Trends in polymeric electrospun fibers and their use as oral biomaterials

Micro- and Nanostructured Fibrous Composites via Electro-Fluid Dynamics: Design and Applications for Brain

The brain consists of an interconnected network of neurons tightly packed in the extracellular matrix (ECM) to form complex and heterogeneous composite tissue. According to recent biomimicry approaches that consider biological features as active components of biomaterials, designing a highly reproducible microenvironment for brain cells can represent a key tool for tissue repair and regeneration. Indeed, this is crucial to support cell growth, mitigate inflammation phenomena and provide adequate structural properties needed to support the damaged tissue, corroborating the activity of the vascular network and ultimately the functionality of neurons. In this context, electro-fluid dynamic techniques (EFDTs), i.e., electrospinning, electrospraying and related techniques, offer the opportunity to engineer a wide variety of composite substrates by integrating fibers, particles, and hydrogels at different scales-from several hundred microns down to tens of nanometers-for the generation of countless patterns of physical and biochemical cues suitable for influencing the in vitro response of coexistent brain cell populations mediated by the surrounding microenvironment. In this review, an overview of the different technological approaches-based on EFDTs-for engineering fibrous and/or particle-loaded composite substrates will be proposed. The second section of this review will primarily focus on describing current and future approaches to the use of composites for brain applications, ranging from therapeutic to diagnostic/theranostic use and from repair to regeneration, with the ultimate goal of providing insightful information to guide future research efforts toward the development of more efficient and reliable solutions.

In Vivo Evaluation of Bone Regenerative Capacity of the Novel Nanobiomaterial: β-Tricalcium Phosphate Polylactic Acid-co-Glycolide (β-TCP/PLLA/PGA) for Use in Maxillofacial Bone Defects

Maxillofacial bone defects are treated by autografting or filling with synthetic materials in various forms and shapes. Electrospun nanobiomaterials are becoming popular due to their easy placement and handling; combining ideal biomaterials extrapolates better outcomes. We used a novel electrospun cotton-like fiber made from two time-tested bioresorbable materials, β-TCP and PLLA/PGA, to check the feasibility of its application to maxillofacial bone defects through an in vivo rat mandibular bone defect model. Novel β-TCP/PLLA/PGA and pure β-TCP blocks were evaluated for new bone regeneration through assessment of bone volume, inner defect diameter reduction, and bone mineral density. Bioactive/osteoconductivity was checked by scoring the levels of Runt-related transcription factor x, Leptin Receptor, Osteocalcin, and Periostin biomarkers. Bone regeneration in both β-TCP/PLLA/PGA and β-TCP was comparable at initial timepoints. Osteogenic cell accumulation was greater in β-TCP/PLLA/PGA than in β-TCP at initial as well as late phases. Periostin expression was more marked in β-TCP/PLLA/PGA. This study demonstrated comparable results between β-TCP/PLLA/PGA and β-TCP in terms of bone regeneration and bioactivity, even with a small material volume of β-TCP/PLLA/PGA and a decreased percentage of β-TCP. Electrospun β-TCP/PLLA/PGA is an ideal nanobiomaterial for inducing bone regeneration through osteoconductivity and bioresorbability in bony defects of the maxillofacial region.

Bioactive Scaffolds as a Promising Alternative for Enhancing Critical-Size Bone Defect Regeneration in the Craniomaxillofacial Region

Reconstruction of critical-size bone defects (CSDs) in the craniomaxillofacial (CMF) region remains challenging. Scaffold-based bone-engineered constructs have been proposed as an alternative to the classical treatments made with autografts and allografts. Scaffolds, a key component of engineered constructs, have been traditionally viewed as biologically passive temporary replacements of deficient bone lacking intrinsic cues to promote osteogenesis. Nowadays, scaffolds are functionalized, giving rise to bioactive scaffolds promoting bone regeneration more effectively than conventional counterparts. This review focuses on the three approaches most used to bioactivate scaffolds: (1) conferring microarchitectural designs or surface nanotopography; (2) loading bioactive molecules; and (3) seeding stem cells on scaffolds, providing relevant examples of in vivo (preclinical and clinical) studies where these methods are employed to enhance CSDs healing in the CMF region. From these, adding bioactive molecules (specifically bone morphogenetic proteins or BMPs) to scaffolds has been the most explored to bioactivate scaffolds. Nevertheless, the downsides of grafting BMP-loaded scaffolds in patients have limited its successful translation into clinics. Despite these drawbacks, scaffolds containing safer, cheaper, and more effective bioactive molecules, combined with stem cells and topographical cues, remain a promising alternative for clinical use to treat CSDs in the CMF complex replacing autografts and allografts.

Preparation of drug-loaded microspheres with a core-shell structure using silk fibroin and poly lactic-co-glycolic acid and their application

BACKGROUND

Advances in bone tissue engineering offer novel options for the regeneration of bone tissue. In the current clinical treatment, the method of accelerating bone tissue regeneration rate by promoting early angiogenesis has been widely accepted.

OBJECTIVE

This study aimed to develop a long-acting slow-release system using the pro-angiogenic drug tetramethylpyrazine (TMPZ) and pro-osteogenic drug icariin (ICA), which can be administered locally to achieve the sequential release of TMPZ and ICA for better clinically efficiency in the treatment of bone defects.

METHODS

This study aimed to prepare microspheres with a core-shell structure using two polymers, poly lactic-co-glycolic acid and silk fibroin, by coaxial electrostatic spraying. Based on the therapeutic model for bone defects, the pro-angiogenic drug TMPZ and pro-osteogenic drug ICA were encapsulated in the shell and core layers of the microspheres, respectively. Subsequently, TMPZ and ICA were released sequentially to promote early angiogenesis and late osteogenesis, respectively, at the site of the bone defect. The optimal preparation parameters for preparing the drug-loaded microspheres were identified using the univariate controlled variable method. Additionally, microsphere morphology and core-shell structure, such as physical properties, drug-loading properties, in vitro degradation and drug release patterns, were characterised using scanning electron microscope and laser scanning confocal microscopy.

RESULTS

The microspheres prepared in this study were well-defined and had a core-shell structure. The hydrophilicity of the drug-loaded microspheres changed compared to the no-load microspheres. Furthermore, in vitro results indicated that the drug-loaded microspheres with high encapsulation and loading efficiencies exhibited good biodegradability and cytocompatibility, slowly releasing the drug for up to three months.

CONCLUSION

The development of the drug delivery system with a dual-step release mechanism has potential clinical applications and implications in the treatment of bone defects.

Synthesis and Biocompatibility Evaluation of PCL Electrospun Membranes Coated with MTA/HA for Potential Application in Dental Pulp Capping

This study aimed to develop polycaprolactone (PCL) electrospun membranes coated with mineral trioxide aggregate/hydroxyapatite (MTA/HA) as a potential material for dental pulp capping. Initially, the PCL membrane was prepared by an electrospinning process, which was further surface coated with MTA (labeled as PCLMTA) and HA (labeled as PCLHA). The physico-chemical characterization of the fabricated membranes was carried out using field emission scanning electron microscopy (FE-SEM)/Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman spectroscopy, and contact angle analysis. The biocompatibility of the human dental pulp stem cells (hDPSCs) on the fabricated membranes was checked by XTT assay, and the hDPSCs adhesion and spreading were assessed by FE-SEM and confocal microscopy. The wound healing ability of hDPSCs in response to different electrospun membrane extracts was examined by scratch assay. The surface morphology analysis of the membranes by FE-SEM demonstrated a uniform nanofibrous texture with an average fiber diameter of 594 ± 124 nm for PCL, 517 ± 159 nm for PCLHA, and 490 ± 162 nm for PCLMTA. The elemental analysis of the PCLHA membrane indicated the presence of calcium and phosphorous elements related to HA, whereas the PCLMTA membrane showed the presence of calcium and silicate, related to MTA. The presence of MTA and HA in the PCL membranes was also confirmed by Raman spectroscopy. The water contact analysis demonstrated the hydrophobic nature of the membranes. The results indicated that PCL, PCLHA, and PCLMTA membranes were biocompatible, while PCLMTA exhibited better cell adhesion, spreading, and migration.

Chain-End Functionalization of Poly(ε-caprolactone) for Chemical Binding with Gelatin: Binary Electrospun Scaffolds with Improved Physico-Mechanical Characteristics and Cell Adhesive Properties

Composite biocompatible scaffolds, obtained using the electrospinning (ES) technique, are highly promising for biomedical application thanks to their high surface area, porosity, adjustable fiber diameter, and permeability. However, the combination of synthetic biodegradable (such as poly(ε-caprolactone) PCL) and natural (such as gelatin Gt) polymers is complicated by the problem of low compatibility of the components. Previously, this problem was solved by PCL grafting and/or Gt cross-linking after ES molding. In the present study, composite fibrous scaffolds consisting of PCL and Gt were fabricated by the electrospinning (ES) method using non-functionalized PCL1 or NHS-functionalized PCL2 and hexafluoroisopropanol as a solvent. To provide covalent binding between PCL2 and Gt macromolecules, NHS-functionalized methyl glutarate was synthesized and studied in model reactions with components of spinning solution. It was found that selective formation of amide bonds, which provide complete covalent bonding of Gt in PCL/Gt composite, requires the presence of weak acid. With the use of the optimized ES method, fibrous mats with different PCL/Gt ratios were prepared. The sample morphology (SEM), hydrolytic resistance (FT-IR), cell adhesion and viability (MTT assay), cell penetration (fluorescent microscopy), and mechanical characteristics of the samples were studied. PCL2-based films with a Gt content of 20 wt% have demonstrated the best set of properties.

Anti-adhesive effect of chondrocyte-derived extracellular matrix surface-modified with poly-L-lysine (PLL)

After an injury, soft tissue structures in the body undergo a natural healing process through specific phases of healing. Adhesions occur as abnormal attachments between tissues and organs through the formation of blood vessels and/or fibrinous adhesions during the regenerative repair process. In this study, we developed an adhesion-preventing membrane with an improved physical protection function by modifying the surface of chondrocyte-derived extracellular matrices (CECM) with anti-adhesion function. We attempted to change the negative charge of the CECM surface to neutral using poly-L-lysine (PLL) and investigated whether it blocked fibroblast adhesion to it and showed an improved anti-adhesion effect in animal models of tissue adhesion. The surface of the membrane was modified with PLL coating (PLL 10), which neutralized the surface charge. We confirmed that the surface characteristics except for the potential difference were maintained after the modification and tested cell attachment in vitro. Adhesion inhibition was identified in a peritoneal adhesion animal model at 1 week and in a subcutaneous adhesion model for 4 weeks. N-CECM suppressed fibroblast and endothelial cell adhesion in vitro and inhibited abdominal adhesions in vivo. The CECM appeared to actively inhibit the infiltration of endothelial cells into the injured site, thereby suppressing adhesion formation, which differed from conventional adhesion barriers in the mode of action. Furthermore, the N-CECM remained intact without degradation for more than four weeks in vivo and exerted anti-adhesion effects for a long time. This study demonstrated that PLL10 surface modification rendered a neutral charge to the polymer on the extracellular matrix surface, thereby inhibiting cell and tissue adhesion. Furthermore, this study suggests a means to modify extracellular matrix surfaces to meet the specific requirements of the target tissue in preventing post-surgical adhesions. This article is protected by copyright. All rights reserved.

Recent advances in electrospun nanofiber vaginal formulations for women's sexual and reproductive health

Electrospinning is an innovative technique that allows production of nanofibers and microfibers by applying a high voltage to polymer solutions of melts. The properties of these fibers - which include high surface area, high drug loading capacity, and ability to be manufactured from mucoadhesive polymers - may be particularly useful in a myriad of drug delivery and tissue engineering applications. The last decade has witnessed a surge of interest in the application of electrospinning technology for the fabrication of vaginal drug delivery systems for the treatment and prevention of diseases associated with women's sexual and reproductive health, including sexually transmitted infections (e.g. infection with human immunodeficiency virus and herpes simplex virus) vaginitis, preterm birth, contraception, multipurpose prevention technology strategies, cervicovaginal cancer, and general maintenance of vaginal health. Due to their excellent mechanical properties, electrospun scaffolds are also being investigated as next-generation materials in the surgical treatment of pelvic organ prolapse. In this article, we review the latest advances in the field.

Antibacterial Poly(ε-CL)/Hydroxyapatite Electrospun Fibers Reinforced by Poly(ε-CL)-b-poly(ethylene phosphoric acid)

In bone surgery and orthopedics, bioresorbable materials can be helpful in bone repair and countering post-op infections. Explicit antibacterial activity, osteoinductive and osteoconductive effects are essential to achieving this objective. Nonwoven electrospun (ES) fibers are receiving the close attention of physicians as promising materials for wound dressing and tissue engineering; potentially, in high contrast with dense materials, ES mats hamper regeneration of the bone extracellular matrix to a lesser extent. The use of the compositions of inherently biodegradable polyesters (poly(ε-caprolactone) PCL, poly(lactoglycolide), etc.), calcium phosphates and antibiotics is highly prospective, but the task of forming ES fibers from such compositions is complicated by the incompatibility of the main organic and inorganic ingredients, polyesters and calcium phosphates. In the present research we report the synthesis of hydroxyapatite (HAp) nanoparticles with uniform morphology, and demonstrate high efficiency of the block copolymer of PCL and poly(ethylene phosphoric acid) (PEPA) as an efficient compatibilizer for PCL/HAp mixtures that are able to form ES fibers with improved mechanical characteristics. The materials obtained in the presence of vancomycin exhibited incremental drug release against Staphylococcus aureus (St. aureus).

Bismuth subsalicylate incorporated in polycaprolactone-gelatin membranes by electrospinning to prevent bacterial colonization

Periodontitis is a chronic, multifactorial, inflammatory disease characterized by the progressive destruction of the periodontal tissues. Guided tissue regeneration (GTR), involving the use of barrier membranes, is one of the most successful clinical procedures for periodontal therapy. Nevertheless, rapid degradation of the membranes and membrane-related infections are considered two of the major reasons for GTR clinical failure. Recently, integration of non-antibiotic, antimicrobial materials to the membranes has emerged as a novel strategy to face the bacterial infection challenge, without increasing bacterial resistance. In this sense, bismuth subsalicylate (BSS) is a non-antibiotic, metal-based antimicrobial agent effective against different bacterial strains, that has been long safely used in medical treatments. Thus, the aim of the present work was to fabricate fibrillar, non-rapidly bioresorbable, antibacterial GTR membranes composed of polycaprolactone (PCL), gelatin (Gel), and BSS as the antibacterial agent. PCL-G-BSS membranes with three different BSS concentrations (2 wt./v%, 4 wt./v%, and 6 wt./v%) were developed by electrospinning and their morphology, composition, water wettability, mechanical properties, Bi release and degradation rate were characterized. The Cytotoxicity of the membranes was studiedin vitrousing human osteoblasts (hFOB) and gingival fibroblasts (HGF-1), and their antibacterial activity was tested againstAggregatibacter actinomycetemcomitans, Escherichia coli, Porphyromonas gingivalisandStaphylococcus aureus.The membranes obtained exhibited adequate mechanical properties for clinical application, and appropriate degradation rates for allowing periodontal defects regeneration. The hFOB and HGF-1 cells displayed adequate viability when in contact with the lixiviated products from the membranes, and, in general, displayed antibacterial activity against the four bacteria strains tested. Thus, the PCL-G-BSS membranes showed to be appropriate as potential barrier membranes for periodontal GTR treatments.

Biomaterials for the Prevention of Oral Candidiasis Development

Thousands of microorganisms coexist within the human microbiota. However, certain conditions can predispose the organism to the overgrowth of specific pathogens that further lead to opportunistic infections. One of the most common such imbalances in the normal oral flora is the excessive growth of Candida spp., which produces oral candidiasis. In immunocompromised individuals, this fungal infection can reach the systemic level and become life-threatening. Hence, prompt and efficient treatment must be administered. Traditional antifungal agents, such as polyenes, azoles, and echinocandins, may often result in severe adverse effects, regardless of the administration form. Therefore, novel treatments have to be developed and implemented in clinical practice. In this regard, the present paper focuses on the newest therapeutic options against oral Candida infections, reviewing compounds and biomaterials with inherent antifungal properties, improved materials for dental prostheses and denture adhesives, drug delivery systems, and combined approaches towards developing the optimum treatment.

Emerging Biofabrication Techniques: A Review on Natural Polymers for Biomedical Applications

Natural polymers have been widely used for biomedical applications in recent decades. They offer the advantages of resembling the extracellular matrix of native tissues and retaining biochemical cues and properties necessary to enhance their biocompatibility, so they usually improve the cellular attachment and behavior and avoid immunological reactions. Moreover, they offer a rapid degradability through natural enzymatic or chemical processes. However, natural polymers present poor mechanical strength, which frequently makes the manipulation processes difficult. Recent advances in biofabrication, 3D printing, microfluidics, and cell-electrospinning allow the manufacturing of complex natural polymer matrixes with biophysical and structural properties similar to those of the extracellular matrix. In addition, these techniques offer the possibility of incorporating different cell lines into the fabrication process, a revolutionary strategy broadly explored in recent years to produce cell-laden scaffolds that can better mimic the properties of functional tissues. In this review, the use of 3D printing, microfluidics, and electrospinning approaches has been extensively investigated for the biofabrication of naturally derived polymer scaffolds with encapsulated cells intended for biomedical applications (e.g., cell therapies, bone and dental grafts, cardiovascular or musculoskeletal tissue regeneration, and wound healing).

Current status and future of delivery systems for prevention and treatment of infections in the oral cavity

Oral health reflects the general health, and it is fundamental to well-being and quality of life. An infection in the oral cavity can be associated with serious complications in human health. Local therapy of these infections offers many advantages over systemic drug administration, targeting directly to the diseased area while minimizing systemic side effects. Specialized drug delivery systems into the oral cavity have to be designed in such a fashion that they resist to the aqueous environment that is constantly bathed in saliva and subject to mechanical forces. Additionally, a prolonged release of drug should also be provided, which would enhance the efficacy and also decrease the repeated dosing. This review is aimed to summarize the current most relevant findings related to local drug delivery of various drug groups for prevention and treatment of infections (viral, bacterial, fungal) and infection-related manifestations in the oral cavity. Current therapeutic challenges in regard to effective local drug delivery systems will be discussed, and the recent approaches to overcome these obstacles will be reviewed. Finally, future prospects will be overviewed to promote novel strategies that can be implemented in clinical management for prevention and treatment of oral infections.

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

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

Microwave-Assisted Fabrication of Mesoporous Silica-Calcium Phosphate Composites for Dental Application

Herein, the microwave-assisted wet precipitation method was used to obtain materials consisting of mesoporous silica (SBA-15) and calcium orthophosphates (CaP). Composites were prepared through immersion of mesoporous silica in different calcification coating solutions and then exposed to microwave radiation. The composites were characterized in terms of molecular structure, crystallinity, morphology, chemical composition, and mineralization potential by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). The application of microwave irradiation resulted in the formation of different types of calcium orthophosphates such as calcium deficient hydroxyapatite (CDHA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP) on the SBA-15 surface, depending on the type of coating solution. The composites for which the progressive formation of hydroxyapatite during incubation in simulated body fluid was observed were further used in the production of final pharmaceutical forms: membranes, granules, and pellets. All of the obtained pharmaceutical forms preserved mineralization properties.

Development of an antibacterial and anti-metalloproteinase dental adhesive for long-lasting resin composite restorations

Despite all the advances in adhesive dentistry, dental bonds are still fragile due to degradation events that start during application of adhesive agents and the inherent hydrolysis of resin-dentin bonds. Here, we combined two outstanding processing methods (electrospinning and cryomilling) to obtain bioactive (antimicrobial and anti-metalloproteinase) fiber-based fillers containing a potent matrix metalloproteinase (MMP) inhibitor (doxycycline, DOX). Poly(ε)caprolactone solutions containing different DOX amounts (0, 5, 25, and 50 wt%) were processed via electrospinning, resulting in non-toxic submicron fibers with antimicrobial activity against Streptococcus mutans and Lactobacillus. The fibers were embedded in a resin blend, light-cured, and cryomilled for the preparation of fiber-containing fillers, which were investigated with antibacterial and in situ gelatin zymography analyzes. The fillers containing 0, 25, and 50 wt% DOX-releasing fibers were added to aliquots of a two-step, etch-and-rinse dental adhesive system. Mechanical strength, hardness, degree of conversion (DC), water sorption and solubility, bond strength to dentin, and nanoleakage analyses were performed to characterize the physico-mechanical, biological, and bonding properties of the modified adhesives. Statistical analyses (ANOVA; Kruskal-Wallis) were used when appropriate to analyze the data (α = 0.05). DOX-releasing fibers were successfully obtained, showing proper morphological architecture, cytocompatibility, drug release ability, slow degradation profile, and antibacterial activity. Reduced metalloproteinases (MMP-2 and MMP-9) activity was observed only for the DOX-containing fillers, which have also demonstrated antibacterial properties against tested bacteria. Adhesive resins modified with DOX-containing fillers demonstrated greater DC and similar mechanical properties as compared to the fiber-free adhesive (unfilled control). Concerning bonding performance to dentin, the experimental adhesives showed similar immediate bond strengths to the control. After 12 months of water storage, the fiber-modified adhesives (except the group consisting of 50 wt% DOX-loaded fillers) demonstrated stable bonds to dentin. Nanoleakage was similar among all groups investigated. DOX-releasing fibers showed promising application in developing novel dentin adhesives with potential therapeutic properties and MMP inhibition ability; antibacterial activity against relevant oral pathogens, without jeopardizing the physico-mechanical characteristics; and bonding performance of the adhesive.

Delivery of Therapeutics from Layer-by-Layer Electrospun Nanofiber Matrix for Wound Healing: An Update

Increasing incidences of chronic wounds urge the development of effective therapeutic wound treatment. As the conventional wound dressings are found not to comply with all the requirements of an ideal wound dressing, the development of alternative and effective dressings is demanded. Over the past few years, electrospun nanofiber has been recognized as a better system for wound dressing and hence has been studied extensively. Most of the electrospun nanofiber dressings were fabricated as single-layer structure mats. However, this design is less favorable for the effective healing of wounds mainly due to its burst release effect. To address this problem and to simulate the organized skin layer's structure and function, a multilayer structure of wound dressing had been proposed. This design enables a sustained release of the therapeutic agent(s), and more resembles the natural skin extracellular matrix. Multilayer structure is also referred to layer-by-layer (LbL), which has been established as an innovative method of drug incorporation and delivery, combines a high surface area of electrospun nanofibers with the multilayer structure mat. This review focuses on LbL multilayer electrospun nanofiber as a superior strategy in designing an optimal wound dressing.

In Vitro Degradation of Electrospun Poly(Lactic-Co-Glycolic Acid) (PLGA) for Oral Mucosa Regeneration

Poly(lactic-co-glycolic acid) (PLGA) has been used in the field of tissue engineering as a scaffold due to its good biocompatibility, biodegradability and mechanical strength. With the aim to explore the degradability of PLGA electrospun nonwoven structures for oral mucosa tissue engineering applications, non-irradiated and gamma irradiated nonwovens were immersed in three different solutions, in which simulated body fluid (SBF) and artificial saliva are important for future oral mucosa tissue engineering. The nonwovens were immersed for 7, 15 and 30 days in SBF, culture media (DMEM) and artificial saliva at 37 °C. Before immersion in the solutions, the dosage of 15 kGy was applied for sterilization in one assay and compared with non-irradiated samples at the same timepoints. Samples were characterized using different techniques such as scanning electron microscopy (SEM), differential scanning calorimetric (DSC) and gel permeation chromatography (GPC) to evaluate the nonwoven degradation and Fourier-transform infrared spectroscopy (FTIR) to evaluate the chain scissions. Our results showed that PLGA nonwovens were constituted by semicrystalline fibers with moderate degradation properties up to thirty days. The non-irradiated samples exhibited slower kinetics of degradation than irradiated nonwovens. For immersion times longer than 7 days in the three different solutions, the mean diameter of irradiated fibers stayed in the same range, but significantly different from the control sample. On non-irradiated samples, the degradation kinetics was slower and the plateau in the diameter value was only attained after 30 days of immersion in the fluids. Plasticization (fluid absorption into the fiber structure) occurred in the bulk material, as confirmed by a decrease in Tg observed by DSC analyses of non-irradiated and irradiated nonwovens, in comparison with the respective controls. In addition, artificial saliva showed a higher capacity of influencing PLGA crystallization than SBF and DMEM. FTIR analyses showed typical PLGA chemical functional groups changes. These results will be important for future application of those PLGA electrospun nonwovens for oral mucosa regeneration.

Injectable Biomaterials for Dental Tissue Regeneration

Injectable biomaterials scaffolds play a pivotal role for dental tissue regeneration, as such materials are highly applicable in the dental field, particularly when compared to pre-formed scaffolds. The defects in the maxilla-oral area are normally small, confined and sometimes hard to access. This narrative review describes different types of biomaterials for dental tissue regeneration, and also discusses the potential use of nanofibers for dental tissues. Various studies suggest that tissue engineering approaches involving the use of injectable biomaterials have the potential of restoring not only dental tissue function but also their biological purposes.

Substituted glycolides from natural sources: preparation, alcoholysis and polymerization

Herein we present a comparative study of substituted glycolides MeGL, iPrGL, iBuGL, BnGL, PhGL and MePhGL, synthesized from natural sources and polymers therefrom.