Aloe Vera-Derived Gel-Blended PHBV Nanofibrous Scaffold for Bone Tissue Engineering

Differentiation of Wharton's Jelly-derived mesenchymal stem cells into insulin-producing beta cells with the enhanced functional level on electrospun PRP-PVP-PCL/PCL fiber scaffold

Diabetes is a global problem that threatens human health. Cell therapy methods using stem cells, and tissue engineering of pancreatic islets as new therapeutic approaches have increased the chances of successful diabetes treatment. In this study, to differentiate Wharton's Jelly-derived mesenchymal stem cells (WJ-MSCs) into insulin-producing cells (IPCs) with improved maturity, and function, platelet-rich plasma (PRP)-Polyvinylpyrrolidone (PVP)-Polycaprolactone (PCL)/PCL scaffold was designed. The two-dimensional (2D) control group included cell culture without differentiation medium, and the experimental groups included 2D, and three-dimensional (3D) groups with pancreatic beta cell differentiation medium. WJ-MSCs-derived IPCs on PRP-PVP-PCL/PCL scaffold took round cluster morphology, the typical pancreatic islets morphology. Real-time PCR, immunocytochemistry, and flowcytometry data showed a significant increase in pancreatic marker genes in WJ-MSCs-derived IPCs on the PRP-PVP-PCL/PCL scaffold compared to the 2D-experimental group. Also, using the ELISA assay, a significant increase in the secretion of insulin, and C-peptide was measured in the WJ-MSCs-derived IPCs of the 3D-experimental group compared to the 2D experimental group, the highest amount of insulin (38 µlU/ml), and C-peptide (43 pmol/l) secretion was in the 3D experimental group, and in response to 25 mM glucose solution, which indicated a significant improvement in the functional level of the WJ-MSCs-derived IPCs in the 3D group. The results showed that the PRP-PVP-PCL/PCL scaffold can provide an appropriate microenvironment for the engineering of pancreatic islets, and the generation of IPCs.

Polyhydroxyalkanoates: the natural biopolyester for future medical innovations

Polyhydroxyalkanoates (PHAs) are a family of natural microbial biopolyesters with the same basic chemical structure and diverse side chain groups. Based on their excellent biodegradability, biocompatibility, thermoplastic properties and diversity, PHAs are highly promising medical biomaterials and elements of medical devices for applications in tissue engineering and drug delivery. However, due to the high cost of biotechnological production, most PHAs have yet to be applied in the clinic and have only been studied at laboratory scale. This review focuses on the biosynthesis, diversity, physical properties, biodegradability and biosafety of PHAs. We also discuss optimization strategies for improved microbial production of commercial PHAs via novel synthetic biology tools. Moreover, we also systematically summarize various medical devices based on PHAs and related design approaches for medical applications, including tissue repair and drug delivery. The main degradation product of PHAs, 3-hydroxybutyrate (3HB), is recognized as a new functional molecule for cancer therapy and immune regulation. Although PHAs still account for only a small percentage of medical polymers, up-and-coming novel medical PHA devices will enter the clinical translation stage in the next few years.

Phytochemical Compounds Involved in the Bone Regeneration Process and Their Innovative Administration: A Systematic Review

Bone metabolism is a complex process which is influenced by the activity of bone cells (e.g., osteocytes, osteoblasts, osteoclasts); the effect of some specific biomarkers (e.g., parathyroid hormone, vitamin D, alkaline phosphatase, osteocalcin, osteopontin, osteoprotegerin, osterix, RANKL, Runx2); and the characteristic signaling pathways (e.g., RANKL/RANK, Wnt/β, Notch, BMP, SMAD). Some phytochemical compounds-such as flavonoids, tannins, polyphenols, anthocyanins, terpenoids, polysaccharides, alkaloids and others-presented a beneficial and stimulating effect in the bone regeneration process due to the pro-estrogenic activity, the antioxidant and the anti-inflammatory effect and modulation of bone signaling pathways. Lately, nanomedicine has emerged as an innovative concept for new treatments in bone-related pathologies envisaged through the incorporation of medicinal substances in nanometric systems for oral or local administration, as well as in nanostructured scaffolds with huge potential in bone tissue engineering.

Recent Development of Polyhydroxyalkanoates (PHA)-Based Materials for Antibacterial Applications: A Review

The diseases caused by microorganisms are innumerable existing on this planet. Nevertheless, increasing antimicrobial resistance has become an urgent global challenge. Thus, in recent decades, bactericidal materials have been considered promising candidates to combat bacterial pathogens. Recently, polyhydroxyalkanoates (PHAs) have been used as green and biodegradable materials in various promising alternative applications, especially in healthcare for antiviral or antiviral purposes. However, it lacks a systematic review of the recent application of this emerging material for antibacterial applications. Therefore, the ultimate goal of this review is to provide a critical review of the state of the art recent development of PHA biopolymers in terms of cutting-edge production technologies as well as promising application fields. In addition, special attention was given to collecting scientific information on antibacterial agents that can potentially be incorporated into PHA materials for biological and durable antimicrobial protection. Furthermore, the current research gaps are declared, and future research perspectives are proposed to better understand the properties of these biopolymers as well as their possible applications.

Effects of ceramic additives and bioactive coatings on the degradation of polylactic acid-based bone scaffolds under hydrolytic conditions

Polylactic acid (PLA) has been extensively used for the manufacturing of scaffolds in bone tissue engineering applications. Due to the low hydrophilicity and the acidic degradation process of this biomaterial, different strategies have been proposed to increase the biofunctionality of the support structure. The use of ceramic particles is a generally preferred option to increase the osteoconductivity of the base material, while acting as buffers to maintain the pH level of the surroundings tissues. Surface modification is another approach to overcome the limitations of PLA for tissue engineering applications. In this work, the degradation profile of 3D-printed PLA scaffolds containing beta-tricalcium phosphate (β-TCP) and calcium carbonate (CaCO3 ) particles has been studied under hydrolytic conditions. Composite samples treated with plasma and coated with Aloe vera extracts were also studied to evaluate the effect of this surface modification method. The characterization of the 3D structures included its morphological, calorimetric and mechanical evaluation. According to the results obtained, the proposed composite scaffolds allowed an adequate maintenance of the pH level of the surrounding medium, with no effects observed on the morphology and mechanical properties of these structures. Hence, these samples showed potential to be further investigated as candidates for bone tissue regeneration.

Evaluation of osteogenic induction potency of miR-27a-3p in adipose tissue-derived human mesenchymal stem cells (AD-hMSCs)

BACKGROUND

Bone tissue as a dynamic tissue is able to repair its minor injuries, however, sometimes the repair cannot be completed by itself due to the size of lesion. In such cases, the best treatment could be bone tissue engineering. The use of stem cells in skeletal disorders to repair bone defects has created bright prospects. On the other hand, changes in the expression level of microRNAs (miRs) can lead to the commitment of mesenchymal stem cells (MSCs) to cell lineage. Many studies reported that post-transcriptional regulations by miRNAs are involved in all stages of osteoblast differentiation.

METHOD

After the preparing adipose tissue-derived mesenchymal stem cells, the target cells from the third passage were cultured in two groups, transfected MSCs with miR-27a-3p (DM.C + P) and control group. In different times, 7 and 14 days after culture, differentiation of these cells into osteoblast were measured using various techniques including the ALP test and calcium content test, Alizarin Red staining, Immunocytochemistry technique (ICC). Also, the relative expression of bone differentiation marker genes including Osteonectin (ON), Osteocalcin (OC), RUNX Family Transcription Factor 2 (RUNX2), Collagen type I alpha 1 (COL1) was investigated by real-time RT PCR.

RESULTS

In comparison with control groups, overexpression of miR-27a-3p in transfected cells resulted in a significant increase in the expression of bone markers genes (ON, OC, RUNX2, COL1), alkaline phosphatase (ALP) activity, and calcium content (p < 0.05). In addition, the results obtained from ICC technique showed that osteocalcin protein is expressed at the surface of bone cells. Furthermore, the expression of APC, as a target of miR-27a-3p, decreased in transfected cells.

CONCLUSION

Our data suggest that miR-27a-3p may positively regulates adipose tissue-derived mesenchymal stem cell differentiation into bone by targeting APC and activating the Wnt/b-catenin pathway.

Synthetic electrospun nanofibers as a supportive matrix in osteogenic differentiation of induced pluripotent stem cells

Continuous remodeling is not able to repair large bone defects. Bone tissue engineering is aimed to repair these defects by creating bone grafts. To do this, several technologies and biomaterials have been employed to fabricate an in vivo-like supportive matrix. Electrospinning is a versatile technique to fabricate porous matrices with interconnected pores and high surface area, replicating in vivo microenvironment. Electrospun scaffolds have been used in a large number of studies to provide a matrix for bone regeneration and osteogenic differentiation of stem cells such as induced pluripotent stem cells (iPSCs). Electrospinning uses both natural and synthetic polymers, either alone or in combination, to fabricate scaffolds. Among them, synthetic polymers have had a great promise in bone regeneration and repair. They allow the fabrication of biocompatible and biodegradable scaffolds with high mechanical properties, suitable for bone engineering. Furthermore, several attempts have done to increase the osteogenic properties of these scaffolds. This paper reviewed the potential of synthetic electrospun scaffolds in osteogenic differentiation of iPSCs. In addition, the approaches to improve the osteogenic differentiation of these scaffolds are addressed.

Comparative review of piezoelectric biomaterials approach for bone tissue engineering

Bone as a minerals' reservoir and rigid tissue of the body generating red and white blood cells supports various organs. Although the self-regeneration property of bone, it cannot regenerate spontaneously in severe damages and still remains as a challenging issue. Tissue engineering offers several techniques for regenerating damaged bones, where various biomaterials are examined to fabricate scaffolds for bone repair. Piezoelectric characteristic plays a crucial role in repairing and regenerating damaged bone by mimicking the bone niche behavior. Piezoelectric biomaterials show significant potential for bone tissue engineering. Herein we try to have a comparative review on piezoelectric and non-piezoelectric biomaterials used in bone tissue engineering, classified them, and discussed their effects on implanted cells and manufacturing techniques. Especially, Polyvinylidene fluoride (PVDF) and its composites are the most practically used piezoelectric biomaterials for bone regeneration. PVDF and its composites have been summarized and discussed to repair damaged bone tissues.

Aloe vera incorporated starch-64S bioactive glass-quail egg shell scaffold for promotion of bone regeneration

Simultaneous promotion of osteoconductive and osteoinductive characteristics through combining bioactive glasses with natural polymers is still a challenge in bone tissue engineering. Starch, 64S bioactive glass (BG), aloe vera (AV) and quail eggshell powder (QE) were utilized to achieve biodegradable, bioactive, biocompatible and mechanically potent multifunctional scaffolds, using freeze-drying mechanism. Cell viability for starch-BG-AV-QE scaffolds at 3 and 7 day intervals was reported to be over 95 %. Acridine orange staining was employed to study live/dead cells cultured on the scaffolds. The high sufficiency of starch-BG-AV-QE scaffolds in osteogenic differentiation and extracellular matrix mineralization was confirmed through alkaline phosphatase activity and alizarin red staining assessments after 7 and 14 days of cell culture. High compressive strength, managed biodegradability and expression of osteocalcin and osteopontin as late markers of osteogenic differentiation were also reached in the range of 30-75 % for starch-BG-AV-QE scaffolds. Hence, starch-BG-AV-QE scaffolds with ideal physico-mechanical and biological characteristics can be considered as promising candidates for promotion of bone regeneration.

Biomedical Applications of Polyhydroxyalkanoate in Tissue Engineering

Tissue engineering technology aids in the regeneration of new tissue to replace damaged or wounded tissue. Three-dimensional biodegradable and porous scaffolds are often utilized in this area to mimic the structure and function of the extracellular matrix. Scaffold material and design are significant areas of biomaterial research and the most favorable material for seeding of in vitro and in vivo cells. Polyhydroxyalkanoates (PHAs) are biopolyesters (thermoplastic) that are appropriate for this application due to their biodegradability, thermo-processability, enhanced biocompatibility, mechanical properties, non-toxicity, and environmental origin. Additionally, they offer enormous potential for modification through biological, chemical and physical alteration, including blending with various other materials. PHAs are produced by bacterial fermentation under nutrient-limiting circumstances and have been reported to offer new perspectives for devices in biological applications. The present review discusses PHAs in the applications of conventional medical devices, especially for soft tissue (sutures, wound dressings, cardiac patches and blood vessels) and hard tissue (bone and cartilage scaffolds) regeneration applications. The paper also addresses a recent advance highlighting the usage of PHAs in implantable devices, such as heart valves, stents, nerve guidance conduits and nanoparticles, including drug delivery. This review summarizes the in vivo and in vitro biodegradability of PHAs and conducts an overview of current scientific research and achievements in the development of PHAs in the biomedical sector. In the future, PHAs may replace synthetic plastics as the material of choice for medical researchers and practitioners.

The role of natural polymers in bone tissue engineering

Bone is a dynamic self-healing organ and a continuous remodeling ensures the restoration of the bone structure and function over time. However, bone remodeling is not able to repair large traumatic injuries. Therefore, surgical interventions and bone substitutes are required. The aim of bone tissue engineering is to repair and regenerate tissues and engineered a bone graft as a bone substitute. To met this goal, several natural or synthetic polymers have been used to develop a biocompatible and biodegradable polymeric construct. Among the polymers, natural polymers have higher biocompatibility, excellent biodegradability, and no toxicity. So far, collagen, chitosan, gelatin, silk fibroin, alginate, cellulose, and starch, alone or in combination, have been widely used in bone tissue engineering. These polymers have been used as scaffolds, hydrogels, and micro-nanospheres. The functionalization of the polymer with growth factors and bioactive glasses increases the potential use of polymers for bone regeneration. As bone is a dynamic highly vascularized tissue, the vascularization of the polymeric scaffolds is vital for successful bone regeneration. Several in vivo and in vitro strategies have been used to vascularize the polymeric scaffolds. In this review, the application of the most commonly used natural polymers is discussed.

Pharmaceutical electrospinning and 3D printing scaffold design for bone regeneration

Bone regenerative engineering provides a great platform for bone tissue regeneration covering cells, growth factors and other dynamic forces for fabricating scaffolds. Diversified biomaterials and their fabrication methods have emerged for fabricating patient specific bioactive scaffolds with controlled microstructures for bridging complex bone defects. The goal of this review is to summarize the points of scaffold design as well as applications for bone regeneration based on both electrospinning and 3D bioprinting. It first briefly introduces biological characteristics of bone regeneration and summarizes the applications of different types of material and the considerations for bone regeneration including polymers, ceramics, metals and composites. We then discuss electrospinning nanofibrous scaffold applied for the bone regenerative engineering with various properties, components and structures. Meanwhile, diverse design in the 3D bioprinting scaffolds for osteogenesis especially in the role of drug and bioactive factors delivery are assembled. Finally, we discuss challenges and future prospects in the development of electrospinning and 3D bioprinting for osteogenesis and prominent strategies and directions in future.

Fabrication and Characterization of Cinnamaldehyde-Loaded Mesoporous Bioactive Glass Nanoparticles/PHBV-Based Microspheres for Preventing Bacterial Infection and Promoting Bone Tissue Regeneration

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is considered a suitable polymer for drug delivery systems and bone tissue engineering due to its biocompatibility and biodegradability. However, the lack of bioactivity and antibacterial activity hinders its biomedical applications. In this study, mesoporous bioactive glass nanoparticles (MBGN) were incorporated into PHBV to enhance its bioactivity, while cinnamaldehyde (CIN) was loaded in MBGN to introduce antimicrobial activity. The blank (PHBV/MBGN) and the CIN-loaded microspheres (PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20) were fabricated by emulsion solvent extraction/evaporation method. The average particle size and zeta potential of all samples were investigated, as well as the morphology of all samples evaluated by scanning electron microscopy. PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20 significantly exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli in the first 3 h, while CIN releasing behavior was observed up to 7 d. Human osteosarcoma cell (MG-63) proliferation and attachment were noticed after 24 h cell culture, demonstrating no adverse effects due to the presence of microspheres. Additionally, the rapid formation of hydroxyapatite on the composite microspheres after immersion in simulated body fluid (SBF) during 7 d revealed the bioactivity of the composite microspheres. Our findings indicate that this system represents an alternative model for an antibacterial biomaterial for potential applications in bone tissue engineering.

Repositioning Natural Antioxidants for Therapeutic Applications in Tissue Engineering

Although a large panel of natural antioxidants demonstrate a protective effect in preventing cellular oxidative stress, their low bioavailability limits therapeutic activity at the targeted injury site. The importance to deliver drug or cells into oxidative microenvironments can be realized with the development of biocompatible redox-modulating materials. The incorporation of antioxidant compounds within implanted biomaterials should be able to retain the antioxidant activity, while also allowing graft survival and tissue recovery. This review summarizes the recent literature reporting the combined role of natural antioxidants with biomaterials. Our review highlights how such functionalization is a promising strategy in tissue engineering to improve the engraftment and promote tissue healing or regeneration.