Bioactivity and Delivery Strategies of Phytochemical Compounds in Bone Tissue Regeneration

Synthesis and characterization of innovative resveratrol nanobelt-like particles and assessment of their bioactivity, antioxidative and antibacterial properties

Recently, many studies have shown various beneficial effects of polyphenol resveratrol (Res) on human health. The most important of these effects include cardioprotective, neuroprotective, anti-cancer, anti-inflammatory, osteoinductive, and anti-microbial effects. Resveratrol has cis and trans isoforms, with the trans isoform being more stable and biologically active. Despite the results of in vitro experiments, resveratrol has limited potential for application in vivo due to its poor water solubility, sensitivity to oxygen, light, and heat, rapid metabolism, and therefore low bioavailability. The possible solution to overcome these limitations could be the synthesis of resveratrol in nanoparticle form. Accordingly, in this study, we have developed a simple, green solvent/non-solvent physicochemical method to synthesize stable, uniform, carrier-free resveratrol nanobelt-like particles (ResNPs) for applications in tissue engineering. UV-visible spectroscopy (UV-Vis) was used to identify the trans isoform of ResNPs which remained stable for at least 63 days. The additional qualitative analysis was performed by Fourier transform infrared spectroscopy (FTIR), while X-ray diffraction (XRD) determined the monoclinic structure of resveratrol with a significant difference in the intensity of diffraction peaks between commercial and nano-belt form. The morphology of ResNPs was evaluated by optical microscopy and field-emission scanning electron microscope (FE-SEM) that revealed a uniform nanobelt-like structure with an individual thickness of less than 1 μm. Bioactivity was confirmed using Artemia salina in vivo toxicity assay, while 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH) reduction assay showed the good antioxidative potential of concentrations of 100 μg/ml and lower. Microdilution assay on several reference strains and clinical isolates showed promising antibacterial potential on Staphylococci, with minimal inhibitory concentration (MIC) being 800 μg/ml. Bioactive glass-based scaffolds were coated with ResNPs and characterized to confirm coating potential. All of the above make these particles a promising bioactive, easy-to-handle component in various biomaterial formulations.

Chitosan-coated and thymol-loaded polymeric semi-interpenetrating hydrogels: An effective platform for bioactive molecule delivery and bone regeneration in vivo

Thymol (2-isopropyl-5-methylphenol; Thy) is a monoterpene phenolic phytocompound with medicinal properties; however, its impact on osteogenesis is yet to be thoroughly investigated. Its distribution is often hampered because of its intricate hydrophobic structure, which reduces its bioavailability. In this study, we synthesized a drug delivery vehicle using semi-interpenetrating polymer network (SIPN) hydrogels containing sodium alginate and poly(2-ethyl-2-oxazoline) (SA/Pox) loaded with Thy at varying concentrations (100, 150, and 200 μM). Subsequently, they were coated with chitosan (CS) to increase bioactivity and for sustained and prolonged release of Thy. Thy-loaded CS-coated SIPN hydrogels (SA/Pox/CS-Thy) were developed using ionic gelation and polyelectrolyte-complexation techniques. The addition of CS to hydrogels enhanced their physicochemical and material properties. These hydrogels were cytofriendly toward mouse mesenchymal stem cells (mMSCs). When mMSCs were cultured on hydrogels, Thy stimulated osteoblastic differentiation, as evidenced by calcium deposits at the cellular level. The expression of RUNX2, a key bone transcriptional factor, and other differentiation biomarkers was significantly enhanced in mMSCs cultured on SA/Pox/CS-Thy hydrogels. Notably, Thy in the SA/Pox/CS hydrogels significantly activated the TGF-β/BMP signaling pathway, which is involved in osteogenesis. A rat tibial bone defect model system revealed that the incorporation of Thy into SA/Pox/CS hydrogels augmented bone regeneration. Thus, sustained and prolonged release of Thy from the SA/Pox/CS hydrogels promoted osteoblast differentiation in vitro and bone formation in vivo. These findings shed light on the effect of Thy bioavailability in fostering osteoblast differentiation and its prospective application in bone rejuvenation.

Advent of phytobiologics and nano-interventions for bone remodeling: a comprehensive review

Bone metabolism constitutes the intricate processes of matrix deposition, mineralization, and resorption. Any imbalance in these processes leads to traumatic bone injuries and serious disease conditions. Therefore, bone remodeling plays a crucial role during the regeneration process maintaining the balance between osteoblastogenesis and osteoclastogenesis. Currently, numerous phytobiologics are emerging as the new therapeutics for the treatment of bone-related complications overcoming the synthetic drug-based side effects. They can either target osteoblasts, osteoclasts, or both through different mechanistic pathways for maintaining the bone remodeling process. Although phytobiologics have been widely used since tradition for the treatment of bone fractures recently, the research is accentuated toward the development of osteogenic phytobioactives, constituent-based drug designing models, and efficacious delivery of the phytobioactives. To achieve this, different plant extracts and successful isolation of their phytoconstituents are critical for osteogenic research. Hence, this review emphasizes the phytobioactives based research specifically enlisting the plants and their constituents used so far as bone therapeutics, their respective isolation procedures, and nanotechnological interventions in bone research. Also, the review enlists the vast array of folklore plants and the newly emerging nano-delivery systems in treating bone injuries as the future scope of research in the phytomedicinal orthopedic applications.

Antimicrobial effects of hydroxyapatite mosaicked polyvinyl alcohol-alginate semi-interpenetrating hydrogel-loaded with ethanolic extract of Glycyrrhiza glabra against oral pathogens

Glycyrrhiza glabra (GG) elicits protective effects against periodontal diseases. However, the sustained bioavailability of GG extract at therapeutic concentration warrants ideal delivery vehicles. Present study has focused on the design, fabrication, and evaluations of ethanolic-crude extract of GG-loaded semi-interpenetrating network (semi-IPN) hydrogel (HAAPS-GG) using alginic acid and polyvinyl alcohol (PVA) hydrogel mosaicked with HA for periodontal regeneration. The study has examined the performance of the hydrogel against the selected oral pathogens S. mutans, E. faecalis, L. acidophilus and C. albicans. HAAPS-GG was successfully fabricated and the surface functional groups were confirmed by attenuated total reflectance-infrared (ATR-IR) spectroscopy. HAAPS-GG displayed interconnecting pores, hydrophilicity and excellent water profile contributing to the biocompatibility as evident from direct contact and MTT assay in L929 fibroblasts. The hydrogel was mechanically stable and was immunocompatible owing to the relatively decreased levels of pro-inflammatory mediators COX2, 5LPO, iNOS and MPO in RAW 264.7 macrophages. In addition, the transcript analysis on RAW 264.7 revealed the down-regulation of inflammatory transcription factor NF-κβ and the pro-inflammatory cytokine TNF-α. Importantly, HAAPS-GG arrested the progression of periodontal pathogens predominantly S. mutans, and C. albicans as evident by disc diffusion assay, MTT assay and confocal microscopy. Overall, the HAAPS-GG system offers promising translational avenues in periodontal regeneration.

Thermo-Responsive Gel Containing Hydroxytyrosol-Chitosan Nanoparticles (Hyt@tgel) Counteracts the Increase of Osteoarthritis Biomarkers in Human Chondrocytes

Although osteoarthritis (OA) is a chronic inflammatory degenerative disease affecting millions of people worldwide, the current therapies are limited to palliative care and do not eliminate the necessity of surgical intervention in the most severe cases. Several dietary and nutraceutical factors, such as hydroxytyrosol (Hyt), have demonstrated beneficial effects in the prevention or treatment of OA both in vitro and in animal models. However, the therapeutic application of Hyt is limited due to its poor bioavailability following oral administration. In the present study, a localized drug delivery platform containing a combination of Hyt-loading chitosan nanoparticles (Hyt-NPs) and in situ forming hydrogel have been developed to obtain the benefits of both hydrogels and nanoparticles. This thermosensitive formulation, based on Pluronic F-127 (F-127), hyaluronic acid (HA) and Hyt-NPs (called Hyt@tgel) presents the unique ability to be injected in a minimally invasive way into a target region as a freely flowing solution at room temperature forming a gel at body temperature. The Hyt@tgel system showed reduced oxidative and inflammatory effects in the chondrocyte cellular model as well as a reduction in senescent cells after induction with H₂O₂. In addition, Hyt@tgel influenced chondrocytes gene expression under pathological state maintaining their metabolic activity and limiting the expression of critical OA-related genes in human chondrocytes treated with stressors promoting OA-like features. Hence, it can be concluded that the formulated hydrogel injection could be proposed for the efficient and sustained Hyt delivery for OA treatment. The next step would be the extraction of “added-value” bioactive polyphenols from by-products of the olive industry, in order to develop a green delivery system able not only to enhance the human wellbeing but also to promote a sustainable environment.

Food-Derived Bioactive Molecules from Mediterranean Diet: Nanotechnological Approaches and Waste Valorization as Strategies to Improve Human Wellness

The beneficial effects of the Mediterranean diet (MedDiet), the most widely followed healthy diet in the world, are principally due to the presence in the foods of secondary metabolites, mainly polyphenols, whose healthy characteristics are widely recognized. However, one of the biggest problems associated with the consumption of polyphenols as nutraceutical adjuvant concerns their bioavailability. During the last decades, different nanotechnological approaches have been developed to enhance polyphenol bioavailability, avoiding the metabolic modifications that lead to low absorption, and improving their retention time inside the organisms. This review focuses on the most recent findings regarding the encapsulation and delivery of the bioactive molecules present in the foods daily consumed in the MedDiet such as olive oil, wine, nuts, spice, and herbs. In addition, the possibility of recovering the polyphenols from food waste was also explored, taking into account the increased market demand of functional foods and the necessity to obtain valuable biomolecules at low cost and in high quantity. This circular economy strategy, therefore, represents an excellent approach to respond to both the growing demand of consumers for the maintenance of human wellness and the economic and ecological exigencies of our society.

Orsellinic acid-loaded chitosan nanoparticles in gelatin/nanohydroxyapatite scaffolds for bone formation in vitro

AIM

Orsellinic acid (2,4-Dimethoxy-6-methylbenzoic acid) (OA) is a hydrophobic polyphenolic compound with therapeutic potential, but its impact on actuating osteogenesis remains unknown. The bioavailability of OA is hampered by its hydrophobic nature. This study aimed to fabricate nano-drug delivery system-based scaffolds for OA and test its potential for osteogenesis in vitro.

MATERIALS AND METHODS

OA was loaded into chitosan nanoparticles (nCS + OA) using the ionic gelation technique at different concentrations. nCS + OA were incorporated onto the scaffolds containing gelatin (Gel) and nanohydroxyapatite (nHAp) by the lyophilization method. Biocomposite scaffolds were examined for their physicochemical and material characteristic properties. The effect of OA in the scaffolds for osteoblast differentiation was determined by alizarin red and von Kossa staining at the cellular level and by reverse transcriptase-qPCR and western blot analysis at the molecular level.

KEY FINDINGS

The scaffolds showed excellent physiochemical and material characteristics and remained cyto-friendly to mouse mesenchymal stem cells (mMSCs, C3H10T1/2). The release of OA from Gel/nHAp/nCS scaffolds enhanced the differentiation of mMSCs towards osteoblasts, as observed through cellular and molecular studies. Moreover, the osteogenic potential of OA was mediated by the activation of FAK and ERK signaling pathways through integrins.

SIGNIFICANCE

The inclusion of OA into Gel/nHAp/nCS biocomposite scaffolds at 80 μM concentration promoted osteoblast differentiation via cell adhesion mediated signaling, compared with that shown by Gel/nHAp/nCS alone. Overall, this study identified the potential therapeutic OA containing Gel/nHAp/nCS scaffolds, accelerating its potential for clinical application towards bone regeneration.

Fabrication and Characterization of Nanocomposite Hydrogel Based on Alginate/Nano-Hydroxyapatite Loaded with Linum usitatissimum Extract as a Bone Tissue Engineering Scaffold

In the current paper, we fabricated, characterized, and applied nanocomposite hydrogel based on alginate (Alg) and nano-hydroxyapatite (nHA) loaded with phenolic purified extracts from the aerial part of Linum usitatissimum (LOH) as the bone tissue engineering scaffold. nHA was synthesized based on the wet chemical technique/precipitation reaction and incorporated into Alg hydrogel as the filler via physical cross-linking. The characterizations (SEM, DLS, and Zeta potential) revealed that the synthesized nHA possess a plate-like shape with nanometric dimensions. The fabricated nanocomposite has a porous architecture with interconnected pores. The average pore size was in the range of 100–200 µm and the porosity range of 80–90%. The LOH release measurement showed that about 90% of the loaded drug was released within 12 h followed by a sustained release over 48 h. The in vitro assessments showed that the nanocomposite possesses significant antioxidant activity promoting bone regeneration. The hemolysis induction measurement showed that the nanocomposites were hemocompatible with negligible hemolysis induction. The cell viability/proliferation confirmed the biocompatibility of the nanocomposites, which induced proliferative effects in a dose-dependent manner. This study revealed the fabricated nanocomposites are bioactive and osteoactive applicable for bone tissue engineering applications.