Biomedical electrosurgery devices containing nanostructure for minimally invasive surgery: reduction of thermal injury and acceleration of wound healing for liver cancer

Safety assessment of electrosurgical electrodes by using mini pig tissue

Electrosurgical electrodes are the main dissecting devices widely used for surgeries throughout the world. The present study aimed to evaluate the thermal injury and safety within animals' organs following a minimally invasive electrosurgery technique with electrosurgical electrode AE40-300 (LIPO) and AE20-80 (LIFT). To ensure the effective application of electrosurgery in a clinical environment, it is crucial to minimize heat-induced injury to nearby tissues. In this study, the skin, liver, kidney, and femoral muscle dissected from 9 minipigs were used in tissue thermal spread experiments. Thermal imaging area analysis, maximum temperature, and time to reach basal temperature were evaluated. Thermography results revealed that the surgical temperature was significantly lower in the minimally invasive electrosurgery with AE40-300 (LIPO) and AE20-80 (LIFT) compared to the predicate device. In addition, AE40-300 (LIPO) and AE20-80 (LIFT) created a relatively small thermal injury area and thermal diffusion. Our results indicated that the tested devices named AE40-300 (LIPO) and AE20-80 (LIFT) reduced excessive thermal injury and could be applied to clinical use safely.

Adsorptive properties of graphene oxide on vitamin B12 and their effect on the promotion of peripheral nerve regeneration

OBJECTIVES

To observe whether Graphene oxide (GO) can absorb vitamin B12 (VB12) and Decellularized scaffold - acellular nerve allograft (ANA) modified GO-VB12 promote the repair of ischiadic nervus defects in a rat model.

METHODS

The adsorption of GO on vitamin and the optimum adsorption conditions were investigated by single factor experiment. The adsorption properties of the material were observed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) to determine the success of adsorption on VB12. GO-VB12-ANA was prepared by vibration mixing method and bridged to injured ischiadic nervus. The nerve action potential, wet weight ratio of gastrocnemius muscle and the expression of GAP-43 were investigated by contrast test to detect its effect on nerve regeneration.

RESULTS

The optimized adsorption conditions for GO on VB12 solution were listed as follows: adsorbent dosage was 6 mg, shaking time was 70 min, the pH value was 6, the optimum concentration of VB12 was 50 mg/L and the theoretical saturated adsorption capacity was 21.51 mg/g. The nerve action potential, wet weight ratio of gastrocnemius muscle and the expression of GAP-43 in nerve fiber of GO-VB12-ANA group were close to the normal values and significantly higher than those of ANA and rotation group.

CONCLUSIONS

Based on the adsorption function of GO on VB12, GO-VB12-ANA can promote regeneration of injured ischiadic nervus, providing the experimental basis for the clinical application of nanomaterials.

A continuum thermomechanical model of in vivo electrosurgical heating of hydrated soft biological tissues

Radio-frequency (RF) heating of soft biological tissues during electrosurgical procedures is a fast process that involves phase change through evaporation and transport of intra- and extra-cellular water, and where variations in physical properties with temperature and water content play significant role. Accurately predicting and capturing these effects would improve the modeling of temperature change in the tissue allowing the development of improved instrument design and better understanding of tissue damage and necrosis. Previous models based on the Pennes' bioheat model neglect both evaporation and transport or consider evaporation through numerical correlations, however, do not account for changes in physical properties due to mass transport or phase change, nor capture the pressure increase due to evaporation within the tissue. While a porous media approach can capture the effects of evaporation, transport, pressure and changes in physical properties, the model assumes free diffusion of liquid and gas without a careful examination of assumptions on transport parameters in intact tissue resulting in significant under prediction of temperature. These different approaches have therefore been associated with errors in temperature prediction exceeding 20% when compared to experiments due to inaccuracies in capturing the effects of evaporation losses and transport. Here, we present a model of RF heating of hydrated soft tissue based on mixture theory where the multiphase nature of tissue is captured within a continuum thermomechanics framework, simultaneously considering the transport, deformation and phase change losses due to evaporation that occur during electrosurgical heating. The model predictions are validated against data obtained for in vivo ablation of porcine liver tissue at various power settings of the electrosurgical unit. The model is able to match the mean experimental temperature data with sharp gradients in the vicinity of the electrode during rapid low and high power ablation procedures with errors less than 7.9%. Additionally, the model is able to capture fast vaporization losses and the corresponding increase in pressure due to vapor buildup which have a significant effect on temperature prediction beyond 100 °C.

Self-Lubricanting Slippery Surface with Wettability Gradients for Anti-Sticking of Electrosurgical Scalpel

Soft tissue sticking on electrosurgical scalpels in minimally invasive surgery can increase the difficulty of operation and easily lead to medical malpractice. It is significant to develop new methods for anti-sticking of soft tissue on electrosurgical scalpels. Based on the characteristics of biomimetic ultra-slippery surface, a self-lubricating slippery surface with wettability gradients on electrosurgical scalpel was designed and fabricated. Non-uniformly distributed cylindrical micro pillars, which constitute the wettability gradients, were prepared by an electrolytic etching process and the theoretic of the spontaneous liquid spreading process was analyzed. The silicophilic property of wettability gradients surface was modified by octadecyltrichlorosilane (OTS) self-assembling coat with biocompatible liquid lubricant dimethyl silicone oil. The contact angle of gradient’s surface at different temperatures was measured. The transportation behaviors of both water and dimethyl silicone oil on the wettability gradient’s surface were investigated; the results illustrate that the wettability gradient’s slippery surface can successfully self-lubricate from regions with low pillar density to regions with high pillar density, ascribed to the unbalanced Young’s force. The anti-sticking capability of the electrosurgical scalpel with self-lubricating slippery surface was tested. Both the adhesion force and adhesion mass under different cycles were calculated. The results suggest that the as-prepared slippery surface has excellent anti-sticking ability associated with better durability.

Effect of high-frequency electric field on the tissue sticking of minimally invasive electrosurgical devices

Generally minimally invasive surgery is performed using an endoscope and other instruments including electrosurgical units (ESUs), and the adhesion of tissue to electrodes is a major concern. The mechanism governing this tissue sticking, especially the influence of high-frequency electric field, is still unclear. In this study, the effect of high-frequency electric field on the tissue sticking upon electrodes was investigated. The electrosurgical cutting test was performed on ex vivo fresh porcine liver under blend mode using a monopolar ESU. A heat-adherence test without electric field was used as a control. For the control group, the electrode was heated and maintained at a certain temperature and directly in contact with porcine liver. Both sticking tissues obtained from these two tests are partially carbonized porcine liver tissue, but their microstructure and bonding with electrode are obviously different. The sticking tissue formed just under heat is composed of biggish nanoparticles of different sizes which are loosely aggregated and has a weak bonding with the electrode, while the sticking tissue from the electrosurgical cutting test consists of tightly packed fine nanoparticles of equable size as a result of thermo-electric coupling and has a strong bonding with the electrode. Obviously, high-frequency electric field plays an extremely important role in the formation of the sticking tissue. It is the thermo-electric coupling that underlies the function of minimally invasive electrosurgical devices, and the effect of high-frequency electric field cannot be ignored in the tissue sticking study and anti-sticking strategies.