Temporal changes guided by mesenchymal stem cells on a 3D microgel platform enhance angiogenesis in vivo at a low-cell dose.

Therapeutic factors secreted by mesenchymal stem cells (MSCs) promote angiogenesis in vivo. However, delivery of MSCs in the absence of a cytoprotective environment offers limited efficacy due to low cell retention, poor graft survival, and the nonmaintenance of a physiologically relevant dose of growth factors at the injury site. The delivery of stem cells on an extracellular matrix (ECM)-based platform alters cell behavior, including migration, proliferation, and paracrine activity, which are essential for angiogenesis. We demonstrate the biophysical and biochemical effects of preconditioning human MSCs (hMSCs) for 96 h on a three-dimensional (3D) ECM-based microgel platform. By altering the macromolecular concentration surrounding cells in the microgels, the proangiogenic phenotype of hMSCs can be tuned in a controlled manner through cell-driven changes in extracellular stiffness and "outside-in" integrin signaling. The softest microgels were tested at a low cell dose (5 × 104 cells) in a preclinical hindlimb ischemia model showing accelerated formation of new blood vessels with a reduced inflammatory response impeding progression of tissue damage. Molecular analysis revealed that several key mediators of angiogenesis were up-regulated in the low-cell-dose microgel group, providing a mechanistic insight of pathways modulated in vivo. Our research adds to current knowledge in cell-encapsulation strategies by highlighting the importance of preconditioning or priming the capacity of biomaterials through cell-material interactions. Obtaining therapeutic efficacy at a low cell dose in the microgel platform is a promising clinical route that would aid faster tissue repair and reperfusion in "no-option" patients suffering from peripheral arterial diseases, such as critical limb ischemia (CLI).

Encapsulation of young donor age dopaminergic grafts in a GDNF-loaded collagen hydrogel further increases their survival, reinnervation, and functional efficacy after intrastriatal transplantation in hemi-Parkinsonian rats.

Biomaterials have been shown to significantly improve the outcome of cellular reparative approaches for Parkinson's disease in experimental studies because of their ability to provide transplanted cells with a supportive microenvironment and shielding from the host immune system. However, given that the margin for improvement in such reparative therapies is considerable, further studies are required to fully investigate and harness the potential of biomaterials in this context. Given that several recent studies have demonstrated improved brain repair in Parkinsonian models when using dopaminergic grafts derived from younger foetal donors, we hypothesized that encapsulating these cells in a supportive biomaterial would further improve their reparative efficacy. Thus, this study aimed to determine the impact of a GDNF-loaded collagen hydrogel on the survival, reinnervation, and functional efficacy of dopaminergic neurons derived from young donors. To do so, hemi-Parkinsonian (6-hydroxydopamine-lesioned) rats received intrastriatal transplants of embryonic day 12 cells extracted from the rat ventral mesencephalon either alone, in a collagen hydrogel, with GDNF, or in a GDNF-loaded collagen hydrogel. Methamphetamine-induced rotational behaviour was assessed at three weekly intervals for a total of 12 weeks, after which rats were sacrificed for postmortem assessment of graft survival. We found that, following intrastriatal transplantation to the lesioned striatum, the GDNF-loaded collagen hydrogel significantly increased the survival (4-fold), reinnervation (5.4-fold), and functional efficacy of the embryonic day 12 dopaminergic neurons. In conclusion, this study further demonstrates the significant potential of biomaterial hydrogel scaffolds for cellular brain repair approaches in neurodegenerative diseases such as Parkinson's disease.

Attenuated Glial Reactivity on Topographically Functionalized Poly(3,4-Ethylenedioxythiophene):P-Toluene Sulfonate (PEDOT:PTS) Neuroelectrodes Fabricated by Microimprint Lithography.

Following implantation, neuroelectrode functionality is susceptible to deterioration via reactive host cell response and glial scar-induced encapsulation. Within the neuroengineering community, there is a consensus that the induction of selective adhesion and regulated cellular interaction at the tissue-electrode interface can significantly enhance device interfacing and functionality in vivo. In particular, topographical modification holds promise for the development of functionalized neural interfaces to mediate initial cell adhesion and the subsequent evolution of gliosis, minimizing the onset of a proinflammatory glial phenotype, to provide long-term stability. Herein, a low-temperature microimprint-lithography technique for the development of micro-topographically functionalized neuroelectrode interfaces in electrodeposited poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (PEDOT:PTS) is described and assessed in vitro. Platinum (Pt) microelectrodes are subjected to electrodeposition of a PEDOT:PTS microcoating, which is subsequently topographically functionalized with an ordered array of micropits, inducing a significant reduction in electrode electrical impedance and an increase in charge storage capacity. Furthermore, topographically functionalized electrodes reduce the adhesion of reactive astrocytes in vitro, evident from morphological changes in cell area, focal adhesion formation, and the synthesis of proinflammatory cytokines and chemokine factors. This study contributes to the understanding of gliosis in complex primary mixed cell cultures, and describes the role of micro-topographically modified neural interfaces in the development of stable microelectrode interfaces.

Nanocellulose reinforced gellan-gum hydrogels as potential biological substitutes for annulus fibrosus tissue regeneration.

Intervertebral disc (IVD) degeneration is associated with both structural damage and aging related degeneration. Annulus fibrosus (AF) defects such as annular tears, herniation and discectomy require novel tissue engineering strategies to functionally repair AF tissue. An ideal construct will repair the AF by providing physical and biological support, facilitating regeneration. The presented strategy herein proposes a gellan gum-based construct reinforced with cellulose nanocrystals (nCell) as a biological self-gelling AF substitute. Nanocomposite hydrogels were fabricated and characterized with respect to hydrogel swelling capacity, degradation rate in vitro and mechanical properties. Rheological evaluation on the nanocomposites demonstrated the GGMA reinforcement with nCell promoted matrix entanglement with higher scaffold stiffness observed upon ionic crosslinking. Compressive mechanical tests demonstrated compressive modulus values close to those of the human AF tissue. Furthermore, cell culture studies with encapsulated bovine AF cells indicated that nanocomposite constructs promoted cell viability and a physiologically relevant cell morphology for up to fourteen days in vitro.

Polymeric Gene Carriers Bearing Pendant ß-Cyclodextrin: The Relevance of Glycoside Permethylation on the "In Vitro" Cell Response.

The incorporation of cyclodextrins (CDs) to nonviral cationic polymer vectors is very attractive due to recent studies that report a clear improvement of their cytocompatibility and transfection efficiency. However, a systematic study on the influence of the CD derivatization is still lacking. In this work, the relevance of ß-CD permethylation has been addressed by preparing and evaluating two series of copolymers of the cationic N-ethyl pyrrolidine methacrylamide (EPA) and styrenic units bearing pendant hydroxylated and permethylated ß-CDs (HCDSt and MeCDSt, respectively). For both cell lines, CDs permethylation shows a strong influence on plasmid DNA complexation, "in vitro" cytocompatibility and transfection efficiency of the resulting copolymers over two murine cell lines. While the incorporation of the hydroxylated CD moiety increased the cytotoxicity of the copolymers in comparison with their homopolycationic counterpart, the permethylated copolymers have shown full cytocompatibility as well as superior transfection efficiency than the controls. This behavior has been related to the different chemical nature of both units and tentatively to a different distribution of units along the polymeric chains. Cellular internalization analysis with fluorescent copo-lymers supports this behavior.

Effects of Polydopamine Functionalization on Boron Nitride Nanotube Dispersion and Cytocompatibility.

Boron nitride nanotubes (BNNTs) have unique physical properties, of value in biomedical applications; however, their dispersion and functionalization represent a critical challenge in their successful employment as biomaterials. In the present study, we report a process for the efficient disentanglement of BNNTs via a dual surfactant/polydopamine (PD) process. High-resolution transmission electron microscopy (HR-TEM) indicated that individual BNNTs become coated with a uniform PD nanocoating, which significantly enhanced dispersion of BNNTs in aqueous solutions. Furthermore, the cytocompatibility of PD-coated BNNTs was assessed in vitro with cultured human osteoblasts (HOBs) at concentrations of 1, 10, and 30 µg/mL and over three time-points (24, 48, and 72 h). In this study it was demonstrated that PD-functionalized BNNTs become individually localized within the cytoplasm by endosomal escape and that concentrations of up to 30 µg/mL of PD-BNNTs were cytocompatible in HOBs cells following 72 h of exposure.

Hyaluronic Acid Based Hydrogels Attenuate Inflammatory Receptors and Neurotrophins in Interleukin-1ß Induced Inflammation Model of Nucleus Pulposus Cells.

Inflammation plays an important role in symptomatic intervertebral disc degeneration and is associated with the production of neurotrophins in sensitizing innervation into the disc. The use of high molecular weight (HMw) hyaluronic acid (HA) hydrogels offers a potential therapeutic biomaterial for nucleus pulposus (NP) regeneration as it exerts an anti-inflammatory effect and provides a microenvironment that is more suitable for NP. Therefore, it was hypothesized that cross-linked HMw HA hydrogels modulate the inflammatory receptor of IL-1R1, MyD88 and neurotrophin expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in an in vitro inflammation model of NP. HA cross-linking was optimized using various concentrations of 4-arm PEG-amine by determination of free carboxyl groups of HA and unreacted free amine groups of PEG-amine. The optimally cross-linked HA hydrogels were characterized for hydrolytic stability, enzymatic degradation and cytotoxicity on NP cells. The therapeutic effect of HA hydrogels was further investigated in IL-1ß induced inflammation on NP cell cultures and the mechanism of HA by examining the expression of cell surface receptor of CD44. Hydrogel was optimally cross-linked at 75 mM PEG, stable in phosphate buffered saline, and showed greater than 40% resistance to enzymatic degradation. No cytotoxic effect of NP cells was observed in the presence of hydrogels for 1, 3, and 7 days. IL-1R1 and MyD88 were significantly suppressed. Additionally, NGF and BDNF mRNA were down-regulated after treatment with cross-linked HA hydrogel. Possible protective mechanism of HA is shown by high expression of CD44 receptor of NP cells after HA treatment in which suggest the binding of HA to CD44 receptor and prevent NP cells from further undergoing inflammation. These results indicate that optimally stabilized cross-linked HMw HA hydrogel has a therapeutic effect in response to inflammation-associated pain and becomes an ideal matrices hydrogel for NP regeneration.

In vitro degradation and antibacterial activity of bacterial cellulose deposited flax fabric reinforced with polylactic acid and polyhydroxybutyrate.

The objective of this study was to prepare biocomposites through the solution casting method followed by compression moulding in which bacterial cellulose (BC) deposited flax fabric (FF) produced through fermentation is coated with minimal amount of polylactic acid (PLA) and polyhydroxybutyrate (PHB). Biocomposites incorporated with 60 % of PLA or PHB (% w/w) show enhanced tensile strength. Cross-sectional morphology showed good superficial interaction of these biopolymers with fibres of FF thereby filling up the gaps present between the fibres. The tensile strength of biocomposites at 60 % PLA and 60 % PHB improved from 37.97 MPa (i.e., BC deposited FF produced in presence of honey) to 67.17 MPa and 56.26 MPa, respectively. Further, 0.25 % of nalidixic acid (NA) (% w/w) and 6 % of oleic acid (OA) (% w/w) incorporation into the biocomposites imparted prolonged antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The in vitro cytotoxicity of biocomposites was determined using L929 mouse fibroblast cells. The 3-(4,5-cime- thylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity tests showed that the PHB derived biocomposites along with antibacterial compounds in it were non-toxic. In vitro degradation of biocomposites was measured for up to 8 weeks in the mimicked physiological environment that showed a gradual rate of degradation over the period.

Redefining biomaterial biocompatibility: challenges for artificial intelligence and text mining.

The surge in 'Big data' has significantly influenced biomaterials research and development, with vast data volumes emerging from clinical trials, scientific literature, electronic health records, and other sources. Biocompatibility is essential in developing safe medical devices and biomaterials to perform as intended without provoking adverse reactions. Therefore, establishing an artificial intelligence (AI)-driven biocompatibility definition has become decisive for automating data extraction and profiling safety effectiveness. This definition should both reflect the attributes related to biocompatibility and be compatible with computational data-mining methods. Here, we discuss the need for a comprehensive and contemporary definition of biocompatibility and the challenges in developing one. We also identify the key elements that comprise biocompatibility, and propose an integrated biocompatibility definition that enables data-mining approaches.

Survival and maturation of human induced pluripotent stem cell-derived dopaminergic progenitors in the parkinsonian rat brain is enhanced by transplantation in a neurotrophin-enriched hydrogel.

Objective.Although human induced pluripotent stem cell (iPSC)-derived cell replacement for Parkinson's disease has considerable reparative potential, its full therapeutic benefit is limited by poor graft survival and dopaminergic maturation. Injectable biomaterial scaffolds, such as collagen hydrogels, have the potential to address these issues via a plethora of supportive benefits including acting as a structural scaffold for cell adherence, shielding from the host immune response and providing a reservoir of neurotrophic factors to aid survival and differentiation. Thus, the aim of this study was to determine if a neurotrophin-enriched collagen hydrogel could improve the survival and maturation of iPSC-derived dopaminergic progenitors (iPSC-DAPs) after transplantation into the rat parkinsonian brain.Approach.Human iPSC-DAPs were transplanted into the 6-hydroxydopamine-lesioned striatum either alone, with the neurotrophins GDNF and BDNF, in an unloaded collagen hydrogel, or in a neurotrophin-loaded collagen hydrogel.Post-mortem, human nuclear immunostaining was used to identify surviving iPSC-DAPs while tyrosine hydroxylase immunostaining was used to identify iPSC-DAPs that had differentiated into mature dopaminergic neurons.Main results.We found that iPSC-DAPs transplanted in the neurotrophin-enriched collagen hydrogel survived and matured significantly better than cells implanted without the biomaterial (8 fold improvement in survival and 16 fold improvement in dopaminergic differentiation). This study shows that transplantation of human iPSC-DAPs in a neurotrophin-enriched collagen hydrogel improves graft survival and maturation in the parkinsonian rat brain.Significance.The data strongly supports further investigation of supportive hydrogels for improving the outcome of iPSC-derived brain repair in Parkinson's disease.

Modification of Living Diatom, Thalassiosira weissflogii, with a Calcium Precursor through a Calcium Uptake Mechanism: A Next Generation Biomaterial for Advanced Delivery Systems.

The diatom's frustule, characterized by its rugged and porous exterior, exhibits a remarkable biomimetic morphology attributable to its highly ordered pores, extensive surface area, and unique architecture. Despite these advantages, the toxicity and nonbiodegradable nature of silica-based organisms pose a significant challenge when attempting to utilize these organisms as nanotopographically functionalized microparticles in the realm of biomedicine. In this study, we addressed this limitation by modulating the chemical composition of diatom microparticles by modulating the active silica metabolic uptake mechanism while maintaining their intricate three-dimensional architecture through calcium incorporation into living diatoms. Here, the diatom Thalassiosira weissflogii was chemically modified to replace its silica composition with a biodegradable calcium template, while simultaneously preserving the unique three-dimensional (3D) frustule structure with hierarchical patterns of pores and nanoscale architectural features, which was evident by the deposition of calcium as calcium carbonate. Calcium hydroxide is incorporated into the exoskeleton through the active mechanism of calcium uptake via a carbon-concentrating mechanism, without altering the microstructure. Our findings suggest that calcium-modified diatoms hold potential as a nature-inspired delivery system for immunotherapy through antibody-specific binding.

Single cyclized molecule versus single branched molecule: a simple and efficient 3D "knot" polymer structure for nonviral gene delivery.

The large research effort focused on enhancing nonviral transfection vectors has clearly demonstrated that their macromolecular structure has a significant effect on their transfection efficacy. The 3D branched polymeric structures, such as dendrimers, have proved to be a very effective structure for polymeric transfection vectors; however, so far the dendritic polymers have not delivered on their promise. This is largely because a wide range of dendritic polymer materials with tailored multifunctional properties and biocompatibility required for such applications are not yet accessible by current routes. Herein, we report the design and synthesis of new 3D "Single Cyclized" polymeric gene vectors with well-defined compositions and functionalities via a one-step synthesis from readily available vinyl monomers. We observe that this polymer structure of a single chain linked to itself interacts differently with plasmid DNA compared to conventional vectors and when tested over a range of cell types, has a superior transfection profile in terms of both luciferase transfection capability and preservation of cell viability. This new knotted structure shows high potential for gene delivery applications through a combination of simplicity in synthesis, scalability, and high performance.

Mannosylated polyethyleneimine-hyaluronan nanohybrids for targeted gene delivery to macrophage-like cell lines.

Nonviral gene delivery systems have a number of limitations including low transfection efficiency, specificity, and cytotoxicity, especially when the target cells are macrophages. To address these issues, the hypothesis tested in this study was that mannose functionalized nanohybrids composed of synthetic and natural polymers will improve transfection efficiency, cell viability, and cell specificity in macrophages. Robust nanohybrids were designed from hyaluronic acid (HA) and branched polyethyleneimine (bPEI) using carbodiimide chemistry. The reaction product, i.e., branched polyethyleneimine-hyaluronic acid (bPEI-HA) copolymer was subsequently functionalized with mannose at the terminal end of the copolymer to obtain mannosylated-bPEI-HA (Man-bPEI-HA) copolymer. UV spectroscopy and gel retardation studies confirmed the formation of polyplexes at polymer to DNA weight ratio ≥ 2. Alamar Blue and MTT assay revealed that the cytotoxicity of the developed nanohybrids were significantly (P < 0.05) lower than that of unmodified bPEI. Mannose functionalization of these nanohybrids showed specificity for both murine and human macrophage-like cell lines RAW 264.7 and human acute monocytic leukemia cell line (THP1), respectively, with a significant level (P < 0.05) of expression of gaussia luciferase (GLuc) and green fluorescent reporter plasmids. Internalization studies indicate that a mannose mediated endocytic pathway is responsible for this higher transfection rate. These results suggest that hyaluronan-based mannosylated nanohybrids could be used as efficient carriers for targeted gene delivery to macrophages.

A protective extracellular matrix-based gene delivery reservoir fabricated by electrostatic charge manipulation.

Gene therapy is a field that offers hope and promise for the treatment of diseases and traumas of a genetic nature and otherwise. However, progress toward the clinic has been delayed because of concerns over the safety of viral vectors and the efficacy of safer nonviral systems, which have low transfection efficacy and short transgene expression. This study describes the fabrication and characterization of a safe gene delivery reservoir system that has the potential to overcome issues associated with nonviral systems. Harnessing the electrostatic charges of collagen and polystyrene, microspheres were fabricated using a template-based method and characterized by microscopy techniques such as scanning electron microscopy, transmission electron microscopy, and atomic force microscopy, with the removal of the polystyrene template confirmed by Fourier transform infrared spectroscopy analysis. Loading and release of polyplexes confirmed the ability of the system to prolong polyplex delivery, with minimal cytotoxicity observed from viability studies on 3T3 fibroblasts. Finally, biological activity of released polyplexes was confirmed by reporter gene expression. Taken together, these properties indicate the potential of this system as a reservoir for gene delivery.

"One-step" preparation of thiol-ene clickable PEG-based thermoresponsive hyperbranched copolymer for in situ crosslinking hybrid hydrogel.

A well-defined poly(ethylene glycol) based hyperbranched thermoresponsive copolymer with high content of acrylate vinyl groups was synthesized via a "one-pot and one-step" deactivation enhanced atom transfer radical polymerization approach, which provided an injectable and in situ crosslinkable system via Michael-type thiol-ene reaction with a thiol-modified hyaluronan biopolymer. The hyperbranched structure, molecular weight, and percentage of vinyl content of the copolymer were characterized by gel permeation chromatography and (1)H NMR. The lower critical solution temperature of this copolymer is close to body temperature, which can result in a rapid thermal gelation at 37 °C. The scanning electron microscopy analysis of crosslinked hydrogel showed the network formation with porous structure, and 3D cell culture study demonstrated the good cell viability after the cells were embedded inside the hydrogel. This injectable and in situ crosslinking hybrid hydrogel system offers great promise as a new class of hybrid biomaterials for tissue engineering.

Thermoresponsive hyperbranched copolymer with multi acrylate functionality for in situ cross-linkable hyaluronic acid composite semi-IPN hydrogel.

Thermoresponsive polymers have been widely used for in situ formed hydrogels in drug delivery and tissue engineering as they are easy to handle and their shape can easily conform to tissue defects. However, non-covalent bonding and mechanical weakness of these hydrogels limit their applications. In this study, a physically and chemically in situ cross-linkable hydrogel system was developed from a novel thermoresponsive hyperbranched PEG based copolymer with multi acrylate functionality, which was synthesized via an 'one pot and one step' in situ deactivation enhanced atom transfer radical co-polymerization of poly(ethylene glycol) diacrylate (PEGDA, M(n) = 258 g mol(-1)), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA, M(n )= 475 g mol(-1)) and (2-methoxyethoxy) ethyl methacrylate (MEO(2)MA). This hyperbranched copolymer was tailored to have the lower critical solution temperature to form physical gelation around 37°C. Meanwhile, with high level of acrylate functionalities, a chemically cross-linked gel was formed from this copolymer using thiol functional cross-linker of pentaerythritol tetrakis (3-mercaptopropionate) (QT) via thiol-ene Michael addition reaction. Furthermore, a semi-interpenetrated polymer networks (semi-IPN) structure was developed by combining this polymer with hyaluronic acid (HA), leading to an in situ cross-linkable hydrogel with significantly increased porosity, enhanced swelling behavior and improved cell adhesion and viability both in 2D and 3D cell culture models.

Therapeutic potential of targeting galectins - A biomaterials-focused perspective.

Among all the biological entities involved in the immune response, galectins, a family of glycan-binding proteins, have been described as key in immune cell homeostasis and modulation. More importantly, only some galectin family members are crucial in the resolution of inflammation, while others perpetuate the immune response in a pathological context. As they are expressed in most major diseases, their potential as targets for new therapies seems promising. Most of the galectin family members' ubiquitous expression points to the need for targeted treatments to ensure effectiveness. Engineered biomaterials are emerging as a promising method to improve galectin-targeted strategies' therapeutic performance. In this review, we provide an overview of the role of galectins in health and disease and their potential as therapeutic targets, as well as the state-of-the-art and future directions of galectin-targeted biomaterials.

Intervertebral Disc Degeneration: Biomaterials and Tissue Engineering Strategies toward Precision Medicine.

Intervertebral disc degeneration is a common cause of discogenic low back pain resulting in significant disability. Current conservative or surgical intervention treatments do not reverse the underlying disc degeneration or regenerate the disc. Biomaterial-based tissue engineering strategies exhibit the potential to regenerate the disc due to their capacity to modulate local tissue responses, maintain the disc phenotype, attain biochemical homeostasis, promote anatomical tissue repair, and provide functional mechanical support. Despite preliminary positive results in preclinical models, these approaches have limited success in clinical trials as they fail to address discogenic pain. This review gives insights into the understanding of intervertebral disc pathology, the emerging concept of precision medicine, and the rationale of personalized biomaterial-based tissue engineering tailored to the severity of the disease targeting early, mild, or severe degeneration, thereby enhancing the efficacy of the treatment for disc regeneration and ultimately to alleviate discogenic pain. Further research is required to assess the relationship between disc degeneration and lower back pain for developing future clinically relevant therapeutic interventions targeted towards the subgroup of degenerative disc disease patients.

3D single cyclized polymer chain structure from controlled polymerization of multi-vinyl monomers: beyond Flory-Stockmayer theory.

Controlled/living radical polymerization (CRP) is a widely used technique that allows the synthesis of defined polymer architectures through precise control of molecular weights and distributions. However, the architectures of polymers prepared by the CRP techniques are limited to linear, cross-linked, and branched/dendritic structures. Here, we report the preparation of a new 3D single cyclized polymer chain structure from an in situ deactivation enhanced atom transfer radical polymerization of multivinyl monomers (MVMs), which are conventionally used for the production of branched/cross-linked polymeric materials as defined by P. Flory and W. Stockmayer nearly 70 years ago. We provide new evidence to demonstrate that it is possible to kinetically control both the macromolecular architecture and the critical gelling point in the polymerization of MVMs, suggesting the classical Flory-Stockmayer mean field theory should be supplemented with a new kinetic theory based on the space and instantaneous growth boundary concept.