Optical and thermal characterization of albumin protein solders

Nanothermometry-Enabled Intelligent Laser Tissue Soldering

While often life-saving, surgical resectioning of diseased tissues puts patients at risk for post-operative complications. Sutures and staples are well-accepted and routinely used to reconnect tissues, however, their mechanical mismatch with biological soft tissue and invasiveness contribute to wound healing complications, infections, and post-operative fluid leakage. In principle, laser tissue soldering offers an attractive, minimally-invasive alternative for seamless soft tissue fusion. However, despite encouraging experimental observations, including accelerated healing and lowered infection risk, critical issues related to temperature monitoring and control during soldering and associated complications have prevented their clinical exploitation to date. Here, intelligent laser tissue soldering (iSoldering) with integrated nanothermometry is introduced as a promising yet unexplored approach to overcome the critical shortcomings of laser tissue soldering. It demonstrates that adding thermoplasmonic and nanothermometry nanoparticles to proteinaceous solders enables heat confinement and non-invasive temperature monitoring and control, offering a route to high-performance, leak-tight tissue sealing even at deep tissue sites. The resulting tissue seals exhibit excellent mechanical properties and resistance to chemically-aggressive digestive fluids, including gastrointestinal juice. The iSolder can be readily cut and shaped by surgeons to optimally fit the tissue defect and can even be applied using infrared light from a medically approved light source, hence fulfilling key prerequisites for application in the operating theatre. Overall, iSoldering enables reproducible and well-controlled high-performance tissue sealing, offering new prospects for its clinical exploitation in diverse fields ranging from cardiovascular to visceral and plastic surgery.

Deep learning-based single-shot phase retrieval algorithm for surface plasmon resonance microscope based refractive index sensing application

A deep learning algorithm for single-shot phase retrieval under a conventional microscope is proposed and investigated. The algorithm has been developed using the context aggregation network architecture; it requires a single input grayscale image to predict an output phase profile through deep learning-based pattern recognition. Surface plasmon resonance imaging has been employed as an example to demonstrate the capability of the deep learning-based method. The phase profiles of the surface plasmon resonance phenomena have been very well established and cover ranges of phase transitions from 0 to 2π rad. We demonstrate that deep learning can be developed and trained using simulated data. Experimental validation and a theoretical framework to characterize and quantify the performance of the deep learning-based phase retrieval method are reported. The proposed deep learning-based phase retrieval performance was verified through the shot noise model and Monte Carlo simulations. Refractive index sensing performance comparing the proposed deep learning algorithm and conventional surface plasmon resonance measurements are also discussed. Although the proposed phase retrieval-based algorithm cannot achieve a typical detection limit of 10^-7 to 10^-8 RIU for phase measurement in surface plasmon interferometer, the proposed artificial-intelligence-based approach can provide at least three times lower detection limit of 4.67 × 10^-6 RIU compared to conventional intensity measurement methods of 1.73 × 10^-5 RIU for the optical energy of 2500 pJ with no need for sophisticated optical interferometer instrumentation.

Fabry-Perot Resonance in 2D Dielectric Grating for Figure of Merit Enhancement in Refractive Index Sensing

We have recently reported in our previous work that one-dimensional dielectric grating can provide an open structure for Fabry–Perot mode excitation. The grating gaps allow the sample refractive index to fill up the grating spaces enabling the sample to perturb the Fabry–Perot mode resonant condition. Thus, the grating structure can be utilized as a refractive index sensor and provides convenient sample access from the open end of the grating with an enhanced figure of merit compared to the other thin-film technologies. Here, we demonstrate that 2D grating structures, such as rectangular pillars and circular pillars, can further enhance refractive index sensing performance. The refractive index theory for rectangular pillars and circular pillars are proposed and validated with rigorous coupled wave theory. An effective refractive index theory is proposed to simplify the 2D grating computation and accurately predict the Fabry–Perot mode positions. The 2D gratings have more grating space leading to a higher resonant condition perturbation and sensitivity. They also provide narrower Fabry–Perot mode reflectance dips leading to a 4.5 times figure of merit enhancement than the Fabry–Perot modes excited in the 1D grating. The performance comparison for thin-film technologies for refractive index sensing is also presented and discussed.

Terahertz three-dimensional monitoring of nanoparticle-assisted laser tissue soldering

In view of minimally-invasive clinical interventions, laser tissue soldering assisted by plasmonic nanoparticles is emerging as an appealing concept in surgical medicine, holding the promise of surgeries without sutures. Rigorous monitoring of the plasmonically-heated solder and the underlying tissue is crucial for optimizing the soldering bonding strength and minimizing the photothermal damage. To this end, we propose a non-invasive, non-contact, and non-ionizing modality for monitoring nanoparticle-assisted laser-tissue interaction and visualizing the localized photothermal damage, by taking advantage of the unique sensitivity of terahertz radiation to the hydration level of biological tissue. We demonstrate that terahertz radiation can be employed as a versatile tool to reveal the thermally-affected evolution in tissue, and to quantitatively characterize the photothermal damage induced by nanoparticle-assisted laser tissue soldering in three dimensions. Our approach can be easily extended and applied across a broad range of clinical applications involving laser-tissue interaction, such as laser ablation and photothermal therapies.

Biodegradable polymer scaffold, semi-solid solder, and single-spot lasing for increasing solder-tissue bonding in suture-free laser-assisted vascular repair

We recently showed the fortifying effect of poly-caprolactone (PCL) scaffold in liquid solder-mediated laser-assisted vascular repair (ssLAVR) of porcine carotid arteries, yielding a mean ± SD leaking point pressure of 488 ± 111 mmHg. Despite supraphysiological pressures, the frequency of adhesive failures was indicative of weak bonding at the solder-tissue interface. As a result, this study aimed to improve adhesive bonding by using a semi-solid solder and single-spot vs. scanning irradiation. In the first experiment, in vitro ssLAVR (n=30) was performed on porcine abdominal aorta strips using a PCL scaffold with a liquid or semi-solid solder and a 670-nm diode laser for dual-pass scanning. In the second experiment, the scanning method was compared to single-spot lasing. The third experiment investigated the stability of the welds following hydration under quasi-physiological conditions. The welding strength was defined by acute breaking strength (BS). Solder-tissue bonding was examined by scanning electron microscopy and histological analysis was performed for thermal damage analysis. Altering solder viscosity from liquid to semi-solid solder increased the BS from 78 ± 22 N/cm(2) to 131 ± 38 N/cm(2) . Compared to scanning ssLAVR, single-spot lasing improved adhesive bonding to a BS of 257 ± 62 N/cm(2) and showed fewer structural defects at the solder-tissue interface but more pronounced thermal damage. The improvement in adhesive bonding was associated with constantly stronger welds during two weeks of hydration. Semi-solid solder and single-spot lasing increased welding strength by reducing solder leakage and improving adhesive bonding, respectively. The improvement in adhesive bonding was associated with enhanced weld stability during hydration.

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. Cells in 96-well plates were pretreated in a 43 degrees C water bath for 30 minutes, followed 4 hours later with a severe heat shock at 45 degrees C for 50 minutes. Bioluminescence was measured at 2, 4, 6, 8, and 10 hours after preshock only (PS) and at 4 hours after preshock with heatshock (PS+HS). Viability was assessed 48 hours later with a fluorescent viability dye. Preshock induced thermotolerance was then evaluated in hsp70-containing Murine Embryo Fibroblast (+/+) cells and Hsp70-deficient MEF cells (-/-) through an Arrhenius damage model across varying temperatures (44.5-46 degrees C).

RESULTS

A time gap of 4 hours between preconditioning and the thermal insult was shown to be the most effective for thermotolerance with statistical confidence of P<0.05. The benefit of preshocking was largely abrogated in Hsp70-deficient cells. The Arrhenius data showed that preshocking leads to increases in the activation energies, E(a), and increases in frequency factors, A. The frequency factor increase was significantly greater in Hsp70-deficient cells.

CONCLUSION

The data shows that HSP70 contributes significantly to cellular thermotolerance but there are other pathways that provide residual thermotolerance in cells deficient in Hsp70.

The heat transfer analysis of nanoparticle heat source in alanine tissue by molecular dynamics

The purpose of this study is to simulate the heat transfer problem when the 3-D Alanine tissue is heated by the gold nanoparticle in the field of molecular dynamics. In this paper, the Alanine molecule is adopted and its parameters are available in the GROMACS protein data bank. A computing algorithm is developed to evaluate the heat transfer phenomena in the nano-scale biological system based on the molecular dynamics and the protein data bank. The value of the thermal conductivity of Alanine is calculated from the autocorrelation function of the Green-Kubo formalism and this result has a roughly approximation with the bulk thermal conductivity reported by experimental data . Two kinds of problems are investigated in the paper. One is the Alanine tissue heated by the constant heat source and the other is by the time-varying heat source. The numerical results show that a temperature jump exists around the source and the temperature profiles drop to the environmental temperature within a very short distance. It concludes that only a small region around the nano-scale heat source is affected by the heated process. Therefore, the results of the nanoparticle-heated method could be applied to the clinical therapy of tumor, and the normal cells are destroyed only within a smaller region than those of chemotherapy or surgery.