Building biointegration of Fe2O3-FeOOH coated titanium implant by regulating NIR irradiation in an infected model

Toehold Strand Displacement-Mediated Exponential HCR for Highly Sensitive and Specific Analysis of miRNA in Living Cells

As an important disease biomarker, the development of sensitive detection strategies for miRNA, especially intracellular miRNA imaging strategies, is helpful for early diagnosis of diseases, pathological research, and drug development. Hybridization chain reaction (HCR) is widely used for miRNA imaging analysis because of its high specificity and lack of biological enzymes. However, the classic HCR reaction exhibits linear amplification with low efficiency, limiting its use for the rapid analysis of trace miRNA in living cells. To address this problem, we proposed a toehold-mediated exponential HCR (TEHCR) to achieve highly sensitive and efficient imaging of miRNA in living cells using β-FeOOH nanoparticles as transfection vectors. The detection limit of TEHCR was as low as 92.7 fM, which was 8.8 × 103 times lower compared to traditional HCR, and it can effectively distinguish single-base mismatch with high specificity. The TEHCR can also effectively distinguish the different expression levels of miRNA in cancer cells and normal cells. Furthermore, TEHCR can be used to construct OR logic gates for dual miRNA analysis without the need for additional probes, demonstrating high flexibility. This method is expected to play an important role in clinical miRNA-related disease diagnosis and drug development as well as to promote the development of logic gates.

External Stimuli-Responsive Strategies for Surface Modification of Orthopedic Implants: Killing Bacteria and Enhancing Osteogenesis

Bacterial infection and insufficient osteogenic activity are the main causes of orthopedic implant failure. Conventional surface modification methods are difficult to meet the requirements for long-term implant placement. In order to better regulate the function of implant surfaces, especially to improve both the antibacterial and osteogenic activity, external stimuli-responsive (ESR) strategies have been employed for the surface modification of orthopedic implants. External stimuli act as "smart switches" to regulate the surface interactions with bacteria and cells. The balance between antibacterial and osteogenic capabilities of implant surfaces can be achieved through these specific ESR manifestations, including temperature changes, reactive oxygen species production, controlled release of bioactive molecules, controlled release of functional ions, etc. This Review summarizes the recent progress on different ESR strategies (based on light, ultrasound, electric, and magnetic fields) that can effectively balance antibacterial performance and osteogenic capability of orthopedic implants. Furthermore, the current limitations and challenges of ESR strategies for surface modification of orthopedic implants as well as future development direction are also discussed.

Photoelectrons Sequentially Regulate Antibacterial Activity and Osseointegration of Titanium Implants

Titanium implants are widely used ; however, implantation occasionally fails due to infections during the surgery or poor osseointegration after the surgery. To solve the problem, an intelligent functional surface on titanium implant that can sequentially eradicate bacteria biofilm at the initial period and promote osseointegration at the late period of post-surgery time is designed. Such surfaces can be excited by near infrared light (NIR), with rare earth nanoparticles to upconvert the NIR light to visible range and adsorb by Au nanoparticles, supported by titanium oxide porous film on titanium implants. Under NIR irradiation, the implant converts the energy of phonon to hot electrons and lattice vibrations, while the former flows directly to the contact substance or partially reacts with the surrounding to generate reactive oxygen species, and the latter leads to the local temperature increase. The biofilm or microbes on the implant surface can be eradicated by NIR treatment in vitro and in vivo. Additionally, the surface exhibits superior biocompatibility for cell survival, adhesion, proliferation, and osteogenic differentiation, which provides the foundation for osseointegration. In vivo implantation experiments demonstrate osseointegration is also promoted. This work thus demonstrates NIR-generated electrons can sequentially eradicate biofilms and regulate the osteogenic process, providing new solutions to fabricate efficient implant surfaces.

Injectable Self-Harden Antibiofilm Bioceramic Cement for Minimally Invasive Surgery

There is an urgent demand for antibacterial bone grafts in clinics. Worryingly, the misuse and overuse of antibiotics accelerate the emergence of drug-resistant bacteria. Therefore, this study prepared a novel injectable bioceramic cement without antibiotics (FS-BCS), which showed good antibacterial properties by loading iron and strontium onto a matrix composed of brushite and calcium sulfate. The setting time, injectability, microstructure, antibacterial properties, anti-biofilm properties, and cytocompatibility of the novel bioceramic cement were evaluated thoroughly. The results showed that the material was highly injectable and antiwashout. The antibacterial tests revealed that FS-BCS inhibited the growth of 99.9% E. coli and S. aureus separately in the broth due to the synergistic effect of strontium and iron. Simultaneously, crystal violet and fluorescent staining tests revealed that the material could significantly inhibit the formation of E. coli and S. aureus biofilms. In addition, the co-incorporation of iron and strontium promoted the proliferation and migration of osteoblasts. Therefore, FS-BCS has good application potential in antibiotic-free anti-infection bone grafting using minimally invasive surgery.

Fluoride releasing photothermal responsive TiO2 matrices for antibiosis, biosealing and bone regeneration

Peri-implantitis induced by infection leads to gingival recession, alveolar resorption and eventual dental implant failure. So, antibiosis and biosealing of abutments as well as osseointegration of roots need to be projected seriously during the whole service lifespan of dental implants. In this work, a multipurpose photothermal therapy strategy based on Si/P/F doped TiO2 matrix is proposed to address the above issues. This TiO2 matrix not only has outstanding photothermal response, but also triggers the release of F ions under near-infrared (NIR) light irradiation. Local hyperthermia assisted with the released F ions reduces adenosine triphosphate (ATP) synthesis of staphylococcus aureus (S. aureus), increases bacterial membrane permeability, and induces abundant of reactive oxygen species, resulting in the oxidation of cellular components and eventual death of bacteria. Furthermore, the synergic action of mild photothermal stimulation and Si/P/F ions of TiO2 matrix up-regulates gingival epithelial cells behavior (e.g., hemidesmosome formation) and osteoblasts response in vitro. In an infected model, this TiO2 matrix obviously eliminates bacteria, reduces inflammatory response, improves epithelial sealing and osseointegration, and reduces alveolar resorption by regulating NIR irradiation.

Environment-Responsive Therapeutic Platforms for the Treatment of Implant Infection

The application of medical implants has greatly improved the survival rate and life quality of patients. Nevertheless, in recent years, there are increasing cases of implant dysfunction or failure because of bacterial infections. Despite significant improvements in biomedicine, there are still serious challenges in the treatment of implant-related infections. With the formation of bacterial biofilms and the development of bacterial resistance, these limitations lead to a low efficacy of conventional antibiotics. To address these challenges, it is urgent to exploit innovative treatment strategies for implant-related infections. Based on these ideas, environment-responsive therapeutic platforms with high selectivity, low drug resistance, and minor dose-limiting toxicity have attracted widespread attention. By using exogenous/endogenous stimuli, the antibacterial activity of therapeutics can be activated on demand and exhibit remarkable therapeutic effects. Exogenous stimuli include photo, magnetism, microwave, and ultrasound. Endogenous stimuli mainly include the pathological characteristics of bacterial infections such as acidic pH, anomalous temperature, and abnormal enzymatic activities. In this review, the recent progress of environment-responsive therapeutic platforms with spatiotemporally controlled drug release/activation is systematically summarized. Afterward, the limitations and opportunities of these emerging platforms are highlighted. Finally, it is hoped that this review will offer novel ideas and techniques to combat implant-related infections.

The current status of stimuli-responsive nanotechnologies on orthopedic titanium implant surfaces

With the continuous innovation and breakthrough of nanomedical technology, stimuli-responsive nanotechnology has been gradually applied to the surface modification of titanium implants to achieve brilliant antibacterial activity and promoted osteogenesis. Regarding to the different physiological and pathological microenvironment around implants before and after surgery, these surface nanomodifications are designed to respond to different stimuli and environmental changes in a timely, efficient, and specific way/manner. Here, we focus on the materials related to stimuli-responsive nanotechnology on titanium implant surface modification, including metals and their compounds, polymer materials and other materials. In addition, the mechanism of different response types is introduced according to different activation stimuli, including magnetic, electrical, photic, radio frequency and ultrasonic stimuli, pH and enzymatic stimuli (the internal stimuli). Meanwhile, the associated functions, potential applications and developing prospect were discussion.

Alkaline "Nanoswords" Coordinate Ferroptosis-like Bacterial Death for Antibiosis and Osseointegration

Ferroptosis is an iron-dependent cell death and is associated with cancer therapy. Can it play a role in resistance of postoperative infection of implants, especially with an extracellular supplement of Fe ions in a non-cytotoxic dose? To answer this, "nanoswords" of Fe-doped titanite are fabricated on a Ti implant surface to resist bacterial invasion by a synergistic action of ferroptosis-like bacteria killing, proton disturbance, and physical puncture. The related antibiosis mechanism is explored by atomic force microscopy and genome sequencing. The nanoswords induce an increased local pH value, which not only weakens the proton motive force, reducing adenosine triphosphate synthesis of Staphylococcus aureus, but also decreases the membrane modulus, making the nanoswords distort and even puncture a bacterial membrane easily. Simultaneously, more Fe ions are taken by bacteria due to increased bacterial membrane permeability, resulting in ferroptosis-like death of bacteria, and this is demonstrated by intracellular iron enrichment, lipid peroxidation, and glutathione depletion. Interestingly, a microenvironment constructed by these nanoswords improves osteoblast behavior in vitro and bone regeneration in vivo. Overall, the nanoswords can induce ferroptosis-like bacterial death without cytotoxicity and have great promise in applications with clinical implants for outstanding antibiosis and biointegration performance.

Surface Bandgap Engineering of Nanostructured Implants for Rapid Photothermal Ion Therapy of Bone Defects

Bone defects are seriously threatening the health of orthopedics patients and it is difficult for implants to accelerate bone regeneration without using bone growth factors. Herein, a fast photothermal ion therapeutic strategy is developed based on the bandgap engineering of nanostructured TiO₂ through (Si/P)-dual elemental doping by micro-arc oxidation treatment of titanium implants. The (Si/P)-dual doping can tune the surface bandgap structure of TiO₂ by decreasing bandgap and broadening valence band simultaneously, which is confirmed by density functional theory calculations. It not only endows the implants with a mildly photothermal effect under near-infrared (NIR) light irradiation, but also creates an (Si/P) ion-rich microenvironment around the implants. This photothermal ion microenvironment can tune the behaviors of osteoblasts by promoting p38/Smad and ERK signaling pathways of osteoblasts, thus significantly upregulating the expression of osteogenesis genes by the synergistic action of mild photothermal stimulation and increased release of Si/P ions. The in vivo results are also in good agreement with in vitro tests, i.e., under NIR light irradiation, the photothermally responsive TiO₂ enhances the bone formation and osteointegration with implants. Therefore, this kind of photothermal ion strategy is a promising remote and noninvasive therapeutic mode for promoting bone regeneration of Ti implants.

Acidity-Activatable Nanoparticles with Glucose Oxidase-Enhanced Photoacoustic Imaging and Photothermal Effect, and Macrophage-Related Immunomodulation for Synergistic Treatment of Biofilm Infection

The pH-responsive theragnostics exhibit great potential for precision diagnosis and treatment of diseases. Herein, acidity-activatable nanoparticles of GB@P based on glucose oxidase (GO) and polyaniline are developed for treatment of biofilm infection. Catalyzed by GO, GB@P triggers the conversion of glucose into gluconic acid and hydrogen peroxide (H₂ O₂ ), enabling an acidic microenvironment-activated simultaneously enhanced photothermal (PT) effect/amplified photoacoustic imaging (PAI). The synergistic effects of the enhanced PT efficacy of GB@P and H₂ O₂ accelerate biofilm eradication because the penetration of H₂ O₂ into biofilm improves the bacterial sensitivity to heat, and the enhanced PT effect destroys the expressions of extracellular DNA and genomic DNA, resulting in biofilm destruction and bacterial death. Importantly, GB@P facilitates the polarization of proinflammatory M1 macrophages that initiates macrophage-related immunity, which enhances the phagocytosis of macrophages and secretion of proinflammatory cytokines, leading to a sustained bactericidal effect and biofilm eradication by the innate immunomodulatory effect. Accordingly, the nanoplatform of GB@P exhibits the synergistic effects on the biofilm eradication and bacterial residuals clearance through a combination of the enhanced PT effect with immunomodulation. This study provides a promising nanoplatform with enhanced PT efficacy and amplified PAI for diagnosis and treatment of biofilm infection.

An Extracellular Matrix-like Surface for Zn Alloy to Enhance Bone Regeneration

Zn-based alloys are promising biodegradable implants for bone defect repair due to their good mechanical performance and degradability. However, local Zn²⁺ released from Zn-based implants can seriously affect adhering cell behaviors as well as new bone formation on implant surfaces. To address this issue, we have fabricated a bone-mimetic extracellular matrix (ECM)-like surface on Zn-1Ca implants using a hybrid process of anodization, hydrothermal treatment (HT), and fluorous-curing. The ECM-like surface consisted of Zn₂SiO₄ nanorods layered with collagen I (Col-I). The Zn₂SiO₄ nanorods were hemicrystallized and transformed by the reaction of Zn(OH)₂ and SiO₄^4- during the HT. The Zn₂SiO₄ nanorods effectively protected the substrate from corrosion; the Col-I layer decreased the degradation of Zn₂SiO₄ nanorods and further reduced Zn²⁺ release into the medium. This ECM-like surface generated a microenvironment with appropriate Zn²⁺ levels, nanorod-like topography, and Col-I. It significantly improved adhesion, proliferation, and differentiation of osteoblasts on implant surfaces and vascularization of endothelial cells in the extract medium. The in vivo results are in good agreement with in vitro tests, with the ECM-like surface significantly enhancing new bone formation and bone-implant contact compared to the bare implant surface. Overall, this bone-mimetic ECM-like material of Col-I layered Zn₂SiO₄ nanorods is a promising scaffold that promotes the bone regeneration of Zn-based implants.

In vitro and in vivo highly effective antibacterial activity of carbon dots-modified TiO2 nanorod arrays on titanium

Light-triggered antibacterial therapy has been proven to be a secure and effective way to treat bacterial infection. Nevertheless, the long-term security of the common photosensitizer remains to be seen in the body. In this work, carbon dots (CDs) with good biocompatibility are incorporated into TiO₂ nanorods to improve the photocatalytic and photothermal ability of titanium implants under the irradiation of visible light (VL) and near-infrared (NIR) light. The C-TiO₂ NR exhibit excellent in vitro and in vivo antimicrobial effect under 660 nm VL and 808 nm NIR light co-irradiation owing to the combined effect of hyperthermia, reactive oxygen species (ROS) and nanorod structure. Besides, C-TiO₂ NR can improve the adhesion and diffusion of bone marrow mesenchymal stem cells (BMSCs).