Huichao Lin

The rapid quantitative detection of Pseudomonas aeruginosa in milk is of great significance to food safety. Quantitative real-time polymerase chain reaction (qPCR) technology is a good choice to meet this requirement. A good qPCR system should show the advantages of being low cost, having low-power consumption, having potential for miniaturization and be portable. However, most of the time-domain-based qPCR systems reported to date do not meet these requirements. In this study, we propose a novel real-time rotary PCR reaction system (RRP) that meets all the abovementioned specifications, and contains four modules: a heating control module, a disposable PCR capillary tube, a mechanical control module, and a photoelectric detection module. The volume of our homemade-PCR capillary tube is only 3 μL. The total manufacturing cost is cheaper than $200, and the capillary tube is about 1.4 cents. The size parameter of the RRP is less than 300 mm × 150 mm × 150 mm, using low mobile power sources to operate. All the features mean that the RRP meets the advantages of low sample volumes, enhanced thermal conductivity and being portable. Through conducting the experimental quantitative detection of Pseudomonas aeruginosa in milk and theoretical simulations by COMSOL, we prove the feasibility of this rotary PCR real-time detection system, which has broad application prospects in the rapid detection of bacteria and food safety.

The photocatalytic material-microorganism hybrid system is an interdisciplinary research field. It has the potential to synthesize various biocompounds by using solar energy, which brings new hope for sustainable green energy development. Many valuable reviews have been published in this field. However, few reviews have comprehensively summarized the combination methods of various photocatalytic materials and microorganisms. In this critical review, we classified the biohybrid designs of photocatalytic materials and microorganisms, and we summarized the advantages and disadvantages of various photocatalytic material/microorganism combination systems. Moreover, we introduced their possible applications, future challenges, and an outlook for future developments.

Cell culture is important for the rapid screening of anti-cancer drug candidates, attracting intense interest. Traditional 2D cell culture has been widely utilized in cancer biological research. However, 3D cellular spheroids are able to recapitulate the in vivo microenvironment of tissues or tumors. Thus far, several 3D cell culture methods have been developed, for instance, the hanging drop method, spinner flasks and micropatterned plates. Nevertheless, these methods have been reported to have some disadvantages, for example, medium replacement is inconvenient or causes cellular damage. Here, we report on an easy-to-operate and useful micro-hole culture chip (SimpleDrop) for 3D cellular spheroid formation and culture and drug analysis, which has advantages over the traditional method in terms of its ease of operation, lack of shear force and environmentally friendliness. On this chip, we observed the formation of a 3D spheroid clearly. Three drugs (paclitaxel, cisplatin and methotrexate) were tested by both cell viability assay and drug-induced apoptotic assay. The results show that the three drugs present a similar conclusion: cell viability decreased over time and concentration. Moreover, the apoptotic experiment showed a similar trend to the live/dead cell assay, in that the fraction of the apoptotic and necrotic cells correlated with the concentration and time. All these results prove that our SimpleDrop method is a useful and easy method for the formation of 3D cellular spheroids, which shows its potential for both cell–cell interaction research, tissue engineering and anticancer drug screening.

Photocatalytic water purification is important for the degradation of organic pollutants, attracting intensive interests. Photocatalysts are preferred to be immobilized on a substrate in order to reduce the laborious separation and recycling steps. To get uniform irradiation, the photocatalysts are preferred to be even/uniform on the substrate without aggregation. Generally, the “coffee ring effect” occurs on the substrate during solvent evaporation, unfortunately resulting in the aggregation of the photocatalysts. This aggregation inevitably blocks the exposure of active sites, reactant exchange, and light absorption. Here, we reported a paper-based photocatalyst immobilization method to solve the “coffee ring” problem. We also used a “drop reactor” to achieve good photocatalytic efficiency with the advantages of large surface area, short diffusion lengths, simple operation, and uniform light absorption. Compared with the coffee ring type, the paper-based method showed higher water purification efficiency, indicating its potential application value in the future.