Intraperitoneal drug delivery systems for peritoneal carcinomatosis: Bridging the gap between research and clinical implementation.

Several abdominal-located cancers develop metastasis within the peritoneum, what is called peritoneal carcinomatosis (PC), constituting a clinical challenge in their therapeutical management, often leading to poor prognoses. Current multidisciplinary strategies, including cytoreductive surgery (CRS), hyperthermic intraperitoneal chemotherapy (HIPEC), and pressurized intraperitoneal aerosol chemotherapy (PIPAC), demonstrate efficacy but have limitations. In response, alternative strategies are explored in the drug delivery field for intraperitoneal chemotherapy. Controlled drug delivery offers a promising avenue, maintaining localized drug concentrations for optimal PC management. Drug delivery systems (DDS), including hydrogels, implants, nanoparticles, and hybrid systems, show potential for sustained and region-specific drug release. The present review aims to offer an overview of the advances and current designs of DDS for PC chemotherapy administration, focusing on their composition, main characteristics, and principal experimental outcomes, highlighting the importance of biomaterial rationale design and in vitro/vivo models for their testing. Moreover, since clinical data for human subjects are scarce, we offer a critical discussion of the gap between bench and bedside in DDS translation, emphasizing the need for further research.

In Vitro Evaluation of Mangostanin as an Antimicrobial and Biocompatible Topical Antiseptic for Skin and Oral Tissues.

Skin and oral tissue infections pose significant health challenges worldwide, necessitating the exploration of new antiseptic agents that are both effective and biocompatible. This study evaluated the antibacterial efficacy and biocompatibility of mangostanin (MGTN), a xanthone derived from Garcinia mangostana L., against commercial antiseptics across various bacterial strains (Porphyromonas gingivalis, Streptococcus mutans, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and Cutibacterium acnes) and in vitro models of skin and oral tissues. MGTN demonstrated significant antimicrobial activity against all tested pathogens concurrently exhibiting negligible cytotoxic effects on human gingival fibroblasts as well as on three-dimensional (3D) models of human epidermis and oral epithelium. Furthermore, using pooled human saliva, MGTN effectively inhibited plaque biofilm formation, suggesting its potential as a natural, biocompatible antiseptic for skin and oral health applications. These findings position MGTN as a promising candidate for further development into antiseptic formulations, offering a natural alternative to current synthetic options.

Intra-articular injection of platelet lysate-derived extracellular vesicles recovers from knee osteoarthritis in an in vivo rat model.

Objective: MSCs and Platelet-Rich Plasma are the main focus in the study of new regenerative treatments aimed to reverse Osteoarthritis (OA). However, extracellular vesicles (EVs) present several advantages to cell-based treatments. Thus, the aim of this study was to compare and evaluate the regenerative potential of MSC-derived EVs (cEVs) and platelet-derived EVs (pEVs) in an OA cartilage rat model. Design: OA in vivo model was established through injection of 6 mg MIA in the rat knee joints. After 14 and 21 days, OA knee joints were treated with 1 × 1010 particles of pEVs or cEVs. At day 28, the animals were sacrificed, plasma was collected to quantify CTX-II and knee joints were excised to be evaluated by Cone Beam Computed Tomography (CBCT). After decalcification, histology was used to determine the OARSI score and to visualize collagen and glycosaminoglycan content. Results: pEVs and cEVs samples did not show significant differences per se but they did in terms of regenerative effects on OA knee joints. pEVs-treated knee joints showed better subchondral bone integrity in CT-analysed parameters when compared to cEVs or OA group, showing similar values to the healthy control group. Moreover, OARSI score indicated that pEVs showed a greater OA reversion in knee joints, especially in female rats, and so indicated the analysed histological images. Conclusions: pEVs are proposed as a viable regeneration treatment for OA since they are not only capable of exerting their regenerative potential on osteoarthritic cartilage, but also outperform cEVs in terms of efficacy, particularly in females. Significance statement: Osteoarthritis (OA) is one of the most age-related diseases. It is estimated that 500 million people suffer from OA worldwide, representing the principal cause of chronic disability in adults. In the present study we evaluated the therapeutic effect of extracellular vesicles (EVs) from different sources (platelet lysate and human umbilical cord mesenchymal stromal cells) in an in vivo rat model. Our results demonstrate that platelet-derived EVs (pEVs) induce an OA reversion in knee joints, thus evidencing the therapeutic potential of pEVs as cell-free regenerative agents for OA treatment. The translational potential of this article: Platelet-derived extracellular vesicles (pEVs) offer a promising cell-free therapy option for OA treatment. Their production could be easily standardized and reproduced without extensive platelet harvesting and amplification, thus paving the way for their clinical translation.

A Sequential Micro-Immunotherapy Medicine Increases Collagen Deposition in Human Gingival Fibroblasts and in an Engineered 3D Gingival Model under Inflammatory Conditions.

Periodontal therapies use immune mediators, but their side effects can increase with dosage. Micro-immunotherapy (MI) is a promising alternative that employs immune regulators at low and ultralow doses to minimize adverse effects. In this study, the effects of 5 capsules and the entire 10-capsule sequence of the sequential MI medicine (MIM-seq) were tested in two in vitro models of periodontitis. Firstly, human gingival fibroblasts (hGFs) exposed to interleukin (IL)-1ß to induce inflammation were treated with five different capsules of MIM-seq for 3 days or with MIM-seq for 24 days. Subsequently, MIM-seq was analyzed in a 3D model of human tissue equivalent of gingiva (GTE) under the same inflammatory stimulus. Simultaneously, a non-IL-1ß-treated control and a vehicle were included. The effects of the treatments on cytotoxicity, collagen deposition, and the secreted levels of IL-1α, IL-6, prostaglandin E2 (PGE2), matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of metalloproteinases-1 (TIMP-1) were evaluated. None of the tested items were cytotoxic. The complete sequence of MIM-seq decreased PGE2 release and restored collagen deposition levels induced by IL-1ß treatment in hGFs exposed to IL-1ß. MIM-seq treatment restored collagen production levels in both models. These promising preclinical findings suggest that MIM-seq should be further investigated for periodontitis treatment.

Induction of Periodontitis via a Combination of Ligature and Lipopolysaccharide Injection in a Rat Model.

Periodontitis (PD) is a highly prevalent, chronic immune-inflammatory disease of the periodontium, that results in a loss of gingival soft tissue, periodontal ligament, cementum, and alveolar bone. In this study, a simple method of PD induction in rats is described. We provide detailed instructions for placement of the ligature model around the first maxillary molars (M1) and a combination of injections of lipopolysaccharide (LPS), derived from Porphyromonas gingivalis at the mesio-palatal side of the M1. The induction of periodontitis was maintained for 14 days, promoting the accumulation of bacteria biofilm and inflammation. To validate the animal model, IL-1ß, a key inflammatory mediator, was determined by an immunoassay in the gingival crevicular fluid (GCF), and alveolar bone loss was calculated using cone beam computed tomography (CBCT). This technique was effective in promoting gingiva recession, alveolar bone loss, and an increase in IL-1ß levels in the GCF at the end of the experimental procedure after 14 days. This method was effective in inducing PD, thus being able to be used in studies on disease progression mechanisms and future possible treatments.

Synthesis and Modification of Gelatin Methacryloyl (GelMA) with Antibacterial Quaternary Groups and Its Potential for Periodontal Applications.

Gelatin methacryloyl (GelMA) hydrogels have been widely used for different biomedical applications due to their tunable physical characteristics and appropriate biological properties. In addition, GelMA could be modified with the addition of functional groups providing inherent antibacterial capabilities. Here, GelMA-based hydrogels were developed through the combination of a GelMA unmodified and modified polymer with quaternary ammonium groups (GelMAQ). The GelMAQ was synthesized from GelMA with a low degree of substitution of methacrylamide groups (DSMA) and grafted with glycidyltrimethylammonium chloride in the free amine groups of the lysine moieties present in the original gelatin. GelMAs with high DSMA and GelMAQ were combined 50/50% or 25/75% (w/w), respectively, and compared to controls GelMA and GelMA with added chlorhexidine (CHX) at 0.2%. The different hydrogels were characterized using 1H-NMR spectroscopy and swelling behavior and tested in (1) Porphyromonas gingivalis to evaluate their antibacterial properties and (2) human gingival fibroblast to evaluate their cell biocompatibility and regenerative properties. GelMA/GelMAQ 25/75% showed good antibacterial properties but also excellent biocompatibility and regenerative properties toward human fibroblasts in the wound healing assay. Taken together, these results suggest that the modification of GelMA with quaternary groups could facilitate periodontal tissue regeneration, with good biocompatibility and added antibacterial properties.

Customizing the extracellular vesicles release and effect by strategizing surface functionalization of titanium.

Metallic material functionalization with Extracellular Vesicles (EVs) is a desirable therapeutic approach to improve regenerative procedures. Among the different functionalization strategies available, here we have compared drop casting on machined Ti surfaces, drop casting on nanostructured TiO2 surfaces and polymeric entrapment with polydopamine. EVs are a heterogeneous population of communication nanovesicles released by cells that are being intensively investigated for their use in therapeutics. We have selected platelet derived EVs for Ti surface coating due to their demonstrated osteoinductive properties. Our results show that each functionalization strategy leads to differences in the size of EV populations attached to and released from the metallic implants, which, in turn, leads to variations in their osteogenic capability measured through alkaline phosphatase activity and calcium deposition. In conclusion, the functionalization strategy used has an important effect on the resulting implant functionality, probably due to the heterogeneous EVs nature. Thus, the methodological approach to metallic material functionalization should be carefully chosen when working with extracellular vesicles in order to obtain the desired therapeutic application.

Labeling of Extracellular Vesicles for Monitoring Migration and Uptake in Cartilage Explants.

Extracellular vesicles (EVs) are used in different studies to prove their potential as a cell-free treatment due to their cargo derived from their cellular source, such as platelet lysate (PL). When used as treatment, EVs are expected to enter the target cells and effect a response from these. In this research, PL-derived EVs have been studied as a cell-free treatment for osteoarthritis (OA). Thus, a method was set up to label EVs and test their uptake on cartilage explants. PL-derived EVs are labeled with the lipophilic dye PKH26, washed twice through a column, and then tested in an in vitro inflammation-driven OA model for 5 h after particle quantification by nanoparticle tracking analysis (NTA). Hourly, cartilage explants are fixed, paraffined, cut into 6 µm sections to mount on slides, and observed under a confocal microscope. This allows verification of whether EVs enter the target cells (chondrocytes) during this period and analyze their direct effect.

Comparative In Vitro Evaluation of Commercial Periodontal Gels on Antibacterial, Biocompatibility and Wound Healing Ability.

In the last years, several studies testing commercial periodontal gels that contain chlorhexidine (CHX) or other antibacterial agents, have raised concerns regarding their cytotoxicity in periodontal tissues. We aimed at comparing the biocompatibility but also the efficacy as regards to the antibacterial and wound healing ability of different commercial periodontal gels. In vitro human gingival fibroblasts (GF) and a 3D model of human tissue equivalents of gingiva (GTE) were used under inflammatory conditions to evaluate wound closure, cytotoxicity and gene expression. Antibacterial effects were also investigated on Porphyromonas gingivalis growth, viability and gingipain activity. In GF and in the bacterial study, we found cytotoxic effects on GF and a high inhibition on bacterial growth rate in gels containing CHX, asiaticoside, enoxolone, cetylpyridinium chloride, propolis and eugenol. Of the two gels that were non-cytotoxic, Syntoss Biogel (containing chondrontin sulfate) and Emdogain (EMD, containing amelogenin and propylene glycol alginate), EMD showed the best wound closure, with no effect on P. gingivalis growth but decreased gingipain activity. On the other hand, Syntoss Biogel reduced viability and gingipain activity of P. gingivalis, but lack wound healing capacity. In the 3D GTE, Syntoss Biogel and EMD showed a good biocompatibility. Among all the tested gels, formulations containing CHX, asiaticoside, enoxolone, cetylpyridinium chloride, propolis and eugenol showed high antibacterial effect but also showed high cytotoxicity in eukaryotic cells. EMD was the one with the best biocompatibility and wound healing ability at the conditions tested.

Platelet-Derived Extracellular Vesicle Functionalization of Ti Implants.

Extracellular Vesicles (EVs) are biological nanovesicles that play a key role in cell communication. Their content includes active biomolecules such as proteins and nucleic acids, which present great potential in regenerative medicine. More recently, EVs derived from Platelet Lysate (PL) have shown an osteogenic capability comparable to PL. Besides, biomaterials are frequently used in orthopedics or dental restoration. Here, we provide a method to functionalize Ti surfaces with PL-derived EVs in order to improve their osteogenic properties. EVs are isolated from PL by size exclusion chromatography, and afterward Ti surfaces are functionalized with PL-EVs by drop casting. Functionalization is proven by EVs release and its biocompatibility by the lactate dehydrogenase (LDH) release assay.

BMP4 micro-immunotherapy increases collagen deposition and reduces PGE2 release in human gingival fibroblasts and increases tissue viability of engineered 3D gingiva under inflammatory conditions.

BACKGROUND: We aimed to evaluate the effect of low doses (LD) bone morphogenetic protein-2 (BMP2) and BMP4 micro-immunotherapy (MI) in two in vitro models of periodontal wound healing/regeneration. METHODS: We first evaluated the effect of LD of BMP2 and BMP4 MI on a 2D cell culture using human gingival fibroblasts (hGF) under inflammatory conditions induced by IL1ß. Biocompatibility, inflammatory response (Prostaglandin E2 (PGE2) release), collagen deposition and release of extracellular matrix (ECM) organization-related enzymes (matrix metalloproteinase-1 (MMP1) and metalloproteinase inhibitor 1 (TIMP1)) were evaluated after short (3 days) and long-term (24 days) treatment with BMP2 or BMP4 MI. Then, given the results obtained in the 2D cell culture, LD BMP4 MI treatment was evaluated in a 3D cell culture model of human tissue equivalent of gingiva (GTE) under the same inflammatory stimulus, evaluating the biocompatibility, inflammatory response and effect on MMP1 and TIMP1 release. RESULTS: LD BMP4 was able to decrease the release of the inflammatory mediator PGE2 and completely re-establish the impaired collagen metabolism induced by IL1ß treatment. In the 3D model, LD BMP4 treatment improved tissue viability compared with the vehicle, with similar levels to 3D tissues without inflammation. No significant effects were observed on PGE2 levels nor MMP1/TIMP1 ratio after LD BMP4 treatment, although a tendency to decrease PGE2 levels was observed after 3 days. CONCLUSIONS: LD BMP4 MI treatment shows anti-inflammatory and regenerative properties on hGF, and improved viability of 3D gingiva under inflammatory conditions. LD BMP4 MI treatment could be used on primary prevention or maintenance care of periodontitis.

Purity Determines the Effect of Extracellular Vesicles Derived from Mesenchymal Stromal Cells.

Extracellular vesicles (EVs) have been recently identified as vital components of cell-based therapies based on the observation that conditioned media from cultured stromal cells reproduce some of the beneficial effects of intact cells. In order to obtain clinically active EVs derived from Mesenchymal Stromal Cells (MSCs) different procedures have been reported in the literature. Usually, non-confluent cells are incubated with culture medium for 48 h either with EV-depleted Fetal Bovine Serum (FBS) or without FBS. Our aim was to compare the effects of EVs isolated by ultracentrifugation from human umbilical cord MSC conditioned media obtained using these two conditions: with EV-depleted FBS (UC) or without FBS (UCw/o) on the mRNA expression levels of extracellular matrix related genes using the mouse chondrogenic cell line ATDC-5. We observed a deleterious effect on chondrogenic cells treated with UCw/o, showing higher mRNA expression levels of different metalloproteinases and decorin (Dcn) and lower collagen (Col1a1 and Col2a1) and aggrecan (Acan) mRNA levels. To elucidate whether this deleterious effect was induced by the EVs or by any proteins co-purified in the EV pellet, we used size exclusion chromatography (SEC) to further purify the EV pellet, obtaining an EV enriched fraction (EV or EVw/o) and a protein enriched fraction (Prot or Protw/o). Our results pointed that the negative effect on the chondrogenic cell line was due to the contaminant proteins coisolated with the EVs by ultracentrifugation and not from the EVs themselves. Thus, these results highlight the importance of working with well purified EV preparations to specifically achieve their therapeutic effect.

Oriented Cell Alignment Induced by a Nanostructured Titanium Surface Enhances Expression of Cell Differentiation Markers.

A key factor for dental implant success is a good sealing between the implant surface and both soft (gum) and hard (bone) tissues. Surface nanotopography can modulate cell response through mechanotransduction. The main objective of this research was the development of nanostructured titanium (Ti) surfaces that promote both soft and hard tissue integration with potential application in dental implants. Nanostructured Ti surfaces were developed by electrochemical anodization-nanopores (NPs) and nanonets (NNs)-and characterized by atomic force microscopy, scanning electronic microscopy, and contact angle analysis. In addition, nanoparticle release and apoptosis activation were analyzed on cell culture. NP surfaces showed nanoparticle release, which increased in vitro cell apoptosis. Primary human gingival fibroblasts (hGFs) and human bone marrow mesenchymal stem cells (hBM-MSCs) were used to test cell adhesion, cytotoxicity, metabolic activity, and differentiation markers. Finally, cell orientation on the different surfaces was analyzed using a phalloidin staining. NN surfaces induced an oriented alignment of both cell types, leading in turn to an improved expression of differentiation markers. Our results suggest that NN structuration of Ti surfaces has great potential to be used for dental implant abutments to improve both soft and hard tissue integration.

Tuning Nanopore Diameter of Titanium Surfaces to Improve Human Gingival Fibroblast Response.

The aim of this study was to determine the optimal nanopore diameter of titanium nanostructured surfaces to improve human gingival fibroblast (hGF) response, with the purpose of promoting gingiva integration to dental implant abutments. Two TiO2 nanoporous groups with different diameters (NP-S ~48 nm and NP-B ~74 nm) were grown on Ti foils using an organic electrolyte containing fluoride by electrochemical oxidation, varying the applied voltage and the interelectrode spacing. The surfaces were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), and contact angle. The hGF were cultured onto the different surfaces, and metabolic activity, cytotoxicity, cell adhesion, and gene expression were analyzed. Bigger porous diameters (NP-B) were obtained by increasing the voltage used during anodization. To obtain the smallest diameter (NP-S), apart from lowering the voltage, a lower interelectrode spacing was needed. The greatest surface area and number of peaks was found for NP-B, despite these samples not being the roughest as defined by Ra. NP-B had a better cellular response compared to NP-S. However, these effects had a significant dependence on the cell donor. In conclusion, nanoporous groups with a diameter in the range of 74 nm induce a better hGF response, which may be beneficial for an effective soft tissue integration around the implant.

Evaluation of the Ideal Implant Insertion Time in Human Bone Biopsies After Sinus Elevation Using a Combination of Autologous Bone and Graft Substitute.

PURPOSE: To evaluate the ideal implant insertion time in human bone biopsies after sinus elevation with a composite graft consisting of an equal amount of biomaterial and autologous bone, by comparing the bone regeneration obtained 4 to 5 months after surgery with that obtained after 6 to 8 months, and using the adjacent native bone as reference. MATERIALS AND METHODS: Twenty-six biopsy specimens of 11 patients were analyzed. Two groups were created depending on the time of implant insertion: group t1 at 4 to 5 months (n = 13) and group t2 at 6 to 8 months (n = 13). The same volume of grafted bone and native bone were analyzed for each biopsy with microcomputed tomography (microCT) and gene expression analysis. RESULTS: Statistically significant differences were found in bone mineral density (BMD), bone volume fraction, and trabecular separation (TbSp) between native and grafted bone in both groups, with higher grafted bone values, except for the variable TbSp, which was lower in the grafted bone. This decrease in TbSp in the grafted bone in both groups can be explained by the significant increase in trabecular thickness in group t2 and the trabecular number in group t1, compared with native bone. No significant differences were found between the two groups in the morphometric parameters and BMD of the grafted bone. Also, no significant changes in the messenger RNA (mRNA) levels of bone formation, bone resorption, and inflammatory markers were found between both groups, with the exception that alkaline phosphatase mRNA levels were significantly lower in group t1 relative to native bone. CONCLUSION: This composite graft showed no differences in three-dimensional microstructure, BMD, or at the molecular level between 4 to 5 months and 6 to 8 months of healing time. Thus, this time can be shortened to 4 months with the security of a grafted area of mature bone.

Bioinspired Quercitrin Nanocoatings: A Fluorescence-Based Method for Their Surface Quantification, and Their Effect on Stem Cell Adhesion and Differentiation to the Osteoblastic Lineage.

Polyphenol-based coatings have several potential applications in medical devices, such as cardiovascular stents, contrast agents, drug delivery systems, or bone implants, due to the multiple bioactive functionalities of these compounds. In a previous study, we fabricated titanium surfaces functionalized with flavonoids through covalent chemistry, and observed their osteogenic, anti-inflammatory, and antifibrotic properties in vitro. In this work, we report a fluorescence-based method for the quantification of the amount of flavonoid grafted onto the surfaces, using 2-aminoethyl diphenylborinate, a boronic ester that spontaneously forms a fluorescent complex with flavonoids. The method is sensitive, simple, rapid, and easy to perform with routine equipment, and could be applied to determine the surface coverage of other plant-derived polyphenol-based coatings. Besides, we evaluated an approach based on reductive amination to covalently graft the flavonoid quercitrin to Ti substrates, and optimized the grafting conditions. Depending on the reaction conditions, the amount of quercitrin grafted was between 64 ± 10 and 842 ± 361 nmol on 6.2 mm Ti coins. Finally, we evaluated the in vitro behavior of bone-marrow-derived human mesenchymal stem cells cultured on the quercitrin nanocoated Ti surfaces. The surfaces functionalized with quercitrin showed a faster stem cell adhesion than control surfaces, probably due to the presence of the catechol groups of quercitrin on the surfaces. A rapid cell adhesion is crucial for the successful performance of an implant. Furthermore, quercitrin-nanocoated surfaces enhanced the mineralization of the cells after 21 days of cell culture. These results indicate that quercitrin nanocoatings could promote the rapid osteointegration of bone implants.

A new role for 5-methoxytryptophol on bone cells function in vitro.

The present study investigates the direct action of 5-methoxytryptophol (5-MTX) in both MC3T3-E1 and RAW264.7 cells and compares it with melatonin (MEL), another 5-methoxyindol known to play a significant role on bone metabolism. We first screened increasing doses of both 5-MTX and MEL to determine their effect on metabolic activity and viability of preosteoblastic MC3T3-E1 cells. The optimal dose was used to determine its effect on differentiation of MC3T3-E1 cells and preosteoclastic RAW264.7 cells. Finally, we investigated the mechanism of action by adding the melatonin receptor antagonist luzindole (LUZ) and detecting the immunostaining of phospho-ERK. In MC3T3-E1 cells, most of the 5-MTX doses reduced slightly the metabolic activity of osteoblasts compared with the control, while MEL only decreased it for the highest dose (2.5 mM). As regards to cytotoxicity, low doses (0.001-0.1 mM) of both indoles showed a protective effect on osteoblasts, while the highest dose of MEL showed a higher cytotoxicity than the 5-MTX one. After 14 days of cell culture, Rankl mRNA levels were decreased, especially for 5-MTX. 5-MTX also induced a higher osteocalcin secretion and mineralization capacity than MEL. In RAW264.7 cells, 5-MTX decreased the number of osteoclast formed and its activity whereas MEL did not affect significantly the number of multinucleated TRAP-positive cells formed and showed a lower activity. Finally, MEL and 5-MTX promoted activation of the ERK1/2 pathway through the phosphorylation of ERK, while LUZ addition suppressed this effect. In conclusion, the present study demonstrates a new role of 5-MTX inhibiting osteoclastogenesis and promoting osteoblast differentiation.

Effect of proline-rich synthetic peptide-coated titanium implants on bone healing in a rabbit model.

PURPOSE: Previous studies have demonstrated the capacity of a designed proline-rich synthetic peptide to stimulate osteoblast differentiation and biomineralization in vitro. Therefore, the aim of the present study was to evaluate the osseointegration capacity of titanium (Ti) implants coated with these peptides in a rabbit model. MATERIALS AND METHODS: Four calibrated defects were prepared in the tibiae of three New Zealand rabbits, and the defects were randomized into a test group (peptide-modified machined Ti implant) and a control group (unmodified machined Ti implant). The performance in vivo was investigated after 4 weeks of implantation by real-time reverse transcriptase polymerase chain reaction of bone and inflammatory markers, microcomputed tomographic analysis of mineralized bone, and histologic examination. RESULTS: The peptides adsorbed in agglomerates on Ti and underwent a change in secondary structure upon adsorption, which induced an increase in surface wettability. Gene expression markers indicated that peptide-coated Ti implants had significantly decreased mRNA levels of tartrate-resistant acid phosphatase. A trend toward increased osteocalcin in the peri-implant bone tissue was also seen. Bone morphometric and histologic parameters did not show significant differences, although the peptide group showed a higher percentage of new bone histologically. CONCLUSIONS: Proline-rich peptides have potential as a biocompatible coating for promoting osseointegration of Ti implants by reducing bone resorption.

Quercitrin and taxifolin stimulate osteoblast differentiation in MC3T3-E1 cells and inhibit osteoclastogenesis in RAW 264.7 cells.

Flavonoids are natural antioxidants that positively influence bone metabolism. The present study screened among different flavonoids to identify biomolecules for potential use in bone regeneration. For this purpose, we used MC3T3-E1 and RAW264.7 cells to evaluate their effect on cell viability and cell differentiation. First, different doses of chrysin, diosmetin, galangin, quercitrin and taxifolin were analyzed to determine the optimum concentration to induce osteoblast differentiation. After 48h of treatment, doses ≥100µM of diosmetin and galangin and also 500µM taxifolin revealed a toxic effect on cells. The same effect was observed in cells treated with doses ≥100µM of chrysin after 14 days of treatment. However, the safe doses of quercitrin (200 and 500µM) and taxifolin (100 and 200µM) induced bone sialoprotein and osteocalcin mRNA expression. Also higher osteocalcin secreted levels were determined in 100µM taxifolin osteoblast treated samples when compared with the control ones. On the other hand, quercitrin and taxifolin decreased Rankl gene expression in osteoblasts, suggesting an inhibition of osteoclast formation. Indeed, osteoclastogenesis suppression by quercitrin and taxifolin treatment was observed in RAW264.7 cells. Based on these findings, the present study demonstrates that quercitrin and taxifolin promote osteoblast differentiation in MC3T3-E1 cells and also inhibit osteoclastogenesis in RAW264.7 cells, showing a positive effect of these flavonoids on bone metabolism.