Preliminary investigation on a new natural based poly(gamma-glutamic acid)/Chitosan bioink

Application of chitosan with different molecular weights in cartilage tissue engineering

Cartilage tissue engineering involves the invention of novel implantable cartilage replacement materials to help heal cartilage injuries that do not heal themselves, aiming to overcome the shortcomings of current clinical cartilage treatments. Chitosan has been widely used in cartilage tissue engineering because of its similar structure to glycine aminoglycan, which is widely distributed in connective tissues. The molecular weight, as an important structural parameter of chitosan, affects not only the method of chitosan composite scaffold preparation but also the effect on cartilage tissue healing. Thus, this review identifies methods for the preparation of chitosan composite scaffolds with low, medium and high molecular weights, as well as a range of chitosan molecular weights appropriate for cartilage tissue repair, by summarizing the application of different molecular weights of chitosan in cartilage repair in recent years.

Chitosan and its derivatives in 3D/4D (bio) printing for tissue engineering and drug delivery applications

Tissue engineering research has undergone to a revolutionary improvement, thanks to technological advancements, such as the introduction of bioprinting technologies. The ability to develop suitable customized biomaterial inks/bioinks, with excellent printability and ability to promote cell proliferation and function, has a deep impact on such improvements. In this context, printing inks based on chitosan and its derivatives have been instrumental. Thus, the current review aims at providing a comprehensive overview on chitosan-based materials as suitable inks for 3D/4D (bio)printing and their applicability in creating advanced drug delivery platforms and tissue engineered constructs. Furthermore, relevant strategies to improve the mechanical and biological performances of this biomaterial are also highlighted.

Poly-gamma-glutamic acid biopolymer: a sleeping giant with diverse applications and unique opportunities for commercialization

Poly-gamma-glutamic acid (γ-PGA) is a biodegradable, non-toxic, ecofriendly, and non-immunogenic biopolymer. Its phenomenal properties have gained immense attention in the field of regenerative medicine, the food industry, wastewater treatment, and even in 3D printing bio-ink. The γ-PGA has the potential to replace synthetic non-degradable counterparts, but the main obstacle is the high production cost and lower productivity. Extensive research has been carried out to reduce the production cost by using different waste; however, it is unable to match the commercialization needs. This review focuses on the biosynthetic mechanism of γ-PGA, its production using the synthetic medium as well as different wastes by L-glutamic acid-dependent and independent microbial strains. Furthermore, various metabolic engineering strategies and the recovery processes for γ-PGA and their possible applications are discussed. Finally, highlights on the challenges and unique approaches to reduce the production cost and to increase the productivity for commercialization of γ-PGA are also summarized.

3D Bioprinted Chitosan-Based Hydrogel Scaffolds in Tissue Engineering and Localised Drug Delivery

Bioprinting is an emerging technology with various applications in developing functional tissue constructs for the replacement of harmed or damaged tissues and simultaneously controlled drug delivery systems (DDSs) for the administration of several active substances, such as growth factors, proteins, and drug molecules. It is a novel approach that provides high reproducibility and precise control over the fabricated constructs in an automated way. An ideal bioink should possess proper mechanical, rheological, and biological properties essential to ensure proper function. Chitosan is a promising natural-derived polysaccharide to be used as ink because of its attractive properties, such as biodegradability, biocompatibility, low cost, and non-immunogenicity. This review focuses on 3D bioprinting technology for the preparation of chitosan-based hydrogel scaffolds for the regeneration of tissues delivering either cells or active substances to promote restoration.

Chitosan-based high-strength supramolecular hydrogels for 3D bioprinting

The loss of tissues and organs is a major challenge for biomedicine, and the emerging 3D bioprinting technology has brought the dawn for the development of tissue engineering and regenerative medicine. Chitosan-based supramolecular hydrogels, as novel biomaterials, are considered as ideal materials for 3D bioprinting due to their unique dynamic reversibility and fantastic biological properties. Although chitosan-based supramolecular hydrogels have wonderful biological properties, the mechanical properties are still under early exploration. This paper aims to provide some inspirations for researchers to further explore. In this review, common 3D bioprinting techniques and the properties required for bioink for 3D bioprinting are firstly described. Then, several strategies to enhance the mechanical properties of chitosan hydrogels are introduced from the perspectives of both materials and supramolecular binding motifs. Finally, current challenges and future opportunities in this field are discussed. The combination of chitosan-based supramolecular hydrogels and 3D bioprinting will hold promise for developing novel biomedical implants.

Engineering Biomimetic Extracellular Matrix with Silica Nanofibers: From 1D Material to 3D Network

Biomaterials at nanoscale is a fast-expanding research field with which extensive studies have been conducted on understanding the interactions between cells and their surrounding microenvironments as well as intracellular communications. Among many kinds of nanoscale biomaterials, mesoporous fibrous structures are especially attractive as a promising approach to mimic the natural extracellular matrix (ECM) for cell and tissue research. Silica is a well-studied biocompatible, natural inorganic material that can be synthesized as morpho-genetically active scaffolds by various methods. This review compares silica nanofibers (SNFs) to other ECM materials such as hydrogel, polymers, and decellularized natural ECM, summarizes fabrication techniques for SNFs, and discusses different strategies of constructing ECM using SNFs. In addition, the latest progress on SNFs synthesis and biomimetic ECM substrates fabrication is summarized and highlighted. Lastly, we look at the wide use of SNF-based ECM scaffolds in biological applications, including stem cell regulation, tissue engineering, drug release, and environmental applications.

A Guide to Polysaccharide-Based Hydrogel Bioinks for 3D Bioprinting Applications

Three-dimensional (3D) bioprinting is an innovative technology in the biomedical field, allowing the fabrication of living constructs through an approach of layer-by-layer deposition of cell-laden inks, the so-called bioinks. An ideal bioink should possess proper mechanical, rheological, chemical, and biological characteristics to ensure high cell viability and the production of tissue constructs with dimensional stability and shape fidelity. Among the several types of bioinks, hydrogels are extremely appealing as they have many similarities with the extracellular matrix, providing a highly hydrated environment for cell proliferation and tunability in terms of mechanical and rheological properties. Hydrogels derived from natural polymers, and polysaccharides, in particular, are an excellent platform to mimic the extracellular matrix, given their low cytotoxicity, high hydrophilicity, and diversity of structures. In fact, polysaccharide-based hydrogels are trendy materials for 3D bioprinting since they are abundant and combine adequate physicochemical and biomimetic features for the development of novel bioinks. Thus, this review portrays the most relevant advances in polysaccharide-based hydrogel bioinks for 3D bioprinting, focusing on the last five years, with emphasis on their properties, advantages, and limitations, considering polysaccharide families classified according to their source, namely from seaweed, higher plants, microbial, and animal (particularly crustaceans) origin.

Polysaccharide 3D Printing for Drug Delivery Applications

3D printing, or additive manufacturing, has gained considerable interest due to its versatility regarding design as well as in the large choice of materials. It is a powerful tool in the field of personalized pharmaceutical treatment, particularly crucial for pediatric and geriatric patients. Polysaccharides are abundant and inexpensive natural polymers, that are already widely used in the food industry and as excipients in pharmaceutical and cosmetic formulations. Due to their intrinsic properties, such as biocompatibility, biodegradability, non-immunogenicity, etc., polysaccharides are largely investigated as matrices for drug delivery. Although an increasing number of interesting reviews on additive manufacturing and drug delivery are being published, there is a gap concerning the printing of polysaccharides. In this article, we will review recent advances in the 3D printing of polysaccharides focused on drug delivery applications. Among the large family of polysaccharides, the present review will particularly focus on cellulose and cellulose derivatives, chitosan and sodium alginate, printed by fused deposition modeling and extrusion-based printing.

Chitosan as an Underrated Polymer in Modern Tissue Engineering

Chitosan is one of the most well-known and characterized materials applied in tissue engineering. Due to its unique chemical, biological and physical properties chitosan is frequently used as the main component in a variety of biomaterials such as membranes, scaffolds, drug carriers, hydrogels and, lastly, as a component of bio-ink dedicated to medical applications. Chitosan's chemical structure and presence of active chemical groups allow for modification for tailoring material to meet specific requirements according to intended use such as adequate endurance, mechanical properties or biodegradability time. Chitosan can be blended with natural (gelatin, hyaluronic acid, collagen, silk, alginate, agarose, starch, cellulose, carbon nanotubes, natural rubber latex, κ-carrageenan) and synthetic (PVA, PEO, PVP, PNIPPAm PCL, PLA, PLLA, PAA) polymers as well as with other promising materials such as aloe vera, silica, MMt and many more. Chitosan has several derivates: carboxymethylated, acylated, quaternary ammonium, thiolated, and grafted chitosan. Its versatility and comprehensiveness are confirming by further chitosan utilization as a leading constituent of innovative bio-inks applied for tissue engineering. This review examines all the aspects described above, as well as is focusing on a novel application of chitosan and its modifications, including the 3D bioprinting technique which shows great potential among other techniques applied to biomaterials fabrication.

Design and optimization of 3D-bioprinted scaffold framework based on a new natural polymeric bioink

OBJECTIVES

This aimed at the design and production of engineered 3D scaffold prototypes using a natural polymeric bioink made of chitosan and poly-γ-glutamic acid with a specific focus on 3D-bioprinting process and on 3D framework geometry.

METHODS

Prototypes were produced using a 3D bioprinter exploiting layer-by-layer deposition technology. The 3D scaffold prototypes were fully characterized concerning pore size and size distribution, stability in different experimental conditions, swelling capability, and human dermal fibroblasts viability.

KEY FINDINGS

Hexagonal framework combined with biopaper allowed stabilizing the 3-layers structure during process manufacturing and during incubation in cell culture conditions. The stability of 3-layers structure was well preserved for 48 h. Crosslinking percentages of 2-layers and 3-layers prototype were 88.2 and 68.39, respectively. The swelling study showed a controlled swelling capability for 2-layers and 3-layers prototype, ∼5%. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay results showed good biocompatibility of 3-layers prototype and their suitability for preserving 48 h cell viability in 3D cultures. Moreover, a significant increment of absorbance value was measured after 48 h, demonstrating cell growth.

CONCLUSIONS

Bioink obtained combining chitosan and poly-γ-glutamic acid represents a good option for 3D bioprinting. A stable 3D structure was realized by layer-by-layer deposition technology; compared with other papers, the present study succeeded in using medical healthcare-grade polymers, no-toxic crosslinker, and solvents according to ICH Topic Q3C (R4).

Biomedical Applications of Bacteria-Derived Polymers

Plastics have found widespread use in the fields of cosmetic, engineering, and medical sciences due to their wide-ranging mechanical and physical properties, as well as suitability in biomedical applications. However, in the light of the environmental cost of further upscaling current methods of synthesizing many plastics, work has recently focused on the manufacture of these polymers using biological methods (often bacterial fermentation), which brings with them the advantages of both low temperature synthesis and a reduced reliance on potentially toxic and non-eco-friendly compounds. This can be seen as a boon in the biomaterials industry, where there is a need for highly bespoke, biocompatible, processable polymers with unique biological properties, for the regeneration and replacement of a large number of tissue types, following disease. However, barriers still remain to the mass-production of some of these polymers, necessitating new research. This review attempts a critical analysis of the contemporary literature concerning the use of a number of bacteria-derived polymers in the context of biomedical applications, including the biosynthetic pathways and organisms involved, as well as the challenges surrounding their mass production. This review will also consider the unique properties of these bacteria-derived polymers, contributing to bioactivity, including antibacterial properties, oxygen permittivity, and properties pertaining to cell adhesion, proliferation, and differentiation. Finally, the review will select notable examples in literature to indicate future directions, should the aforementioned barriers be addressed, as well as improvements to current bacterial fermentation methods that could help to address these barriers.

Current achievements in 3D bioprinting technology of chitosan and its hybrids

Chitosan and its hybrids, as an appropriate bioink in 3D printing technology, for the fabrication of engineered constructions.

Overview of Current Advances in Extrusion Bioprinting for Skin Applications

Bioprinting technologies, which have the ability to combine various human cell phenotypes, signaling proteins, extracellular matrix components, and other scaffold-like biomaterials, are currently being exploited for the fabrication of human skin in regenerative medicine. We performed a systematic review to appraise the latest advances in 3D bioprinting for skin applications, describing the main cell phenotypes, signaling proteins, and bioinks used in extrusion platforms. To understand the current limitations of this technology for skin bioprinting, we briefly address the relevant aspects of skin biology. This field is in the early stage of development, and reported research on extrusion bioprinting for skin applications has shown moderate progress. We have identified two major trends. First, the biomimetic approach uses cell-laden natural polymers, including fibrinogen, decellularized extracellular matrix, and collagen. Second, the material engineering line of research, which is focused on the optimization of printable biomaterials that expedite the manufacturing process, mainly involves chemically functionalized polymers and reinforcement strategies through molecular blending and postprinting interventions, i.e., ionic, covalent, or light entanglement, to enhance the mechanical properties of the construct and facilitate layer-by-layer deposition. Skin constructs manufactured using the biomimetic approach have reached a higher level of complexity in biological terms, including up to five different cell phenotypes and mirroring the epidermis, dermis and hypodermis. The confluence of the two perspectives, representing interdisciplinary inputs, is required for further advancement toward the future translation of extrusion bioprinting and to meet the urgent clinical demand for skin equivalents.