Biological cells are major building blocks of tissues and organs of living organisms. These cells are also being used as biomarkers for diagnosis and sources for regenerative medicine. To better understand and even regulate diverse activities of cells, materials capable of interacting with cells have been designed by integrating various material chemistry, characterization, and processing techniques. These materials are often integrated with various nano- and microscale engineering devices. In this article, we provide an overview of materials for biological modulation, sensing, and imaging and also discuss opportunities for the future development of multifunctional materials for sensing and therapies.

A growing trend in tissue engineering and regenerative medicine is to view cells, matrices, and whole tissues from a materials science perspective. The rationale behind this novel approach to considering biological problems is that the material properties at these different length scales both define their physical stability and also provide instructive cues. These cues can maintain homeostasis in healthy tissues or drive dynamic events during development, wound healing, and disease progression. However, one must map and characterize the physical properties of the natural extracellular matrix environment found in vivo in order to guide the design of synthetic or naturally derived materials to control cell function. This article reviews the study of natural tissues as materials, and sheds light on the use of this information to develop novel synthetic materials that guide cell function.

Recently, biomaterial scientists have married materials engineering and immunobiology to conceptualize new immunomodulatory materials. This special class of biomaterials can modulate and harness the innate properties of immune functionality for enhanced therapeutic efficacy. Generally, two fundamental strategies are followed in the design of immunomodulatory biomaterials: (1) immuno-evasive (immuno-mimetic, immuno-suppressing, or immuno-inert) biomaterials and (2) immuno-activating or immuno-enhancing biomaterials. This article highlights the development and application of a number of immunomodulatory materials, categorized by these two general approaches.

Drug delivery systems are becoming increasingly sophisticated, with the ability to target and penetrate specific tissues and release drugs based upon the local environment. While these advanced systems often offer advantages over their less sophisticated counterparts, the final product may be more complex and require additional manufacturing steps. In this article, we review a body of work based on genetically encoded elastin-like polypeptides (ELPs) that offer a route to modular, multifunctional delivery systems that are simple to manufacture. ELPs are temperature-sensitive biopolymers that can be designed on the genetic level and expressed in cell-based protein production systems. The tools of molecular biology and versatility of proteins are used to engineer polymers with precise composition and molecular weight that self-assemble to form drug delivery systems with an impressive variety of features and functions. Due to their versatility and ease of production, ELPs are likely to contribute to the goal of designing simple and effective “smart” delivery systems.

Theranostics was proposed as a combined process of therapeutics and diagnostics methodology for increasing treatment efficacy and safety with simultaneous monitoring of the response to treatment. In the past two decades, nanotechnology has been the focus of developing strategies for drug delivery and imaging functions, and it has expanded to the design of multifunctional nanoparticles and the creation of “nanotheranostics” (i.e., theranostic nanomedicines). Nanotheranostics also shows potential in gene therapy; however, nanoparticle-mediated delivery of genes still faces major obstacles related to (1) the uptake by the reticuloendothelial system, (2) the ability to get across the target cell membranes through endocytosis, and (3) the ability to accumulate in organs with permeable vasculature. Here, we review the development and application of nanotheranostics, highlighting their relevance to gene therapy as well as molecular imaging.

Improving the biological relevance of organs-on-chips is one of the main issues in biomedical engineering. The microvascular system is related to numerous biological phenomena throughout the life of organs. Although many in vitro microvascular systems have been developed, current organ-on-chip systems fail to fully integrate three-dimensional microvasculature, which results in decreased similarity of the systems with in vivo conditions. In this review, we propose that the microvascular system is an essential component for engineering organs-on-chips to achieve greater biological relevance. Various methods for engineering microvessels in vitro are reviewed, as well as recent representative efforts to engineer vascularized organs-on-chips. Material considerations for designing organs-on-chips are also reviewed.

A number of systems based on synthetic molecules, among them cationic liposomes and poly(ethylene imine)-based polymers, have been proposed as delivery vehicles for nucleic acids. Some of these systems have even reached the market, ensuring efficient and transient transfection levels in a variety of cell types. However, toxicity issues have limited their application in vivo. In this context, chitosan, a biocompatible and biodegradable polysaccharide, has been proposed as a promising alternative for the delivery of nucleic acid-based molecules. Here we present an overview of the state of the art of chitosan-based vectors for nucleic acid delivery and the most recent data on the in vivo testing of the proposed systems. We additionally express our view on the barriers that might be hampering the translation of this knowledge into clinical practice and the challenges that need to be fulfilled for these promising vehicles to reach patients.

The field of nuclear materials encompasses numerous opportunities to address and ultimately solve longstanding industrial problems by improving the fundamental understanding of materials through the integration of experiments with multiscale modeling and high-performance simulation. A particularly noteworthy example is an ongoing study of axial power distortions in a nuclear reactor induced by corrosion deposits, known as CRUD (Chalk River unidentified deposits). We describe how progress is being made toward achieving scientific advances and technological solutions on two fronts. Specifically, the study of thermal conductivity of CRUD phases has augmented missing data as well as revealed new mechanisms. Additionally, the development of a multiscale simulation framework shows potential for the validation of a new capability to predict the power distribution of a reactor, in effect direct evidence of technological impact. The material- and system-level challenges identified in the study of CRUD are similar to other well-known vexing problems in nuclear materials, such as irradiation accelerated corrosion, stress corrosion cracking, and void swelling; they all involve connecting materials science fundamentals at the atomistic- and meso-scales to technology challenges at the macroscale.