4D hydrogels: fabrication strategies, stimulation mechanisms, and biomedical applications.

Shape-morphing hydrogels have emerged as a promising biomaterial due to their ability to mimic the anisotropic tissue composition by creating a gradient in local swelling behavior. In this case, shape deformations occur due to the non-uniform distribution of internal stresses, asymmetrical swelling, and shrinking of different parts of the same hydrogel. Herein, we discuss the four-dimensional (4D) fabrication techniques (extrusion-based printing, dynamic light processing, and solvent casting) employed to prepare shape-shifting hydrogels. The important distinction between mono- and dual-component hydrogel systems, the capabilities of 3D constructs to undergo uni- and bi-directional shape changes, and the advantages of composite hydrogels compared to their pristine counterparts are presented. Subsequently, various types of actuators such as moisture, light, temperature, pH, and magnetic field and their role in achieving the desired and pre-determined shapes are discussed. These 4D gels have shown remarkable potential as programmable scaffolds for tissue regeneration and drug-delivery systems. Finally, we present futuristic insights into integrating piezoelectric biopolymers and sensors to harvest mechanical energy from motions during shape transformations to develop self-powered biodevices.

Progress in the development of piezoelectric biomaterials for tissue remodeling.

Piezoelectric biomaterials have demonstrated significant potential in the past few decades to heal damaged tissue and restore cellular functionalities. Herein, we discuss the role of bioelectricity in tissue remodeling and explore ways to mimic such tissue-like properties in synthetic biomaterials. In the past decade, biomedical engineers have adopted emerging functional biomaterials-based tissue engineering approaches using innovative bioelectronic stimulation protocols based on dynamic stimuli to direct cellular activation, proliferation, and differentiation on engineered biomaterial constructs. The primary focus of this review is to discuss the concepts of piezoelectric energy harvesting, piezoelectric materials, and their application in soft (skin and neural) and hard (dental and bone) tissue regeneration. While discussing the prospective applications as an engineered tissue, an important distinction has been made between piezoceramics, piezopolymers, and their composites. The superiority of piezopolymers over piezoceramics to circumvent issues such as stiffness mismatch, biocompatibility, and biodegradability are highlighted. We aim to provide a comprehensive review of the field and identify opportunities for the future to develop clinically relevant and state-of-the-art biomaterials for personalized and remote health care.

Application of Nanoscale Materials and Nanotechnology Against Viral Infection: A Special Focus on Coronaviruses.

INTRODUCTION: In recent years, viral infections and associated diseases have become a big challenge for humanity due to high morbidity rates globally. However, timely, accurate, and rapid detection of viral infection may lead to the control of morbidity as well as provide enough time for vaccine preparation and early antiviral therapy. Existing virus detection methods based on immunological and molecular diagnosis found drawbacks, such as its time-consuming and costly one. Recently, the introduction of nanomaterials having multiple unique properties with a series of smart and innovative nano-based technologies have been under investigation for rapid viral detection. This chapter aims to critically review recent literature to illustrate the encompassing applications of nano-engineered materials and further highlighting the role of their active surface in improving the virus detection with high sensitivity and detection range, and in a short time. METHODS: The authors review the research findings related to emerging nanotechnology-based virus detection systems and their applicability for diagnostics of infectious viruses. RESULTS: Recent advances in nanotechnology allow for the development of robust, rapid, and sensitive detection of infectious virus to overcome deficiencies of conventional detection technologies. Nanoparticles have several distinctive physical and chemical characteristics such as unique optical, electronic, and magnetic properties compared to their bulk form enabling them the detection of biological agents like viruses. Further, high surface area to volume ratios of nanoparticles also provides a platform for multi-functionalization with various organic or biological ligands for the selective binding and detection of biological targets like viruses. For instance, colloidal gold nanoparticle-based lateral-flow (AuNP-LF) provides rapid diagnosis and on-site diagnosis of SARS-CoV-2 virus via the IgM detection using the indirect immune-chromatography method. CONCLUSION: The distinct properties of nanomaterials such as plasmon resonance absorption, conductivity, redox behavior, etc. along with surface functionalization might be used in the development of the nano-sensing system with high accuracy and rapid detection of infectious viral diagnosis at the point of care application.