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As the first barrier for food against pollution, food packaging plays a crucial role in food production, which greatly impacts both the quality and safety of food. Recently, the increasing use of conventional plastic packaging has posed a significant threat to the environment. Meanwhile, cases of foodborne poisoning caused by microbial contamination emerge endlessly. On this background, biodegradable antimicrobial film prepared with natural biological materials has a broad application in future food packaging materials. This article reviews the research progress of biodegradable and antimicrobial films based on biological materials (polysaccharides, proteins, and lipids) and their application in food packaging. And introduces the application of different antimicrobial agents (Synthetic and natural antimicrobial agents) in antimicrobial films. Moreover, discusses the effect of the addition of antibacterial agents on the properties of packing and the antibacterial activities of films. Finally, the shortcomings of food packaging-related fields are discussed. The development of biodegradable antimicrobial food packaging films in the future is prospected. [ABSTRACT FROM AUTHOR]

Microplastics are high molecular-weight polymers with micro- or nano-meter size, which have become a major global environmental issue in recent decades due to their ubiquity in the environment, bioavailability and potential toxicity. New analytical methods for the characterization of microplastics and nanoplastics are quickly emerging, such as particle size measurement, component identification and quantification. Many techniques have been developed and applied for the characterization of microplastics, such as Fourier-transform infrared spectroscopy, Raman spectroscopy and mass spectrometry (MS), etc. In recent years, the continuous development of MS technology has drawn more and more attention to the characterization and the environmental impact of microplastics. This paper mainly reviewed the state-of-the-art development and application of MS in microplastics analysis during the past decade. The principles and characteristics of various MS techniques used in the qualitative and quantitative analysis of microplastics were described, including thermal analysis coupled with MS-based techniques, elemental analytical MS, MALDI-ToF MS, LC-MS and ToF-SIMS. MS can provide chemical structure, molecular weight, degree of polymerization, additives, main functional groups and other information about the polymers, so it can be widely applied for chemical characterization, particle size determination and semi-quantitative/quantitative analysis of microplastics of small size. It has the advantages of replicable, fast real-time in situ analysis and high throughput detection, which can not only detect microplastics in the environment but also in biological tissues or cells in situ, showing great application potential in the research on the source, migration, transformation and interaction with biological organisms. The microplastics have been detected in the ocean, atmosphere, soil, consumer products, organisms and even human tissue, including polyethylene, polyamide, polyvinyl chloride, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, etc. The health risks of ingestion of microplastics deserve further exploration, especially nano plastics. The continuous development of MS technique and its combination with other separation/characterization methods will greatly promote the analysis of microplastics, and MS will become a more and more powerful tool in this research field and provide important scientific basis for the control of microplastic pollution. [ABSTRACT FROM AUTHOR]

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Based on the study of the relationship between strut angle of a stent and the radial supporting strength, a novel design method was proposed herein. Specifically, unequal-height supporting rings were used to increase the strut angle after expansion and furthermore improve the radial strength. Using this method, three kinds of biodegradable polymer vascular stents were designed. Radial strength, radial recoil, axial foreshortening and bending stiffness of the three stents were anayzed by finite element method and compared with Abbott bioresorbable vascular scaffolds(BVS). The influences of the structures on properties of the stents were studied. The radial strength of the deigned JS(J-type stent), OCSC open C-type stent) and CCSCclosed C-type stent) is as 14 %, 34% and 42% higher than that of the BVS, respectively. The recoil of the designed stents is about 21 % lower than that of the BVS. Meanwhile, all the designed stents have no axial shortening. The bending stiffness of the JS and OCS, which have open cells, is comparable to that of BVS and is about 73% lower than that of the CCS, which has closed cells. The radial supporting strength and radial recoil mainly depend on the structural form of the supporting rings. These two properties may be effectively improved by employing unequal-height supporting rings. The axial foreshortening is mainly determined by the structural form and the connection positions of the bridges. The axial shortening of the stents may be avoided by using bridges with curved structures and setting the connection positions in the middle of the straight section of the supporting elements. The bending stiffness is mainly affected by he connection form between the bridges and the supporting rings. The bending stiffness is lower if the tent has open cells. [ABSTRACT FROM AUTHOR]