Hyaluronic Acid in the Third Millennium

Recent developments in regenerative ophthalmology

Regenerative medicine (RM) is one of the most promising disciplines for advancements in modern medicine, and regenerative ophthalmology (RO) is one of the most active fields of regenerative medicine. This review aims to provide an overview of regenerative ophthalmology, including the range of tools and materials being used, and to describe its application in ophthalmologic subspecialties, with the exception of surgical implantation of artificial tissues or organs (e.g., contact lens, artificial cornea, intraocular lens, artificial retina, and bionic eyes) due to space limitations. In addition, current challenges and limitations of regenerative ophthalmology are discussed and future directions are highlighted.

When polymers meet carbon nanostructures: expanding horizons in cancer therapy

The development of hybrid materials, which combine inorganic with organic materials, is receiving increasing attention by researchers. As a consequence of carbon nanostructures high chemical versatility, they exhibit enormous potential for new highly engineered multifunctional nanotherapeutic agents for cancer therapy. Whereas many groups are working on drug delivery systems for chemotherapy, the use of carbon nanohybrids for radiotherapy is rarely applied. Thus, nanotechnology offers a wide range of solutions to overcome the current obstacles of conventional chemo- and/or radiotherapies. Within this review, the structure and properties of carbon nanostructures (carbon nanotubes, nanographene oxide) functionalized preferentially with different types of polymers (synthetic, natural) are discussed. In short, synthesis approaches, toxicity investigations and anticancer efficacy of different carbon nanohybrids are described.

Hyaluronic Acid and Controlled Release: A Review

Hyaluronic acid (HA) also known as hyaluronan, is a natural polysaccharide—an anionic, non-sulfated glycosaminoglycan—commonly found in our bodies. It occurs in the highest concentrations in the eyes and joints. Today HA is used during certain eye surgeries and in the treatment of dry eye disease. It is a remarkable natural lubricant that can be injected into the knee for patients with knee osteoarthritis. HA has also excellent gelling properties due to its capability to bind water very quickly. As such, it is one the most attractive controlled drug release matrices and as such, it is frequently used in various biomedical applications. Due to its reactivity, HA can be cross-linked or conjugated with assorted bio-macromolecules and it can effectively encapsulate several different types of drugs, even at nanoscale. Moreover, the physiological significance of the interactions between HA and its main membrane receptor, CD44 (a cell-surface glycoprotein that modulates cell–cell interactions, cell adhesion and migration), in pathological processes, e.g., cancer, is well recognized and this has resulted in an extensive amount of studies on cancer drug delivery and tumor targeting. HA acts as a therapeutic but also as a tunable matrix for drug release. Thus, this review focuses on controlled or sustained drug release systems assembled from HA and its derivatives. More specifically, recent advances in controlled release of proteins, antiseptics, antibiotics and cancer targeting drugs from HA and its derivatives were reviewed. It was shown that controlled release from HA has many benefits such as optimum drug concentration maintenance, enhanced therapeutic effects, improved efficiency of treatment with less drug, very low or insignificant toxicity and prolonged in vivo release rates.

Fish-based Bioactives as Potent Nutraceuticals: Exploring the Therapeutic Perspective of Sustainable Food from the Sea

Recent developments in nutraceuticals and functional foods have confirmed that bioactive components present in our diet play a major therapeutic role against human diseases. Moreover, there is a huge emphasis on food scientists for identifying and producing foods with better bioactive activity, which can ultimately provide wellness and well-being to human health. Among the several well-known foods with bioactive constituents, fish has always been considered important, due to its rich nutritional values and by-product application in food industries. Nutritionists, food scientists, and other scientific communities have been working jointly to uncover new bioactive molecules that could increase the potential and therapeutic benefits of these bioactive components. Despite the innumerable benefits of fish and known fish bioactive molecules, its use by food or pharmaceutical industries is scarce, and even research on fish-based nutraceuticals is not promising. Therefore, this review focuses on the current information/data available regarding fish bioactive components, its application as nutraceuticals for therapeutic purposes in the treatment of chronic diseases, ethnic issues related to consumption of fish or its by-products. Especial emphasis is given on the utilization of fish wastes and its by-products to fulfill the world demand for cheap dietary supplements specifically for underdeveloped/least developed countries.

The Effects of High Molecular Weight Hyaluronic Acid Eye Drop Application in Environmental Dry Eye Stress Model Mice

Hyaluronic acid (HA) ophthalmic solution is widely used in dry eye treatment worldwide. However, there are no reports comparing the dry eye treatment effects of high molecular weight HA with low molecular weight HA. Sixty eight-week-old C57BL/6 mice were assigned to the following 6 groups and exposed to environmental dry eye stress (EDES) that mimics office work environment: 1) 0.1% low molecular weight HA (LMWHA) eye drops, 2) 0.3% LMWHA eye drops, 3) 3% diquafosol sodium (DQ) eye drops, 4) 0.15% high molecular weight HA (HMWHA) eye drops, 5) no treatment with exposure to EDES (EDES+/Treatment-), and 6) no treatment without exposure to EDES (EDES-/Treatment-). After EDES, the HMWHA group had significantly longer break-up time (BUT) than the 0.1%, 0.3% LMWHA groups and the DQ group. After EDES, the HMWHA group had significantly lower lissamine green staining scores than the LMWHA and DQ groups. Subepithelial presumed dendritic cell density in the HMWHA group was significantly lower than the EDES+/Treatment- group. After EDES exposure, Conjunctival Muc5AC mRNA expression in the HMWHA group was significantly higher than the 0.1 and 0.3% LMWHA groups. Ophthalmic HMWHA solution may have a better dry eye treatment effect than LMWHA or DQ solution, owing to its anti-inflammatory effect.

Biotechnology Applied to Cosmetics and Aesthetic Medicines

Biotechnology uses microorganisms and/or enzymes to obtain specific products through fermentative processes and/or genetic engineering techniques. Examples of these products are active ingredients, such as hyaluronic acid, kojic acid, resveratrol, and some enzymes, which are used in skin anti-aging products. In addition, certain growth factors, algae, stem cells, and peptides have been included in cosmetics and aesthetic medicines. Thus, biotechnology, cosmetics and aesthetic medicines are now closely linked, through the production of high-quality active ingredients, which are more effective and safer. This work describes the most used active ingredients that are produced from biotechnological processes. Although there are a vast number of active ingredients, the number of biotechnological active ingredients reported in the literature is not significantly high.

Hyaluronic acid-Based wound dressings: A review

Hyaluronic acid (HA), a non-sulfated glycosaminoglycan (GAG), is a major component of skin extracellular matrix (ECM) and it is involved in the inflammatory response, angiogenesis, and tissue regeneration process. Due to the intrinsic properties of HA (such as biocompatibility, biodegradability and hydrophilic character), it has been used to produce different wound dressings, namely sponges, films, hydrogels, and electrospun membranes. Herein, an overview of the different HA-based wound dressings that have been produced so far is provided as well as the future directions regarding the strategies aimed to improve the mechanical stability of HA-based wound dressings, along with the incorporation of biomolecules intended to ameliorate their biological performance during the healing process.

Hyaluronic Acid and Regenerative Medicine: New Insights into the Stroke Therapy

Stroke is known as one of the very important public health problems that are related to societal burden and tremendous economic losses. It has been shown that there are few therapeutic approaches for the treatment of this disease. In this regard, the present therapeutic platforms aim to obtain neuroprotection, reperfusion, and neuro recovery. Among these therapies, regenerative medicine-based therapies have appeared as new ways of stroke therapy. Hyaluronic acid (HA) is a new candidate, which could be applied as a regenerative medicine-based therapy in the treatment of stroke. HA is a glycosaminoglycan composed of disaccharide repeating elements (N-acetyl-Dglucosamine and D-glucuronic acid). Multiple lines of evidence demonstrated that HA has critical roles in normal tissues. It can be a key player in different physiological and pathophysiological conditions such as water homeostasis, multiple drug resistance, inflammatory processes, tumorigenesis, angiogenesis, and changed viscoelasticity of the extracellular matrix. HA has very important physicochemical properties i.e., availability of reactive functional groups and its solubility, which make it a biocompatible material for application in regenerative medicine. Given that HAbased bioscaffolds and biomaterials do not induce inflammation or allergies and are hydrophilic, they are used as soft tissue fillers and injectable dermal fillers. Several studies indicated that HA could be employed as a new therapeutic candidate in the treatment of stroke. These studies documented that HA and HA-based therapies exert their pharmacological effects via affecting stroke-related processes. Herein, we summarized the role of the extracellular matrix in stroke pathogenesis. Moreover, we highlighted the HA-based therapies for the treatment of stroke.

An Enteric-Coated Polyelectrolyte Nanocomplex Delivers Insulin in Rat Intestinal Instillations when Combined with a Permeation Enhancer

The use of nanocarriers is being researched to achieve oral peptide delivery. Insulin-associated anionic polyelectrolyte nanoparticle complexes (PECs) were formed that comprised hyaluronic acid and chitosan in an optimum mass mixing ratio of 5:1 (MR 5), followed by coating with a pH-dependent polymer. Free insulin was separated from PECs by size exclusion chromatography and then measured by HPLC. The association efficiency of insulin in PECs was >95% and the loading was ~83 µg/mg particles. Dynamic light scattering and nanoparticle tracking analysis of PECs revealed low polydispersity, a negative zeta potential range of −40 to −50 mV, and a diameter range of 95–200 nm. Dissolution studies in simulated small intestinal fluid (FaSSIF-V2) revealed that the PECs were colloidally stable. PECs that were coated with Eudragit^® L-100 delayed insulin release in FaSSIF-V2 and protected insulin against pancreatin attack more than uncoated PECs. Uncoated anionic PECs interacted weakly with mucin in vitro and were non-cytotoxic to Caco-2 cells. The coated and uncoated PECs, both concentrated further by ultrafiltration, permitted dosing of 50 IU/kg in rat jejunal instillations, but they failed to reduce plasma glucose or deliver insulin to the blood. When ad-mixed with the permeation enhancer (PE), sucrose laurate (100 mM), the physicochemical parameters of coated PECs were relatively unchanged, however blood glucose was reduced by 70%. In conclusion, the use of a PE allowed for the PEC-released bioactive insulin to permeate the jejunum. This has implications for the design of orally delivered particles that can release the payload when formulated with enhancers.

The Role of Glycosaminoglycans in Protection from Neonatal Necrotizing Enterocolitis: A Narrative Review

Necrotizing enterocolitis, a potentially fatal intestinal inflammatory disorder affecting primarily premature infants, is a significant cause of morbidity and mortality in neonates. While the etiology of the disease is, as yet, unknown, a number of risk factors for the development of necrotizing enterocolitis have been identified. One such risk factor, formula feeding, has been shown to contribute to both increased incidence and severity of the disease. The protective influences afforded by breastfeeding are likely attributable to the unique composition of human milk, an extremely potent, biologically active fluid. This review brings together knowledge on the pathogenesis of necrotizing enterocolitis and current thinking on the instrumental role of one of the more prominent classes of bioactive components in human breast milk, glycosaminoglycans.

3D Bioprinting of Tissue Models with Customized Bioinks

The ordered assembly of multicellular structures mimicking native tissues has lately come into prominence for various applications of biomedicine. In this respect, three-dimensional bioprinting (3DP) of cells and other biologics through additive manufacturing techniques has brought the possibility to develop functional in vitro tissue models and perhaps creating de novo transplantable tissues or organs in time. Bioinks, which can be defined as the printable analogues of the extracellular matrix, represent the foremost component of 3DP. In this chapter, we attempt to elaborate the major classes of bioinks which are prevalently being evaluated for the 3DP of a wide range of tissue models.

Hyaluronan-based hydrogels via ether-crosslinking: Is HA molecular weight an effective means to tune gel performance?

Hyaluronan (HA)-based hydrogels obtained by crosslinking the biopolymer via ether bonds are widely used in clinical practice. There is interest in improving the design of these gels to match specific properties. Here, the possibility to tune HA-hydrogel behavior by adjusting the molecular weight distribution of the biopolymer undergoing crosslinking was investigated. Three HA samples (500, 1100 and 1600 kDa) underwent reaction with 1,4-butandioldiglycidyl-ether(BDDE) under reported conditions and the crosslinked products were characterized for chemical modification extent, swelling, rheological behavior, cohesivity, sensitivity to enzymatic degradation and effect on Human Dermal Fibroblasts (HDF). HA hydrolysis, under the highly alkaline crosslinking conditions, was also studied for the first time. The main achievements are that 1) varying HA chain length affects hydrogel behavior less than expected, due to the de-polymerization occurring alongside crosslinking, that reduces the differences in sample size 2) when differences in chain length persist notwithstanding hydrolysis, lowering HA size is a means to prepare more concentrated formulations, expected to exhibit longer duration and better cohesivity in vivo, while retaining a certain rigidity, preserving biocompatibility and slightly influencing HDF behavior in relation to CollagenI production. The study shed light on aspects concerning BDDE-HA gel manufacturing and contributed to the improvement of their design.

Key Factors for A One-Pot Enzyme Cascade Synthesis of High Molecular Weight Hyaluronic Acid

In the last decades, interest in medical or cosmetic applications of hyaluronic acid (HA) has increased. Size and dispersity are key characteristics of biological function. In contrast to extraction from animal tissue or bacterial fermentation, enzymatic in vitro synthesis is the choice to produce defined HA. Here we present a one-pot enzyme cascade with six enzymes for the synthesis of HA from the cheap monosaccharides glucuronic acid (GlcA) and N-acetylglucosamine (GlcNAc). The combination of two enzyme modules, providing the precursors UDP–GlcA and UDP–GlcNAc, respectively, with hyaluronan synthase from Pasteurella multocida (PmHAS), was optimized to meet the kinetic requirements of PmHAS for high HA productivity and molecular weight. The Mg²⁺ concentration and the pH value were found as key factors. The HA product can be tailored by different conditions: 25 mM Mg²⁺ and 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (HEPES)-NaOH pH 8 result into an HA product with high M_w HA (1.55 MDa) and low dispersity (1.05). Whereas with 15 mM Mg²⁺ and HEPES–NaOH pH 8.5, we reached the highest HA concentration (2.7 g/L) with a yield of 86.3%. Our comprehensive data set lays the basis for larger scale enzymatic HA synthesis.

Strategies for Hyaluronic Acid-Based Hydrogel Design in Drug Delivery

Hyaluronic acid (HA) is a natural, linear, endogenous polysaccharide that plays important physiological and biological roles in the human body. Nowadays, among biopolymers, HA is emerging as an appealing starting material for hydrogels design due to its biocompatibility, native biofunctionality, biodegradability, non-immunogenicity, and versatility. Since HA is not able to form gels alone, chemical modifications, covalent crosslinking, and gelling agents are always needed in order to obtain HA-based hydrogels. Therefore, in the last decade, different strategies for the design of physical and chemical HA hydrogels have been developed, such as click chemistry reactions, enzymatic and disulfide crosslinking, supramolecular assembly via inclusion complexation, and so on. HA-based hydrogels turn out to be versatile platforms, ranging from static to smart and stimuli-responsive systems, and for these reasons, they are widely investigated for biomedical applications like drug delivery, tissue engineering, regenerative medicine, cell therapy, and diagnostics. Furthermore, the overexpression of HA receptors on various tumor cells makes these platforms promising drug delivery systems for targeted cancer therapy. The aim of the present review is to highlight and discuss recent advances made in the last years on the design of chemical and physical HA-based hydrogels and their application for biomedical purposes, in particular, drug delivery. Notable attention is given to HA hydrogel-based drug delivery systems for targeted therapy of cancer and osteoarthritis.

Hyaluronic Acid: Molecular Mechanisms and Therapeutic Trajectory

Hyaluronic acid (also known as hyaluronan or hyaluronate) is naturally found in many tissues and fluids, but more abundantly in articular cartilage and synovial fluid (SF). Hyaluronic acid (HA) content varies widely in different joints and species. HA is a non-sulfated, naturally occurring non-protein glycosaminoglycan (GAG), with distinct physico-chemical properties, produced by synoviocytes, fibroblasts, and chondrocytes. HA has an important role in the biomechanics of normal SF, where it is partially responsible for lubrication and viscoelasticity of the SF. The concentration of HA and its molecular weight (MW) decline as osteoarthritis (OA) progresses with aging. For that reason, HA has been used for more than four decades in the treatment of OA in dogs, horses and humans. HA produces anti-arthritic effects via multiple mechanisms involving receptors, enzymes and other metabolic pathways. HA is also used in the treatment of ophthalmic, dermal, burns, wound repair, and other health conditions. The MW of HA appears to play a critical role in the formulation of the products used in the treatment of diseases. This review provides a mechanism-based rationale for the use of HA in some disease conditions with special reference to OA.

Electrospun Bilayer Chitosan/Hyaluronan Material and Its Compatibility with Mesenchymal Stem Cells

A bilayer nonwoven material for tissue regeneration was prepared from chitosan (CS) and hyaluronic acid (HA) by needleless electrospinning wherein 10-15 wt% (with respect to polysaccharide) polyethylene oxide was added as spinning starter. A fiber morphology study confirmed the material's uniform defect-free structure. The roughness of the bilayer material was in the range of 1.5-3 μm, which is favorable for cell growth. Electrospinning resulted in the higher orientation of the polymer structure compared with that of corresponding films, and this finding may be related to the orientation of the polymer chains during the spinning process. These structural changes increased the intermolecular interactions. Thus, despite a high swelling degree of 1.4-2.8 g/g, the bilayer matrix maintained its shape due to the large quantity of polyelectrolyte contacts between the chains of oppositely charged polymers. The porosity of the bilayer CS-HA nonwoven material was twice lower, while the Young's modulus and break stress were twice higher than that of a CS monolayer scaffold. Therefore, during the electrospinning of the second layer, HA may have penetrated into the pores of the CS layer, thereby increasing the polyelectrolyte contacts between the two polymers. The bilayer CS-HA scaffold exhibited good compatibility with mesenchymal stem cells. This characteristic makes the developed material promising for tissue engineering applications.

Hyaluronic Acid Nanocapsules as a Platform for Needle-Free Vaccination

Vaccination faces many challenges nowadays, and among them the use of adjuvant molecules and needle-free administration are some of the most demanding. The combination of transcutaneous vaccination and nanomedicine through a rationally designed new-formulation could be the solution to this problem. This study focuses on this rational design. For this purpose, new hyaluronic acid nanocapsules (HA-NCs) have been developed. This new formulation has an oily nucleus with immunoadjuvant properties (due to α tocopherol) and a shell made of hyaluronic acid (HA) and decorated with ovalbumin (OVA) as the model antigen. The resulting nanocapsules are smaller than 100 nm, have a negative superficial charge and have a population that is homogeneously distributed. The systems show high colloidal stability in storage and physiological conditions and high OVA association without losing their integrity. The elevated interaction of the novel formulation with the immune system was demonstrated through complement activation and macrophage viability studies. Ex vivo studies using a pig skin model show the ability of these novel nanocapsules to penetrate and retain OVA in higher quantities in skin when compared to this antigen in the control solution. Due to these findings, HA-NCs are an interesting platform for needle-free vaccination.

In-Cell Synthesis of Bioorthogonal Alkene Tag S-Allyl-Homocysteine and Its Coupling with Reprogrammed Translation

In this study, we report our initial results on in situ biosynthesis of S-allyl-l-homocysteine (Sahc) by simple metabolic conversion of allyl mercaptan in Escherichia coli, which served as the host organism endowed with a direct sulfhydration pathway. The intracellular synthesis we describe in this study is coupled with the direct incorporation of Sahc into proteins in response to methionine codons. Together with O-acetyl-homoserine, allyl mercaptan was added to the growth medium, followed by uptake and intracellular reaction to give Sahc. Our protocol efficiently combined the in vivo synthesis of Sahc via metabolic engineering with reprogrammed translation, without the need for a major change in the protein biosynthesis machinery. Although the system needs further optimisation to achieve greater intracellular Sahc production for complete protein labelling, we demonstrated its functional versatility for photo-induced thiol-ene coupling and the recently developed phosphonamidate conjugation reaction. Importantly, deprotection of Sahc leads to homocysteine-containing proteins-a potentially useful approach for the selective labelling of thiols with high relevance in various medical settings.

Acellular biomaterial strategies for endodontic regeneration

Dental decay is treated by removing infected dental tissues such as dentine and restoring the tooth with a material. However, the vast majority of these materials have been designed to be mechanically robust and bioinert, whereas the potential regenerative properties of a biomaterial have not been considered. In endodontics for example, materials are used to seal the pulp cavity to avoid bacterial colonisation of the tooth and prevent further infection. While these treatments are effective in the short term, many of these materials have not been designed to interface with the pulp tissue in a biocompatible manner and are often cytotoxic. This can lead to less favourable long-term outcomes such as devitalisation of the tooth via root-canal therapy or extraction of the tooth. Clinical outcomes could be improved if regenerative approaches were followed whereby the biology of the tooth is engineered for repair and regeneration often with the support of a biomaterial. Within these, acellular or cell homing approaches are particularly interesting, as some regulatory hurdles associated with cellular therapies could be circumvented which may aid their clinical translation. In this review, we highlight progress in regenerative dentistry and focus on exciting developments using acellular biomaterials for regenerating dental tissues.

In vitro characterization of physico-chemical properties, cytotoxicity, bioactivity of urea-crosslinked hyaluronic acid and sodium ascorbyl phosphate nasal powder formulation

An innovative lyophilized dry powder formulation consisting of urea-crosslinked hyaluronic acid (HA-CL) and sodium ascorbyl phosphate (SAP) - LYO HA-CL - SAP- was prepared and characterized in vitro for physico-chemical and biological properties. The aim was to understand if LYO HA-CL - SAP could be used as adjuvant treatment for nasal inflammatory diseases. LYO HA-CL - SAP was suitable for nasal delivery and showed to be not toxic on human nasal septum carcinoma-derived cells (RPMI 2650 cells) at the investigated concentrations. It displayed porous, polygonal particles with unimodal, narrow size distribution, mean geometric diameter of 328.3 ± 27.5 µm, that is appropriate for nasal deposition with no respirable fraction and 88.7% of particles with aerodynamic diameter >14.1 µm. Additionally, the formulation showed wound healing ability on RPMI 2650 cells, and reduced interleukin-8 (IL-8) level in primary nasal epithelial cells pre-induced with lipopolysaccharide (LPS). Transport study across RPMI 2650 cells showed that HA-CL could act not only as carrier for SAP and active ingredient itself, but potentially also as mucoadhesive agent. In conclusion, these results suggest that HA-CL and SAP had anti-inflammatory activity and acted in combination to accelerate wound healing. Therefore, LYO HA-CL - SAP could be a potential adjuvant in nasal anti-inflammatory formulations.