Design and fabrication of a new class of nano hybrid materials based on reactive polymeric molecular cages

Functionalized poly(lactic acid) based nano-fabric for anti-viral applications

This study endeavoured to explore and fabricate antiviral and antibacterial facemasks using zinc (oligo-lactate) (ZL), developed through a microwave synthesis technique. The prepared nano-fabric layer has excellent antiviral and antibacterial properties against Newcastle Disease Virus (NDV) and E. coli and S. aureus, respectively. Thermogravimetric analysis (TGA) of ZL shows a two-step thermal degradation, which confirms the formation of low molecular weight end group lactyl units with zinc ions. Another investigation using varying ZL concentration and silk nanocrystal (SNC) with poly(lactic acid) (PLA) and electrospinning them into nanofibres led to the fabrication of a facile and sustainable nanofabric that can be utilized as a protective layer for facemasks. Morphological analysis revealed the successful preparation of the nanofabric with proper distribution and uniformity in fibre diameter. Hydrophobicity of the prepared nanofabric confirmed excellent protection from water droplets that may transpire during coughing or sneezing by an infected individual. Breathability and reusability tests confirmed that the prepared facemask could be reused by ethanol washing without compromising its surface properties till 4 cycles. The PLA/ZL nanofabric layer demonstrated 97% antiviral efficacy against NDV in 10 minutes. In conclusion, the electrospun nanofabric layer can be used as a facemask having high hydrophobicity, good breathability, antibacterial, and antiviral properties to control the spread of contagious diseases.

Rapid Antibacterial Effects of Silk Fabric Constructed through Enzymatic Grafting of Modified PEI and AgNP Deposition

Enzymatic antibacterial finishing is an eco-friendly alternative to develop functional silk-based materials. However, the low accessibility of tyrosine residues distributed in fibroin chains restricts the laccase-mediated functionalization of silk fibers (SF). To address this issue, a highly reactive p-hydroxyphenylacetic acid-modified polyethyleneimine (mPEI) was enzymatically grafted onto fibroin using laccase, aiming at constructing an antibacterial matrix of mPEI on the fiber surface. Subsequently, in situ deposition of silver nanoparticles (i.e., AgNPs) into the newly built mPEI network was performed to form a rapid antibacterial layer. The results indicated that laccase efficiently catalyzes the mPEI coupling, the zeta potential of SF-g-mPEI increases from -32 to 21.70 mV, and the silver content reaches 1.81% after AgNP embedment. Based on the combined two-step treatments, the obtained silk fabric exhibited excellent antibacterial abilities against two bacteria, including Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The antibacterial rates of both bacteria reached 99.9% within 30 min of contact, remaining over 99.9% within 18 h of contact even after washing 10 times. The present work provides an enzyme-mediated method for construction of silk fabric with durable and rapid antibacterial activity.

Dental Applications of Systems Based on Hydroxyapatite Nanoparticles—An Evidence-Based Update

Hydroxyapatite is one of the most studied biomaterials in the medical and dental field, because of its biocompatibility; it is the main constituent of the mineral part of teeth and bones. In dental science, hydroxyapatite nanoparticles (HAnps) or nano-hydroxyapatite (nano-HA) have been studied, over the last decade, in terms of oral implantology and bone reconstruction, as well in restorative and preventive dentistry. Hydroxyapatite nanoparticles have significant remineralizing effects on initial enamel lesions, and they have also been used as an additive material in order to improve existing and widely used dental materials, mainly in preventive fields, but also in restorative and regenerative fields. This paper investigates the role of HAnps in dentistry, including recent advances in the field of its use, as well as their advantages of using it as a component in other dental materials, whether experimental or commercially available. Based on the literature, HAnps have outstanding physical, chemical, mechanical and biological properties that make them suitable for multiple interventions, in different domains of dental science. Further well-designed randomized controlled trials should be conducted in order to confirm all the achievements revealed by the in vitro or in vivo studies published until now.

Primary and Secondary Mesoscopic Hybrid Materials of Au Nanoparticles@Silk Fibroin and Applications

In this work, we demonstrate the principle of mesoscopic construction of silk fibroin (SF) hybrid materials, which endows the materials with new performance. In implementing this strategy, mediating molecules, wool keratin (WK) molecules, were adopted to in-line synthesize Au nanoparticles (WK@AuNPs), which further create the stable linkage of AuNPs with SF nanofibril networks via templated β-crystallization. Fourier transform infrared spectroscopy, X-ray diffraction, and atomic force microscopy demonstrate that the mesoscopic hybrid network structure of the hybrid materials is different from neat SF materials, which gives rise to various new performances, that is, long-stable fluorescence emission. As the fluorescence emission can be characteristically annealed by Cu ions, therefore be adopted as the highly selective ion probes. Moreover, as WK@AuNPs are homogeneously connected to SF nanofibril networks, the carbonization of the materials leads to secondary hybrid materials of carbon-Au, where nano-sized Au particles are well distributed in carbonized mesoscopic conductive carbon networks. Such hybrid materials of carbon-Au can be further fabricated into electrochemical (i.e., dopamine) sensors, which are demonstrated to have excellent sensing performance.

One-Step Synthesis of Ag@TiO₂ Nanoparticles for Enhanced Photocatalytic Performance

Polyamide network polymers (PNP) modified TiO₂ nanoparticles (NPs) were decorated with Ag NPs in hydrothermal gel method, forming one-step synthesized photocatalysts, Ag@TiO₂ NPs. The effect of PNP and the amount of Ag NPs added were investigated in this work. PNP acted as a nanocage to prevent TiO₂ aggregation and capture Ag accurately, which could effectively control product sizes and improve dispersibility in solvents. Simultaneously, TiO₂ NPs modified with Ag NPs exhibited remarkable photocatalytic effects. One-step synthesis simplified the experimental process and avoided the agglomeration of silver ions during the secondary reaction, achieving the purpose of uniform distribution at a specific location of TiO₂ NPs. The prepared Ag@TiO₂ NPs-0.5 could remove 79.49% of Methyl Orange (MO) after 3 h of ultraviolet light irradiation, which was 2.7 times higher than the reaction rate of pure TiO₂ NPs. It also exhibited good photoactivity under Visible light conditions. Moreover, the mineralization rate of MO over the Ag@TiO2 NPs-0.5 could be up to 72.32% under UV light and 47.08% under Visible light irradiation, which revealed that the prepared catalysts could effectively degrade most of the MO to CO₂ and H₂O. The samples also demonstrated the excellent stability and easy recyclability with over 90% of the original catalytic level for MO degradation. The photocatalysts studied also exerted broad application prospects such as photovoltaic hydrogen production, electronic sensors and biomedicine.

Synthesis of TiO2NWS@AuNPS Composite Catalyst for Methylene Blue Removal

In this article, HBP-NH₂-modified titania nanowire (TiO_2NWS)-decorated Au nanoparticles (TiO_2NWS@Au_NPS) were synthesized by one-step method. The role of HBP-NH₂ concentration in the formation of TiO_2NWS was investigated. The fineness and uniformity of pure TiO_2NWS were enhanced by absorbed amino groups from amino-terminated hyperbranched polymer (HBP-NH₂). The morphology and crystal structure of TiO_2NWS and TiO_2NWS@Au_NPS were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fournier transform infrared (FTIR) spectroscopy. The chemical states of gold, titanium and oxygen were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that at the concentration of HBP-NH₂ 100 g/L, the mean diameter of TiO_2NWS was nearly 72 nm and Au nanoparticles were uniformly distributed on the surface of TiO_2NWS. The presence of Au_NPS improved the photocatalytic properties of TiO_2NWS under UV light irradiation. The Au load was believed to improve the utilization rate of the photoelectron and activated the adsorbed oxygen. The obtained TiO_2NWS@Au_NPS decomposed 99.6% methylene blue (MB) after 300 min when subjected to UV light irradiation. After five cycles of the catalyzing process, the TiO_2NWS@Au_NPS still retained over 90% of its catalytic ability for MB. The Au deposition was found responsible for the high catalytic activity of TiO_2NWS@Au_NPS.

Facile crosslinking synthesis of hyperbranch-substrate nanonetwork magnetite nanocomposite for the fast and highly efficient removal of lead ions and anionic dyes from aqueous solutions

The aim of the present work was to investigate the effect of surface functional group density on the adsorption behaviors of functionalized mesoporous Fe₃O₄.

Sunlight induced unique morphological transformation in graphene based nanohybrids: appearance of a new tetra-nanohybrid and tuning of functional property of these nanohybrids

In this study, sunlight was used for in situ preparation of gel-based various nanohybrid systems. A naturally occurring amino acid, l-phenylalanine derivative formed a hydrogel with graphene oxide (GO)/reduced graphene oxide (rGO) at physiological pH. This hydrogel was then used in the presence of silver ions and diffuse sunlight to form initially a tri-nanohybrid system consisting of six atom silver nanoclusters, nanosheets, and nanofibers. Interestingly, a time-dependent morphological transformation occurs in this nanohybrid system to form one tri-nanohybrid to another tri-nanohybrid with the appearance of a novel, nanoscopic intermediate tetra-nanohybrid system consisting of four distinctly different nanomaterials (nanofibers, nanosheets, nanospheres, and nanoparticles). UV-Vis and fluorescence spectroscopic analyses, transmission electron microscopic, X-ray photo electron spectroscopic and MALDI-TOF mass spectral analyses with time were applied to characterise these morphological transformations in gel based nanohybrids. Time-dependent X-ray photo electron spectroscopic (XPS) analysis was used to uncover the mechanism for the transformation of silver nanoclusters to silver nanoparticles in the hydrogel matrix. Sunlight was used to trigger time-dependent structural transformation in the nanohybrid systems. Interestingly, one of these tri-nanohybrid systems (silver nanoparticles containing rGO based hydrogel) shows a catalytic property of reducing nitroarenes to aminoarenes and the catalytic efficiency can be modulated by changing the size of the silver nanoparticles with time in diffuse sunlight. The mechanism for different catalytic activities for different hybrids with varying size of silver nanoparticles has also been deciphered.