Synthetic polymer scaffolds for soft tissue engineering

Application of Bioactive Materials for Osteogenic Function in Bone Tissue Engineering

Bone tissue defects present a major challenge in orthopedic surgery. Bone tissue engineering using multiple versatile bioactive materials is a potential strategy for bone-defect repair and regeneration. Due to their unique physicochemical and mechanical properties, biofunctional materials can enhance cellular adhesion, proliferation, and osteogenic differentiation, thereby supporting and stimulating the formation of new bone tissue. 3D bioprinting and physical stimuli-responsive strategies have been employed in various studies on bone regeneration for the fabrication of desired multifunctional biomaterials with integrated bone tissue repair and regeneration properties. In this review, biomaterials applied to bone tissue engineering, emerging 3D bioprinting techniques, and physical stimuli-responsive strategies for the rational manufacturing of novel biomaterials with bone therapeutic and regenerative functions are summarized. Furthermore, the impact of biomaterials on the osteogenic differentiation of stem cells and the potential pathways associated with biomaterial-induced osteogenesis are discussed.

Low-Temperature Extrusion of Waterborne Polyurethane-Polycaprolactone Composites for Multi-Material Bioprinting of Engineered Elastic Cartilage

3D bioprinting of elastic cartilage tissues that are mechanically and structurally comparable to their native counterparts, while exhibiting favorable cellular behavior, is an unmet challenge. A practical solution for this problem is the multi-material bioprinting of thermoplastic polymers and cell-laden hydrogels using multiple nozzles. However, the processing of thermoplastic polymers requires high temperatures, which can damage hydrogel-encapsulated cells. In this study, the authors developed waterborne polyurethane (WPU)-polycaprolactone (PCL) composites to allow multi-material co-printing with cell-laden gelatin methacryloyl (GelMA) hydrogels. These composites can be extruded at low temperatures (50-60 °C) and high speeds, thereby reducing heat/shear damage to the printed hydrogel-capsulated cells. Furthermore, their hydrophilic nature improved the cell behavior in vitro. More importantly, the bioprinted structures exhibited good stiffness and viscoelasticity compared to native elastic cartilage. In summary, this study demonstrated low-temperature multi-material bioprinting of WPU-PCL-based constructs with good mechanical properties, degradation time-frames, and cell viability, showcasing their potential in elastic cartilage bio-fabrication and regeneration to serve broad biomedical applications in the future.

Photo-/thermo-responsive bioink for improved printability in extrusion-based bioprinting

Extrusion-based bioprinting has demonstrated significant potential for manufacturing constructs, particularly for 3D cell culture. However, there is a greatly limited number of bioink candidates exploited with extrusion-based bioprinting, as they meet the opposing requirements for printability with indispensable rheological features and for biochemical functionality with desirable microenvironment. In this study, a blend of silk fibroin (SF) and iota-carrageenan (CG) was chosen as a cell-friendly printable material. The SF/CG ink exhibited suitable viscosity and shear-thinning properties, coupled with the rapid sol-gel transition of CG. By employing photo-crosslinking of SF, the printability with Pr value close to 1 and structural integrity of the 3D constructs were significantly improved within a matter of seconds. The printed constructs demonstrated a Young's modulus of approximately 250 kPa, making them suitable for keratinocyte and myoblast cell culture. Furthermore, the high cell adhesiveness and viability (maximum >98%) of the loaded cells underscored the considerable potential of this 3D culture scaffold applied for skin and muscle tissues, which can be easily manipulated using an extrusion-based bioprinter.

3D printed polycaprolactone/β-tricalcium phosphate/carbon nanotube composite - Physical properties and biocompatibility

Three-dimensional (3D) printing is a bio-fabrication technique used to process tissue-engineered scaffolds for bone repair and remodeling. Polycaprolactone (PCL)/β-tricalcium phosphate (TCP) has been used as a base and osteoconductive biomaterial for bone tissue engineering in the past decades. The current study reveals the fabrication of a polycaprolactone (PCL)/β-tricalcium phosphate (TCP) scaffold by incorporating carbon nanotubes (CNT) via 3D printing. The physical properties and cytocompatibility of a new type of tissue engineering composite from polycaprolactone/β-tri-calcium phosphate/carbon nanotubes were investigated, and it was an absorbable scaffold prepared via furnace deposition 3D printing technology. The scaffold was designed with CAD software, and the composite material was fabricated via 3D printing. The printed composite material was tested for mechanical strength, scanning electron microscope (SEM) analysis, porosity calculation, systemic toxicity test, hemolysis rate determination, and effect on the proliferation of rat adipose-derived stem cells cultured in vitro. A composite scaffold with a length of 15 mm, width of 10 mm, and height of 5 mm was manufactured through CAD software drawing and 3D printing technology. Scanning electron microscopy measurements and analysis of the internal pore size of the stent are appropriate; the pores are interconnected, and the mechanical strength matches the strength of human cancellous bone. The calculated porosity of the stent was >60%, non-toxic, and non-hemolytic. The proliferation activity of the ADSC co-cultured with different scaffold materials was as follows: polycaprolactone/β-tricalcium phosphate/0.2% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate/0.1% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate/0.3% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate scaffolds (P < 0.05). The results showed that polycaprolactone/β-tricalcium phosphate/0.2% carbon nanotube scaffolds promoted the adhesion and proliferation of ADSC. The combination of 3D printing technology and CAD software can be used to print personalized composite stents, which have the characteristics of repeatability, high precision, and low cost. Through 3D printing technology, combining a variety of materials with each other can provide the greatest advantages of materials. The waste of resources was avoided. The prepared polycaprolactone/β-tri-calcium phosphate/0.2% carbon nanotube scaffold has a good pore structure and mechanical properties that mimic human cancellous bone, is non-toxic and non-hemolytic, and is effective in promoting ADSC proliferation in vitro. Given this correspondence, 3D printed scaffold shows good biocompatibility and strength, and the fabrication method provides a proof of concept for developing scaffolds for bone tissue engineering applications.

Chondroitin sulfate and caseinophosphopeptides doped polyurethane-based highly porous 3D scaffolds for tendon-to-bone regeneration

Tendon disorders are common injuries, which can be greatly debilitating as they are often accompanied by great pain and inflammation. Moreover, several problems are also related to the laceration of the tendon-to-bone interface (TBI), a specific region subjected to great mechanical stresses. The techniques used nowadays for the treatment of tendon and TBI injuries often involve surgery. However, one critical aspect of this procedure involves the elevated risk of fail due to the tissues weakening and the postoperative alterations of the normal joint mechanics. Synthetic polymers, such as thermoplastic polyurethane, are of special interest in the tissue engineering field as they allow the production of scaffolds with tunable elastic and mechanical properties, that could guarantee an effective support during the new tissue formation. Based on these premises, the aim of this work was the design and the development of highly porous 3D scaffolds based on thermoplastic polyurethane, and doped with chondroitin sulfate and caseinophosphopeptides, able to mimic the structural, biomechanical, and biochemical functions of the TBI. The obtained scaffolds were characterized by a homogeneous microporous structure, and by a porosity optimal for cell nutrition and migration. They were also characterized by remarkable mechanical properties, reaching values comparable to the ones of the native tendons. The scaffolds promoted the tenocyte adhesion and proliferation when caseinophosphopetides and chondroitin sulfate are present in the 3D structure. In particular, caseinophosphopeptides' optimal concentration for cell proliferation resulted 2.4 mg/mL. Finally, the systems evaluation in vivo demonstrated the scaffolds' safety, since they did not cause any inflammatory effect nor foreign body response, representing interesting platforms for the regeneration of injured TBI.

Soft Hydrogels with Double Porosity Modified with RGDS for Tissue Engineering

This study develops and characterizes novel biodegradable soft hydrogels with dual porosity based on N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers cross-linked by hydrolytically degradable linkers. The structure and properties of the hydrogels are designed as scaffolds for tissue engineering and they are tested in vitro with model mesenchymal stem cells (rMSCs). Detailed morphological characterization confirms dual porosity suitable for cell growth and nutrient transport. The dual porosity of hydrogels slightly improves rMSCs proliferation compared to the hydrogel with uniform pores. In addition, the laminin coating supports the adhesion of rMSCs to the hydrogel surface. However, hydrogels modified by heptapeptide RGDSGGY significantly stimulate cell adhesion and growth. Moreover, the RGDS-modified hydrogels also affect the topology of proliferating rMSCs, ranging from single-cell to multicellular clusters. The 3D reconstruction of the hydrogels with cells obtained by laser scanning confocal microscopy (LSCM) confirms cell penetration into the inner structure of the hydrogel and its corresponding microstructure. The prepared biodegradable oligopeptide-modified hydrogels with dual porosity are suitable candidates for further in vivo evaluation in soft tissue regeneration.

Biological Activity of Poly(1,3-propanediol citrate) Films and Nonwovens: Mechanical, Thermal, Antimicrobial, and Cytotoxicity Studies

Polymers are of great interest for medical and cosmeceutical applications. The current trend is to combine materials of natural and synthetic origin in order to obtain products with appropriate mechanical strength and good biocompatibility, additionally biodegradable and bioresorbable. Citric acid, being an important metabolite, is an interesting substance for the synthesis of materials for biomedical applications. Due to the high functionality of the molecule, it is commonly used in biomaterials chemistry as a crosslinking agent. Among citric acid-based biopolyesters, poly(1,8-octanediol citrate) is the best known. It shows application potential in soft tissue engineering. This work focuses on a much less studied polyester, poly(1,3-propanediol citrate). Porous and non-porous materials based on the synthesized polyesters are prepared and characterized, including mechanical, thermal, and surface properties, morphology, and degradation. The main focus is on assessing the biocompatibility and antimicrobial properties of the materials.

Peptide-containing nanoformulations: Skin barrier penetration and activity contribution

Transdermal drug delivery presents a less invasive pathway, circumventing the need to pass through the gastrointestinal tract and liver, thereby reducing drug breakdown, initial metabolism, and gastrointestinal discomfort. Nevertheless, the unique composition and dense structure of the stratum corneum present a significant barrier to transdermal delivery. This article presents an overview of the current developments in peptides and nanotechnology to address this challenge. Initially, we sum up peptide-containing nanoformulations for transdermal drug delivery, examining them through the lenses of both inorganic and organic materials. Particular emphasis is placed on the diverse roles that peptides play within these nanoformulations, including conferring functionality upon nanocarriers and enhancing the biological efficacy of drugs. Subsequently, we summarize innovative strategies for enhancing skin penetration, categorizing them into passive and active approaches. Lastly, we discuss the therapeutic potential of peptide-containing nanoformulations in addressing a range of diseases, drawing insights from the biological activities and functions of peptides. Furthermore, the challenges hindering clinical translation are also discussed, providing valuable insights for future advancements in transdermal drug delivery.

Electric field bridging-effect in electrified microfibrils' scaffolds

Introduction: The use of biocompatible scaffolds combined with the implantation of neural stem cells, is increasingly being investigated to promote the regeneration of damaged neural tissue, for instance, after a Spinal Cord Injury (SCI). In particular, aligned Polylactic Acid (PLA) microfibrils' scaffolds are capable of supporting cells, promoting their survival and guiding their differentiation in neural lineage to repair the lesion. Despite its biocompatible nature, PLA is an electrically insulating material and thus it could be detrimental for increasingly common scaffolds' electric functionalization, aimed at accelerating the cellular processes. In this context, the European RISEUP project aims to combine high intense microseconds pulses and DC stimulation with neurogenesis, supported by a PLA microfibrils' scaffold. Methods: In this paper a numerical study on the effect of microfibrils' scaffolds on the E-field distribution, in planar interdigitated electrodes, is presented. Realistic microfibrils' 3D CAD models have been built to carry out a numerical dosimetry study, through Comsol Multiphysics software. Results: Under a voltage of 10 V, microfibrils redistribute the E-field values focalizing the field streamlines in the spaces between the fibers, allowing the field to pass and reach maximum values up to 100 kV/m and values comparable with the bare electrodes' device (without fibers). Discussion: Globally the median E-field inside the scaffolded electrodes is the 90% of the nominal field, allowing an adequate cells' exposure.

Bacterial cellulose: Biopolymer with novel medical applications

Due to the growing importance of green chemistry, the search for alternatives to cellulose has begun, leading to the rediscovery of bacterial cellulose (BC). The material is produced by Gluconacetobacter and Acetobacter bacteria, mainly Komagataeibacter xylinus. It is a pure biopolymer, without lignin or hemicellulose, forming a three-dimensional mesh, showing much lower organization than its plant counterpart. Thanks to its design, it has proven itself in completely unprecedented applications - especially in the field of biomedical sciences. Coming in countless forms, it has found use in applications such as wound dressings, drug delivery systems, or tissue engineering. The review article focuses on discussing the main structural differences between plant and bacterial cellulose, methods of bacterial cellulose synthesis, and the latest trends in BC applications in biomedical sciences.

Investigation of Physochimechal and Biological Properties of Composite Sodium Alginate for Tissue Engineering

The current study involves synthesis of a composite films of sodium alginate (Alg), polyvinylalcohol and NanoGraphene oxide (GO) for tissue engineering applications. Solvent casting was used to make the polymeric composite films (Alg-Pva-Go), which may exhibit a synergic activity of the components for tissue repair. The influence of various GO concentrations on the films properties was also investigated. The scaffold has outstanding physicochemical and biological properties. The composite film's high swelling degree and contact angle reveals its high hydrophilicity, making it appropriate for tissue engineering. The antimicrobial activity on Staphylococcus aureus were studied. Furthermore, the antimicrobial test showed that the films composite was resistant to S. aureus. Seeding (AD-MSC) cells into the composite films exhibited an increase in cell adhesion and proliferation when compared to the Alginate and Polyvinylalcohol film in vitro experiments, indicating that the GO has a good influence on the films characteristics, which can utilization in tissue engineering applications.

Cellulose-Acetate-Based Films Modified with Ag2O and ZnS as Nanocomposites for Highly Controlling Biological Behavior for Wound Healing Applications

For wound healing, functional films with certain physicochemical and biological properties are needed. Thus, the current work aimed to fabricate multifunctional materials comprising metal oxide nanoparticles loaded with an efficient polymer to be used as dressing material. A composite containing polymeric phases of cellulose acetate (CA) blended with zinc sulfide (ZnS), silver oxide (Ag₂O), and graphene oxide (GO) was successfully synthesized. The prepared composite crystallinity was studied using the X-ray diffraction technique (XRD). Further, the functional groups and the elemental analysis were investigated using Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). Furthermore, the surface morphology was studied using scanning electron microscopy (SEM) to obtain the shape and size of particles. SEM showed that the particles were formed in wide distribution in the range of 18-915 nm with an average size of 235 nm for Ag₂O/ZnS/GO/CA. The particle size of Ag₂O in the CA film was in the range between 19 and 648 nm with an average size of 216 nm, while the particle size of ZnS in CA was in the range of 12-991 nm with an average age particle size of 158 mm. In addition, EDX, based on SEM investigation, detected high carbon and oxygen quantities at around 94.21% of the composite. The contact angle decreased and reached 26.28° ± 2.12° in Ag₂O/ZnS/CA. Furthermore, thermogravimetric analysis (TGA) was used to investigate the thermal stability, and the composition was thermally stable until 300 °C. Moreover, the cell viability of "normal lung cells" reached 102.66% in vitro at a concentration of 1250 µg/mL. The antibacterial activity of Ag₂O/ZnS/GO/CA was also detected against E. coli with a zone of inhibition reaching 17.7 ± 0.5 mm. Therefore, the composite can be used in biomedical applications due to its biocompatibility and antibacterial activity.

Advancements and Utilizations of Scaffolds in Tissue Engineering and Drug Delivery

The drug development process requires a thorough understanding of the scaffold and its three-dimensional structure. Scaffolding is a technique for tissue engineering and the formation of contemporary functioning tissues. Tissue engineering is sometimes referred to as regenerative medicine. They also ensure that drugs are delivered with precision. Information regarding scaffolding techniques, scaffolding kinds, and other relevant facts, such as 3D nanostructuring, are discussed in depth in this literature. They are specific and demonstrate localized action for a specific reason. Scaffold's acquisition nature and flexibility make it a new drug delivery technology with good availability and structural parameter management.

Synergistic fabrication of micro-nano bioactive ceramic-optimized polymer scaffolds for bone tissue engineering by in situ hydrothermal deposition and selective laser sintering

Biodegradable three-dimensional porous scaffolds have attracted increasing attention as promising implants in bone tissue engineering. The micro/nano surface structure of scaffolds has also attracted significant attention due to its significant effects on scaffold physicochemical properties and cell behavior. Herein, polycaprolactone-polylactic acid-nano hydroxyapatite (PCL-PLA-nHA) ternary composite porous scaffolds with micro-nano bioactive surfaces were fabricated by combining selective laser sintering (SLS) and in situ hydrothermal deposition processes. The mechanical properties, micro/nano surface morphology, wettability, and cytocompatibility of the composite scaffolds were systematically evaluated. The results showed that the blending of PLA enhanced the compressive and tensile strength of the PCL scaffold, while also enhancing the modulus, but did not significantly change the tensile elongation. Moreover, the blending of PLA changed the fracture mode of the scaffold from ductile to brittle and its fracture mechanism was proposed. In addition, the formation mechanism of micro-nano surfaces under hydrothermal conditions was also summarized according to the micro-morphology of scaffolds. Besides, the PCL-PLA-nHA scaffold exhibited higher mineralization ability, excellent wettability, and better cytocompatibility, indicating its remarkable promise in bone tissue engineering applications.

A Strategy for Magnetic and Electric Stimulation to Enhance Proliferation and Differentiation of NPCs Seeded over PLA Electrospun Membranes

Neural progenitor cells (NPCs) have been shown to serve as an efficient therapeutic strategy in different cell therapy approaches, including spinal cord injury treatment. Despite the reported beneficial effects of NPC transplantation, the low survival and differentiation rates constrain important limitations. Herein, a new methodology has been developed to overcome both limitations by applying a combination of wireless electrical and magnetic stimulation to NPCs seeded on aligned poly(lactic acid) nanofibrous scaffolds for in vitro cell conditioning prior transplantation. Two stimulation patterns were tested and compared, continuous (long stimulus applied once a day) and intermittent (short stimulus applied three times a day). The results show that applied continuous stimulation promotes NPC proliferation and preferential differentiation into oligodendrocytic and neuronal lineages. A neural-like phenotypic induction was observed when compared to unstimulated NPCs. In contrast, intermittent stimulation patterns did not affect NPC proliferation and differentiation to oligodendrocytes or astrocytes morphology with a detrimental effect on neuronal differentiation. This study provides a new approach of using a combination of electric and magnetic stimulation to induce proliferation and further neuronal differentiation, which would improve therapy outcomes in disorders such as spinal cord injury.

In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs

Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.

Application of Injectable, Crosslinked, Fibrin-Containing Hyaluronic Acid Scaffolds for In Vivo Remodeling

The present research aimed to characterize soft tissue implants that were prepared with the use of crosslinked hyaluronic acid (HA) using two different crosslinkers and multiple reagent concentrations, alone or in combination with fibrin. The effect of the implants was evaluated in an in vivo mouse model, after 4 weeks in one group and after 12 weeks in the other. The explants were compared using analytical methods, evaluating microscopic images, and a histology analysis. The kinetics of the degradation and remodeling of explants were found to be greatly dependent on the concentration and type of crosslinker; generally, divinyl sulfone (DVS) resists degradation more effectively compared to butanediol diglycidyl ether (BDDE). The presence of fibrin enhances the formation of blood vessels, and the infiltration of cells and extracellular matrix. In summary, if the aim is to create a soft tissue implant with easier degradation of the HA content, then the use of 2-5% BDDE is found to be optimal. For a longer degradation time, 5% DVS is the more suitable crosslinker. The use of fibrin was found to support the biological process of remodeling, while keeping the advances of HA in void filling, enabling the parallel degradation and remodeling processes.

Cross-linked polyvinyl alcohol-xanthan gum hydrogel fabricated by freeze/thaw technique for potential application in soft tissue engineering

The search for materials and process parameters capable of generating hydrogels for soft tissue engineering applications, based on an experimental design strategy that allows the evaluation of several factors involved in their development and performance, has greatly increased. Nevertheless, the fabrication technique can influence their mechanical properties, swelling, crystallinity, and even their susceptibility to contamination by microorganisms, compromising their performance within the tissue or organ. This study aimed to evaluate the influence of the freeze/thaw technique on different characteristics of polyvinyl alcohol-xanthan gum hydrogel. Methods: this research analyzed the critical variables of the freeze/thaw process through a systematic study of a 2 k factorial design of experiments, such as the proportion and concentration of polymers, freezing time and temperature, and freeze/thaw cycles. Additionally, physicochemical analysis, susceptibility to bacterial growth, and cell viability tests were included to approximate its cytotoxicity. The optimized hydrogel consisted of polyvinyl alcohol and xanthan gum at a 95 : 5 ratio, polymer mixture concentration of 15%, and 12 h of freezing with three cycles of freeze/thaw. The hydrogel was crystalline, flexible, and resistant, with tensile strengths ranging from 9 to 87 kPa. The hydrogel was appropriate for developing scaffolds for soft tissue engineering such as the cardiac and skeletal muscle, dermis, thyroid, bladder, and spleen. Also, the hydrogel did not expose an in vitro cytotoxic effect, rendering it a candidate for biomedical applications.

Electrospun Antibacterial Composites for Cartilage Tissue Engineering

Implantation of biomaterials capable of the controlled release of antibacterials during articular cartilage repair may prevent postoperative infections. Herein, biomaterials are prepared with biomimetic architectures (nonwoven mats of fibers) via electrospinning that are composed of poly(ɛ-caprolactone), poly(lactic acid), and Bombyx mori silk fibroin (with varying ratios) and, optionally, an antibiotic drug (cefixime trihydrate). The composition, morphology, and mechanical properties of the nanofibrous mats are characterized using scanning electron microscope, Fourier transform infrared spectroscopy, and tensile testing. The nonwoven mats have nanoscale fibers (typical diameters of 324-725 nm) and are capable of controlling the release profiles of the drug, with antibacterial activity against Gram +ve and Gram -ve bacteria (two common strains of human pathogenic bacteria, Staphylococcus aureus and Escherichia coli) under in vitro static conditions. The drug loaded nanofiber mats display cytocompatibility comparable to pure poly(ɛ-caprolactone) nanofibers when cultured with National Institutes of Health (NIH) NIH-3T3 fibroblast cell line and have long-term potential for clinical applications in the field of pharmaceutical sciences.

Natural polymer-based scaffolds for soft tissue repair

Soft tissues such as skin, muscle, and tendon are easily damaged due to injury from physical activity and pathological lesions. For soft tissue repair and regeneration, biomaterials are often used to build scaffolds with appropriate structures and tailored functionalities that can support cell growth and new tissue formation. Among all types of scaffolds, natural polymer-based scaffolds attract much attention due to their excellent biocompatibility and tunable mechanical properties. In this comprehensive mini-review, we summarize recent progress on natural polymer-based scaffolds for soft tissue repair, focusing on clinical translations and materials design. Furthermore, the limitations and challenges, such as unsatisfied mechanical properties and unfavorable biological responses, are discussed to advance the development of novel scaffolds for soft tissue repair and regeneration toward clinical translation.

Development of 3D Thermoplastic Polyurethane (TPU)/Maghemite (ϒ-Fe2O3) Using Ultra-Hard and Tough (UHT) Bio-Resin for Soft Tissue Engineering

The use of soft tissue engineering scaffolds is an advanced approach to repairing damaged soft tissue. To ensure the success of this technique, proper mechanical and biocompatibility properties must be taken into consideration. In this study, a three-dimensional (3D) scaffold was developed using digital light processing (DLP) and ultra-hard and tough (UHT) bio-resin. The 3D scaffold structure consisted of thermoplastic polyurethane (TPU) and maghemite (ϒ-Fe2O3) nanoparticles mixed with UHT bio-resin. The solution sample for fabricating the scaffolds was varied with the concentration of the TPU (10, 12.5, and 15% wt/v) and the amount of ϒ-Fe2O3 (1, 3, and 5% v/v) added to 15% wt/v of TPU. Before developing the real geometry of the sample, a pre-run of the DLP 3D printing process was done to determine the optimum curing time of the structure to be perfectly cured, which resulted in 30 s of curing time. Then, this study proceeded with a tensile test to determine the mechanical properties of the developed structure in terms of elasticity. It was found that the highest Young's Modulus of the scaffold was obtained with 15% wt/v TPU/UHT with 1% ϒ-Fe2O3. Furthermore, for the biocompatibility study, the degradation rate of the scaffold containing TPU/UHT was found to be higher compared to the TPU/UHT containing ϒ-Fe2O3 particles. However, the MTT assay results revealed that the existence of ϒ-Fe2O3 in the scaffold improved the proliferation rate of the cells.

Biomedical engineering aspects of nanocellulose: a review

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Adipose tissue derived stromal cells in a gelatin based 3D matrix with exclusive ascorbic acid signalling emerged as a novel neural tissue engineering construct – An innovative prototype for soft tissue

The current study investigated a triad, which comprises of adipose tissue derived stem cells isolated from infrapatellar fat pad and gelatin/polyvinyl alcohol (PVA)-based matrix with exclusive ascorbic acid signalling. Though, the bio-mechanical properties of the gelatin–PVA blended scaffolds in wet condition are equivalent to the ECM of soft tissues in general, in this study, the triad was tested as a model for neural tissue engineering. Apart from being cytocompatible and biocompatible, the porosity of the scaffold has been designed in such a manner that it facilitates the cell signalling and enables the exchange of nutrients and gases. The highly proliferative stem cells from Passage 2 were characterized using both, mesenchymal and embryonic stem cell markers. As an initial exploration the mesenchymal stem cells at Passage 4 were exposed to ascorbic acid and basic fibroblast growth factor signalling for neuronal differentiation in 2D environment independently. The MSCs successfully differentiated and acquired neuron specific markers related to cytoskeleton and synapses. Subsequently, three phases of experiments have been conducted on the 3D gelatin/PVA matrix to prove their efficacy, the growth of stem cells, growth of differentiated neurons and the in situ growth and differentiation of MSCs. The scaffold was conducive and directed MSCs to neuronal lineage under specific signalling. Overall, this organotypic model triad could open a new avenue in the field of soft tissue engineering as a simple and effective tissue construct.

A review of current advancements for wound healing: Biomaterial applications and medical devices

Wound healing is a complex process that is critical in restoring the skin's barrier function. This process can be interrupted by numerous diseases resulting in chronic wounds that represent a major medical burden. Such wounds fail to follow the stages of healing and are often complicated by a pro‐inflammatory milieu attributed to increased proteinases, hypoxia, and bacterial accumulation. The comprehensive treatment of chronic wounds is still regarded as a significant unmet medical need due to the complex symptoms caused by the metabolic disorder of the wound microenvironment. As a result, several advanced medical devices, such as wound dressings, wearable wound monitors, negative pressure wound therapy devices, and surgical sutures, have been developed to correct the chronic wound environment and achieve skin tissue regeneration. Most medical devices encompass a wide range of products containing natural (e.g., chitosan, keratin, casein, collagen, hyaluronic acid, alginate, and silk fibroin) and synthetic (e.g., polyvinyl alcohol, polyethylene glycol, poly[lactic‐co‐glycolic acid], polycaprolactone, polylactic acid) polymers, as well as bioactive molecules (e.g., chemical drugs, silver, growth factors, stem cells, and plant compounds). This review addresses these medical devices with a focus on biomaterials and applications, aiming to deliver a critical theoretical reference for further research on chronic wound healing.

Polymeric Systems for Cancer Immunotherapy: A Review

Immunotherapy holds enormous promise to create a new outlook of cancer therapy by eliminating tumors via activation of the immune system. In immunotherapy, polymeric systems play a significant role in improving antitumor efficacy and safety profile. Polymeric systems possess many favorable properties, including magnificent biocompatibility and biodegradability, structural and component diversity, easy and controllable fabrication, and high loading capacity for immune-related substances. These properties allow polymeric systems to perform multiple functions in immunotherapy, such as immune stimulants, modifying and activating T cells, delivery system for immune cargos, or as an artificial antigen-presenting cell. Among diverse immunotherapies, immune checkpoint inhibitors, chimeric antigen receptor (CAR) T cell, and oncolytic virus recently have been dramatically investigated for their remarkable success in clinical trials. In this report, we review the monotherapy status of immune checkpoint inhibitors, CAR-T cell, and oncolytic virus, and their current combination strategies with diverse polymeric systems.

Bio-inspired hydrogels with fibrous structure: A review on design and biomedical applications

Numerous tissues in the human body have fibrous structures, including the extracellular matrix, muscles, and heart, which perform critical biological functions and have exceptional mechanical strength. Due to their high-water content, softness, biocompatibility and elastic nature, hydrogels resemble biological tissues. Traditional hydrogels, on the other hand, have weak mechanical properties and lack tissue-like fibrous structures, limiting their potential applications. Thus, bio-inspired hydrogels with fibrous architectures have piqued the curiosity of biomedical researchers. Here, we review fabrication strategies for fibrous hydrogels and their recent progress in the biomedical fields of wound dressings, drug delivery, tissue engineering scaffolds and bioadhesives. Challenges and future perspectives are also discussed.

Implantable nerve guidance conduits: Material combinations, multi-functional strategies and advanced engineering innovations

Nerve guidance conduits (NGCs) have attracted much attention due to their great necessity and applicability in clinical use for the peripheral nerve repair. Great efforts in recent years have been devoted to the development of high-performance NGCs using various materials and strategies. The present review provides a comprehensive overview of progress in the material innovation, structural design, advanced engineering technologies and multi functionalization of state-of-the-art nerve guidance conduits NGCs. Abundant advanced engineering technologies including extrusion-based system, laser-based system, and novel textile forming techniques in terms of weaving, knitting, braiding, and electrospinning techniques were also analyzed in detail. Findings arising from this review indicate that the structural mimetic NGCs combined with natural and synthetic materials using advanced manufacturing technologies can make full use of their complementary advantages, acquiring better biomechanical properties, chemical stability and biocompatibility. Finally, the existing challenges and future opportunities of NGCs were put forward aiming for further research and applications of NGCs.

Biocompatible Synthetic Polymers for Tissue Engineering Purposes

Synthetic polymers have been an integral part of modern society since the early 1960s. Besides their most well-known applications to the public, such as packaging, construction, textiles and electronics, synthetic polymers have also revolutionized the field of medicine. Starting with the first plastic syringe developed in 1955 to the complex polymeric materials used in the regeneration of tissues, their contributions have never been more prominent. Decades of research on polymeric materials, stem cells, and three-dimensional printing contributed to the rapid progress of tissue engineering and regenerative medicine that envisages the potential future of organ transplantations. This perspective discusses the role of synthetic polymers in tissue engineering, their design and properties in relation to each type of application. Additionally, selected recent achievements of tissue engineering using synthetic polymers are outlined to provide insight into how they will contribute to the advancement of the field in the near future. In this way, we aim to provide a guide that will help scientists with synthetic polymer design and selection for different tissue engineering applications.

Biomaterials-assisted exosomes therapy in osteoarthritis

Due to the avascular characteristic of articular cartilage, its self-repair capacity is limited. When cartilage is damaged or forms osteoarthritis, clinical treatment is necessary. However, conventional treatments, including joint replacement, microfracture, cell and drug therapies, have certain limits. Lately, the exosomes derived from mesenchymal stem cells (MSCs-EXO), which consist of complex transcription factors, proteins and targeting ligand components, have shown great therapeutic potentials. With recent advancements in various biomaterials to extend MSCs-EXO's retention time and control the release properties in vivo, biomaterials-assisted exosomes therapy has been soon becoming a practically powerful tool in treating OA. This review analyzes the effects of MSCs-EXO on osteoarthritis inflammation, metabolism, ageing and apoptosis, and introduces the combinational systems of MSCs-EXO with biomaterials to enhance the repair, anti-inflammatory, and homeostasis regulation functions. Moreover, different types of natural or synthetic biomaterials and their applications with MSCs-EXO were also described and discussed. And finally, we presage the future perspective in the development of biomaterial-assisted exosome therapies, as well as the potential to incorporate with other treatments to enhance their therapeutic effects in osteoarthritis.

A Bilayered, Electrospun Poly(Glycerol-Sebacate)/Polyurethane-Polyurethane Scaffold for Engineering of Endothelial Basement Membrane

In the cardiovascular system, heart valves and vessels are subjected to continuous cyclic mechanical loadings due to the pulsatile nature of blood flow. Hence, in leveraging tissue engineering (TE) strategies to regenerate such a system, the candidate scaffold should not only be biocompatible with the desired biodegradation rate, but it should also be mechanically competent to provide a supportive structure for facilitating stem cells retention, growth, and differentiation. To this end, herein, we introduced a novel scaffold composed of poly(glycerol-sebacate) (PGS) and polyurethane (PU), which comprises of two layers: an electrospun pure PU layer beneath another electrospun PGS/PU layer with a different ratio of PGS to PU (3:2, 1:1, 2:3 Wt:Wt). The electrospun PGS/PU-PU scaffold was mechanically competent and showed intended hydrophilicity and a good biodegradation rate. Moreover, the PGS/PU-PU scaffold indicated cell viability and proliferation within ten days of in vitro cell culture and upon 7 day vascular endothelial growth factor (VEGF) stimulation, supported endothelial differentiation of mesenchymal stem cells by significant overexpression of platelet-endothelial cell adhesion molecule-1, von Willebrand factor, and VEGF receptor 2. The results of this study could be implemented in cardiovascular TE strategies when regeneration of blood vessel or heart valve is desired.

Bone Scaffolds: An Incorporation of Biomaterials, Cells, and Biofactors

Large injuries to bones are still one of the most challenging musculoskeletal problems. Tissue engineering can combine stem cells, scaffold biomaterials, and biofactors to aid in resolving this complication. Therefore, this review aims to provide information on the recent advances made to utilize the potential of biomaterials for making bone scaffolds and the assisted stem cell therapy and use of biofactors for bone tissue engineering. The requirements and different types of biomaterials used for making scaffolds are reviewed. Furthermore, the importance of stem cells and biofactors (growth factors and extracellular vesicles) in bone regeneration and their use in bone scaffolds and the key findings are discussed. Lastly, some of the main obstacles in bone tissue engineering and future trends are highlighted.

The effect of modifying the nanostructure of gelatin fiber scaffolds on early angiogenesisin vitroandin vivo

Early angiogenesis is one of the key challenges in tissue regeneration. Crosslinking mode and fiber diameter are critical factors to affect the adhesion and proliferation of cells. However, whether and how these two factors affect early angiogenesis remain largely unknown. To address the issue, the optimal crosslinking mode and fiber diameter of gelatin fiber membrane for early angiogenesisin vivoandin vitrowere explored in this work. Compared with the post crosslinked gelatin fiber membrane with the same fiber diameter, the 700 nm diameterin situcrosslinked gelatin fiber membrane was found to have smaller roughness (230.67 ± 19 nm) and stronger hydrophilicity (54.77° ± 1.2°), which were suitable for cell growth and adhesion. Moreover, thein situcrosslinked gelatin fiber membrane with a fiber diameter of 1000 nm had significant advantages in early angiogenesis over the two with fiber diameters of 500 and 700 nm by up-regulating the expression of Ang1, VEGF, and integrin-β1. Our findings indicated that thein situcrosslinked gelatin fiber membrane with a diameter of 1000 nm might solve the problem of insufficient blood supply in the early stage of soft tissue regeneration and has broad clinical application prospects in promoting tissue regeneration.

Bacterial cellulose-based composites for biomedical and cosmetic applications: Research progress and existing products

Bacterial cellulose (BC) is a promising unique material for various biomedical and cosmetic applications due to its morphology, mechanical strength, high purity, high water uptake, non-toxicity, chemical controllability, and biocompatibility. Today, extensive investigation is into the manufacturing of BC-based composites with other components such as nanoparticles, synthetic polymers, natural polymers, carbon materials, and biomolecules, which will allow the development of a wide range of biomedical and cosmetic products. Moreover, the addition of different reinforcement substances into BC and the organized arrangement of BC nano-fibers have proven a promising improvement in their properties for biomedical applications. This review paper highlights the progress in synthesizing BC-based composites and their applications in biomedical fields, such as wound healing, drug delivery, tissue engineering, and cancer treatment. It emphasizes high-performance BC-based materials and cosmetic applications. Furthermore, it presents challenges yet to be defeated and future possibilities for BC-based composites for biomedical and cosmetic applications.

Chemically Modified Biopolymers for the Formation of Biomedical Hydrogels

Biopolymers are natural polymers sourced from plants and animals, which include a variety of polysaccharides and polypeptides. The inclusion of biopolymers into biomedical hydrogels is of great interest because of their inherent biochemical and biophysical properties, such as cellular adhesion, degradation, and viscoelasticity. The objective of this Review is to provide a detailed overview of the design and development of biopolymer hydrogels for biomedical applications, with an emphasis on biopolymer chemical modifications and cross-linking methods. First, the fundamentals of biopolymers and chemical conjugation methods to introduce cross-linking groups are described. Cross-linking methods to form biopolymer networks are then discussed in detail, including (i) covalent cross-linking (e.g., free radical chain polymerization, click cross-linking, cross-linking due to oxidation of phenolic groups), (ii) dynamic covalent cross-linking (e.g., Schiff base formation, disulfide formation, reversible Diels-Alder reactions), and (iii) physical cross-linking (e.g., guest-host interactions, hydrogen bonding, metal-ligand coordination, grafted biopolymers). Finally, recent advances in the use of chemically modified biopolymer hydrogels for the biofabrication of tissue scaffolds, therapeutic delivery, tissue adhesives and sealants, as well as the formation of interpenetrating network biopolymer hydrogels, are highlighted.

Lipid-Based Drug Delivery Systems in Regenerative Medicine

The most important goal of regenerative medicine is to repair, restore, and regenerate tissues and organs that have been damaged as a result of an injury, congenital defect or disease, as well as reversing the aging process of the body by utilizing its natural healing potential. Regenerative medicine utilizes products of cell therapy, as well as biomedical or tissue engineering, and is a huge field for development. In regenerative medicine, stem cells and growth factor are mainly used; thus, innovative drug delivery technologies are being studied for improved delivery. Drug delivery systems offer the protection of therapeutic proteins and peptides against proteolytic degradation where controlled delivery is achievable. Similarly, the delivery systems in combination with stem cells offer improvement of cell survival, differentiation, and engraftment. The present review summarizes the significance of biomaterials in tissue engineering and the importance of colloidal drug delivery systems in providing cells with a local environment that enables them to proliferate and differentiate efficiently, resulting in successful tissue regeneration.

Synthesis and Characterization of Porous, Electro-Conductive Chitosan-Gelatin-Agar-Based PEDOT: PSS Scaffolds for Potential Use in Tissue Engineering

Herein we report the synthesis and characterization of electro-conductive chitosan-gelatin-agar (Cs-Gel-Agar) based PEDOT: PSS hydrogels for tissue engineering. Cs-Gel-Agar porous hydrogels with 0-2.0% (v/v) PEDOT: PSS were fabricated using a thermal reverse casting method where low melting agarose served as the pore template. Sample characterizations were performed by means of scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD) and electrochemical impedance spectroscopy (EIS). Our results showed enhanced electrical conductivity of the cs-gel-agar hydrogels when mixed with DMSO-doped PEDOT: PSS wherein the optimum mixing ratio was observed at 1% (v/v) with a conductivity value of 3.35 × 10-4 S cm-1. However, increasing the PEDOT: PSS content up to 1.5 % (v/v) resulted in reduced conductivity to 3.28 × 10-4 S cm-1. We conducted in vitro stability tests on the porous hydrogels using phosphate-buffered saline (PBS) solution and investigated the hydrogels' performances through physical observations and ATR-FTIR characterization. The present study provides promising preliminary data on the potential use of Cs-Gel-Agar-based PEDOT: PSS hydrogel for tissue engineering, and these, hence, warrant further investigation to assess their capability as biocompatible scaffolds.

Terpolymer-chitosan membranes as biomaterial

The present study shows a novel copolymer synthesis, its application in the membrane design and the physicochemical and biological characterization of the biomaterial obtained. Terpolymer starting diisopropyl fumarate (F), vinyl benzoate (V) and 2-hydroxyethyl methacrylate (H) was prepared by thermal radical polymerization. This polymer (FVH) was obtained in several monomer ratios and characterized by spectroscopic and chromatographic methods (FTIR, ¹ H-NMR and SEC). The best relationship of F:V:H was 5:4:1, which allows efficient interaction with chitosan through cross-linking with borax to achieve scaffolds for potential biomedical applications. The membranes were obtained by solvent casting and analyzed by scanning electron microscopy (SEM), swelling behavior and mechanical properties. In addition, we studied the possible cytotoxicity and biocompatibility of these materials using a murine macrophage-like cell line (RAW 264.7) and bone marrow mesenchymal progenitor cells (BMPC), respectively, taking into account their intended applications. The results of this study show that the terpolymer obtained and its combination with a natural polymer is a very interesting strategy to obtain a biomaterial with possible applications in regenerative medicine and this could be extended to other structurally related systems.

Poly(α-l-lysine)-based nanomaterials for versatile biomedical applications: Current advances and perspectives

Poly(α-l-lysine) (PLL) is a class of water-soluble, cationic biopolymer composed of α-l-lysine structural units. The previous decade witnessed tremendous progress in the synthesis and biomedical applications of PLL and its composites. PLL-based polymers and copolymers, till date, have been extensively explored in the contexts such as antibacterial agents, gene/drug/protein delivery systems, bio-sensing, bio-imaging, and tissue engineering. This review aims to summarize the recent advances in PLL-based nanomaterials in these biomedical fields over the last decade. The review first describes the synthesis of PLL and its derivatives, followed by the main text of their recent biomedical applications and translational studies. Finally, the challenges and perspectives of PLL-based nanomaterials in biomedical fields are addressed.

Assessment of Naturally Sourced Mineral Clays for the 3D Printing of Biopolymer-Based Nanocomposite Inks

The present study investigated the possibility of obtaining 3D printed composite constructs using biomaterial-based nanocomposite inks. The biopolymeric matrix consisted of methacrylated gelatin (GelMA). Several types of nanoclay were added as the inorganic component. Our aim was to investigate the influence of clay type on the rheological behavior of ink formulations and to determine the morphological and structural properties of the resulting crosslinked hydrogel-based nanomaterials. Moreover, through the inclusion of nanoclays, our goal was to improve the printability and shape fidelity of nanocomposite scaffolds. The viscosity of all ink formulations was greater in the presence of inorganic nanoparticles as shear thinning occurred with increased shear rate. Hydrogel nanocomposites presented predominantly elastic rather than viscous behavior as the materials were crosslinked which led to improved mechanical properties. The inclusion of nanoclays in the biopolymeric matrix limited hydrogel swelling due the physical barrier effect but also because of the supplementary crosslinks induced by the clay layers. The distribution of inorganic filler within the GelMA-based hydrogels led to higher porosities as a consequence of their interaction with the biopolymeric ink. The present study could be useful for the development of soft nanomaterials foreseen for the additive manufacturing of customized implants for tissue engineering.

Exploration of Bioengineered Scaffolds Composed of Thermo-Responsive Polymers for Drug Delivery in Wound Healing

Innate and adaptive immune responses lead to wound healing by regulating a complex series of events promoting cellular cross-talk. An inflammatory response is presented with its characteristic clinical symptoms: heat, pain, redness, and swelling. Some smart thermo-responsive polymers like chitosan, polyvinylpyrrolidone, alginate, and poly(ε-caprolactone) can be used to create biocompatible and biodegradable scaffolds. These processed thermo-responsive biomaterials possess 3D architectures similar to human structures, providing physical support for cell growth and tissue regeneration. Furthermore, these structures are used as novel drug delivery systems. Locally heated tumors above the polymer lower the critical solution temperature and can induce its conversion into a hydrophobic form by an entropy-driven process, enhancing drug release. When the thermal stimulus is gone, drug release is reduced due to the swelling of the material. As a result, these systems can contribute to the wound healing process in accelerating tissue healing, avoiding large scar tissue, regulating the inflammatory response, and protecting from bacterial infections. This paper integrates the relevant reported contributions of bioengineered scaffolds composed of smart thermo-responsive polymers for drug delivery applications in wound healing. Therefore, we present a comprehensive review that aims to demonstrate these systems' capacity to provide spatially and temporally controlled release strategies for one or more drugs used in wound healing. In this sense, the novel manufacturing techniques of 3D printing and electrospinning are explored for the tuning of their physicochemical properties to adjust therapies according to patient convenience and reduce drug toxicity and side effects.

Surface-Modified Highly Biocompatible Bacterial-poly(3-hydroxybutyrate-co-4-hydroxybutyrate): A Review on the Promising Next-Generation Biomaterial

Polyhydroxyalkanoates (PHAs) are bacteria derived bio-based polymers that are synthesised under limited conditions of nutritional elements with excess carbon sources. Among the members of PHAs, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [(P(3HB-co-4HB)] emerges as an attractive biomaterial to be applied in medical applications owing to its desirable mechanical and physical properties, non-genotoxicity and biocompatibility eliciting appropriate host tissue responses. The tailorable physical and chemical properties and easy surface functionalisation of P(3HB-co-4HB) increase its practicality to be developed as functional medical substitutes. However, its applicability is sometimes limited due to its hydrophobic nature due to fewer bio-recognition sites. In this review, we demonstrate how surface modifications of PHAs, mainly P(3HB-co-4HB), will overcome these limitations and facilitate their use in diverse medical applications. The integration of nanotechnology has drastically enhanced the functionality of P(3HB-co-4HB) biomaterials for application in complex biological environments of the human body. The design of versatile P(3HB-co-4HB) materials with surface modifications promise a non-cytotoxic and biocompatible material without inducing severe inflammatory responses for enhanced effective alternatives in healthcare biotechnology. The enticing work carried out with P(3HB-co-4HB) promises to be one of the next-generation materials in biomedicines which will facilitate translation into the clinic in the future.

Topographical and Biomechanical Guidance of Electrospun Fibers for Biomedical Applications

Electrospinning is gaining increasing interest in the biomedical field as an eco-friendly and economic technique for production of random and oriented polymeric fibers. The aim of this review was to give an overview of electrospinning potentialities in the production of fibers for biomedical applications with a focus on the possibility to combine biomechanical and topographical stimuli. In fact, selection of the polymer and the eventual surface modification of the fibers allow selection of the proper chemical/biological signal to be administered to the cells. Moreover, a proper design of fiber orientation, dimension, and topography can give the opportunity to drive cell growth also from a spatial standpoint. At this purpose, the review contains a first introduction on potentialities of electrospinning for the obtainment of random and oriented fibers both with synthetic and natural polymers. The biological phenomena which can be guided and promoted by fibers composition and topography are in depth investigated and discussed in the second section of the paper. Finally, the recent strategies developed in the scientific community for the realization of electrospun fibers and for their surface modification for biomedical application are presented and discussed in the last section.

Review of Synthetic and Hybrid Scaffolds in Cartilage Tissue Engineering

Cartilage tissue is under extensive investigation in tissue engineering and regenerative medicine studies because of its limited regenerative potential. Currently, many scaffolds are undergoing scientific and clinical research. A key for appropriate scaffolding is the assurance of a temporary cellular environment that allows the cells to function as in native tissue. These scaffolds should meet the relevant requirements, including appropriate architecture and physicochemical and biological properties. This is necessary for proper cell growth, which is associated with the adequate regeneration of cartilage. This paper presents a review of the development of scaffolds from synthetic polymers and hybrid materials employed for the engineering of cartilage tissue and regenerative medicine. Initially, general information on articular cartilage and an overview of the clinical strategies for the treatment of cartilage defects are presented. Then, the requirements for scaffolds in regenerative medicine, materials intended for membranes, and methods for obtaining them are briefly described. We also describe the hybrid materials that combine the advantages of both synthetic and natural polymers, which provide better properties for the scaffold. The last part of the article is focused on scaffolds in cartilage tissue engineering that have been confirmed by undergoing preclinical and clinical tests.

Hydrosoluble collagen based biodegradable hybrid hydrogel for biomedical scaffold

Hydrogel scaffolds are explored as efficient methods to repair damaged organs or tissues. In this study, we developed a hybrid hydrogel system based on collagen (Col) and PEG-derived polymer (PEGF) for biomedical scaffold. The Col-PEGF hybrid hydrogel, in which different materials were combined and sequential interpenetrating networks were built, achieved significantly enhanced mechanical strength and viscoelasticity compared with the corresponding Col hydrogel or PEGF hydrogel. Degradation test indicated that Col enabled the hybrid hydrogel to be broken down via enzymatic degradation while PEGF contributed to the anti-degradation of the hydrogel. This balanced biodegradability of Col-PEGF hydrogel would be advantageous to the application for tissue engineering and regenerative medicine. Moreover, the Col-PEGF hybrid hydrogel with micron-sized pores and variable moisture performed good biocompatibility to NIH-3T3 cells, and supplied a favorable environment for cell growth and proliferation. Therefore, the Col-PEGF hydrogel will provide a promising biomedical scaffold for the therapy of tissue defects.

Application of mesenchymal stem cell for tympanic membrane regeneration by tissue engineering approach

Regeneration is a biological process of cell renewal that takes place in damaged tissues or organs. It is naturally stimulated by the release of different growth factors, cytokines, surface molecules, and stem cells at the wounded sites. The tympanic membrane (TM) is an essential component of the hearing process in the auditory system, which can amplify and transmit sound vibrations through a chain of mobile ossicles. Middle ear infection, external sound pressure, insertion of sharp objects into the ear, and severe trauma are the main causes of TM perforations (TMPs), which could result in deficient hearing function. So far, otolaryngologists have employed surgical procedures (myringoplasty or tympanoplasty) to close the perforated eardrum. Because of limitations such as side effects, discomfort, and high cost to patients, there is a need for better alternatives to surgical procedures. Tissue engineering is a promising tool that can overcome the operational risk and restore, maintain, and improve the function of the TM using a range of biocompatible scaffolds, commercially available growth factors, and stem cells. Currently, multipotent mesenchymal stem cells (MSCs) are a good therapeutic option for the treatment of TMPs because of their self-renewing, and autocrine and paracrine activities. As there are fewer risks of isolation in the use of MSCs for the treatment of TMPs, they are more advantageous for tissue regeneration. The delivery of either MSCs alone or a combination of MSCs with biomaterials and growth factors (GFs) at the ruptured TM sites may enhance the activation of epithelial stem cell markers and increase the migration and proliferation of keratinocytes resulting in faster closure of TMPs. This review focuses on the current strategies used to treat TMPs and the importance of MSCs in TM regeneration. Particularly, we have discussed the synergistic effect of MSCs and scaffolds or GFs or scaffolds/GFs in TM regeneration. Finally, with the advancement of tissue engineering technologies such as 3D and 4D bioprinting, MSCs can be used to design patient-specific scaffolds, which may contain physical and chemical guidance cues to improve the extent and rate of targeted tissue regeneration.

Proteins and Peptides as Important Modifiers of the Polymer Scaffolds for Tissue Engineering Applications-A Review

Polymer scaffolds constitute a very interesting strategy for tissue engineering. Even though they are generally non-toxic, in some cases, they may not provide suitable support for cell adhesion, proliferation, and differentiation, which decelerates tissue regeneration. To improve biological properties, scaffolds are frequently enriched with bioactive molecules, inter alia extracellular matrix proteins, adhesive peptides, growth factors, hormones, and cytokines. Although there are many papers describing synthesis and properties of polymer scaffolds enriched with proteins or peptides, few reviews comprehensively summarize these bioactive molecules. Thus, this review presents the current knowledge about the most important proteins and peptides used for modification of polymer scaffolds for tissue engineering. This paper also describes the influence of addition of proteins and peptides on physicochemical, mechanical, and biological properties of polymer scaffolds. Moreover, this article sums up the major applications of some biodegradable natural and synthetic polymer scaffolds modified with proteins and peptides, which have been developed within the past five years.

Nanostructured Materials for Artificial Tissue Replacements

This paper review current trends in applications of nanomaterials in tissue engineering. Nanomaterials applicable in this area can be divided into two groups: organic and inorganic. Organic nanomaterials are especially used for the preparation of highly porous scaffolds for cell cultivation and are represented by polymeric nanofibers. Inorganic nanomaterials are implemented as they stand or dispersed in matrices promoting their functional properties while preserving high level of biocompatibility. They are used in various forms (e.g., nano- particles, -tubes and -fibers)-and when forming the composites with organic matrices-are able to enhance many resulting properties (biologic, mechanical, electrical and/or antibacterial). For this reason, this contribution points especially to such type of composite nanomaterials. Basic information on classification, properties and application potential of single nanostructures, as well as complex scaffolds suitable for 3D tissues reconstruction is provided. Examples of practical usage of these structures are demonstrated on cartilage, bone, neural, cardiac and skin tissue regeneration and replacements. Nanomaterials open up new ways of treatments in almost all areas of current tissue regeneration, especially in tissue support or cell proliferation and growth. They significantly promote tissue rebuilding by direct replacement of damaged tissues.

Developments in Antibiotic-Eluting Scaffolds for the Treatment of Osteomyelitis

Osteomyelitis is a devastating disease caused by the infection of bone tissue and is associated with significant morbidity and mortality. It is treated with antibiotic therapy and surgical debridement. A high dose of systemic antibiotics is often required due to poor bone penetration and this is often associated with unacceptable side-effects. To overcome this, local, implantable antibiotic carriers such as polymethyl methacrylate have been developed. However, this is a non-biodegradable material that requires a second surgery to be removed. Attention has therefore shifted to new antibiotic-eluting scaffolds which can be created with a range of unique properties. The purpose of this review is to assess the level of evidence that exists for these novel local treatments. Although this field is still developing, these strategies seem promising and provide hope for the future treatment of chronic osteomyelitis.