A genetically engineered Fc-binding amphiphilic polypeptide for congregating antibodies in vivo

Designed modular protein hydrogels for biofabrication

Designing proteins that fold and assemble over different length scales provides a way to tailor the mechanical properties and biological performance of hydrogels. In this study, we designed modular proteins that self-assemble into fibrillar networks and, as a result, form hydrogel materials with novel properties. We incorporated distinct functionalities by connecting separate self-assembling (A block) and cell-binding (B block) domains into single macromolecules. The number of self-assembling domains affects the rigidity of the fibers and the final storage modulus G' of the materials. The mechanical properties of the hydrogels could be tuned over a broad range (G' = 0.1 - 10 kPa), making them suitable for the cultivation and differentiation of multiple cell types, including cortical neurons and human mesenchymal stem cells. Moreover, we confirmed the bioavailability of cell attachment domains in the hydrogels that can be further tailored for specific cell types or other biological applications. Finally, we demonstrate the versatility of the designed proteins for application in biofabrication as 3D scaffolds that support cell growth and guide their function. STATEMENT OF SIGNIFICANCE: Designed proteins that enable the decoupling of biophysical and biochemical properties within the final material could enable modular biomaterial engineering. In this context, we present a designed modular protein platform that integrates self-assembling domains (A blocks) and cell-binding domains (B blocks) within a single biopolymer. The linking of assembly domains and cell-binding domains this way provided independent tuning of mechanical properties and inclusion of biofunctional domains. We demonstrate the use of this platform for biofabrication, including neural cell culture and 3D printing of scaffolds for mesenchymal stem cell culture and differentiation. Overall, this work highlights how informed design of biopolymer sequences can enable the modular design of protein-based hydrogels with independently tunable biophysical and biochemical properties.

IgG Fc Affinity Ligands and Their Applications in Antibody-Involved Drug Delivery: A Brief Review

Antibodies are not only an important class of biotherapeutic drugs, but also are targeting moieties for achieving active targeting drug delivery. Meanwhile, the rapidly increasing application of antibodies and Fc-fusion proteins has inspired the emerging development of downstream processing technologies. Thus, IgG Fc affinity ligands have come into being and have been widely exploited in antibody purification strategies. Given the high binding affinity and specificity to IgGs, binding stability in physiological medium conditions, and favorable toxicity and immunogenicity profiles, Fc affinity ligands are gradually applied to antibody delivery, non-covalent antibody-drug conjugates or antibody-mediated active-targeted drug delivery systems. In this review, we will briefly introduce IgG affinity ligands that are widely used at present and summarize their diverse applications in the field of antibody-involved drug delivery. The challenges and outlook of these systems are also discussed.

Rational Design of Peptide-based Smart Hydrogels for Therapeutic Applications

Peptide-based hydrogels have captivated remarkable attention in recent times and serve as an excellent platform for biomedical applications owing to the impressive amalgamation of unique properties such as biocompatibility, biodegradability, easily tunable hydrophilicity/hydrophobicity, modular incorporation of stimuli sensitivity and other functionalities, adjustable mechanical stiffness/rigidity and close mimicry to biological molecules. Putting all these on the same plate offers smart soft materials that can be used for tissue engineering, drug delivery, 3D bioprinting, wound healing to name a few. A plethora of work has been accomplished and a significant progress has been realized using these peptide-based platforms. However, designing hydrogelators with the desired functionalities and their self-assembled nanostructures is still highly serendipitous in nature and thus a roadmap providing guidelines toward designing and preparing these soft-materials and applying them for a desired goal is a pressing need of the hour. This review aims to provide a concise outline for that purpose and the design principles of peptide-based hydrogels along with their potential for biomedical applications are discussed with the help of selected recent reports.

Recapitulation of Thymic Function by Tissue Engineering Strategies

The thymus is responsible for the development and selection of T lymphocytes, which in turn also participate in the maturation of thymic epithelial cells. These events occur through the close interactions between hematopoietic stem cells and developing thymocytes with the thymic stromal cells within an intricate 3D network. The complex thymic microenvironment and function, and the current therapies to induce thymic regeneration or to overcome the lack of a functional thymus are herein reviewed. The recapitulation of the thymic function using tissue engineering strategies has been explored as a way to control the body's tolerance to external grafts and to generate ex vivo T cells for transplantation. In this review, the main advances in the thymus tissue engineering field are disclosed, including both scaffold- and cell-based strategies. In light of the current gaps and limitations of the developed systems, the design of novel biomaterials for this purpose with unique features is also discussed.

Recent Advancements in Regenerative Approaches for Thymus Rejuvenation

The thymus plays a key role in adaptive immunity by generating a diverse population of T cells that defend the body against pathogens. Various factors from disease and toxic insults contribute to the degeneration of the thymus resulting in a fewer output of T cells. Consequently, the body is prone to a wide host of diseases and infections. In this review, first, the relevance of the thymus is discussed, followed by thymic embryological organogenesis and anatomy as well as the development and functionality of T cells. Attempts to regenerate the thymus include in vitro methods, such as forming thymic organoids aided by biofabrication techniques that are transplantable. Ex vivo methods that have shown promise in enhancing thymic regeneration are also discussed. Current regenerative technologies have not yet matched the complexity and functionality of the thymus. Therefore, emerging techniques that have shown promise and the challenges that lie ahead are explored.

Self-assembling peptides as vectors for local drug delivery and tissue engineering applications

Molecular self-assembly has forged a new era in the development of advanced biomaterials for local drug delivery and tissue engineering applications. Given their innate biocompatibility and biodegradability, self-assembling peptides (SAPs) have come in the spotlight of such applications. Short and water-soluble SAP biomaterials associated with enhanced pharmacokinetic (PK) and pharmacodynamic (PD) responses after the topical administration of the therapeutic systems, or improved regenerative potential in tissue engineering applications will be the focus of the current review. SAPs are capable of generating supramolecular structures using a boundless array of building blocks, while peptide engineering is an approach commonly pursued to encompass the desired traits to the end composite biomaterials. These two elements combined, expand the spectrum of SAPs multi-functionality, constituting them potent biomaterials for use in various biomedical applications.

Chemically-Induced Cross-Linking of Peptidic Fibrils for Scaffolding Polymeric Particles and Macrophages

EAK16-II (EAK) is a self-assembling peptide (SAP) that forms β-sheets and β-fibrils through ionic-complementary interactions at physiological ionic strengths. The soft materials can be injected in vivo, creating depots of drugs and cells for rendering pharmacological and biological actions. The scope of the applications of EAK is sought to extend to tissues through which the flow of extracellular fluid tends to be limited. In such anatomical locales the rate and extent of the fibrilization are limited insofar as drug delivery and cellular scaffolding would be impeded. A method is generated utilizing a carbodiimide cross-linker by which EAK fibrils are pre-assembled yet remain injectable soft materials. It is hypothesized that the resulting de novo covalent linkages enhance the stacking of the β-sheet bilayers, thereby increasing the lengths of the fibrils and the extent of their cross-linking, as evidenced in Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, scanning electron microscopy, and atomic force microscopy analyses. The cross-linked EAK (clEAK) retains polymeric microspheres with an average diameter of 1 µm. Macrophages admixed with clEAK remain viable and do not produce the inflammatory mediator interleukin-1β. These results indicate that clEAK should be investigated further as a platform for delivering particles and cells in vivo.

Hydrogel Dressings for Chronic Wound Healing in Diabetes: Beyond Hydration

Chronic wounds caused by diabetes are a significant medical challenge. Complications from non-healing can result in dire consequences for patients and cost the healthcare system billions of dollars annually. Non-healing in wounds for diabetic patient's results from a combination of factors which impair clearing of injured tissue, proliferation of healthy cell populations and increase risk of infection. Wound dressings continue to form the basis for the treatment of chronic wounds. Traditionally, these focused solely on hydration of the wound site and mitigating infection risk. Hydrogel systems are ready made to meet these basic requirements due to their intrinsic hydration properties and ability to deliver active ingredients. Flexibility in materials and methods of release allowed these systems to remain targets of research into the 21st century. Improved understanding of the wound environment and healing cascades has led to the development of more advanced systems which incorporate endogenous growth factors and living cells. Despite their promise, clinical efficacy of these systems has remained a challenge. Further, the regulatory pathways for approval add a layer of complexity to translate pre-clinical work into marketed products. In this review, we discuss systems currently in clinical use, pre-clinical directions and regulatory challenges for hydrogels in the treatment of diabetic chronic wounds.

Synthetic peptide hydrogels as 3D scaffolds for tissue engineering

The regeneration of tissues and organs poses an immense challenge due to the extreme complexity in the research work involved. Despite the tissue engineering approach being considered as a promising strategy for more than two decades, a key issue impeding its progress is the lack of ideal scaffold materials. Nature-inspired synthetic peptide hydrogels are inherently biocompatible, and its high resemblance to extracellular matrix makes peptide hydrogels suitable 3D scaffold materials. This review covers the important aspects of peptide hydrogels as 3D scaffolds, including mechanical properties, biodegradability and bioactivity, and the current approaches in creating matrices with optimized features. Many of these scaffolds contain peptide sequences that are widely reported for tissue repair and regeneration and these peptide sequences will also be discussed. Furthermore, 3D biofabrication strategies of synthetic peptide hydrogels and the recent advances of peptide hydrogels in tissue engineering will also be described to reflect the current trend in the field. In the final section, we will present the future outlook in the design and development of peptide-based hydrogels for translational tissue engineering applications.

A drug delivery perspective on intratumoral-immunotherapy in renal cell carcinoma

In less than 5years immune checkpoint inhibitors (ICI) went from first FDA approval to become first-line options in advanced renal cell carcinoma. Despite that many patients have benefited from ICI, a significant fraction of individuals are refractory to these new immunological treatments. In this review, we discussed using intratumoral (i.t.) route of drug administration as an alternative to systemic therapy to increase the response rates and to circumvent potential drug-induced systemic adverse events. We provided a historic account of i.t. drug treatments in cancer and reviewed the contemporary experience in local drug delivery. We discussed the potential for enhancing the therapeutic impact of ICI by leveraging hydrogels as drug delivery vehicles and presented an outlook for implementing i.t. in renal cell carcinoma.

Summary From the First Kidney Cancer Research Summit, September 12-13, 2019: A Focus on Translational Research

Kidney cancer is one of the 10 most common cancers both in the United States and worldwide. Until this year, there had not previously been a conference focused on translational studies in the broad and heterogeneous group of kidney cancers. Therefore, a group of researchers, clinicians, and patient advocates dedicated to renal cell carcinoma launched the Kidney Cancer Research Summit (KCRS) to spur collaboration and further therapeutic advances in these tumors. This commentary aims to summarize the oral presentations and serve as a record for future iterations of this meeting. The KCRS sessions addressed the tumor microenvironment, novel methods of drug delivery, single cell sequencing strategies, novel immune checkpoint blockade and cellular therapies, predictive biomarkers, and rare variants of kidney cancers. In addition, the meeting included 2 sessions to promote scientific mentoring and kidney cancer research collaborations. A subsequent KCRS will be planned for the fall of 2020.

Designer Self-Assembling Peptide Hydrogels to Engineer 3D Cell Microenvironments for Cell Constructs Formation and Precise Oncology Remodeling in Ovarian Cancer

Designer self-assembling peptides form the entangled nanofiber networks in hydrogels by ionic-complementary self-assembly. This type of hydrogel has realistic biological and physiochemical properties to serve as biomimetic extracellular matrix (ECM) for biomedical applications. The advantages and benefits are distinct from natural hydrogels and other synthetic or semisynthetic hydrogels. Designer peptides provide diverse alternatives of main building blocks to form various functional nanostructures. The entangled nanofiber networks permit essential compositional complexity and heterogeneity of engineering cell microenvironments in comparison with other hydrogels, which may reconstruct the tumor microenvironments (TMEs) in 3D cell cultures and tissue-specific modeling in vitro. Either ovarian cancer progression or recurrence and relapse are involved in the multifaceted TMEs in addition to mesothelial cells, fibroblasts, endothelial cells, pericytes, immune cells, adipocytes, and the ECM. Based on the progress in common hydrogel products, this work focuses on the diverse designer self-assembling peptide hydrogels for instructive cell constructs in tissue-specific modeling and the precise oncology remodeling for ovarian cancer, which are issued by several research aspects in a 3D context. The advantages and significance of designer peptide hydrogels are discussed, and some common approaches and coming challenges are also addressed in current complex tumor diseases.