Environmental hazard of polypropylene microplastics from disposable medical masks: acute toxicity towards Daphnia magna and current knowledge on other polypropylene microplastics

The COVID-19 pandemic has increased the use of disposable plastics, including medical masks, which have become a necessity in our daily lives. As these are often improperly disposed of, they represent an important potential source of microplastics in the environment. We prepared microplastics from polypropylene medical masks and characterised their size, shape, organic chemical leaching, and acute toxicity to the planktonic crustacean Daphnia magna. The three layers of the masks were separately milled and characterised. Each of the inner frontal, middle filtering, and outer layers yielded different types of microplastics: fibres were obtained from the inner and outer layer, but irregular fragments from the middle layer. The shape of the obtained microplastics differed from the initial fibrous structure of the intact medical mask layers, which indicates that the material is deformed during cryo-milling. The chemical compositions of plastics-associated chemicals also varied between the different layers. Typically, the inner layer contained more chemicals related to antimicrobial function and flavouring. The other two layers also contained antioxidants and their degradation products, plasticisers, cross-linking agents, antistatic agents, lubricants, and non-ionic surfactants. An acute study with D. magna showed that these microplastics do not cause immobility but do physically interact with the daphnids. Further long-term studies with these microplastics are needed using a suite of test organisms. Indeed, studies with other polypropylene microplastics have shown numerous adverse effects on other organisms at concentrations that have already been reported in the environment. Further efforts should be made to investigate the environmental hazards of polypropylene microplastics from medical masks and how to handle this new source of environmental burden.

Penentuan Total Fenolik, Uji Antioksidan, Dan Uji Antibakteri Pada Ekstrak Etanol Jantung Pisang Ambon (Musa acuminate Colla)

Banana plant is one type of plant that contains chemical compounds that can be used for treatment. One part of the plant that has not been fully utilized is the heart of the Ambon banana (Musa acuminate Colla). Banana flower is known to contain flavonoid compounds, phenols, alkaloids, tannins, saponins, and coumarins. One of the compounds belonging to the flavonoid group which generally includes natural antioxidant compounds and has an antimicrobial function is phenolic compounds. The purpose of this study was to determine the total phenols, to examine the activity of antioxidants, antibacterials, and the ethanol extract of Ambon banana flower (Musa acuminate Colla). Determination of total phenol using the GAE (Gallic Acid Equivalence) method, antioxidant analysis using the FRAP method, and the antibacterial activity test using the paper disc method. The total phenol yield obtained was 17.7291 ± 0.102 mg GAE/g extract, the results from the antioxidant test were obtained with an EC50 value of 0.0628 µmolFe2+/g sampel extract, which means that the ethanolic extract of Ambon banana flower has a high antioxidant activity value, and antibacterial results in the extract. with a medium average (5-10 mm). From the results of tests carried out, the ethanol extract of Ambon banana flower has antioxidant activity and has little antibacterial power.Keywords : Banana plants; Ambon banana flower; antioxidants; antibacterial; total phenol AbstrakTanaman pisang merupakan salah satu jenis tanaman yang mengandung senyawa kimia yang dapat digunakan untuk pengobatan. Salah satu bagian tanaman yang belum dimanfaatkan secara maksimal adalah jantung pisang ambon (Musa acuminate Colla). Jantung pisang diketahui mengandung senyawa flavonoid, fenol, alkaloid, tannin, saponin, dan kumarin. Salah satu senyawa yang termasuk golongan flavonoid yang umumnya termasuk senyawa antioksidan alami dan memiliki fungsi antimikroba yaitu senyawa fenolik. Tujuan dari penelitian ini yaitu penentuan total fenol, meneliti aktivitas antioksidan, antibakteri, dan pada ekstrak etanol jantung pisang ambon (Musa acuminate Colla). Penentuan total fenol menggunakan metode GAE (Equivalensi Asam Galat), analisis antioksidan menggunakan metode FRAP, dan uji aktivitas antibakteri menggunakan metode kertas cakram. Hasil total fenol yang diperoleh 17,7291 ± 0,102 mg GAE/g ekstrak, hasil dari uji antioksidan didapat dengan nilai EC50 pada ekstrak 0,0628 µmolFe2+/g sampel yang berarti ekstrak etanol jantung pisang ambon mempunyai nilai aktivitas antioksidan yang tinggi, dan hasil antibakteri pada ekstrak dengan rata-rata sedang (5-10 mm). Dari hasil pengujian yang dilakukan ekstrak etanol jantung pisang ambon mempunyai aktivitas antioksidan dan mempunyai sedikit daya antibakteri. Kata kunci : Tanaman pisang; jantung pisang ambon; antioksidan; antibakteri; total fenol.

Hyaluronic Acid Derivative Molecular Weight-Dependent Synthesis and Antimicrobial Effect of Hybrid Silver Nanoparticles

Silver nanoparticles (Ag NPs) appeared as promising antimicrobial candidates to face the development of antibiotic resistance. Although reported as toxic towards mammalian cells, their combination with biomolecules have shown reduced toxicity, while maintaining the antimicrobial function. Herein, hyaluronic acid (HA) with low (40 kDa), medium (200 and 600 kDa) and high (2 MDa) molecular weight (Mw) was modified with adipic acid dihydrazide (ADH) and used as reducing and capping agents to synthesise antimicrobial hybrid Ag NPs. The Mw of the polymer played a crucial role in the morphology, size and antibacterial activity of the Ag NPs. The 600 and 200 kDa HA-ADH-Ag NPs were able to reduce the Escherichia coli and Staphylococcus aureus concentration by more than 3 logs, while the 40 kDa NPs reached ~2 logs reduction. The 2 MDa HA-ADH failed to form homogenous NPs with strong bactericidal activity. A mechanistic study of the interaction with a model bacterial membrane using Langmuir isotherms confirmed the greater interaction between bacteria and higher Mw polymers and the effect of the NP’s morphology. The nanocomposites low toxicity to human skin cells was demonstrated in vitro, showing more than 90% cell viability after incubation with the NPs.

Carbon “quantum” dots for bioapplications

Carbon “quantum” dots or carbon dots (CDots) exploit and enhance the intrinsic photoexcited state properties and processes of small carbon nanoparticles via effective nanoparticle surface passivation by chemical functionalization with organic species. The optical properties and photoinduced redox characteristics of CDots are competitive to those of established conventional semiconductor quantum dots and also fullerenes and other carbon nanomaterials. Highlighted here are major advances in the exploration of CDots for their serving as high-performance yet nontoxic fluorescence probes for one- and multi-photon bioimaging in vitro and in vivo, and for their uniquely potent antimicrobial function to inactivate effectively and efficiently some of the toughest bacterial pathogens and viruses under visible/natural or ambient light conditions. Opportunities and challenges in the further development of the CDots platform and related technologies are discussed.

Sequence edition of single domains modulates the final immune and antimicrobial potential of a new generation of multidomain recombinant proteins

Combining several innate immune peptides into a single recombinant antimicrobial and immunomodulatory polypeptide has been recently demonstrated. However, the versatility of the multidomain design, the role that each domain plays and how the sequence edition of the different domains affects their final protein activity is unknown. Parental multidomain antimicrobial and immunomodulatory protein JAMF1 and several protein variants (JAMF1.2, JAMF2 and AM2) have been designed and recombinantly produced to explore how the tuning of domain sequences affects their immunomodulatory potential in epithelial cells and their antimicrobial capacity against Gram-positive and Gram-negative bacteria. The replacement of the sequence of defensin HD5 and phospholipase sPLA2 by shorter active fragments of both peptides improves the final immunomodulatory (IL-8 secretion) and antimicrobial function of the multidomain protein against antimicrobial-resistant Klebsiella pneumoniae and Enterococcus spp. Further, the presence of Jun and Fos leucine zippers in multidomain proteins is crucial in preventing toxic effects on producer cells. The generation of antimicrobial proteins based on multidomain polypeptides allows specific immunomodulatory and antimicrobial functions, which can be easily edited by modifying of each domain sequence.

Functionality of Films from Nigella sativa Defatted Seed Cake Proteins Plasticized with Grape Juice: Use in Wrapping Sweet Cherries

The main aim of this work is to improve the functionality of Nigella sativa protein concentrate (NSPC) films by using grape juice (GJ). The film’s mechanical, antioxidant, and antimicrobial activities were evaluated. The obtained results showed, for the first time, that GJ at concentrations of 2%–10% (v/v) are able to act as plasticizer for the NSPC films with promising film properties. The results showed that the tensile strength and Young’s modulus of NSPC films were reduced significantly when the GJ increased. However, the NSPC films prepared with 6% GJ observed a higher elongation at break compared with other films. Moreover, the obtained films showed very interesting and promising results for their antioxidant and antimicrobial properties compared with the control films. The sweet cherries wrapped with NSPC film showed that the TSS (Brix) was significantly lower compared to the control, after 10 days of storage. However, the titratable acidity, pH value, and L* of all cherries, either wrapped or not, was not significantly different in all storage times. On the other hand, hue angle was significantly lower after 10 days of storage at −18 °C compared with control films. GJ has a multi-functional effect for protein-based films as plasticizer, antioxidant, and antimicrobial function.

Taxonomic bias in AMP prediction of invertebrate peptides

Invertebrate antimicrobial peptides (AMPs) are at the forefront in the search for agents of therapeutic utility against multi-resistant microbial pathogens, and in recent years substantial advances took place in the in silico prediction of antimicrobial function of amino acid sequences. A yet neglected aspect is taxonomic bias in the performance of these tools. Owing to differences in the prediction algorithms and used training data sets between tools, and phylogenetic differences in sequence diversity, physicochemical properties and evolved biological functions of AMPs between taxa, notable discrepancies may exist in performance between the currently available prediction tools. Here we tested if there is taxonomic bias in the prediction power in 10 tools with a total of 20 prediction algorithms in 19 invertebrate taxa, using a data set containing 1525 AMP and 3050 non-AMP sequences. We found that most of the tools exhibited considerable variation in performance between tested invertebrate groups. Based on the per-taxa performances and on the variation in performances across taxa we provide guidance in choosing the best-performing prediction tool for all assessed taxa, by listing the highest scoring tool for each of them.

Antibacterial Mechanism of N-PMI and the Characteristics of PMMA-co-N-PMI Copolymer

Aiming at the excellent killing effect of N-phenylmaleimide (N-PMI) on microorganisms, this paper used structural simulation analysis, fluorescence analysis, confocal laser scanning microscope and SEM to find that the double bond in N-PMI could interact with the sulfur groups in the membrane protein, changing its conformation, rupturing the plasma membrane of the cell, leaking the contents, and ultimately causing the death of the microorganisms. Therefore, once the double bond participated in the polymerization, N-PMI loosed its antimicrobial function. N-PMI could achieve azeotropic copolymerization with MMA through reactive extrusion polymerization, and didn’t follow the law of reactivity ratio of classic copolymerization. N-PMI with a content of 5% can be evenly inserted into the PMMA chain segment during the copolymerization reaction, thereby increasing the Tg of pure PMMA by up to 15°C, which provided the PMMA-co-PMI copolymer with resistance to boiling water sterilization advantageous conditions. In addition, the copolymer was superior to the commercially available pure PMMA in terms of bending strength and modulus. At the same time, N-PMI with a content of 5% has little effect on the transparency of PMMA after participating in the copolymerization. Moreover, the trace amount of residual N-PMI made the material have excellent antimicrobial function, and the bacteriostatic zone is extremely small, which provided an excellent guarantee for the safety and durability of the material. As a medical biological material, the PMMA-co-PMI copolymer has a good industrialization application prospects.

Small proline-rich proteins (SPRRs) are epidermally produced antimicrobial proteins that defend the cutaneous barrier by direct bacterial membrane disruption

Human skin functions as a physical barrier, preventing the entry of foreign pathogens while also accommodating a myriad of commensal microorganisms. A key contributor to the skin landscape is the sebaceous gland. Mice devoid of sebocytes are prone to skin infection, yet our understanding of how sebocytes function in host defense is incomplete. Here we show that the small proline-rich proteins, SPRR1 and SPRR2 are bactericidal in skin. SPRR1B and SPPR2A were induced in human sebocytes by exposure to the bacterial cell wall component lipopolysaccharide (LPS). Further, LPS injected into mouse skin triggered the expression of the mouse SPRR orthologous genes, Sprr1a and Sprr2a, through stimulation of MYD88. Both mouse and human SPRR proteins displayed potent bactericidal activity against MRSA (methicillin-resistant Staphylococcus aureus), Pseudomonas aeruginosa and skin commensals. Thus, Sprr1a-/-;Sprr2a-/- mice are more susceptible to MRSA and Pseudomonas aeruginosa skin infection. Lastly, mechanistic studies demonstrate that SPRR proteins exert their bactericidal activity through binding and disruption of the bacterial membrane. Taken together, these findings provide insight into the regulation and antimicrobial function of SPRR proteins in skin and how the skin defends the host against systemic infection.