Search

Microdroplets have been widely used in biology, chemistry, material science and engineering, and the microdroplet generation methods are becoming more efficient and controllable. The development of the generation of microdroplets experienced tradition methods, microfluidic chip-based methods, and off-chip methods proposed recently. In this review, we first briefly summarized the typical traditional methods and the microfluidic chip-based methods for microdroplet generation, and then emphatically introduced the principles, devices, and applications of the recently developed microdroplet generation methods. The advantages and disadvantages of these methods were discussed and the future development of microdroplet generation technology was also prospected.

A new conceptual modality for nano-cryosurgical ablation of tumors is proposed in this article. The main strategy is to apply MgO nanoparticles (NPs), which are nontoxic, biodegradable, and have few side-effects on the human body, to mediate the freezing procedure effectively. Detailed investigation via animal experiments and nucleation analysis demonstrated that delivery of MgO NPs into the target tissues would significantly improve the cryosurgical outcome. The formation of an iceball during the freezing process is accelerated and enlarged due to the excellent thermal properties of MgO NPs. In addition this method could promote the generation of ice nuclei and thus enhance cryoinjury to the target cells. Therefore, combining the biodegradability and nontoxicity of MgO NPs with their relatively lightweight properties, excellent thermal properties would help develop a high-performance cryosurgery. These findings may lead to methods for safe and targeted nano-cryosurgery and possibly break through the barriers facing current clinical treatments of cancer. From the Clinical Editor Cryosurgery is a promising evolving modality to address malignancies. The work presented in this paper may add a novel concept to the field of nanomedicine by demonstrating that MgO nanoparticles enable more efficient ice-ball formation and cryoinjury in the target tissue.

Infrared thermography has been proved to be a useful tool to detect thermal physiologic changes associated with various diseases. However, static and single point temperature mapping on skin surface provided by the infrared thermography has not been able to meet the requirements for evaluating the complicated physiological status of human body. In order to explore more physiological variables for possible disease diagnostics, the present paper has developed a laser induced dynamic thermographic modality to estimate the average velocity of the superficial blood flow by means of tracking thermal transport along blood flow direction. A conceptual in vivo experiment is designed to record dynamic temperature response of rabbit auricle skin by thermograph, which is then used to estimate the blood flow velocity through a derived theoretical model. In addition, the lumped parameter model is developed to calibrate the estimated error by compensating the thermal response time induced by the tissue temperature change that the current infrared thermal imaging system with limited thermal sensitivity may fail to capture. The final calibrated results are fitting well with that from the Doppler ultrasound measurement, which indeed verified the practicality and feasibility of the method developed in this work.

This study presented the first in vivo animal experiments of using nano-cryosurgical modality to completely freezing tumor tissues embedded with large blood vessels, which is a tough issue to tackle otherwise. Three-dimensional theoretical simulations were also performed on the complex freezing problems by considering flow and heat transfer of blood flow in large vessels. According to the experimental measurements and numerical predictions, injecting the nanoparticles with high thermal conductivity into the freezing target can significantly reduce the heating effect of blood vessel, shorten the freezing time, and enlarge the freezing range. Most importantly, the introduction of nanoparticles successfully overcomes the classical challenges in completely ablating the tumor region with large blood vessel and enhancing the freezing efficacy of cryosurgery. This investigation consolidates the practical and theoretical foundation for nano-cryosurgery which suggests a highly efficient freezing strategy for treating late stage tumor.

Nanoparticles mediated cryosurgery was recently established as an efficient way to significantly improve the output of a conventional freezing therapy. To further improve this newly emerging nanomedicine way for ablating target tumor, here the ultrasound preprocessing was proposed for the first time to enhance the freezing strength to a better level on the tissues. In vitro experiments were carried out to evaluate the effects of a single ultrasound preprocessing, a single nanoparticle loading or their combination in enhancing the cryosurgery. Meanwhile, the mechanisms of the ultrasound preprocessing to improve nanoparticles’ mediated freezing capability were also theoretically interpreted. Experimental measurements demonstrate that, the ultrasound preprocessing on the target tissue site injected with nanoparticles not only evidently expended the freezing area, but also helps realize a much lower temperature scale and offers higher freezing rate during the nanocryosurgical process. Two main reasons to contribute to such effects were identified as the enhanced convective heat transfer in micro scale and the varied cellular impermeability caused by the ultrasound. The combined effect of ultrasound preprocessing and nanoparticles would be greater than the sum of their individual effects in mediating the nanocryosurgery. As a convinced approach, the present method opens a new way for the improved freezing ablation on tumor which can possibly be used in future clinics.Copyright © 2013 by ASME

This study presented the first in vivo animal experiments of using nano-cryosurgical modality to completely freezing tumor tissues embedded with large blood vessels, which is a tough issue to tackle otherwise. Three-dimensional theoretical simulations were also performed on the complex freezing problems by considering flow and heat transfer of blood flow in large vessels. According to the experimental measurements and numerical predictions, injecting the nanoparticles with high thermal conductivity into the freezing target can significantly reduce the heating effect of blood vessel, shorten the freezing time, and enlarge the freezing range. Most importantly, the introduction of nanoparticles successfully overcomes the classical challenges in completely ablating the tumor region with large blood vessel and enhancing the freezing efficacy of cryosurgery. This investigation consolidates the practical and theoretical foundation for nano-cryosurgery which suggests a highly efficient freezing strategy for treating late stage tumor.

The aim of the recently proposed nano cryosurgery is to exactly kill all tumor cells within the target region, which is defined by the characters of the tissues, such as bulk feature, shape, type and so on. It is easy to see that nano particles play a very critical role in cryosurgery. However, the amounts of nano particles could be loaded generally differ significantly due to variation of different tissue structures. This is particularly true for tumors situated at or surrounding some important organs. Therefore, treatment planning and understanding tissue temperature responses during a nano cryosurgery is rather important for the success of such innovated therapy. This study is dedicated to evaluate the temperature responses of different tissue types when subjected to cryosurgery by adjuvant use of nano particles. It was shown that for each organ, individuation must be considered for controlling the cooling dose in a nano cryosurgery in order to avoiding negative effect. Mechanisms coming from the diverse porosity, water content, density, blood perfusion, thermal conductivity, specific heat, and so on for each tissue were preliminarily interpreted.

It is important for laser-induced thermal therapy to exactly destroy all tumor cells within a desired region. In medical practice, it has been demonstrated that nano particles will extravasate and accumulate in tumors and serve to enhance absorptance of near infrared light. However, few efforts have yet been made to evaluate such improvement. This study proposed using infrared images to quantify the nano particles enhanced laser energy deposition effects. Its feasibility was demonstrated through several typical in vitro experiments and digital image analysis. It was shown that the ratio of tissue heating area with nano particles over that without loading nano particles has increased to different extent. Absorptance elevation for the case of nano Ag assisted CO2 laser heating appears the most evident one. Infrared images is expected to serve as a promising method to perform nano thermotherapy in future oncological clinics.