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Herein, silk fibroin nanoparticles (FNPs) were explored as a potential oral delivery system, with 04 representative oral drugs belonged to different Biopharmaceutics Classification System (BCS) classes, including ascorbic acid (class I), dextromethorphan (class II), paracetamol (class III), and paclitaxel (class IV). The 04 drug-loaded FNP formulas demonstrated spherical nanosized particles of 300–420 nm with dominant silk-II structures, negative zeta potentials of − 17 mV, varied entrapment efficiencies, and physico-chemical stabilities of > 3 months. In the gastrointestinal condition, the particles significantly enhanced the class-II- and class-IV-drug solubility and sustained their release rates to > 72 h. For the BCS class-I- and class-III-drugs, the particles prolonged the drug release to 6 h. Moreover, the FNP could bypass the pH variations in the gastrointestinal tract and increase the drug permeability across the intestinal membrane by facilitating the drug cellular internalizations. Conclusively, the FNP is a versatile system for the oral delivery of different pharmaceutical agents. Graphical abstract

Guava (Psidium guajava L.) is a well-known plant containing high levels of natural antioxidants, the phenolic compounds, which have been employed in numerous cosmetic products. However, these molecules are unstable to oxidants, light, temperature, pH, water, and enzymatic activities. Therefore, to enhance their stability and preserve their antioxidant activity, this study investigated the silk fibroin nanoparticles (SFNs) ability to encapsulate, deliver, and heat-protect the phenolic compounds of the guava leaves ethanolic extract. Firstly, the guava ethanolic extract was produced by maceration, which possessed a total phenolic content of 312.6 mg GAE/g DPW and a high antioxidant activity (IC 50 = 5.397 ± 0.618 µg/mL). Then, the extract loaded SFNs were manufactured by desolvation method, and the particles demonstrated appropriate sizes of 200-700 nm with narrow size distribution, spherical shape, silk-II crystalline structure, high drug entrapment efficiency of > 70% (dependent on the fibroin content), and a two-phase sustained drug release for at least 210 min. Using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the antioxidant activity of the guava extract was well-preserved in the extract loaded SFNs. Finally, after being treated with high temperature of 70 °C for 24 h, the guava extract almost loses all of its antioxidant property (5 times decrement), whereas the extract loaded SFNs could retain the extract activity. Conclusively, the SFNs proved much potential to deliver and heat-protect the guava extract phenolic compounds, and preserve their antioxidant activity. Confirmed by this case, SFNs could be further explored in protecting other natural compounds from environmental factors.

Perovskite BaTiO3 nanoparticles were synthesized by a hydrothermal method. BaTiO3/chitosan (CS)/Polyvinyl alcohol (PVA) nanofibers with an average diameter of 265.3 ± 52 nm were fabricated via an electrospinning method. The nanofibers were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), and thermal analysis method (TGA). The photoanodes of dye-sensitized solar cells (DSSC) were fabricated based on the BaTiO3/CS/PVA nanofibers. The photovoltaic properties of the cells were calculated based on the current density – voltage curves. The maximum power conversion efficiency of DSSC with CS/PVA/BaTiO3 nanofibers was 0.49% with the natural dye sensitizer extracted from the leaf of the magenta plant.

In this study, AuM (M = Pt, Pd) bimetallic hexagonals (AuM BHGs) were successfully combined with graphene quantum dots (GQDs) by a simple method at ambient temperature (~ 30 °C) to form AuM BHGs/GQDs nanocomposites with enhanced properties and electro-activities. The synthesized AuM BHGs/GQDs were also characterized by UV–Vis, XRD, FTIR, XPS, AFM, TEM, and EDS. The novel AuM BHGs/GQDs were successfully synthesized, possessed an average particle size of AuM BHGs (~ 50–60 nm) and GQDs (~ 6–16 nm), and were homogeneously distributed in the dispersion. Furthermore, AuM BHGs/GQDs nanocomposites were also investigated as a sensitive sensor in the H 2 O 2 detection by cyclic voltammetry method, with a low H 2 O 2 limit of detection (LOD) of 0.865 nM, high sensitivity of 1.27 μAnM −1 cm −2 and a wide detection range from 10 –12 to 10 –3 M. Therefore, AuM BHG/GQDs nanocomposites could be used to detect H 2 O 2 with high sensitivity and fast response. Graphical abstract

In this study, the novel Au/Cu 2 O/Graphene quantum dots nanocomposites have been synthesized via a fast, simple and environmentally friendly method for the first time. Specifically, Cu 2 O nanocubes (Cu 2 O NCBs) synthesized by a reduction reaction at room temperature were combined with Au nanoparticles (Au NPs) and Graphene quantum dots (GQDs) obtained from low-cost and naturally abundant material. The synthesized Au/Cu 2 O/GQDs were characterized by UV-vis, FTIR, XRD, TEM, FESEM, and EDS. The results show that the Au/Cu 2 O/GQDs have an average size of about 32-36 nm, in which the diameter of Au NPs is ~28-32 nm, Cu 2 O particles have the form of nanocube with the size of ~29-33 nm and GQDs are small spherical with an average size of ~5 nm. In addition, the electrochemical properties of the Au/Cu 2 O/GQDs electrodes were investigated using the cyclic voltammetry (CV) technique. The obtained results show that the Au/Cu 2 O/GQDs have high electroactivity, which are very potential and promising to be used in glucose sensor with a very wide concentration of glucose detection range from 10 -10 M to 1 M with a the LOD of 70 nM (7×10 -8 M) and a high sensitivity of 32.5 μAμM -1 cm -2 . Therefore, Au/Cu 2 O/GQDs will be potential candidate for non-enzymatic sensitive glucose sensors in the future. Graphical abstract Cu 2 O nanocubes (Cu 2 O NCBs) were successfully combined with Au nanoparticles (Au NPs) and Graphene quantum dots (GQDs) to generate Au/Cu 2 O/GQDs nanocomposites. The properties and morphology of synthesized Au/Cu 2 O/GQDs were also studied. Au/Cu 2 O/GQDs showed promising electrochemical activity and performed its applicability for glucose detection with a wide concentration of glucose detection range from 10 -10 M to 1 M.

In this study, AuPt bimetallic nanocubes (AuPt NCBs) were successfully combined with graphene quantum dots (GQDs) by a simple and easy-to-implement method at 80 °C for 90 min. In particular, graphene quantum dots were synthesized by hydrothermal method at 190 °C for 8 h, using raw material from wheat flour which is eco-friendly, available and abundant in nature. Besides, AuPt bimetallic nanocubes in the form of AuPt core/shell nanocubes (AuPt NCBs) were generated from the reaction at 140 °C for 2 h by hydrothermal method. Furthermore, the synthesized AuPt NCBs/GQDs nanocomposites were also characterized, shape, size and composition by: UV–vis, FTIR, XRD, TEM, EDX, XPS, and AFM. The obtained results show that the Au nanocubes (Au NCBs) have an average size of ~ 39 nm; while, the average size of AuPt NCBs and GQDs are ~ 40–44 and  ~ 3–5 nm, respectively. In addition, AuPt NCBs/GQDs nanocomposites were also used as non-enzymatic catalysts for the oxidation/reduction of glucose by cyclic voltammetry technique. The obtained results indicated that the AuPt NCBs/GQDs nanocomposites have high catalytic activity and are capable of detecting glucose in a wide concentration range from 10 −12 to 1 M, with an extremely low limit of detection of concentration glucose levels (~ 10 −12  M). Therefore, AuPt NCBs/GQDs are novel and promising materials that can be applied as catalysts with high activity oriented to many fields such as environmental treatment, fuel energy cells, or sensors to make bio-chip devices for early diagnosis of serious diseases such as diabetes, gout or cancer, etc., in present and the future. Graphical abstract

Perovskite BaTiO 3 nanoparticles were synthesized by a hydrothermal method. BaTiO 3 /chitosan (CS)/Polyvinyl alcohol (PVA) nanofibers with an average diameter of 265.3 ± 52 nm were fabricated via an electrospinning method. The nanofibers were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), and thermal analysis method (TGA). The photoanodes of dye-sensitized solar cells (DSSC) were fabricated based on the BaTiO 3 /CS/PVA nanofibers. The photovoltaic properties of the cells were calculated based on the current density – voltage curves. The maximum power conversion efficiency of DSSC with CS/PVA/BaTiO 3 nanofibers was 0.49% with the natural dye sensitizer extracted from the leaf of the magenta plant.

In this study, AuPt bimetallic nanocubes (AuPt NCBs) were successfully combined with graphene quantum dots (GQDs) by a simple and easy-to-implement method at 80oC for 90 min. In particular, graphene quantum dots (GQDs) nanoparticles were synthesized by hydrothermal method at 190oC for 8 h, using raw materials from wheat flour, which are environmentally friendly materials, available and abundant in nature. AuPt bimetallic nanocubes were obtained from the synthesis of Au nanocubes (Au NCBs), followed by AuPt nanoparticles obtained when reacted at 140oC for 2 h by hydrothermal method to form AuPt core/shell nanocubes (AuPt NCBs). Besides, the synthesized AuPt NCBs/GQDs nanocomposites were also characterized, shape, size and composition by: UV-vis, FTIR, XRD, TEM, EDX, XPS, and AFM. The obtained results show that the Au nanocubes (Au NCBs) have an average particle size of ~39 nm; the size of AuPt NCBs and GQDs nanoparticles are ~40-44 nm and ~3-5 nm in size, respectively. Furthermore, AuPt NCBs/GQDs nanocomposites are also used as non-enzymatic catalysts for the oxidation/reduction of glucose by cyclic voltammetry (CV). The obtained results indicate that the AuPt NCBs/GQDs nanocomposites with high catalytic activity are capable of detecting glucose in a wide concentration range from 10-12 M to 1 M, with an extremely low limit of detection (LOD) of concentration glucose levels (~10-12 M). Therefore, AuPt NCBs/GQDs are novel and promising nano-catalysts that can be applied as catalysts with high activity oriented to many fields such as environmental treatment, fuel energy cells, or sensors to make bio-chip devices for early diagnosis of serious diseases such as diabetes, gout or cancer, etc., in present and the future.

The pathogenesis of severe dengue is not well understood. Maternally derived subneutralizing levels of dengue virus-reactive IgG are postulated to be a critical risk factor for severe dengue during infancy. In this study, we found that, in healthy Vietnamese infants, there was a strong temporal association between the Fc-dependent, dengue virus infection-enhancing activity of neat plasma and the age-related epidemiology of severe dengue. We then postulated that disease severity in infants with primary infections would be associated with a robust immune response, possibly as a consequence of higher viral burdens in vivo. Accordingly, in infants hospitalized with acute dengue, the activation phenotype of peripheral-blood NK cells and CD8+ and CD4+ T cells correlated with overall disease severity, but HLA-A*1101-restricted NS3133–142-specific CD8+ T cells were not measurable until early convalescence. Plasma levels of cytokines/chemokines were generally higher in infants with dengue shock syndrome. Collectively, these data support a model of dengue pathogenesis in infants whereby antibody-dependent enhancement of infection explains the age-related case epidemiology and could account for antigen-driven immune activation and its association with disease severity. These results also highlight potential risks in the use of live attenuated dengue vaccines in infants in countries where dengue is endemic.

A second cluster of COVID-19 cases imported from Europe occured in Vietnam from early March 2020. We describe 44 SARS-CoV-2 RT-PCR positive patients (cycle threshold value <30) admitted to the National Hospital for Tropical Diseases in Hanoi between March 6 and April 15 2020. Whole SARS-CoV-2 genomes from these patients were sequenced using Illumina Miseq and analysed for common genetic variants and relationships to local and globally circulating strains. Results showed that 32 cases were Vietnamese with a median age of 37 years (range 15–74 years), and 23 were male. Most cases were acquired outside Vietnam, mainly from the UK (n = 15), other European countries (n = 14), Russia (n = 6) and countries in Asia (n = 3). No cases had travelled from China. Forty-one cases had symptoms at admission, typically dry cough (n = 36), fever (n = 20), sore throat (n = 14) and diarrhoea (n = 12). Hospitalisation was long with a median of 25 days, most commonly from 20–29 days. All SARS-CoV-2 genomes were similar (92–100% sequence homology) to the reference sequence Wuhan_1 (NC_045512), and 32 strains belonged to the B.1.1 lineage. The three most common variants were linked, and included C3037T, C14408T (nsp12: P323L) and A23403G (S: D614G) mutations. This group of mutations often accompanied variant C241T (39/44 genomes) or GGG 28881..28883 AAC (33/44 genomes). The prevalence of the former reflected probable European origin of viruses, and the transition D614G was dominant in Vietnam. New variants were identified; however, none could be associated with disease severity.