.D. degree in Physical Chemistry in 1940, all from the University of Pennsylvania. From Cambridge University he received his second Ph.D. degree in Physiology in 1942, and a D.Sc. (Doctor of Science) degree in 1952. He became a faculty member at the University of Pennsylvania in 1941, and conducted research and teaching there for 70 years. After he became the University Professor Emeritus in 1983, Chance continued active and fruitful research for nearly 30 years till the last few days of his life. He passed away peacefully on November 16th, 2010 at the Hospital of the University of Pennsylvania.