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A series of cinnamic acid (CA)-esterified debranched starch (CDS) containing aromatic systems were prepared and successfully fabricated as nanoparticles to encapsulate curcumin by taking advantage of the additional π-π interactions provided from CA. The CDS nanoparticles (CDS NPs) have good dispersion (polydispersity index of 0.124-0.314) and sizes range of 130-330 nm. The excellent biosafety of CDS NPs was demonstrated by hemolysis, cytotoxicity and mutagenicity assays. Efficient encapsulation (LC = 26.86 %) and sustained release of curcumin were achieved, and the curcumin-encapsulated CDS NPs (CDS-Cur NPs) increased 266-fold water solubility and 2.3-6.5-fold photothermal stability for curcumin, compared to free curcumin. Functional studies showed that CDS-Cur NPs exhibited superior biofilm scavenging ability, with a 2-4.3-fold improvement compared to free curcumin. In addition, CDS-Cur NPs also exhibited far superior antibacterial effects than free curcumin in a bacteriostatic food model of chicken breast. This study not only provides a new scheme for the efficient loading of curcumin, but also provides new ideas for the usage of starch-based materials in antibacterial applications.

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Combined pollution consisted of various types of microplastics (MPs) was extensively detected in the environment; however, little is known about their interaction on degradation behavior during exposure in sunlight. This study investigated the effects of polystyrene (PS) MPs and mechanisms on photodegradation of pure and commercial polypropylene (PP) MPs co-existed in aquatic environment. Results showed that PS MPs significantly accelerated photodegradation of co-existed PP, including faster oxidation and fragmentation. Photodegradation route of PP MPs such as the reaction priority of partial chemical bindings was even altered with the presence of PS MPs, highlighting the important role of PS in photodegradation process of PP. Analysis of leachate and free radical indicated that the critical effects were derived from photosensitization of PS polymer itself and its released dissolved organic matter (PS-DOM); here, more important role of PS itself in initial period and that of PS-DOM in later period. Among generated ROS, OH· was the key species for accelerating photodegradation of PP by PS itself and its released DOM, which were generated from the reaction of polymer radical with dissolved oxygen. The findings firstly reveal the important role of PS in photodegradation of co-existed MPs and suggested the shorter duration of (micro)plastics in combined system than that in the single, which provide useful information to assess environmental behavior and fate of MPs more holistically.

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Photocatalysis has been regarded as a promising inactivation technology targeting to reduce drug-resistant bacteria contamination, but developing efficient photocatalysts with broad visible light harvesting capability is still a challenge. Here we report a MOFs-derived BPQDs/Cu2O/N-doped hollow porous carbon (BP/CNC) with indirect Z-scheme heterojunctions (BPQDs/Cu2O), which can inactivate 99.99999% Methicillin-resistant Staphylococcus aureus (MRSA) at a concentration of only 10 mg/L. Combining photoelectrochemical techniques and electrochemical measurements, the efficient inactivation process was attributed to the synergistic effect of enhanced light utilization and effective suppression of photogenerated carrier recombination. The mechanism of gradually damaged cell membrane for MRSA was studied by employing scanning electron microscopy (SEM), fluorescence staining and coagulase titer test to further decipher the changes in bacterial cells. We propose that reactive oxygen species (ROS) destroys the cell wall membrane and causes the leakage of cell contents, eventually leading to death. In addition, a series of in vitro and in vivo toxicity tests were conducted to evaluate the biocompatibility of the antibacterial system and its potential use in practice. This strategy of BPQDs/Cu2O indirect heterojunction fabrication can spatially inhibit the recombination of photogenerated carriers, expands the light absorption range, providing a feasible method for disinfecting microbial contaminated water.

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Pullulanase debranching and subsequent hydroxypropylation were applied to prepare a series of dual-modified starches (Hydroxypropylated debranched starch, HPDS) with different degrees of hydroxypropyl substitution. Their structural and physicochemical properties varied with the degree of hydroxypropyl substitution, and all HPDS exhibited the ability to self-assemble into well-shaped nanospheres (100-150 nm, PDI < 0.2). These HPDS nanospheres were attempted to encapsulate curcumin with the aim of improving the bioavailability, solubility and stability of curcumin. Their structural characteristics, thermal stability, iodine staining, morphology, safety, encapsulation efficiency, in vitro gastrointestinal release behavior, and anti-inflammatory activity were evaluated. The results showed that curcumin could be effectively encapsulated into the HPDS nanospheres, and the encapsulation efficiency, water solubility and physical stability were positively correlated with the degree of hydroxypropyl substitution. After encapsulation, the water solubility and physical stability of curcumin could be increased up to 226-fold and 6-fold, respectively. The HPDS nanospheres also exhibited good safety (including hemolysis and cytotoxicity) and sustainable release of curcumin. Evaluation of anti-inflammatory activity showed that the activity of curcumin-encapsulated HPDS was enhanced by 170% compared to unencapsulated curcumin. These suggest that HPDS nanospheres encapsulation may be a more suitable option for the development of functional foods containing bioactive compounds.

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