Novel Ti surface coated with PVA hydrogel and chitosan nanoparticles with antibacterial drug release: An experimental in vitro study

OBJECTIVES

The aims of this study were to design a novel titanium surface coated with a PVA hydrogel matrix and chitosan-based nanoparticles and to investigate the antibiotic release and its ability to inhibit microbial activity.

METHODS

Two drug delivery systems were developed and mixed. Chitosan-based nanoparticles (NP) and a polyvinyl alcohol film (PVA). The size, ζ-potential, stability, adhesive properties, and encapsulation profile of NP, as well as the release kinetics of drug delivery systems and their antimicrobial ability of PVA and PVANP films, were studied on Ti surfaces. The systems were loaded with doxycycline, vancomycin, and doxepin hydrochloride.

RESULTS

Nanoparticles presented a ζ-potential greater than 30 mV for 45 days and the efficiency drug encapsulation was 26.88% ± 1.51% for doxycycline, 16.09% ± 10.24% for vancomycin and 17.57% ± 11.08% for doxepin. In addition, PVA films were loaded with 125 μg/mL of doxycycline, 125 μg/mL of vancomycin, and 100 μg/mL of doxepin. PVANP-doxycycline achieved the antibacterial effect at 4 h while PVA-doxycycline maintained its effect at 24 h.

Smart stimuli-responsive strategies for titanium implant functionalization in bone regeneration and therapeutics

With the increasing and aging of global population, there is a dramatic rise in the demand for implants or substitutes to rehabilitate bone-related disorders which can considerably decrease quality of life and even endanger lives. Though titanium and its alloys have been applied as the mainstream material to fabricate implants for load-bearing bone defect restoration or temporary internal fixation devices for bone fractures, it is far from rare to encounter failed cases in clinical practice, particularly with pathological factors involved. In recent years, smart stimuli-responsive (SSR) strategies have been conducted to functionalize titanium implants to improve bone regeneration in pathological conditions, such as bacterial infection, chronic inflammation, tumor and diabetes mellitus, etc. SSR implants can exert on-demand therapeutic and/or pro-regenerative effects in response to externally applied stimuli (such as photostimulation, magnetic field, electrical and ultrasound stimulation) or internal pathology-related microenvironment changes (such as decreased pH value, specific enzyme secreted by bacterial and excessive production of reactive oxygen species). This review summarizes recent progress on the material design and fabrication, responsive mechanisms, and in vitro and in vivo evaluations for versatile clinical applications of SSR titanium implants. In addition, currently existing limitations and challenges and further prospective directions of these strategies are also discussed.

The paradigm of miRNA and siRNA influence in Oral-biome

Short nucleotide sequences like miRNA and siRNA have attracted a lot of interest in Oral-biome investigations. miRNA is a small class of non-coding RNA that regulates gene expression to provide effective regulation of post-transcription. On contrary, siRNA is 21-25 nucleotide dsRNA impairing gene function post-transcriptionally through inhibition of mRNA for homologous dependent gene silencing. This review highlights the application of miRNA in oral biome including oral cancer, dental implants, periodontal diseases, gingival fibroblasts, oral submucous fibrosis, radiation-induced oral mucositis, dental Pulp, and oral lichenoid disease. Moreover, we have also discussed the application of siRNA against the aforementioned disease along with the impact of miRNA and siRNA to the various pathways and molecular effectors pertaining to the dental diseases. The influence of upregulation and downregulation of molecular effector post-treatment with miRNA and siRNA and their impact on the clinical setting has been elucidated. Thus, the mentioned details on application of miRNA and siRNA will provide a novel gateway to the scholars to not only mitigate the long-lasting issue in dentistry but also develop new theragnostic approaches.

Gene-activated titanium implants for gene delivery to enhance osseointegration

Osseointegration is the direct and intimate contact between mineralized tissue and titanium implant at the bone-implant interface. Early establishment and stable maintenance of osseointegration is the key to long-term implant success. However, in patients with compromised conditions such as osteoporosis and patients beginning early load-bearing activities such as walking, lower osseointegration around titanium implants is often observed, which might result in implant early failure. Gene-activated implants show an exciting prospect of combining gene delivery and biomedical implants to solve the problems of poor osseointegration formation, overcoming the shortcomings of protein therapy, including rapid degradation and overdose adverse effects. The conception of gene-activated titanium implants is based on "gene-activated matrix" (GAM), which means scaffolds using non-viral vectors for in situ gene delivery to achieve a long-term and efficient transfection of target cells. Current preclinical studies in animal models have shown that plasmid DNA (pDNA), microRNA (miRNA), and small interference RNA (siRNA) functionalized titanium implants can enhance osseointegration with safety and efficiency, leading to the expectation of applying this technique in dental and orthopedic clinical scenarios. This review aims to comprehensively summarize fabrication strategies, current applications, and futural outlooks of gene-activated implants, emphasizing nucleic acid targets, non-viral vectors, implant surface modification techniques, nucleic acid/vector complexes loading strategies.

Selenomethionine-Modified Polyethylenimine-Based Nanoparticles Loaded with miR-132-3p Inhibitor-Biofunctionalized Titanium Implants for Improved Osteointegration

Titanium and its alloys have been widely used as bone implants, but for reduced treatment span, improvements are urgently needed to achieve faster and better osteointegration. In this study, we found that miR-132-3p inhibited bone-marrow-derived stem cell (BMSC) osteogenic differentiation via targeting BMP2, and that inhibiting miR-132-3p could significantly improve the osteogenic capability of BMSCs. Moreover, we fabricated a biocompatible selenomethionine (SEMET)-modified polyethylene glycol (PEG)/polyethylenimine (PEI) nanoparticle (SeNP) cross-linked with 0.2% gelatin solutions and delivered miR-132-3p inhibitor to biofunctionalize alkali heat-treated titanium implants, resulting in the development of a novel coating for reverse transfection. The biological performances of PEG/PEI/miR-132-3p inhibitor and SeNP/miR-132-3p inhibitor-biofunctionalized titanium were compared. The biological effects, including cell viability, cytotoxicity, adhesion, cellular uptake, and osteogenic capacity of SeNP/miR-132-3p inhibitor-biofunctionalized titanium implants, were then assessed. Results showed that SeNPs presented appropriate morphology, diameter, and positive zeta potential for efficient gene delivery. The transfection efficiency of the SeNP/miR-132-3p inhibitor was comparable to that of the PEG/PEI/miR-132-3p inhibitor, but the former induced less reactive oxygen species (ROS) production and lower apoptosis rates. Confocal laser scanning microscopy (CLSM) demonstrated that SeNP/miR-132-3p inhibitor nanoparticles released from the titanium surfaces and were taken up by adherent BMSCs. In addition, the release profile showed that transfection could obtain a long-lasting silencing effect for more than 2 weeks. The cell viability, cytotoxicity, and cell spreading of SeNP/miRNA-132-3p inhibitor-biofunctionalized titanium were comparable with those of untreated titanium and the SeNP/miRNA-132-3p inhibitor negative control (NC)-biofunctionalized titanium but resulted in higher ALP activity and osteogenic gene expression levels. In vivo animal studies further certified that SeNP/miRNA-132-3p inhibitor nanoparticles from titanium surfaces promoted osteointegration, which was revealed by microcomputed tomography (micro-CT) and histological observations. Taken together, these findings suggested that selenomethionine-modified PEI-based nanoparticles could achieve better biocompatibility. Moreover, titanium implants biofunctionalized by SeNP/miRNA-132-3p inhibitor nanoparticles might have significant clinical potential for more effective osteointegration.

A novel tunable, highly biocompatible and injectable DNA-chitosan hybrid hydrogel fabricated by electrostatic interaction between chitosan and DNA backbone

The injectable hydrogel is an ideal reservoir for drug delivery. In this study, a new injectable DNA hydrogel was fabricated. Firstly, the DNA pre-gel was obtained by heat-cool treatments to induce cross-linkage through base-paring. Then, the pre-gel was cross-linked with chitosan (CS) through electrostatic interaction, which was confirmed by ATR-FTIR and XPS analysis. The DNA-CS hybrid gel showed finely tunable various properties such as porosity and viscosity. To simulate the biomedical application, the dexamethasone (Dex) was loaded into the gel and coated onto titanium implant surface to induce macrophages M2 polarization. Due to the excellent biocompatibility and Dex delivery, the decorated implant surface was favorable for RAW264.7 cells growth and showed powerful effects of inducing M2 polarization both in vitro and in vivo. In conclusion, it is the first report of DNA hydrogel synthesis via CS cross-linkage and the injectable DNA-CS hybrid gel was superb for therapeutic delivery.

Chitosan-miRNA functionalized microporous titanium oxide surfaces via a layer-by-layer approach with a sustained release profile for enhanced osteogenic activity

BACKGROUND

The biofunctionalization of titanium implants for high osteogenic ability is a promising approach for the development of advanced implants to promote osseointegration, especially in compromised bone conditions. In this study, polyelectrolyte multilayers (PEMs) were fabricated using the layer-by-layer approach with a chitosan-miRNA (CS-miRNA) complex and sodium hyaluronate (HA) as the positively and negatively charged polyelectrolytes on microarc-oxidized (MAO) Ti surfaces via silane-glutaraldehyde coupling.

METHODS

Dynamic contact angle and scanning electron microscopy measurements were conducted to monitor the layer accumulation. RiboGreen was used to quantify the miRNA loading and release profile in phosphate-buffered saline. The in vitro transfection efficiency and the cytotoxicity were investigated after seeding mesenchymal stem cells (MSCs) on the CS-antimiR-138/HA PEM-functionalized microporous Ti surface. The in vitro osteogenic differentiation of the MSCs and the in vivo osseointegration were also evaluated.

RESULTS

The surface wettability alternately changed during the formation of PEMs. The CS-miRNA nanoparticles were distributed evenly across the MAO surface. The miRNA loading increased with increasing bilayer number. More importantly, a sustained miRNA release was obtained over a timeframe of approximately 2 weeks. In vitro transfection revealed that the CS-antimiR-138 nanoparticles were taken up efficiently by the cells and caused significant knockdown of miR-138 without showing significant cytotoxicity. The CS-antimiR-138/HA PEM surface enhanced the osteogenic differentiation of MSCs in terms of enhanced alkaline phosphatase, collagen production and extracellular matrix mineralization. Substantially enhanced in vivo osseointegration was observed in the rat model.

CONCLUSIONS

The findings demonstrated that the novel CS-antimiR-138/HA PEM-functionalized microporous Ti implant exhibited sustained release of CS-antimiR-138, and notably enhanced the in vitro osteogenic differentiation of MSCs and in vivo osseointegration. This novel miRNA-functionalized Ti implant may be used in the clinical setting to allow for more effective and robust osseointegration.

The non-viral vectors and main methods of loading siRNA onto the titanium implants and their application

Surface modification of titanium implants by siRNA is quite efficient for improving implant osseointegration. Loading siRNA onto their surface is a crucial factor for siRNA-functionalized implants to realize their biological function. Direct binding of siRNA to implants has low siRNA binding and releasing rate, so usually it needs to be mediated by vectors. Polymeric, nonmaterial-mediated and lipid-based vectors are types of non-viral vectors which are commonly used for delivering siRNA. Three major methods of loading process, namely simple physical adsorption, layer-by-layer assembly and electrodeposition, are also summarized. A brief introduction, the basic principle and the general procedure of each method are included. The loading efficiency, which can be measured both qualitatively and quantitatively, together with gene knockdown efficiency, cytotoxicity assay and osteogenesis of the three methods are compared. A good many applications in osteogenesis have also been described in this review.

Insights into Theranostic Properties of Titanium Dioxide for Nanomedicine

Titanium dioxide (TiO2) nanostructures exhibit a broad range of theranostic properties that make them attractive for biomedical applications. TiO2 nanostructures promise to improve current theranostic strategies by leveraging the enhanced quantum confinement, thermal conversion, specific surface area, and surface activity. This review highlights certain important aspects of fabrication strategies, which are employed to generate multifunctional TiO2 nanostructures, while outlining post-fabrication techniques with an emphasis on their suitability for nanomedicine. The biodistribution, toxicity, biocompatibility, cellular adhesion, and endocytosis of these nanostructures, when exposed to biological microenvironments, are examined in regard to their geometry, size, and surface chemistry. The final section focuses on recent biomedical applications of TiO2 nanostructures, specifically evaluating therapeutic delivery, photodynamic and sonodynamic therapy, bioimaging, biosensing, tissue regeneration, as well as chronic wound healing.

Role of ILK/p38 pathway in mediating the enhanced osteogenic differentiation of bone marrow mesenchymal stem cells on amorphous carbon coating

Amorphous carbon (a-C) film is a promising candidate for metallic implant surface coatings to improve corrosion resistance and osteogenesis in vivo.

Calcium-MicroRNA Complex-Functionalized Nanotubular Implant Surface for Highly Efficient Transfection and Enhanced Osteogenesis of Mesenchymal Stem Cells

Controlling mesenchymal stem cell (MSC) differentiation by RNA interference (RNAi) is a promising approach for next-generation regenerative medicine. However, efficient delivery of RNAi therapeutics is still a limiting factor. In this study, we have developed a simple, biocompatible, and highly effective delivery method of small RNA therapeutics into human MSCs (hMSCs) from an implant surface by calcium ions. First, we demonstrated that simple Ca/siRNA targeting green fluorescent protein (GFP) nanocomplexes were able to efficiently silence GFP in GFP-expressing hMSCs with adequate Ca²⁺ concentration (>5 mM). In addition, a single transfection could obtain a long-lasting silencing effect for more than 2 weeks. All three of the main endocytosis pathways (clathrin- and caveolin-mediated endocytosis and macropinocytosis) were involved in the internalization of the Ca/siRNA complexes by MSCs, and macropinocytosis plays the most dominant role. Furthermore, the Ca/siRNA complexes could be efficiently loaded onto the titanium implant surface when pretreated with anodization to create a nanotube (NT) layer. Because of the hydrophilic property of the NT surface, the Ca/siRNA was quickly loaded (less than 4 h) with high efficiency (nearly 100%), forming an even amorphous coating. The Ca/siRNA-coated NT surface showed an initial burst release of 80% of the siRNA complexes over 2 h, which is adequate to achieve robust gene silencing of attached hMSCs. To demonstrate the therapeutic potential of our Ca/siRNA coating technology, Ca/antimiR-138 complexes were loaded on to the NT surface, which strongly enhanced the osteogenic differentiation of hMSCs. In conclusion, our findings suggest that Ca²⁺ is an effective and biocompatible carrier to deliver small RNA therapeutics into hMSCs, both in solution and from functionalized surfaces, which provides a novel approach to control the MSC differentiation and tissue regeneration.

Dual-Functionalized Graphene Oxide Based siRNA Delivery System for Implant Surface Biomodification with Enhanced Osteogenesis

Surface functionalization by small interfering RNA (siRNA) is a novel strategy for improved implant osseointegration. A gene delivery system with safety and high transfection activity is a crucial factor for an siRNA-functionalized implant to exert its biological function. To this end, polyethylene glycol (PEG) and polyethylenimine (PEI) dual-functionalized graphene oxide (GO; nGO-PEG-PEI) may present a promising siRNA vector. In this study, nanosized nGO-PEG-PEI was prepared and optimized for siRNA delivery. Titania nanotubes (NTs) fabricated by anodic oxidation were biomodified with nGO-PEG-PEI/siRNA by cathodic electrodeposition, designated as NT-GPP/siRNA. NT-GPP/siRNA possessed benign cytocompatibility, as evaluated by cell adhesion and proliferation. Cellular uptake and knockdown efficiency of the NT-GPP/siRNA were assessed by MC3T3-E1 cells, which exhibited high siRNA delivery efficiency and sustained target gene silencing. Casein kinase-2 interacting protein-1 (Ckip-1) is a negative regulator of bone formation. siRNA-targeting Ckip-1 (siCkip-1) was introduced to the implant, and a series of in vitro and in vivo experiments were carried out to evaluate the osteogenic capacity of NT-GPP/siCkip-1. NT-GPP/siCkip-1 dramatically improved the in vitro osteogenic differentiation of MC3T3-E1 cells in terms of improved osteogenesis-related gene expression, and increased alkaline phosphatase (ALP) production, collagen secretion, and extracellular matrix (ECM) mineralization. Moreover, NT-GPP/siCkip-1 led to apparently enhanced in vivo osseointegration, as indicated by histological staining and EDX line scanning. Collectively, these findings suggest that NT-GPP/siRNA represents a practicable and promising approach for implant functionalization, showing clinical potential for dental and orthopedic applications.

Effects of tripolyphosphate on cellular uptake and RNA interference efficiency of chitosan-based nanoparticles in Raw 264.7 macrophages

Tumor necrosis factor-α (TNF-α) is a major pro-inflammatory cytokine that is mainly secreted by macrophages during inflammation. Here, we synthesized a series of N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan chlorides (HTCCs), and then used a complex coacervation technique or tripolyphosphate (TPP)-assisted ionotropic gelation strategy to complex the HTCCs with TNF-α siRNA (siTNF) to form nanoparticles (NPs). The resultant NPs had a desirable particle size (210-279nm), a slightly positive zeta potential (14-22mV), and negligible cytotoxicity against Raw 264.7 macrophages and colon-26 cells. Subsequent cellular uptake tests demonstrated that the introduction of TPP to the NPs markedly increased their cellular uptake efficiency (to nearly 100%) compared with TPP-free NPs, and yielded a correspondingly higher intracellular concentration of siRNA. Critically, in vitro gene silencing experiments revealed that all of the TPP-containing NPs showed excellent efficiency in inhibiting the mRNA expression level of TNF-α (by approximately 85-92%, which was much higher than that obtained using Oligofectamine/siTNF complexes). Collectively, these results obviously suggest that our non-toxic TPP-containing chitosan-based NPs can be exploited as efficient siTNF carriers for the treatment of inflammatory diseases.

Antibacterial and biological properties of biofunctionalized nanocomposites on titanium for implant application

Titanium implants possessing excellent antibacterial activity are highly desirable for the prevention of implant-associated infections. In this study, we demonstrate a simple one-step, water-based procedure for the fabrication of biofunctionalized nanocomposites on titanium for implant application. The formation of biofunctionalized silver nanoparticles with varied biomolecule templates is confirmed by Fourier-transform infrared spectroscopic, contact angle, field-emission scanning electron microscopy, and inductively coupled plasma atomic emission spectrometry analysis. Antibacterial properties of the specimens were determined by challenging them against Staphylococcus aureus. The Ag-incorporated titanium shows excellent antibacterial ability against planktonic bacteria in the suspension and ability to prevent bacterial adhesion. The specimens with optimized biomolecule/silver ratio promote osteoblast differentiation. These biofunctionalized silver nanoparticles-doped titanium specimens, with improved antibacterial activity while maintaining healthy osteoblast cellular activity, have promising application in orthopedics, dentistry, and other biomedical devices.

Urocanic acid-modified chitosan nanoparticles can confer anti-inflammatory effect by delivering CD98 siRNA to macrophages

CD98 plays an important role in the development and progression of inflammation. Here, CD98 siRNA (siCD98) was complexed with urocanic acid-modified chitosan (UAC) to form nanoparticles (NPs), which were transfected into Raw 264.7 macrophages in an effort to convey anti-inflammatory effects. Characterization showed that the generated NPs had a desirable particle size (156.0-247.1nm), a slightly positive zeta potential (15.8-17.5mV), and no apparent cytotoxicity against Raw 264.7 macrophages and colon-26 cells compared to control NPs fabricated by Oligofectamine (OF) and siRNA. Cellular uptake experiments demonstrated that macrophages exhibited a time-dependent accumulation profile of UAC/siRNA NPs. Further in vitro gene silencing experiments revealed that UAC/siCD98 NPs with a weight ratio of 60:1 yielded the most efficient knockdowns of CD98 and the pro-inflammatory cytokine, TNF-α. Indeed, the RNAi efficiency obtained with our NPs was even higher than that of the positive control OF/siCD98 NPs. These results suggest that UAC/siCD98 NPs might be a safe, efficient and promising candidate for the treatment of inflammatory disease.