Recent advances of biomaterials in biotherapy

In Vivo Bone Tissue Engineering Strategies: Advances and Prospects

Reconstruction of critical-sized bone defects remains a tremendous challenge for surgeons worldwide. Despite the variety of surgical techniques, current clinical strategies for bone defect repair demonstrate significant limitations and drawbacks, including donor-site morbidity, poor anatomical match, insufficient bone volume, bone graft resorption, and rejection. Bone tissue engineering (BTE) has emerged as a novel approach to guided bone tissue regeneration. BTE focuses on in vitro manipulations with seed cells, growth factors and bioactive scaffolds using bioreactors. The successful clinical translation of BTE requires overcoming a number of significant challenges. Currently, insufficient vascularization is the critical limitation for viability of the bone tissue-engineered construct. Furthermore, efficacy and safety of the scaffolds cell-seeding and exogenous growth factors administration are still controversial. The in vivo bioreactor principle (IVB) is an exceptionally promising concept for the in vivo bone tissue regeneration in a predictable patient-specific manner. This concept is based on the self-regenerative capacity of the human body, and combines flap prefabrication and axial vascularization strategies. Multiple experimental studies on in vivo BTE strategies presented in this review demonstrate the efficacy of this approach. Routine clinical application of the in vivo bioreactor principle is the future direction of BTE; however, it requires further investigation for overcoming some significant limitations.

A Generative Approach to Materials Discovery, Design, and Optimization

Despite its potential to transform society, materials research suffers from a major drawback: its long research timeline. Recently, machine-learning techniques have emerged as a viable solution to this drawback and have shown accuracies comparable to other computational techniques like density functional theory (DFT) at a fraction of the computational time. One particular class of machine-learning models, known as "generative models", is of particular interest owing to its ability to approximate high-dimensional probability distribution functions, which in turn can be used to generate novel data such as molecular structures by sampling these approximated probability distribution functions. This review article aims to provide an in-depth understanding of the underlying mathematical principles of popular generative models such as recurrent neural networks, variational autoencoders, and generative adversarial networks and discuss their state-of-the-art applications in the domains of biomaterials and organic drug-like materials, energy materials, and structural materials. Here, we discuss a broad range of applications of these models spanning from the discovery of drugs that treat cancer to finding the first room-temperature superconductor and from the discovery and optimization of battery and photovoltaic materials to the optimization of high-entropy alloys. We conclude by presenting a brief outlook of the major challenges that lie ahead for the mainstream usage of these models for materials research.

Equine platelet lysate gel: a matrix for mesenchymal stem cell delivery

A variety of bio-scaffolds have been developed as carriers for the delivery of Mesenchymal Stem Cells (MSCs) however many of them are unable to provide direct cell nourishment, a critical factor for survival and retention of MSCs at the site of delivery. Platelet lysate (PL) is a plasma derived product rich in growth factors, that can be turned into a gel matrix following the addition of calcium chloride. Our objective was to characterize growth factor and cytokine release of equine PL gel (ePL gel) encapsulated with MSCs over time and to measure the viability and proliferation of ePL gel-encapsulated MSCs for up to 14 days. Release of interleukin-1β (IL-1β), interleukin-10 (IL-10), transforming growth factor beta (TGF-β), vascular endothelial growth factor (VEGF), and platelet derived growth factor (PDGF-BB), as well as fibrinogen degradation, were measured from ePL gel with and without equine bone marrow derived MSCs and compared to MSCs in monolayer. MSC proliferation and viability within the gel were assessed up to 14 days. Compared to monolayer MSC cultures, significantly higher concentrations of IL-1β, IL-10, and TGF-β were measured from supernatants collected from ePL gel containing MSCs at various time points. Significantly lower concentrations of PDGF-BB were measured in the supernatant when MSCs were incorporated in ePL gel while VEGF tended to be increased compared to MSCs in monolayer. Incorporation in ePL gel for up to 14 days did not appear to affect viability and proliferation rates of MSCs as these were found to be similar to those measured in monolayer cell culture. ePL gel may have the potential to serve as bio-scaffold for MSC delivery since it appears to support the proliferation and viability of MSCs for up to 14 days.

RGD-Hydrogel Improves the Therapeutic Effect of Bone Marrow-Derived Mesenchymal Stem Cells on Phosgene-Induced Acute Lung Injury in Rats

Mesenchymal stem cells (MSCs) have promising potential in the treatment of various diseases, such as the therapeutic effect of bone marrow-derived MSCs for phosgene-induced acute lung injury (P-ALI). However, MSC-related therapeutics are limited due to poor cell survival, requiring appropriate MSC delivery systems to maximise therapeutic capacity. Biomaterial RGD-hydrogel is a potential cell delivery vehicle as it can mimic the natural extracellular matrix and provide cell adhesion support. The application of RGD-hydrogel in the MSC treatment of respiratory diseases is scarce. This study reports that RGD-hydrogel has good biocompatibility and can increase the secretion of Angiopoietin-1, hepatocyte growth factor, epidermal growth factor, vascular endothelial cell growth factor, and interleukin-10 in vitro MSCs. The hydrogel-encapsulated MSCs could further alleviate P-ALI and show better cell survival in vivo. Overall, RGD-hydrogel could improve the MSC treatment of P-ALI by modulating cell survival and reparative activities. It is exciting to see more and more ways to unlock the therapeutic potential of MSCs.

Supramolecular protein assembly in cell-free protein synthesis system

Protein-based biomaterials have the characteristics of stability and biocompatibility. Based on these advantages, various bionic materials have been manufactured and used in different fields. However, current protein-based biomaterials generally need to form monomers in cells and be purified before being assembled in vitro. The preparation process takes a long time, and the complex cellular environment is challenging to be optimized for producing the target protein product. Here this study proposed technology for in situ synthesis and assembly of the target protein, namely the cell-free protein synthesis (CFPS), which allowed to shorten the synthesis time and increase the flexibility of adding or removing natural or synthetic components. In this study, successful expression and self-assembly of the dihedral symmetric proteins proved the applicability of the CFPS system for biomaterials production. Furthermore, the fusion of different functional proteins to these six scaffold proteins could form active polymers in the CFPS system. Given the flexibility, CFPS is expected to become a powerful tool as the prototyping and manufacturing technology for protein-based biomaterials in the future.

Pro-angiogenic approach for skeletal muscle regeneration

The angiogenesis process is a phenomenon in which numerous molecules participate in the stimulation of the new vessels' formation from pre-existing vessels. Angiogenesis is a crucial step in tissue regeneration and recovery of organ and tissue function. Muscle diseases affect millions of people worldwide overcome the ability of skeletal muscle to self-repair. Pro-angiogenic therapies are key in skeletal muscle regeneration where both myogenesis and angiogenesis occur. These therapies have been based on mesenchymal stem cells (MSCs), exosomes, microRNAs (miRs) and delivery of biological factors. The use of different calls of biomaterials is another approach, including ceramics, composites, and polymers. Natural polymers are use due its bioactivity and biocompatibility in addition to its use as scaffolds and in drug delivery systems. One of these polymers is the natural rubber latex (NRL) which is biocompatible, bioactive, versatile, low-costing, and capable of promoting tissue regeneration and angiogenesis. In this review, the advances in the field of pro-angiogenic therapies are discussed.

Amphiphilic Poly(N-Vinylpyrrolidone) Nanoparticles Loaded with DNA Plasmids Encoding Gn and Gc Glycoproteins of the Rift Valley Fever Virus: Preparation and In Vivo Evaluation

The aim of the study was to develop amphiphilic poly(N-vinylpyrrolidone) (PVP) nanoparticles (NPs) loaded with DNA plasmids encoding Gn and Gc glycoproteins of the Rift Valley fever virus (RVFV) and to study the humoral response in vivo. DNA plasmids were protected from extracellular nucleases by loading in NPs from PVP derivatives modified with amino acids β-alanine (Ala7-PVPOD4000) or glycine (Gly7.5-PVP-OD4000) fabricated by the original self-assembly technique. The obtained NPs were administered in mice and the enhancement of humoral response compared to this one in case of immunization with native DNA plasmids was demonstrated. The NPs loaded with DNA plasmids are promising for the fabrication of various DNA particulate vaccines.

Preparation of ROS active and photothermal responsive hydroxyapatite nanoplatforms for anticancer therapy

Photothermal responsive nanoplatforms are attracting for photothermal therapy (PTT) of cancer. Herein, we propose a strategy to prepare IR-780 modified hydroxyapatite (HAP) nanorods as photothermic agents (HAP@IR-780). The results demonstrated that the obtained HAP@IR-780 was photothermal responsive under near-infrared laser irradiation the photothermal conversion efficiency was 69.3%, and it remained photostability after 4 cycles of irradiation. This advantage overcomes the optical instability of IR780. MTT and cellular uptake research proved that HAP@IR-780 was biocompatible in appropriate concentration range (0-20 μg/mL) without laser irradiation. Concentration-dependent internalization and reactive oxygen species (ROS) related apoptosis of HAP@IR-780 for MCF-7 cells were observed. Animal experiments showed that the gathered HAP@IR-780 at the tumor site reached a photothermal responsive temperature up to 57.9 °C, which could almost ablate the tumor with volumes as large as 1500 mm³. In general, our photothermal material has good photothermal conversion characteristics, and may have the least safety problems while showing excellent therapeutic effects. Therefore, HAP@IR-780 has a brilliant prospect in the field of tumor photothermal therapy.

Harnessing biomaterials for therapeutic strategies against COVID-19

With the emergence of the coronavirus disease 2019 (COVID-19), the world is experiencing a profound human health crisis. The number of infections and deaths due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to increase every minute, pinpointing major shortcomings in our ability to prevent viral outbreaks. Although several COVID-19 vaccines have been recently approved for emergency use, therapeutic options remain limited, and their long-term potency has yet to be validated. Biomaterials science has a pivotal role to play in pushing the boundaries of emerging technologies for antiviral research and treatment. In this perspective, we discuss how biomaterials can be harnessed to develop accurate COVID-19 infection models, enhance antiviral drug delivery, foster new antiviral strategies, and boost vaccine efficacy. These efforts will not only contribute to stop or mitigate the current pandemic but will also provide unorthodox platforms to understand, prevent, and protect us from future viral outbreaks.

MgO Nanoparticles-Incorporated PCL/Gelatin-Derived Coaxial Electrospinning Nanocellulose Membranes for Periodontal Tissue Regeneration

Electrospinning technique has attracted considerable attention in fabrication of cellulose nanofibrils or nanocellulose membranes, in which polycaprolactone (PCL) could be used as a promising precursor to prepare various cellulose nanofibril membranes for periodontal tissue regeneration. Conventional bio-membranes and cellulose films used in guided tissue regeneration (GTR) can prevent the downgrowth of epithelial cells, fibroblasts, and connective tissue in the area of tooth root but have limitations related to osteogenic and antimicrobial properties. Cellulose nanofibrils can be used as an ideal drug delivery material to encapsulate and carry some drugs. In this study, magnesium oxide (MgO) nanoparticles-incorporated PCL/gelatin core-shell nanocellulose periodontal membranes were fabricated using coaxial electrospinning technique, which was termed as Coaxial-MgO. The membranes using single-nozzle electrospinning technique, namely Blending-MgO and Blending-Blank, were used as control. The morphology and physicochemical property of these nanocellulose membranes were characterized by scanning electron microscopy (SEM), energy-dispersive spectrum of X-ray (EDS), transmission electron microscopy (TEM), contact angle, and thermogravimetric analysis (TGA). The results showed that the incorporation of MgO nanoparticles barely affected the morphology and mechanical property of nanocellulose membranes. Coaxial-MgO with core-shell fiber structure had better hydrophilic property and sustainable release of magnesium ion (Mg²⁺). CCK-8 cell proliferation and EdU staining demonstrated that Coaxial-MgO membranes showed better human periodontal ligament stem cells (hPDLSCs) proliferation rates compared with the other group due to its gelatin shell with great biocompatibility and hydrophilicity. SEM and immunofluorescence assay results illustrated that the Coaxial-MgO scaffold significantly enhanced hPDLSCs adhesion. In vitro osteogenic and antibacterial properties showed that Coaxial-MgO membrane enhanced alkaline phosphatase (ALP) activity, formation of mineralized nodules, osteogenic-related genes [ALP, collagen type 1 (COL1), runt-related transcription factor 2 (Runx2)], and high antibacterial properties toward Escherichia coli (E. coli) and Actinobacillus actinomycetemcomitans (A. a) when compared with controls. Our findings suggested that MgO nanoparticles-incorporated coaxial electrospinning PCL-derived nanocellulose periodontal membranes might have great prospects for periodontal tissue regeneration.

Non-viral Gene Delivery Methods for Bone and Joints

Viral carrier transport efficiency of gene delivery is high, depending on the type of vector. However, viral delivery poses significant safety concerns such as inefficient/unpredictable reprogramming outcomes, genomic integration, as well as unwarranted immune responses and toxicity. Thus, non-viral gene delivery methods are more feasible for translation as these allow safer delivery of genes and can modulate gene expression transiently both in vivo, ex vivo, and in vitro. Based on current studies, the efficiency of these technologies appears to be more limited, but they are appealing for clinical translation. This review presents a summary of recent advancements in orthopedics, where primarily bone and joints from the musculoskeletal apparatus were targeted. In connective tissues, which are known to have a poor healing capacity, and have a relatively low cell-density, i.e., articular cartilage, bone, and the intervertebral disk (IVD) several approaches have recently been undertaken. We provide a brief overview of the existing technologies, using nano-spheres/engineered vesicles, lipofection, and in vivo electroporation. Here, delivery for microRNA (miRNA), and silencing RNA (siRNA) and DNA plasmids will be discussed. Recent studies will be summarized that aimed to improve regeneration of these tissues, involving the delivery of bone morphogenic proteins (BMPs), such as BMP2 for improvement of bone healing. For articular cartilage/osteochondral junction, non-viral methods concentrate on targeted delivery to chondrocytes or MSCs for tissue engineering-based approaches. For the IVD, growth factors such as GDF5 or GDF6 or developmental transcription factors such as Brachyury or FOXF1 seem to be of high clinical interest. However, the most efficient method of gene transfer is still elusive, as several preclinical studies have reported many different non-viral methods and clinical translation of these techniques still needs to be validated. Here we discuss the non-viral methods applied for bone and joint and propose methods that can be promising in clinical use.

A comparative study of autogenous, allograft and artificial bone substitutes on bone regeneration and immunotoxicity in rat femur defect model

Repair and reconstruction of large bone defect were often difficult, and bone substitute materials, including autogenous bone, allogenic bone and artificial bone, were common treatment strategies. The key to elucidate the clinical effect of these bone repair materials was to study their osteogenic capacity and immunotoxicological compatibility. In this paper, the mechanical properties, micro-CT imaging analysis, digital image analysis and histological slice analysis of the three bone grafts were investigated and compared after different time points of implantation in rat femur defect model. Autogenous bone and biphasic calcium phosphate particular artificial bone containing 61.4% HA and 38.6% β-tricalcium phosphate with 61.64% porosity and 0.8617 ± 0.0068 g/cm³ density (d ≤ 2 mm) had similar and strong bone repair ability, but autogenous bone implant materials caused greater secondary damage to experimental animals; allogenic bone exhibited poor bone defect repair ability. At the early stage of implantation, the immunological indexes such as Immunoglobulin G, Immunoglobulin M concentration and CD4 cells' population of allogenic bone significantly increased in compared with those of autologous bone and artificial bone. Although the repair process of artificial bone was relatively inefficient than autologous bone graft, the low immunotoxicological indexes and acceptable therapeutic effects endowed it as an excellent alternative material to solve the problems with insufficient source and secondary trauma of autogenous bone.

Merging 3D printing with electrospun biodegradable small-caliber vascular grafts immobilized with VEGF

The major challenge of commercially available vascular substitutes comes from their limitations in terms of hydrophobic surface, which is hostile to cell growth. To date, tissue-engineered and synthetic grafts have not translated well to clinical trials when looking at small diameters. We conceptualized a cell-free structurally reinforced biodegradable vascular graft recapitulating the anisotropic feature of a native blood vessel. The nanofibrous scaffold is designed in such a way that it will gradually degrade systematically to yield a neo-vessel, facilitated by an immobilized bioactive molecule-vascular endothelial growth factor (VEGF). The nano-topographic cue of the device is capable of direct host cell infiltration. We evaluated the burst pressure, histology, hemocompatibility, compression test, and mechanical analysis of the new graft. The graft implanted into the carotid artery of a porcine model demonstrated a good patency rate as early as two week post-implantation. This graft reinforced design approach when employed in vascular tissue engineering might strongly influencing regenerative medicine.

Bottom-Up Self-assembled Hydrogel-Mineral Composites Regenerate Rabbit Ulna Defect without Added Growth Factors

Hydrogel-based biomaterials have advanced bone tissue engineering approaches in the last decade, through their ability to serve as a carrier for potent growth factor, bone morphogenic protein-2 (BMP-2). However, biophysical properties of hydrogels such as multiscale structural hierarchy and bone extracellular matrix (ECM)-mimetic microarchitecture are underutilized while designing current bone grafts. Incorporation of these properties offers great potential to create a favorable biomimetic microenvironment to harness their regenerative potential. Here, we present our approach to fabricate collagen-inspired bioactive hydrogel scaffolds (referred to as "RegenMatrix") to guide and enhance bone regeneration in a rabbit ulna defect model through the mimicry of multiscale architecture of bone ECM, i.e., native collagen. Specifically, we employed polyelectrolyte complexation to promote bottom-up self-assembly of oppositely charged polysaccharides (chitosan and kappa-carrageenan) at multiple length scales forming fibrils, which further assemble into fibers. The self-assembly and bioinspired scaffold fabrication method resulted in robust cylindrical RegenMatrix with excellent retention of the multiscale architecture and uniform mineral deposition throughout the scaffolds. RegenMatrix, in both nonmineralized and mineralized forms, enhanced bone regeneration in the semiload-bearing ulna defect when compared to the empty defect. RegenMatrix also showed greater histocompatibility without any fibrous tissue formation. Collectively, the RegenMatrix developed in this study has a great potential as a bioactive bone graft without any added growth factors.

A Combinatorial Approach for the Fabrication of Magneto-Optical Hybrid Nanoparticles

Introduction

The increasing demands for better resolution combined with anatomical information in biomedical imaging necessitate the development of multimodal contrast agents. In this respect, the multivalency of nanotechnology enables the integration of nanomaterials with distinct biophysical properties into a unique probe, capable to exert superior imaging characterstics through synergistic enhancement unmatched by any single modality.

Materials and methods

Novel magneto-optical hybrid nanoparticles (MOHNPs), comprise semiconductor quantum dots (QDs) tethered on the surface of superparamagnetic iron oxide (SPIO) NPs, were synthesized using a combinatorial approach. The semiconductor components utilized for the synthesis of the hybrid NPs contained cadmium-free QDs, which were stabilized by a variety of functional ligands including thiols, polyethyleneimine (PEI) and amphiphilic polymers. While SPIO NPs were further modified with silica or PEI on the outermost layer. The main mechanism to assemble semiconductor QDs onto the SPIO NPs employed a core-shell approach, in which covalent bonding and electrostatic interaction held the components together.

Results

The versatility of the NP assembling mechanism described in this work offered a robust and flexible fabrication of MOHNPs. A proof-of-concept study demonstrated desterous coating of folic acid onto the surface of MOHNPs to create a targeted imaging probe. The emission of the resulted hybrid NPs extended in the near-infrared region, suitable for in vivo applications.

Conclusion

This novel assembling technology offers far-reaching capabilities to generate complex multimodal nanoiamging probes.

The proper strategy to compress and protect plasmid DNA in the Pluronic L64-electropulse system for enhanced intramuscular gene delivery

Intramuscular expression of functional proteins is a promising strategy for therapeutic purposes. Previously, we developed an intramuscular gene delivery method by combining Pluronic L64 and optimized electropulse, which is among the most efficient methods to date. However, plasmid DNAs (pDNAs) in this method were not compressed, making them unstable and inefficient in vivo. We considered that a proper compression of pDNAs by an appropriate material should facilitate gene expression in this L64-electropulse system. Here, we reported our finding of such a material, Epigallocatechin gallate (EGCG), a natural compound in green teas, which could compress and protect pDNAs and significantly increase intramuscular gene expression in the L64-electropulse system. Meanwhile, we found that polyethylenimine (PEI) could also slightly improve exogenous gene expression in the optimal procedure. By analysing the characteristic differences between EGCG and PEI, we concluded that negatively charged materials with strong affinity to nucleic acids and/or other properties suitable for gene delivery, such as EGCG, are better alternatives than cationic materials (like PEI) for muscle-based gene delivery. The results revealed that a critical principle for material/pDNA complex benefitting intramuscular gene delivery/expression is to keep the complex negatively charged. This proof-of-concept study displays the breakthrough in compressing pDNAs and provides a principle and strategy to develop more efficient intramuscular gene delivery systems for therapeutic applications.

Soft-Nanoparticle Functionalization of Natural Hydrogels for Tissue Engineering Applications

Tissue engineering has emerged as an important research area that provides numerous research tools for the fabrication of biologically functional constructs that can be used in drug discovery, disease modeling, and the treatment of diseased or injured organs. From a materials point of view, scaffolds have become an important part of tissue engineering activities and are usually used to form an environment supporting cellular growth, differentiation, and maturation. Among various materials used as scaffolds, hydrogels based on natural polymers are considered one of the most suitable groups of materials for creating tissue engineering scaffolds. Natural hydrogels, however, do not always provide the physicochemical and biological characteristics and properties required for optimal cell growth. This review discusses the properties and tissue engineering applications of widely used natural hydrogels. In addition, methods of modulation of their physicochemical and biological properties using soft nanoparticles as fillers or reinforcing agents are presented.

Challenges of gene delivery to the central nervous system and the growing use of biomaterial vectors

Gene therapy is a promising form of treatment for those suffering from neurological disorders or central nervous system (CNS) injury, however, obstacles remain that limit its translational potential. The CNS is protected by the blood brain barrier, and this barrier blocks genes from traversing into the CNS if administered outside of the CNS. Viral and non-viral gene delivery vehicles, commonly referred to as vectors, are modified to enhance delivery efficiency to target locations in the CNS. Still, there are few gene therapy approaches approved by the FDA for CNS disease or injury treatment. The lack of viable clinical approaches is due, in part, to the unpredictable nature of many vector systems. In particular, safety concerns exist with the use of viral vectors for CNS gene delivery. To seek some alternatives to viral vectors, development of new non-viral, biomaterial vectors is occurring at a rapid rate. This review discusses the challenges of delivering various forms of genetic material to the CNS, the use and limitations of current viral vector delivery systems, and the use of non-viral, biomaterial vectors for CNS applications.

Accelerated construction of an in vitro model of human periodontal ligament tissue: vacuum plasma combined with fibronectin coating and a polydimethylsiloxane matrix

Tying shape memory wires to crowded teeth causes the wires to deform according to the dental arch. This deformation results in a resilient force that is delivered to the tooth. The appropriate amount of force can activate the osteogenetic and osteoclastic ability of the periodontal ligament (PDL) and the tooth can be moved. This is the biological basis of orthodontic treatment. To achieve further insight into the mechanisms underlying orthodontic treatment, we examined whether accelerated construction of an in vitro human PDL fibroblast (HPdLF) stretching model can be achieved by combining fibronectin coating and vacuum plasma treatment with polydimethylsiloxane (PDMS) cell-culture chambers. Each chamber was randomly assigned to a no-surface modification (NN), fibronectin coating (FN), vacuum plasma treatment (PN), or vacuum plasma treatment followed by a fibronectin coating (PF) treatment protocol. The physical and chemical features and ability to promote cellular proliferation of the PDMS chamber surfaces were evaluated. Cellular adhesion of four materials were evaluated and two best-proliferated groups were considered as better model-constructing surfaces and used in subsequent experiments and used in subsequent experiments. HPdLFs were cultured on these two kinds of chambers without stretching for 3 days, then with stretching for 7 days. Time-course gene expression cellular morphology were evaluated. Chambers in the PN group had high wettability and surface component changes. The FN and PF chambers had high cellular proliferation ability. They were selected into subsequent experiments. After 3 days of culturing HPdLFs on the PF and PN chambers, the cells in the PF chambers had significantly higher levels of runt-related transcription factor 2 (Runx-2) and osteocalcin (OCN) gene expression compared with the cells in the PN chambers. After cyclic stretch application to the cells in the PN and PF chambers, expression of the type-3 collagen (COL-3) gene in PF group continued to increase for 7 days and was significantly higher than that in the PN group from day 5 onwards. The HPdLFs in the PF group showed parallel alignment from days 3 to 7 after imposition of cyclic stretch, while those in the PN group aligned in parallel from day 5 on. Our results suggested that applying a fibronectin coating to a PDMS chamber after plasma treatment can accelerate establishment of an in vitro PDL stretching model.

Tunable biomaterials from synthetic, sequence-controlled polymers

Polymeric biomaterials have many applications including therapeutic delivery vehicles, medical implants and devices, and tissue engineering scaffolds. Both naturally-derived and synthetic materials have successfully been used for these applications in the clinic. However, the increasing complexity of these applications requires materials with advanced properties, especially customizable or tunable materials with bioactivity. To address this issue, there have been recent efforts to better recapitulate the properties of natural materials using synthetic biomaterials composed of sequence-controlled polymers. Sequence control mimics the primary structure found in biopolymers, and in many cases, provides an extra handle for functionality in synthetic polymers. Here, we first review the advances in synthetic methods that have enabled sequence-controlled biomaterials on a relevant scale, and discuss strategies for choosing functional sequences from a biomaterials engineering context. Then, we highlight several recent studies that show strong impact of sequence control on biomaterial properties, including in vitro and in vivo behavior, in the areas of hydrogels, therapeutic materials, and novel applications such as molecular barcodes for medical devices. The role of sequence control in biomaterials properties is an emerging research area, and there remain many opportunities for investigation. Further study of this topic may significantly advance our understanding of bioactive or smart materials, as well as contribute design rules to guide the development of synthetic biomaterials for future applications in tissue engineering and regenerative medicine.

Nanoparticles: Properties and Applications in Cancer Immunotherapy

BACKGROUND

Tumours are no longer regarded as isolated masses of aberrantly proliferating epithelial cells. Rather, their properties depend on complex interactions between epithelial cancer cells and the surrounding stromal compartment within the tumour microenvironment. In particular, leukocyte infiltration plays a role in controlling tumour development and is now considered one of the hallmarks of cancer. Thus, in the last few years, immunotherapy has become a promising strategy to fight cancer, as its goal is to reprogram or activate antitumour immunity to kill tumour cells, without damaging the normal cells and provide long-lasting results where other therapies fail. However, the immune-related adverse events due to the low specificity in tumour cell targeting, strongly limit immunotherapy efficacy. In this regard, nanomedicine offers a platform for the delivery of different immunotherapeutic agents specifically to the tumour site, thus increasing efficacy and reducing toxicity. Indeed, playing with different material types, several nanoparticles can be formulated with different shape, charge, size and surface chemical modifications making them the most promising platform for biomedical applications.

AIM

In this review, we will summarize the different types of cancer immunotherapy currently in clinical trials or already approved for cancer treatment. Then, we will focus on the most recent promising strategies to deliver immunotherapies directly to the tumour site using nanoparticles.

CONCLUSION

Nanomedicine seems to be a promising approach to improve the efficacy of cancer immunotherapy. However, additional investigations are needed to minimize the variables in the production processes in order to make nanoparticles suitable for clinical use.

Non-Viral Vectors for Gene Delivery

Introduction:

Gene therapy has emerged out as a promising therapeutic pave for the treatment of genetic and acquired diseases. Gene transfection into target cells using naked DNA is a simple and safe approach which has been further improved by combining vectors or gene carriers. Both viral and non-viral approaches have achieved a milestone to establish this technique, but non-viral approaches have attained a significant attention because of their favourable properties like less immunotoxicity and biosafety, easy to produce with versatile surface modifications, etc. Literature is rich in evidences which revealed that undoubtedly, non–viral vectors have acquired a unique place in gene therapy but still there are number of challenges which are to be overcome to increase their effectiveness and prove them ideal gene vectors.

Conclusion:

To date, tissue specific expression, long lasting gene expression system, enhanced gene transfection efficiency has been achieved with improvement in delivery methods using non-viral vectors. This review mainly summarizes the various physical and chemical methods for gene transfer in vitro and in vivo.

Bone Mesenchymal Stem Cell-Enriched β-Tricalcium Phosphate Scaffold Processed by the Screen-Enrich-Combine Circulating System Promotes Regeneration of Diaphyseal Bone Non-Union

Bone non-union after fracture, considered a therapeutic challenge for orthopedics, always needs a reversion surgery, including autograft transplantation (AGT). However, adverse events related to autograft harvest cannot be ignored. Our group designed a novel system called the bone marrow stem cell Screen-Enrich-Combine Circulating System (SECCS) by seeding mesenchymal stem cells (MSCs) into β-tricalcium phosphate (β-TCP) during surgery to thereafter rapidly process bioactive bone implantation. In this retrospective case-control study, 30 non-union patients who accepted SECCS therapy and 20 non-union patients who accepted AGT were enrolled. By SECCS therapy, the MSC-enriched β-TCP particles were implanted into the non-union gap. During the enrichment procedure, a significant proportion of MSCs were screened and enriched from bone marrow into porous β-TCP particles, and the cells possessed the capacity for three-line differentiation and were CD90⁺/CD105⁺/CD34^-/CD45^-. Approximately 82.0±10.7% of MSCs were enriched from 60 mL bone marrow without damaging cell viability, and approximately 11,444.0±6,018 MSCs were transplanted per patient. No implant-related infections occurred in any case. After 9 months of follow-up, 27 patients (90%) in the SECCS group acquired clinical union, compared with 18 patients (90%) in the AGT group (clinical union time, P = 0.064), and postoperative radiographic union score at 9 months post-operation was similar between the two groups. In conclusion, the SECCS could concentrate a large proportion of MSCs from bone marrow to acquire enough effective cells for therapy without in vitro cell culture. Bone substitutes processed by SECCS demonstrated encouraging promotion of bone regeneration and showed a satisfactory clinical curative effect for diaphyseal bone non-union, which was non-inferior to AGT.

Lyophilized Scaffolds Fabricated from 3D-Printed Photocurable Natural Hydrogel for Cartilage Regeneration

Repair of cartilage defects is highly challenging in clinical treatment. Tissue engineering provides a promising approach for cartilage regeneration and repair. As a core component of tissue engineering, scaffolds have a crucial influence on cartilage regeneration, especially in immunocompetent large animal and human. Native polymers, such as gelatin and hyaluronic acid, have known as ideal biomimetic scaffold sources for cartilage regeneration. However, how to precisely control their structure, degradation rate, and mechanical properties suitable for cartilage regeneration remains a great challenge. To address these issues, a series of strategies were introduced in the current study to optimize the scaffold fabrication. First, gelatin and hyaluronic acid were prepared into a hydrogel and 3D printing was adopted to ensure precise control in both the outer 3D shape and internal pore structure. Second, methacrylic anhydride and a photoinitiator were introduced into the hydrogel system to make the material photocurable during 3D printing. Finally, lyophilization was used to further enhance mechanical properties and prolong degradation time. According to the current results, by integrating photocuring 3D printing and lyophilization techniques, gelatin and hyaluronic acid were successfully fabricated into human ear- and nose-shaped scaffolds, and both scaffolds achieved shape similarity levels over 90% compared with the original digital models. The scaffolds with 50% infill density achieved proper internal pore structure suitable for cell distribution, adhesion, and proliferation. Besides, lyophilization further enhanced mechanical strength of the 3D-printed hydrogel and slowed its degradation rate matching to cartilage regeneration. Most importantly, the scaffolds combined with chondrocytes successfully regenerated mature cartilage with typical lacunae structure and cartilage-specific extracellular matrixes both in vitro and in the autologous goat model. The current study established novel scaffold-fabricated strategies for native polymers and provided a novel natural 3D scaffold with satisfactory outer shape, pore structure, mechanical strength, degradation rate, and weak immunogenicity for cartilage regeneration.

Evaluation of RGD functionalization in hybrid hydrogels as 3D neural stem cell culture systems

The use of neural stem cells (NSCs) in cell therapy has become a powerful tool used for the treatment of central nervous system diseases, including traumatic brain and spinal cord injuries. However, a significant drawback is related to the limited viability after transplantation in situ. The design of three-dimensional (3D) scaffolds that are capable of resembling the architecture and physico-chemical features of an extracellular environment could be a suitable approach to improve cell survival and preserve their cellular active phase over time. In this study, we investigated NSC adhesion and proliferation in hydrogel systems. In particular, we evaluated the effect of RGD binding domains on cell fate within the polymeric scaffold. The introduction of a tripeptide via hydrogel chemical functionalization improved the percentage of proliferating cells until 8 days after seeding when compared to the unmodified scaffold. The beneficial effects of this 3D culture system was further evident when compared to a NSC monolayer (2D) culture, resulting in an approximately 40% increase in cells in the active phases at 4 and 8 days, and maintained a difference of 25% until 21 days after seeding.

Tissue engineering using 3D printed nano-bioactive glass loaded with NELL1 gene for repairing alveolar bone defects

The purposes of this study were to construct a novel tissue engineered bone composed of 3D-printed bioactive glass block/chitosan nanoparticles (BD/CSn) composites loaded with Nel-like Type I molecular-1 DNA (pDNA-NELL1) and/or bone marrow mesenchymal stem cells (BMSCs), and study their osteogenic activities by repairing bone defects in rhesus monkeys. CSn with NELL1 gene plasmid and rhesus monkey BMSCs were composited with a BD scaffold to prepare the tissue-engineered bone. Four adult female rhesus monkeys with 10- to 12-years old and 5-7 kg in weight were used in animal experiments. The first and second premolar teeth from four regions of each monkey were removed to form bone defects with size of 10 × 10 × 5 mm, which were then implanted with above-mentioned tissue engineered bone. At 12 weeks after the implantation, gross observations, X-ray and micro-CT observations revealed that the new bone was extremely close to normal bone in mass, density, hardness, and structure. The bony cortex was smooth and closely connected to the surrounding normal bone. Histological observations revealed moderate inflammation in the repair area, and the new bone tissues were similar to normal ones. In conclusion, tissue engineered bone of this study exhibited good osteoconductivity for promoting the formation of new alveolar bone tissue, and NELL1 gene played a promotional role in bone regeneration.

Expanding One-Pot Cell-Free Protein Synthesis and Immobilization for On-Demand Manufacturing of Biomaterials

Fabrication of protein-based biomaterials is an arduous and time-consuming procedure with multiple steps. In this work, we describe a portable toolkit that integrates both cell-free protein synthesis (CFPS) and protein immobilization in one pot just by mixing DNA, solid materials, and a CFPS system. We have constructed a modular set of plasmids that fuse the N-terminus of superfolded green fluorescent protein (sGFP) with different peptide tags (poly(6X)Cys, poly(6X)His, and poly(6X)Lys), which drive the immobilization of the protein on the tailored material (agarose beads with different functionalities, gold nanorods, and silica nanoparticles). This system also enables the incorporation of azide-based amino acids into the nascent protein for its selective immobilization through copper-free click reactions. Finally, this technology has been expanded to the synthesis and immobilization of enzymes and antibody-binding proteins for the fabrication of functional biomaterials. This synthetic biological platform has emerged as a versatile tool for on-demand fabrication of therapeutic, diagnostic, and sensing biomaterials.

The supramolecular polymer complexes with oppositely charged calixresorcinarene: hydrophobic domain formation and synergistic binding modes

The association of branched polyethyleneimine (PEI) with a series of octacarboxy-calixresorcinarenes bearing different low-rim substituents leads to the formation of nanosized supramolecular complexes. The PEI-macrocycle complexes have fine-tunable sizes regulated by variations in the self-association capacity of the calixresorcinarenes. In the supramolecular complexes, hydrophobic fragments of the polymer and calixresorcinarenes form cooperative hydrophobic domains which provide synergistic enhancement of guest molecule binding. The formation of the supramolecular complexes was investigated by NMR FT-PGSE, NMR 2D NOESY, DLS and TEM methods. In addition, fluorimetry and UV-vis methods were used with the help of optical probes, namely water-soluble Crystal Violet and water-insoluble Orange OT. The investigation demonstrates the first example of the formation of cooperative hydrophobic domains in supramolecular polyelectrolyte-macrocycle complexes which enhance the binding of both water-soluble and water-insoluble organic compounds. The presented supramolecular systems have potential as sensory and drug delivery systems.

A review on cationic lipids with different linkers for gene delivery

Cationic lipids have become known as one of the most versatile tools for the delivery of DNA, RNA and many other therapeutic molecules, and are especially attractive because they can be easily designed, synthesized and characterized. Most of cationic lipids share the common structure of cationic head groups and hydrophobic portions with linker bonds between both domains. The linker bond is an important determinant of the chemical stability and biodegradability of cationic lipid, and further governs its transfection efficiency and cytotoxicity. Based on the structures of linker bonds, they can be grouped into many types, such as ether, ester, amide, carbamate, disulfide, urea, acylhydrazone, phosphate, and other unusual types (carnitine, vinyl ether, ketal, glutamic acid, aspartic acid, malonic acid diamide and dihydroxybenzene). This review summarizes some research results concerning the nature (such as the structure and orientation of linker groups) and density (such as the spacing and the number of linker groups) of linker bond for improving the chemical stability, biodegradability, transfection efficiency and cytotoxicity of cationic lipid to overcome the critical barriers of in vitro and in vivo transfection.

A macroporous heparin-releasing silk fibroin scaffold improves islet transplantation outcome by promoting islet revascularisation and survival

Islet transplantation is considered the most promising therapeutic option with the potential to cure diabetes. However, efficacy of current clinical islet transplantation is limited by long-term graft dysfunction and attrition. We have investigated the therapeutic potential of a silk fibroin macroporous (SF) scaffold for syngeneic islet transplantation in diabetic mice. The SF scaffold was prepared via lyophilisation, which enables incorporation of active compounds including cytokines, peptide and growth factors without compromising their biological activity. For the present study, a heparin-releasing SF scaffold (H-SF) in order to evaluate the versatility of the SF scaffold for biological functionalisation. Islets were then co-transplanted with H-SF or SF scaffolds in the epididymal fat pad of diabetic mice. Mice from both H-SF and SF groups achieved 100% euglycaemia, which was maintained for 1year. More importantly, the H-SF-islets co-transplantation led to more rapid reversal of hyperglycaemia, complete normalisation of glucose responsiveness and lower long-term blood glucose levels. This superior transplantation outcome is attributable to H-SF-facilitated islet revascularisation and cell proliferation since significant increase of islet endocrine and endothelial cells proliferation was shown in grafts retrieved from H-SF-islets co-transplanted mice. Better intra-islet vascular reformation was also evident, accompanied by VEGF upregulation. In addition, when H-SF was co-transplanted with islets extracted from vegfr2-luc transgenic mice in vivo, sustained elevation of bioluminescent signal that corresponds to vegfr2 expression was collected, implicating a role of heparin-dependent activation of endogenous VEGF/VEGFR2 pathway in promoting islet revascularisation and proliferation. In summary, the SF scaffolds provide an open platform as scaffold development for islet transplantation. Furthermore, given the pro-angiogenic, pro-survival and minimal post-transplantation inflammatory reactions of H-SF, our data also support the feasibility of clinical implementation of H-SF to improve islet transplantation outcome.

STATEMENT OF SIGNIFICANCE

1) The silk fibroin scaffold presented in the present study provides an open platform for scaffold development in islet transplantation, with heparinisation as an example. 2) Both heparin and silk fibroin have been used clinically. The excellent in vivo therapeutic outcome reported here may therefore be clinically relevant and provide valuable insights for bench to bed translation. 3) Compared to conventional clinical islet transplantation, during which islets are injected via the hepatic portal vein, the physical/mechanical properties of silk fibroin scaffolds create a more accessible transplantation site (i.e., within fat pad), which significantly reduces discomfort. 4) Islet implantation into the fat pad also avoids an instant blood mediated inflammatory response, which occurs upon contact of islet with recipient's blood during intraportal injection, and prolongs survival and function of implanted islets.

The Good the Bad and the Ugly of Glycosaminoglycans in Tissue Engineering Applications

High sulfation, low cost, and the status of heparin as an already FDA- and EMA- approved product, mean that its inclusion in tissue engineering (TE) strategies is becoming increasingly popular. However, the use of heparin may represent a naïve approach. This is because tissue formation is a highly orchestrated process, involving the temporal expression of numerous growth factors and complex signaling networks. While heparin may enhance the retention and activity of certain growth factors under particular conditions, its binding 'promiscuity' means that it may also inhibit other factors that, for example, play an important role in tissue maintenance and repair. Within this review we focus on articular cartilage, highlighting the complexities and highly regulated processes that are involved in its formation, and the challenges that exist in trying to effectively engineer this tissue. Here we discuss the opportunities that glycosaminoglycans (GAGs) may provide in advancing this important area of regenerative medicine, placing emphasis on the need to move away from the common use of heparin, and instead focus research towards the utility of specific GAG preparations that are able to modulate the activity of growth factors in a more controlled and defined manner, with less off-target effects.

Self-assembled PEG-b-PDPA-b-PGEM copolymer nanoparticles as protein antigen delivery vehicles to dendritic cells: preparation, characterization and cellular uptake

Antigen uptake by dendritic cells (DCs) is a key step for initiating antigen-specific T cell immunity. In the present study, novel synthetic polymeric nanoparticles were prepared as antigen delivery vehicles to improve the antigen uptake by DCs. Well-defined cationic and acid-responsive copolymers, monomethoxy poly(ethylene glycol)-block-poly(2-(diisopropyl amino) ethyl methacrylate)-block-poly(2-(guanidyl) ethyl methacrylate) (mPEG-b-PDPA-b-PGEM, PEDG) were synthesized by reversible addition-fragmentation chain transfer polymerization of 2-(diisopropylamino)ethyl methacrylate) and N-(tert-butoxycarbonyl) amino ethyl methacrylate monomers, followed by deprotection of tert-butyl protective groups and guanidinylation of obtained primary amines. 1H NMR, 13C NMR and GPC results indicated the successful synthesis of well-defined PEDG copolymers. PEDG copolymers could self-assemble into nanoparticles in aqueous solution, which were of cationic surface charges and showed acid-triggered disassembly contributed by PGEM and PDPA moieties, respectively. Significantly, PEDG nanoparticles could effectively condense with negatively charged model antigen ovalbumin (OVA) to form OVA/PEDG nanoparticle formulations with no influence on its secondary and tertiary structures demonstrating by far-UV circular dichroism and UV-vis spectra. In vitro antigen cellular uptake by bone marrow DCs (BMDCs) indicated using PEDG nanoparticles as antigen delivery vehicles could significantly improve the antigen uptake efficiency of OVA compared with free OVA or the commercialized Alum adjuvant. Moreover, as the surface cationic charges of OVA/PEDG nanoparticle formulations reduced, the uptake efficiency decreased correspondingly. Collectively, our work suggests that guanidinylated, cationic and acid-responsive PEDG nanoparticles represent a new kind of promising antigen delivery vehicle to DCs and hold great potential to serve as immunoadjuvants in the development of vaccines.

Differences in the performance of PCL-based vascular grafts as abdominal aorta substitutes in healthy and diabetic rats

Diabetes exacerbates the regeneration process after in vivo implantation of vascular graft.