Electrically Conductive Polymers for Additive Manufacturing.

The use of electrically conductive polymers (CPs) in the development of electronic devices has attracted significant interest due to their unique intrinsic properties, which result from the synergistic combination of physicochemical properties in conventional polymers with the electronic properties of metals or semiconductors. Most conventional methods adopted for the fabrication of devices with nonplanar morphologies are still challenged by the poor ionic/electronic mobility of end products. Additive manufacturing (AM) brings about exciting prospects to the realm of CPs by enabling greater design freedom, more elaborate structures, quicker prototyping, relatively low cost, and more environmentally friendly electronic device creation. A growing variety of AM technologies are becoming available for three-dimensional (3D) printing of conductive devices, i.e., vat photopolymerization (VP), material extrusion (ME), powder bed fusion (PBF), material jetting (MJ), and lamination object manufacturing (LOM). In this review, we provide an overview of the recent research progress in the area of CPs developed for AM, which advances the design and development of future electronic devices. We consider different AM techniques, vis-à-vis, their development progress and respective challenges in printing CPs. We also discuss the material requirements and notable advances in 3D printing of CPs, as well as their potential electronic applications including wearable electronics, sensors, energy storage and conversion devices, etc. This review concludes with an outlook on AM of CPs.

Self-Healing Polymeric Materials and Composites for Additive Manufacturing.

Self-healing polymers have received widespread attention due to their ability to repair damage autonomously and increase material stability, reliability, and economy. However, the processability of self-healing materials has yet to be studied, limiting the application of rich self-healing mechanisms. Additive manufacturing effectively improves the shortcomings of conventional processing while increasing production speed, accuracy, and complexity, offering great promise for self-healing polymer applications. This article summarizes the current self-healing mechanisms of self-healing polymers and their corresponding additive manufacturing methods, and provides an outlook on future developments in the field.

A non-invasive smart scaffold for bone repair and monitoring.

Existing strategies for bone defect repair are difficult to monitor. Smart scaffold materials that can quantify the efficiency of new bone formation are important for bone regeneration and monitoring. Carbon nanotubes (CNT) have promising bioactivity and electrical conductivity. In this study, a noninvasive and intelligent monitoring scaffold was prepared for bone regeneration and monitoring by integrating carboxylated CNT into chemically cross-linked carboxymethyl chitosan hydrogel. CNT scaffold (0.5% w/v) demonstrated improved mechanical properties with good biocompatibility and electrochemical responsiveness. Cyclic voltammetry and electrochemical impedance spectroscopy of CNT scaffold responded sensitively to seed cell differentiation degree in both cellular and animal levels. Interestingly, the CNT scaffold could make up the easy deactivation shortfall of bone morphogenetic protein 2 by sustainably enhancing stem cell osteogenic differentiation and new bone tissue formation through CNT roles. This research provides new ideas for the development of noninvasive and electrochemically responsive bioactive scaffolds, marking an important step in the development of intelligent tissue engineering.

Antibody-Antimicrobial Conjugates for Combating Antibiotic Resistance.

As the development of new antibiotics lags far behind the emergence of drug-resistant bacteria, alternative strategies to resolve this dilemma are urgently required. Antibody-drug conjugate is a promising therapeutic platform to delivering cytotoxic payloads precisely to target cells for efficient disease treatment. Antibody-antimicrobial conjugates (AACs) have recently attracted considerable interest from researchers as they can target bacteria in the target sites and improve the effectiveness of drugs (i.e., reduced drug dosage and adverse effects), abating the upsurge of antimicrobial resistance. In this review, the selection and progress of three essential blocks that compose the AACs: antibodies, antimicrobial payloads, and linkers are discussed. The commonly used conjugation strategies and the latest applications of AACs in recent years are also summarized. The challenges and opportunities of this booming technology are also discussed at the end of this review.

Structural and photoactive properties of self-assembled peptide-based nanostructures and their optical bioapplication in food analysis.

BACKGROUND: Food processing plays an important role in the modern industry because food quality and security directly affect human health, life safety, and social and economic development. Accurate, efficient, and sensitive detection technology is the basis for ensuring food quality and security. Optosensor-based technology with the advantage of fast and visual real-time detection can be used to detect pesticides, metal ions, antibiotics, and nutrients in food. As excellent optical centres, self-assembled peptide-based nanostructures possess attractive advantages, such as simple preparation methods, controllable morphology, tunable functionality, and inherent biocompatibility. AIM OF REVIEW: Self-assembled peptide nanostructures with good fabrication yield, stability, dispersity in a complex sample matrix, biocompatibility, and environmental friendliness are ideal development goals in the future. Owing to its flexible and unique optical properties, some short peptide self-assemblies can possibly be used to achieve the purpose of rapid and sensitive detection of composition in food, agriculture, and the environment, expanding the understanding and application of peptide-based optics in analytical chemistry. KEY SCIENTIFIC CONCEPT OF REVIEW: The self-assembly process of peptides is driven by noncovalent interactions, including hydrogen bonding, electrostatic interactions, hydrophobic interactions, and π-π stacking, which are the key factors for obtaining stable self-assembled peptide nanostructures with peptides serving as assembly units. Controllable morphology of self-assembled peptide nanostructures can be achieved through adjustment in the type, concentration, and pH of organic solvents and peptides. The highly ordered nanostructures formed by the self-assembly of peptides have been proven to be novel biological structures and can be used for the construction of optosensing platforms in biological or other systems. Optosensing platforms make use of signal changes, including optical signals and electrical signals caused by specific reactions between analytes and active substances, to determine the content or concentration of an analyte.

Recent advances in the use of the CRISPR-Cas system for the detection of infectious pathogens.

Infectious diseases cause great economic loss and individual and even social anguish. Existing detection methods lack sensitivity and specificity, have a poor turnaround time, and are dependent on expensive equipment. In recent years, the clustered regularly interspaced short palindromic repeats (CRISPR)|-CRISPR-associated protein (Cas) system has been widely used in the detection of pathogens that cause infectious diseases owing to its high specificity, sensitivity, and speed, and good accessibility. In this review, we discuss the discovery and development of the CRISPR-Cas system, summarize related analysis and interpretation methods, and discuss the existing applications of CRISPR-based detection of infectious pathogens using Cas proteins. We conclude the challenges and prospects of the CRISPR-Cas system in the detection of pathogens.

Motion Detecting, Temperature Alarming, and Wireless Wearable Bioelectronics Based on Intrinsically Antibacterial Conductive Hydrogels.

Hydrogels have attracted considerable interest in developing flexible bioelectronics such as wearable devices, brain-machine interface products, and health-monitoring sensors. However, these bioelectronics are always challenged by microbial contamination, which frequently reduces their service life and durability due to a lack of antibacterial property. Herein, we report a class of inherently antibacterial conductive hydrogels (ACGs) as bioelectronics for motion and temperature detection. The ACGs were composed of poly(N-isopropylacrylamide) (pNIPAM) and silver nanowires (AgNWs) via a two-step polymerization strategy, which increased the crosslink density for enhanced mechanical properties. The introduction of AgNWs improved the conductivity of ACGs and endowed them with excellent antibacterial activity against both Gram-positive and -negative bacteria. Meanwhile, pNIPAM existed in ACGs and exhibited a thermal responsive behavior, thereby inducing sharp changes in their conductivity around body temperature, which was successfully employed to assemble a temperature alarm. Moreover, ACG-based sensors exhibited excellent sensitivity (within a small strain of 5%) and the capability of capturing various motion signals (finger bending, elbow bending, and even throat vibrating). Benefiting from the superiority of ACG-based sensors, we further demonstrated a wearable wireless system for the remote control of a vehicle, which is expected to help disabled people in the future.

Multiphoton Upconversion Materials for Photocatalysis and Environmental Remediation.

Solar-driven photocatalysis holds great potential for energy conversion, environmental remediation, and sustainable chemistry. However, practical applications of conventional photocatalytic systems have been constrained by their insufficient ability to harvest solar radiation in the infrared spectrum. Lanthanide-doped upconversion materials possess high photostability, tunable absorption, and the ability to convert low-energy infrared radiation into high-energy emission, making them attractive for infrared-driven photocatalysis. This review highlights essential principles for rational design of efficient photocatalysts. Particular emphasis is placed on current state-of-the-arts that offer enhanced upconversion luminescence efficiency. We also summarize recent advances in lanthanide-doped upconversion materials for photocatalysis. We conclude with new challenges and prospects for future developments of infrared-driven photocatalysts.

Emerging strategies in developing multifunctional nanomaterials for cancer nanotheranostics.

Cancer involves a collection of diseases with a common trait - dysregulation in cell proliferation. At present, traditional therapeutic strategies against cancer have limitations in tackling various tumors in clinical settings. These include chemotherapeutic resistance and the inability to overcome intrinsic physiological barriers to drug delivery. Nanomaterials have presented promising strategies for tumor treatment in recent years. Nanotheranostics combine therapeutic and bioimaging functionalities at the single nanoparticle level and have experienced tremendous growth over the past few years. This review highlights recent developments of advanced nanomaterials and nanotheranostics in three main directions: stimulus-responsive nanomaterials, nanocarriers targeting the tumor microenvironment, and emerging nanomaterials that integrate with phototherapies and immunotherapies. We also discuss the cytotoxicity and outlook of next-generation nanomaterials towards clinical implementation.

One-step vapor deposition of fluorinated polycationic coating to fabricate antifouling and anti-infective textile against drug-resistant bacteria and viruses.

The ongoing pandemic caused by the novel coronavirus has turned out to be one of the biggest threats to the world, and the increase of drug-resistant bacterial strains also threatens the human health. Hence, there is an urgent need to develop novel anti-infective materials with broad-spectrum anti-pathogenic activity. In the present study, a fluorinated polycationic coating was synthesized on a hydrophilic and negatively charged polyester textile via one-step initiated chemical vapor deposition of poly(dimethyl amino methyl styrene-co-1H,1H,2H,2H-perfluorodecyl acrylate) (P(DMAMS-co-PFDA), PDP). The surface characterization results of SEM, FTIR, and EDX demonstrated the successful synthesis of PDP coating. Contact angle analysis revealed that PDP coating endowed the polyester textile with the hydrophobicity against the attachment of different aqueous foulants such as blood, coffee, and milk, as well as the oleophobicity against paraffin oil. Zeta potential analysis demonstrated that the PDP coating enabled a transformation of negative charge to positive charge on the surface of polyester textile. The PDP coating exhibited excellent contact-killing activity against both gram-negative Escherichia coli and gram-positive methicillin-resistant Staphylococcus aureus, with the killing efficiency of approximate 99.9%. In addition, the antiviral capacity of PDP was determined by a green fluorescence protein (GFP) expression-based method using lentivirus-EGFP as a virus model. The PDP coating inactivated the negatively charged lentivirus-EGFP effectively. Moreover, the coating showed good biocompatibility toward mouse NIH 3T3 fibroblast cells. All the above properties demonstrated that PDP would be a promising anti-pathogenic polymeric coating with wide applications in medicine, hygiene, hospital, etc., to control the bacterial and viral transmission and infection.

Recent Insights into Emerging Coronavirus: SARS-CoV-2.

The SARS-CoV-2 outbreak that emerged at the end of 2019 has affected more than 58 million people with more than 1.38 million deaths and has had an incalculable impact on the world . Extensive prevention and treatment measures have been implemented since the pandemic. In this Review, we summarize current understanding on the source, transmission characteristics, and pathogenic mechanism of SARS-CoV-2. We also detail the recent development of diagnostic methods and potential treatment strategies of COVID-19 with focus on the ongoing clinical trials of antibodies, vaccines, and inhibitors for combating the emerging coronavirus.

The Strategies of Pathogen-Oriented Therapy on Circumventing Antimicrobial Resistance.

The emerging antimicrobial resistance (AMR) poses serious threats to the global public health. Conventional antibiotics have been eclipsed in combating with drug-resistant bacteria. Moreover, the developing and deploying of novel antimicrobial drugs have trudged, as few new antibiotics are being developed over time and even fewer of them can hit the market. Alternative therapeutic strategies to resolve the AMR crisis are urgently required. Pathogen-oriented therapy (POT) springs up as a promising approach in circumventing antibiotic resistance. The tactic underling POT is applying antibacterial compounds or materials directly to infected regions to treat specific bacteria species or strains with goals of improving the drug efficacy and reducing nontargeting and the development of drug resistance. This review exemplifies recent trends in the development of POTs for circumventing AMR, including the adoption of antibiotic-antibiotic conjugates, antimicrobial peptides, therapeutic monoclonal antibodies, nanotechnologies, CRISPR-Cas systems, and microbiota modulations. Employing these alternative approaches alone or in combination shows promising advantages for addressing the growing clinical embarrassment of antibiotics in fighting drug-resistant bacteria.

Combating the Coronavirus Pandemic: Early Detection, Medical Treatment, and a Concerted Effort by the Global Community.

The World Health Organization (WHO) has declared the outbreak of 2019 novel coronavirus, known as 2019-nCoV, a pandemic, as the coronavirus has now infected over 2.6 million people globally and caused more than 185,000 fatalities as of April 23, 2020. Coronavirus disease 2019 (COVID-19) causes a respiratory illness with symptoms such as dry cough, fever, sudden loss of smell, and, in more severe cases, difficulty breathing. To date, there is no specific vaccine or treatment proven effective against this viral disease. Early and accurate diagnosis of COVID-19 is thus critical to curbing its spread and improving health outcomes. Reverse transcription-polymerase chain reaction (RT-PCR) is commonly used to detect the presence of COVID-19. Other techniques, such as recombinase polymerase amplification (RPA), loop-mediated isothermal amplification (LAMP), clustered regularly interspaced short palindromic repeats (CRISPR), and microfluidics, have allowed better disease diagnosis. Here, as part of the effort to expand screening capacity, we review advances and challenges in the rapid detection of COVID-19 by targeting nucleic acids, antigens, or antibodies. We also summarize potential treatments and vaccines against COVID-19 and discuss ongoing clinical trials of interventions to reduce viral progression.

Recent innovations in artificial skin.

The skin is a "smart", multifunctional organ that is protective, self-healing and capable of sensing and many forms of artificial skins have been developed with properties and functionalities approximating those of natural skin. Starting from specific commercial products for the treatment of burns, progress in two fields of research has since allowed these remarkable materials to be viable skin replacements for a wide range of dermatological conditions. This review maps out the development of bioengineered skin replacements and synthetic skin substitutes, including electronic skins. The specific behaviors of these skins are highlighted, and the performances of both types of artificial skins are evaluated against this. Moving beyond mere replication, highly advanced artificial skin materials are also identified as potential augmented skins that can be used as flexible electronics for health-care monitoring and other applications.

Unprecedented Acid-Promoted Polymerization and Gelation of Acrylamide: A Serendipitous Discovery.

Dilute acid polymerizes degassed, aqueous acrylamide with concomitant gelation, without the need for added free radical initiator or cross-linking agent. This reaction is accelerated by sonication or UV irradiation, but inhibited by adventitious oxygen or the addition of a free radical inhibitor, suggesting an acid-accelerated free radical process. The resulting hydrogels are thixotropic in nature and partially disrupted by the addition of chaotropic agents, indicating the importance of hydrogen bonding to the 3D network. This discovery was made while trying to prepare pectin-polyacrylamide hydrogels. We observed that pectin initiated the gelation of acrylamide, but only if the aqueous pectin samples had a pH lower than ca. 5.

Pectin as a rheology modifier: Origin, structure, commercial production and rheology.

Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of α-1,4-linked d-galacturonic acids in common. They have been widely used as emulsifiers, gelling agents, glazing agents, stabilizers, and/or thickeners in food, pharmaceutical, personal care and polymer products. Commercial pectin is classified as high methoxy pectin (HMP) with a degree of methylation (DM) >50% and low methoxy pectin (LMP) with a DM <50%. Amidated low methoxy pectins (ALMP) can be obtained through aminolysis of HMP. Gelation of HMP occurs by cross-linking through hydrogen bonds and hydrophobic forces between the methyl groups, assisted by a high co-solute concentration and low pH. In contrast, gelation of LMP occurs by the formation of ionic linkages via calcium bridges between two carboxyl groups from two different chains in close proximity, known as the 'egg-box' model. Pectin gels exhibit Newtonian behaviour at low shear rates and shear-thinning behaviour when the shear rate is increased. An overview of pectin from its origin to its physicochemical properties is presented in this review.

Electrospun Pectin-Polyhydroxybutyrate Nanofibers for Retinal Tissue Engineering.

Natural polysaccharide pectin has for the first time been grafted with polyhydroxybutyrate (PHB) via ring-opening polymerization of ß-butyrolactone. This copolymer, pectin-polyhydroxybutyrate (pec-PHB), was blended with PHB in various proportions and electrospun to produce nanofibers that exhibited uniform and bead-free nanostructures, suggesting the miscibility of PHB and pec-PHB. These nanofiber blends exhibited reduced fiber diameters from 499 to 336-426 nm and water contact angles from 123.8 to 88.2° on incorporation of pec-PHB. They also displayed 39-335% enhancement of elongation at break relative to pristine PHB nanofibers. pec-PHB nanofibers were found to be noncytotoxic and biocompatible. Human retinal pigmented epithelium (ARPE-19) cells were seeded onto pristine PHB and pec-PHB nanofibers as scaffold and showed good proliferation. Higher proportions of pec-PHB (pec-PHB10 and pec-PHB20) yielded higher densities of cells with similar characteristics to normal RPE cells. We propose, therefore, that nanofibers of pec-PHB have significant potential as retinal tissue engineering scaffold materials.

Recent Advances in Shape Memory Soft Materials for Biomedical Applications.

Shape memory polymers (SMPs) are smart and adaptive materials able to recover their shape through an external stimulus. This functionality, combined with the good biocompatibility of polymers, has garnered much interest for biomedical applications. In this review, we discuss the design considerations critical to the successful integration of SMPs for use in vivo. We also highlight recent work on three classes of SMPs: shape memory polymers and blends, shape memory polymer composites, and shape memory hydrogels. These developments open the possibility of incorporating SMPs into device design, which can lead to vast technological improvements in the biomedical field.

Thixotropic Supramolecular Pectin-Poly(Ethylene Glycol) Methacrylate (PEGMA) Hydrogels.

Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-d-galacturonic acid units. This naturally occurring, renewable and biodegradable polymer is underutilized in polymer science due to its insolubility in organic solvents, which renders conventional polymerization methods impractical. To circumvent this problem, cerium-initiated radical polymerization was utilized to graft methoxy-poly(ethylene glycol) methacrylate (mPEGMA) onto pectin in water. The copolymers were characterized by ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), and used in the formation of supramolecular hydrogels through the addition of α-cyclodextrin (α-CD) to induce crosslinking. These hydrogels possessed thixotropic properties; shear-thinning to liquid upon agitation but settling into gels at rest. In contrast to most of the other hydrogels produced through the use of poly(ethylene glycol) (PEG)-grafted polymers, the pectin-PEGMA/α-CD hydrogels were unaffected by temperature changes.

Effect of extraction conditions on the yield and chemical properties of pectin from cocoa husks.

Different extraction conditions were applied to investigate the effect of temperature, extraction time and substrate-extractant ratio on pectin extraction from cocoa husks. Pectin was extracted from cocoa husks using water, citric acid at pH 2.5 or 4.0, or hydrochloric acid at pH 2.5 or 4.0. Temperature, extraction time and substrate-extractant ratio affected the yields, uronic acid contents, degrees of methylation (DM) and degrees of acetylation (DA) of the extracted pectins using the five extractants differently. The yields and uronic acid contents of the extracted pectins ranged from 3.38-7.62% to 31.19-65.20%, respectively. The DM and DA of the extracted pectins ranged from 7.17-57.86% to 1.01-3.48%, respectively. The highest yield of pectin (7.62%) was obtained using citric acid at pH 2.5 [1:25 (w/v)] at 95 °C for 3.0 h. The highest uronic acid content (65.20%) in the pectin was obtained using water [1:25 (w/v)] at 95 °C for 3.0 h.