Conductive Scaffolds for Bone Tissue Engineering: Current State and Future Outlook

Bone tissue engineering strategies attempt to regenerate bone tissue lost due to injury or disease. Three-dimensional (3D) scaffolds maintain structural integrity and provide support, while improving tissue regeneration through amplified cellular responses between implanted materials and native tissues. Through this, scaffolds that show great osteoinductive abilities as well as desirable mechanical properties have been studied. Recently, scaffolding for engineered bone-like tissues have evolved with the use of conductive materials for increased scaffold bioactivity. These materials make use of several characteristics that have been shown to be useful in tissue engineering applications and combine them in the hope of improved cellular responses through stimulation (i.e., mechanical or electrical). With the addition of conductive materials, these bioactive synthetic bone substitutes could result in improved regeneration outcomes by reducing current factors limiting the effectiveness of existing scaffolding materials. This review seeks to overview the challenges associated with the current state of bone tissue engineering, the need to produce new grafting substitutes, and the promising future that conductive materials present towards alleviating the issues associated with bone repair and regeneration.

Titania Nanosheet Generates Peroxynitrite-Dependent S-Nitrosylation and Enhances p53 Function in Lung Cancer Cells

Metal nanomaterials can enhance the efficacy of current cancer therapies. Here, we show that Ti_0.8O₂ nanosheets cause cytotoxicity in several lung cancer cells but not in normal cells. The nanosheet-treated cells showed certain apoptosis characteristics. Protein analysis further indicated the activation of the p53-dependent death mechanism. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses revealed the cellular uptake of the nanosheets and the induction of cell morphological change. The nanosheets also exhibited a substantial apoptosis effect on drug-resistant metastatic primary lung cancer cells, and it was found that the potency of the nanosheets was dramatically higher than standard drugs. Ti_0.8O₂ nanosheets induce apoptosis through a molecular mechanism involving peroxynitrite (ONOO⁻) generation. As peroxynitrite is known to be a potent inducer of S-nitrosylation, we further found that the nanosheets mediated the S-nitrosylation of p53 at C182, resulting in higher protein-protein complex stability, and this was likely to induce the surrounding residues, located in the interface region, to bind more strongly to each other. Molecular dynamics analysis revealed that S-nitrosylation stabilized the p53 dimer with a ΔGbindresidue of <−1.5 kcal/mol. These results provide novel insight on the apoptosis induction effect of the nanosheets via a molecular mechanism involving S-nitrosylation of the p53 protein, emphasizing the mechanism of action of nanomaterials for cancer therapy.

Fabrication of Quasi-2D Shape-Tailored Microparticles using Wettability Contrast-Based Platforms

The ability to fabricate materials with ultrathin architectures enables the breakthrough of low-dimensional structures with high surface area that showcase distinctive properties from their bulk counterparts. They are exploited in a wide range of fields, including energy harvesting, catalysis, and biomedicine. Despite such versatility, the fine tuning of the lateral dimensions and geometry of these structures remains challenging. Prepatterned platforms gain significant attention as enabling technologies to process materials with highly controlled shapes and dimensions. Herein, different nanometer-thick particles of various lateral sizes and geometries (e.g., squares, circles, triangles, hexagons) are processed with high precision and definition, taking advantage of the wettability contrast of oleophilic-oleophobic patterned surfaces. Quasi-2D polymeric microparticles with high shape- and size-fidelity can be retrieved as freestanding objects in a single step. These structures show cell-mediated pliability, and their integration in gravity-enforced human adipose-derived stem cell spheroids leads to an enhanced metabolic activity and a modulated secretion of proangiogenic factors.

Designs of Biomaterials and Microenvironments for Neuroengineering

Recent clinical research on neuroengineering is primarily focused on biocompatible materials, which can be used to provide electroactive and topological cues, regulate the microenvironment, and perform other functions. Novel biomaterials for neuroengineering have been received much attention in the field of research, including graphene, photonic crystals, and organ-on-a-chip. Graphene, which has the advantage of high mechanical strength and chemical stability with the unique electrochemical performance for electrical signal detection and transmission, has significant potential as a conductive scaffolding in the field of medicine. Photonic crystal materials, known as a novel concept in nerve substrates, have provided a new avenue for neuroengineering research because of their unique ordered structure and spectral attributes. The "organ-on-a-chip" systems have shown significant prospects for the developments of the solutions to nerve regeneration by mimicking the microenvironment of nerve tissue. This paper presents a review of current progress in the designs of biomaterials and microenvironments and provides case studies in developing nerve system stents upon these biomaterials. In addition, we compose a conductive patterned compounded biomaterial, which could mimic neuronal microenvironment for neuroengineering by concentrating the advantage of such biomaterials.

Applications of Nanosheets in Frontier Cellular Research

Several types of nanosheets, such as graphene oxide (GO) nanosheet, molybdenum disulfide (MoS₂) and poly(l-lactic acid) (PLLA) nanosheets, have been developed and applied in vitro in cellular research over the past decade. Scientists have used nanosheet properties, such as ease of modification and flexibility, to develop new cell/protein sensing/imaging techniques and achieve regulation of specific cell functions. This review is divided into three main parts based on the application being examined: nanosheets as a substrate, nanosheets as a sensitive surface, and nanosheets in regenerative medicine. Furthermore, the applications of nanosheets are discussed, with two subsections in each section, based on their effects on cells and molecules. Finally, the application prospects of nanosheets in cellular research are summarized.

Electrospun 3D Scaffolds for Tissue Regeneration

Tissue engineering aims to fabricate and functionalise constructs that mimic the native extracellular matrix (ECM) in the closest way possible to induce cell growth and differentiation in both in vitro and in vivo conditions. Development of scaffolds that can function as tissue substitutes or augment healing of tissues is an essential aspect of tissue regeneration. Although there are many techniques for achieving this biomimicry in 2D structures and 2D cell cultures, translation of successful tissue regeneration in true 3D microenvironments is still in its infancy. Electrospinning, a well known electrohydrodynamic process, is best suited for producing and functionalising, nanofibrous structures to mimic the ECM. A systematic control of the processing parameters coupled with novel process innovations, has recently resulted in novel 3D electrospun structures. This chapter gives a brief account of the various 3D electrospun structures that are being tried as tissue engineering scaffolds. Combining electrospinning with other 3D structure forming technologies, which have shown promising results, has also been discussed. Electrospinning has the potential to bridge the gap between what is known and what is yet to be known in fabricating 3D scaffolds for tissue regeneration.

Material chemistry of graphene oxide-based nanocomposites for theranostic nanomedicine

This review summarizes and discusses the development of the design, fabrication and biomedical applications of GO-based functional composites.