Current Nanoscience - Volume 18, Issue 6, 2022

Nanostructured hybrid materials (NHMs) based on nanostructures, such as graphene or graphene-related materials and semiconductor quantum dots (QDs) or nanoparticles, have attracted a great deal of attention from the scientific community in the last decade. Their potential applications range from more conventional optoelectronic uses (e.g., photodetectors and solar cells), passing through the field of photocatalysis and spanning to the biotechnology arena, as they have been used in bioimaging applications. In this perspective paper, a summary of the developments achieved in this type of NHM is presented, along with an outlook on the main challenges that are still needed to be overcome.

The electrodes are the basis for building flexible lithium-ion batteries (FLIBs), and many attempts have been made to develop flexible electrodes with high efficiency in terms of electrical conductivity, chemical and mechanical properties. Most studies showed relatively satisfactory results when testing the electrochemical properties of laboratory-produced electrodes, but most of these electrodes could not meet the expected requirements of flexible electrodes in practical applications. Quantitative production faces many problems that must be overcome, such as the gradual decline in electrochemical performance, deformation of the electrode structure, high production costs, and difficulties in the production process itself. In this research, developments in the production of flexible electrodes, especially those that depend on carbon materials and metal nanoparticles, will be discussed and summarized in this research. The electrochemical performance and stability of the produced flexible electrodes will be compared. The factors contributing to the progress in the production of flexible lithium-ion batteries will also be discussed.

Disorders of the central and peripheral nervous systems are still major human health issues. Researchers have been seeking ways to boost neuroregeneration and neuroprotection since ancient times in order to overcome the brain's, spinal cord's, and peripheral nerves' limited ability to regenerate spontaneously. In this scenario, nanopolymers have shown great potential in terms of drug delivery systems and scaffolds, diminishing the scale of tissue damage and promoting functional recovery in both acute and chronic injuries. A diversity of natural and synthetic polymers has been exploited due to the unique characteristics of these polymers regarding their mechanical and biological properties. These properties dictate how the biomaterial interact with biological systems and how they are distinct in each polymer. This makes them suitable for numerous applications that range from the controlled release of an anti-inflammatory drug to axonal guidance. The versatility of nanopolymers makes them a rich source for therapeutic approaches in the neuroscience field, especially in neuroprotection and neuroregeneration.

Conventional treatment modalities for tumors face a variety of pitfalls, including nonspecific interactions leading to multiple adverse effects. These adverse effects are being overcome through innovations that are highly intense and selective delivery of therapeutic agents. More recently, Photodynamic therapy (PDT) has gained its value over conventional chemo- and radiotherapies due to the use of photosensitizers (PS) with an illuminating light source. Photosensitizers have crossed three generations with Photofrin being the first clinically approved PS for PDT. Even though these PS have proved to have cytotoxic effects against tumor cells, they suffer the selective distribution and concentration into the tumor sites that are deeply localized. To overcome these disadvantages, nanoformulations are currently being employed due to their unmatched physicochemical and surface properties. These nanoformulations include the encapsulation of PS acting as a nanocarrier for the PS or the functionalization of PS onto the surface of nanoparticles. The design of such nanoformulations involved in PDT is critical and valuable to consider. Along with PDT, several multifunctional approaches are being uplifted in the current trend where combined therapy and diagnosis are of great importance. Furthermore, targeted, selective, and specific delivery of the PS-loaded nanoformulations with receptor- mediated endocytosis is of interest to achieve better internalization into the tumor site. ROS generation with the interaction of PS augments cell death mechanisms exhibited due to PDT, leading to the immunogenic response that further results in an adaptive immune memory that prevents recurrence of tumor metastasis. Therefore, this review concentrates on the mechanisms of PDT, examples of nanocarriers and nanoparticles that are employed in PDT, combined therapies, and theranostics with PDT. Moreover, molecular mechanisms of nano-based PDT agents in killing tumor sites and designing considerations for better PDT outcomes have been discussed.

Due to micro-/nanorobots having several propulsion mechanisms, drug delivery through micro/nanorobots is moving to the forefront of nanomedical research. However, low biocompatibility and low imaging efficiency have become major obstacles in the further development of micro- /nanorobots. This article firstly introduces the application of micro-/nanorobots in the field of nanomedicine in recent years, expresses the importance of micro-/nanorobots in terms of nanomedicine, and then summarizes and compares several propulsion mechanisms. The improvement and optimization of the preparation methodologies and structures in terms of micro-/nanorobots are also reviewed. The imaging effect and biocompatibility of micro-/nanorobots have been improved to the extent that it is suitable for clinical medicine while ensuring the efficiency of drug delivery. Then, the advantages of different propulsion mechanisms, imaging effects, and biocompatibility are compared. The aim of the review is to enable people of various knowledge backgrounds to learn directly and choose suitable modified methods based on realistic situations. Finally, future development trends and further prospects of micro-/nanorobots are discussed.

Throughout the research of flexible nanomaterials and sensing technology in recent years, electronic skin has been widely developed as well as applied in many fields. As a bionic flexible tactile sensor, electronic skin can simulate the touching of human skin with external signals as well as collect and detect dynamic information of the physical surface. This paper reviews the flexible substrate materials and electrode nanomaterials of electronic skin. The stable support of the flexible substrate largely determines the mechanical properties of the electronic skin. At the outset, this article introduces the flexible substrate materials commonly used in electronic skins. PDMS, PI, and PET are typical representatives of flexible substrate materials. Then, the nanomaterials used for electrodes are discussed, including one-dimensional and two-dimensional nanomaterials, especially emphasizing the innovation of the sensor performance about the advanced electronic skin along with the use of different nanomaterials under the integrated application background. In addition, these electrode nanomaterials need to be appropriately embedded in flexible substrate materials. The response time, sensitivity, detection limit, response range, and the cycle of electronic skin are selected for comparison. Finally, the opportunities and challenges of electronic skin in nanomaterials and sensing technology are summarized.

Background: The spread of new coronavirus 2019, the causative agent of viral pneumonia documented in Wuhan, brought a recent public health crisis globally. The best solution to overcome this pandemic is developing suitable and effective vaccines and therapeutics. However, discovering and creating a new drug is a lengthy process requiring rigorous testing and validation. Objective: Despite many newly discovered and old repurposed COVID-19 drugs under clinical trial, more emphasis should be given to research on COVID-19 NPs-based medicines, which could improve the efficacy of antiviral drugs to reduce their side effects. The use of NPs as carriers can reduce the frequency and duration of drug ingestion, enhance approved antiviral therapeutics' effectiveness, and overcome their limitations, such as low bioavailability. Besides, they can play a crucial role in fighting against the COVID-19 pandemic. In this regard, nanotechnology provides opportunities to develop new strategies for preventing, diagnosing, and treating COVID-19. Conclusion: This review highlighted the importance of NMs-based technical solutions in antiviral drugs for testing against the SARS-CoV-2 virus emergencies in the form of nanotherapeutics.

Background: Copper oxide nanoparticles have become very important due to their numerous applications and ease of synthesis. Out of the two oxides of copper, cuprous oxide exhibits better antibacterial, antimicrobial, and antifouling properties. Objective: The study aimed to find a way of synthesizing stable and eco-friendly oxide of copper and test it for antibacterial properties. Methods: The precipitation method was employed for the synthesis of nanoparticles. NaOH and Moringa oleifera leaves extract were used as the reducing agents to obtain two different sets of samples. Results: Good phases of copper oxides were formed for all the samples (cuprous as well as cupric oxides). SEM studies showed that the structure of cupric oxide (CuO), formed at higher calcination temperatures, is well defined when synthesized using a hybrid method. Conclusion: Our studies indicate that the hybrid method of synthesis used by us is a more effective and quicker way of synthesizing cuprous oxide (Cu2O), which exhibits higher antibacterial properties as compared to cupric oxide (CuO).

Background: The rapid mutation of the H1N1 strain of the Influenza virus makes it quite difficult to treat once the infection has spread. The development of new treatments based on the destabilization of the genetic material, regardless of the sequence, is necessary. Objective: The study aims to evaluate the antiviral properties of Pt/TiO2-SiO2 bionanocatalysts against Influenza A (H1N1) virus in a post-infection model and to characterize the morphology of the nanoparticles. Methods: The bionanocatalysts were synthesized by the sol-gel method. Electron Microscopy studies were performed to evaluate the grain size and morphology of pure nanoparticles. Madin-Darby Canine Kidney (MDCK) epithelial cells were infected with Influenza A (H1N1) virus. They were treated with 500 μL of three viral suspensions (1:50, 1:100, and 1:1000) and 500 μL of a nanoparticle suspension (2 ng/mL). The presence of the virus was identified by Polymerase Chain Reaction (PCR) endpoint and the antiviral properties of the nanoparticles were identified in terms of infection reduction calculated by real-time PCR using Influenza A and H1N1 subtype primers. The percentage of infection reduction was calculated by comparing control samples and samples treated with the bionanocatalysts. Results: The Pt/TiO2-SiO2 bionanocatalysts showed highly surface-dispersed platinum nanoparticles with an average particle size of 1.23 ± 0.36 nm in the amorphous oxide matrix. The nanoparticles showed antiviral properties with a maximum reduction in viral proliferation of 65.2 ± 3.3%. Conclusion: Pt/TiO2-SiO2 bionanocatalysts were able to reduce Influenza A (H1N1) viral infection 65.2 ± 3.3%; the results suggest the biocompatibility with healthy tissues and in vitro antiviral properties. Further studies should be conducted to identify the concentration required to achieve total virus clearance. However, the outcome of the present work suggests the possibility of implementing bionanocatalysts as treatments for Influenza A (H1N1) virus infection, especially at an advanced stage of infection.

Background: The antimicrobial properties of silver can be enhanced in the form of silver nanoparticles due to their specific physical, chemical, and biological properties, thus enabling their use in different antibacterial applications against antibiotic-resistant bacteria. Objective: Present study was planned to evaluate the antibacterial activity of silver nanoparticles synthesized from bark extract of Terminalia arjuna. Methods: Silver nanoparticles were synthesized using 80% methanolic extract of Terminalia arjuna bark, followed by their characterization using UV-Visible spectroscopy, particle size analysis, and atomic force microscopy. The antibacterial activity of synthesized silver nanoparticles was analyzed against Escherichia coli MTCC1687, Pseudomonas aeruginosa ATCC9027, and Staphylococcus aureus ATCC6538. Results: The silver nanoparticles were observed to inhibit microbial growth in a concentrationdependent manner (2-0.5mg/mL), and the cell death was confirmed using fluorescent microscopy. Conclusion: The antibacterial activity of these nanoparticles suggests that the synthesized nanoparticles can be used to treat bacterial infections of the skin.

Aim: In this study, the antibacterial activity of zinc oxide (ZnO) nanostructures of different shapes, including nanoparticles, nanoflowers, and nanoflakes, was evaluated. Methods: The optical and morphological properties of the synthesized nanostructures were characterized by double-beam ultraviolet-visible (UV-Vis) analysis, X-ray diffraction (XRD) analysis, Energy Dispersive X-ray Analysis (EDX), and Scanning Electron Microscopy (SEM). Microdilution method was conducted, and minimum inhibitory concentration (MIC) was calculated to compare the antibacterial activity of the morphologically different nanostructures. Results: The SEM showed that ZnO-NPs were spherical in shape with a size of 100 nm. The EDX spectrum also showed that the synthesized ZnO-NPs were mainly composed of zinc, with the minimum contaminants being carbon and oxygen. The XRD analysis confirmed that the nature of the synthesized materials was ZnO with an average grain size of 3 nm to 21 nm. The greatest antibacterial activity of ZnO nanoparticles was against Pseudomonas aeruginosa, and for ZnO nanoflakes, against Escherichia coli. Conclusion: The study demonstrated that the antibacterial activity of nano-ZnO is shape-dependent.