Static and Dynamic Biomaterial Engineering for Cell Modulation

In the biological microenvironment, cells are surrounded by an extracellular matrix (ECM), with which they dynamically interact during various biological processes. Specifically, the physical and chemical properties of the ECM work cooperatively to influence the behavior and fate of cells directly and indirectly, which invokes various physiological responses in the body. Hence, efficient strategies to modulate cellular responses for a specific purpose have become important for various scientific fields such as biology, pharmacy, and medicine. Among many approaches, the utilization of biomaterials has been studied the most because they can be meticulously engineered to mimic cellular modulatory behavior. For such careful engineering, studies on physical modulation (e.g., ECM topography, stiffness, and wettability) and chemical manipulation (e.g., composition and soluble and surface biosignals) have been actively conducted. At present, the scope of research is being shifted from static (considering only the initial environment and the effects of each element) to biomimetic dynamic (including the concepts of time and gradient) modulation in both physical and chemical manipulations. This review provides an overall perspective on how the static and dynamic biomaterials are actively engineered to modulate targeted cellular responses while highlighting the importance and advance from static modulation to biomimetic dynamic modulation for biomedical applications.

Triggering biological processes: methods and applications of photocaged peptides and proteins

There has been a significant push in recent years to deploy fundamental knowledge and methods of photochemistry toward biological ends. Photoreactive groups have enabled chemists to activate biological function using the concept of photocaging. By granting spatiotemporal control over protein activation, these photocaging methods are fundamental in understanding biological processes. Peptides and proteins are an important group of photocaging targets that present conceptual and technical challenges, requiring precise chemoselectivity in complex polyfunctional environments. This review focuses on recent advances in photocaging techniques and methodologies, as well as their use in living systems. Photocaging methods include genetic and chemical approaches that require a deep understanding of structure-function relationships based on subtle changes in primary structure. Successful implementation of these ideas can shed light on important spatiotemporal aspects of living systems.

Peptides and pseudopeptide ligands: a powerful toolbox for the affinity purification of current and next-generation biotherapeutics

Following the consolidation of therapeutic proteins in the fight against cancer, autoimmune, and neurodegenerative diseases, recent advancements in biochemistry and biotechnology have introduced a host of next-generation biotherapeutics, such as CRISPR-Cas nucleases, stem and car-T cells, and viral vectors for gene therapy. With these drugs entering the clinical pipeline, a new challenge lies ahead: how to manufacture large quantities of high-purity biotherapeutics that meet the growing demand by clinics and biotech companies worldwide. The protein ligands employed by the industry are inadequate to confront this challenge: while featuring high binding affinity and selectivity, these ligands require laborious engineering and expensive manufacturing, are prone to biochemical degradation, and pose safety concerns related to their bacterial origin. Peptides and pseudopeptides make excellent candidates to form a new cohort of ligands for the purification of next-generation biotherapeutics. Peptide-based ligands feature excellent target biorecognition, low or no toxicity and immunogenicity, and can be manufactured affordably at large scale. This work presents a comprehensive and systematic review of the literature on peptide-based ligands and their use in the affinity purification of established and upcoming biological drugs. A comparative analysis is first presented on peptide engineering principles, the development of ligands targeting different biomolecular targets, and the promises and challenges connected to the industrial implementation of peptide ligands. The reviewed literature is organized in (i) conventional (α-)peptides targeting antibodies and other therapeutic proteins, gene therapy products, and therapeutic cells; (ii) cyclic peptides and pseudo-peptides for protein purification and capture of viral and bacterial pathogens; and (iii) the forefront of peptide mimetics, such as β-/γ-peptides, peptoids, foldamers, and stimuli-responsive peptides for advanced processing of biologics.

Near-infrared emitting lanthanide(iii) complexes as prototypes of optical imaging agents with peptide targeting ability: a methodological approach

A methodological approach to design prototypes of specific near-infrared emitting imaging agents based on a small molecular compound combining a lanthanide(iii) ion, the cyclen derivative as a coordinating unit and the azo-dye as a sensitizer with a Arg-Gly-Asp cyclopeptide as a targeting moiety, is presented here.

NIR Ln(iii) complexes combining a cyclen derivative, azo-dye as a sensitizer and a cRGD peptide as a targeting moiety.

Optoregulated Biointerfaces to Trigger Cellular Responses

Optoregulated biointerfaces offer the possibility to manipulate the interactions between cell membrane receptors and the extracellular space. This Invited Feature Article summarizes recent efforts by our group and others during the past decade to develop light-responsive biointerfaces to stimulate cells and elicit cellular responses using photocleavable protecting groups (PPG) as our working tool. This article begins by providing a brief introduction to available PPGs, with a special focus on the widely used o-nitrobenzyl family, followed by an overview of molecular design principles for the control of bioactivity in the context of cell-material interactions and the characterization methods to use in following the photoreaction at surfaces. We present various light-guided cellular processes using PPGs, including cell adhesion, release, migration, proliferation, and differentiation, both in vitro and in vivo. Finally, this Invited Feature Article closes with our perspective on the current status and future challenges of this topic.

Three-Dimensional Microstructured Azobenzene-Containing Gelatin as a Photoactuable Cell Confining System

In materials science, there is a considerable interest in the fabrication of highly engineered biomaterials that can interact with cells and control their shape. In particular, from the literature, the role played by physical cell confinement in cellular structural organization and thus in the regulation of its functions has been well-established. In this context, the addition of a dynamic feature to physically confining platforms aiming at reproducing in vitro the well-known dynamic interaction between the cells and their microenvironment would be highly desirable. To this aim, we have developed an advanced gelatin-based hydrogel that can be finely micropatterned by two-photon polymerization and stimulated in a controlled way by light irradiation thanks to the presence of an azobenzene cross-linker. Light-triggered expansion of gelatin microstructures induced an in-plane nuclear deformation of physically confined NIH-3T3 cells. The microfabricated photoactuable gelatin shown in this work paves the way to new "dynamic" caging culture systems that can find applications, for example, as "engineered stem cell niches".

Controlling the orientation of a cell-synthesized extracellular matrix by using engineered gelatin-based building blocks

Surface micropatterned gelatin building blocks clearly increment the alignment degree of collagen-based microtissues synthesized by human dermal fibroblasts.

Photoactive and Physical Properties of an Azobenzene-Containing Coordination Framework

A new three-dimensional coordination framework, [Zn4(tbazip)3(bpe)2(OH)2]·bpe·{solvent} (where bpe = 1,2-di(4-pyridyl)ethene) containing the novel photoactive ligand tbazip (tbazip = 5-((4-tert-butyl)phenylazo)isophthalic acid) has been synthesised and crystallographically characterised. The photoactivity of discrete tbazip was investigated and compared with its photoactivity while incorporated within the framework. The effect of isomerisation of the incorporated azobenzene on the chemical and physical properties of the framework were investigated using UV-vis and Raman spectroscopies. The framework is porous only to hydrogen gas at 77 K, but displayed an appreciable uptake for CO2 at 195 K.

Spatiotemporal Photopatterning on Polycarbonate Surface through Visible Light Responsive Polymer Bound DASA Compounds

Besides interesting applications in drug delivery, photoresponsive molecules have great potential to serve as an efficient basis for postfunctionalization photopatterning of polymer surfaces. To the best of our knowledge, only UV light sources have been exploited as a photoinducer for creating patterned templates with or without hydrogels. In this work, we present a practically facile method for grafting visible light responsive donor-acceptor stenhouse adducts (DASAs) on amino-functionalized polycarbonate surfaces. DASA grafted surfaces have shown excellent lithographic performance using visible light. The functionalized surfaces exhibit significant changes of their physical properties after being illuminated with visible light. By using suitable masks, well-defined patterns can be replicated with high precision and resolution. Since the DASA ligand synthesis and surface functionalization is not cumbersome, this method may serve as a facile protocol for obtaining photopatterned polymer surfaces for various applications.