Complete Prevention of Bubbles in a PDMS-Based Digital PCR Chip with a Multifunction Cavity

In a chamber-based digital PCR (dPCR) chip fabricated with polydimethylsiloxane (PDMS), bubble generation in the chambers at high temperatures is a critical issue. Here, we found that the main reason for bubble formation in PDMS chips is the too-high saturated vapor pressure of water at an elevated temperature. The bubbles should be completely prevented by reducing the initial pressure of the system to under 13.6 kPa to eliminate the effects of increased-pressure water vapor. Then, a cavity was designed and fabricated above the PCR reaction layer, and Parylene C was used as a shell covering the chip. The cavity was used for the negative generator in sample loading, PDMS degassing, PCR solution degassing in the digitization process and water storage in the thermal reaction process. The analysis was confirmed and finally achieved a desirable bubble-free, fast-digitization, valve-free and no-tubing connection dPCR.

Designing Flexible but Tough Slippery Track for Underwater Gas Manipulation

Lubricant-infused slippery surface exhibits a series of superior properties such as pressure tolerance, self-healing, oil-repellence, etc. Especially when being applied in an aqueous environment, the reliable bubble manipulating ability of slippery surface offers great opportunities to develop advanced systems in the field of gas transport, water splitting, etc. To improve the strength and the functionality of slippery surfaces, a sliced lubricant-infused slippery (SLIS) track is presented here, possessing both flexibility and toughness for underwater bubble manipulation. The rigid slippery slices with hydrophobic porous structure are linked by the liquid bridge of silicone oil, resulting in a continuous lubricant layer for bubble transfer. Taking advantage of this unique assembled structure, the in situ bubble controlling process, that is, pinning and moving, is achieved via the stretching/releasing of an elastic SLIS track. Besides, on the basis of the integrated design, a hypothesis of underwater gas mining is proved in the all-in-one process including the micro-bubble generation, bubble collection, and gas transport. The current design paves an avenue to reinforce the structure of slippery surfaces, and should promote the function of underwater bubble manipulation toward real-world applications.

Droplet and Particle Generation on Centrifugal Microfluidic Platforms: A Review

The use of multiphase flows in microfluidics to carry dispersed phase material (droplets, particles, bubbles, or fibers) has many applications. In this review paper, we focus on such flows on centrifugal microfluidic platforms and present different methods of dispersed phase material generation. These methods are classified into three specific categories, i.e., step emulsification, crossflow, and dispenser nozzle. Previous works on these topics are discussed and related parameters and specifications, including the size, material, production rate, and rotational speed are explicitly mentioned. In addition, the associated theories and important dimensionless numbers are presented. Finally, we discuss the commercialization of these devices and show a comparison to unveil the pros and cons of the different methods so that researchers can select the centrifugal droplet/particle generation method which better suits their needs.

Biomimetic Engineering of a Scavenger-Free Nitric Oxide-Generating/Delivering System to Enhance Radiation Therapy

Nitric oxide (NO) is a potent tumor-cell radiosensitizer but it can be readily scavenged by hemoglobin (Hb) in vivo. A biomimetic incubator that can generate and deliver NO in a scavenger (Hb)-free environment to enhance its radiosensitizing effect to maximize its efficacy in radiotherapy is proposed. This NO incubator comprises a poly(lactic-co-glycolic acid) (PLGA) hollow microsphere (HM) that contains an NO donor (NONOate) and a surfactant molecule (sodium caprate, SC) in its aqueous core. In acidic tumorous environments, the PLGA shell of the HM allows the penetration of protons from the outside, activating the hydrolytic cleavage of NONOate, spontaneously generating NO bubbles, which are immediately trapped/stabilized by SC. The SC-stabilized NO bubbles in the HM are then squeezed through the spaces of its PLGA matrices by the elevated internal pressure. Upon leaving the HM, the entrapped NO molecules may passively diffuse through their SC-stabilized/protected layer gradually to the tumor site, having a long-lasting radiosensitizing effect and inhibiting tumor growth. The entire process of NO generation and delivery is conducted in a scavenger (Hb)-free environment, mimicking the development of young ovoviviparous fish inside their mothers' bodies in the absence of predators before birth.

In Situ Self-Assembling Micellar Depots that Can Actively Trap and Passively Release NO with Long-Lasting Activity to Reverse Osteoporosis

Treatment with exogenous nitric oxide (NO) donors is regarded as being effective against osteoporosis. However, NO has a short half-life, limiting its clinical usefulness. To overcome this limitation, an injectable microparticle (MP) system is developed that consists of phase-change materials capric acid (CA) and octadecane, and encapsulates a NO donor. The therapeutic efficacy of the MPs is evaluated in ovariectomized (OVX) rats with osteoporosis. Upon subcutaneous administration, the MPs undergo a phase transition, leaching out the NO donor and generating NO bubbles that are instantly covered by a layer of tightly packed CA surfactant molecules, forming micellar depots. The in situ self-assembling micellar depots can actively protect the NO bubbles, prolonging their half-life, while the entrapped NO may passively diffuse through the micellar depots over time, performing a long-lasting therapeutic function, reversing the OVX-induced osteoporosis. It is possible to use the concept of in situ self-assembling micellar depots developed herein to expand the therapeutic effect of NO in its diverse range of clinical applications.

Thermoresponsive pegylated bubble liposome nanovectors for efficient siRNA delivery via endosomal escape

AIM

Improving the delivery of siRNA into cancer cells via bubble liposomes. Designing a thermoresponsive pegylated liposome through the introduction of ammonium bicarbonate salt into liposomes so as to control their endosomal escape for gene therapy.

METHODS

A sub-200 nm nanovector was fully characterized and examined for cellular uptake, cytotoxicity, endosomal escape and gene silencing.

RESULTS

The siRNA-liposomes were internalized into cancer cells within 5 min and then released siRNAs in the cytosol prior to lysosomal degradation upon external temperature elevation. This was confirmed by confocal bioimaging and gene silencing reaching up to 90% and further demonstrated by the protein inhibition of both target genes.

CONCLUSION

The thermoresponsiveness of ammonium bicarbonate containing liposomes enabled the rapid endosomal escape of the particles and resulted in an efficient gene silencing.