Near-infrared light II - assisted rapid biofilm elimination platform for bone implants at mild temperature

Biocompatible silane adhesion layer on titanium implants improves angiogenesis and osteogenesis

Silane adhesion layer strategy has been widely used to covalently graft biomolecules to the titanium implant surface, thereby conferring the implant bioactivity to ameliorate osseointegration. However, few researchers pay attention to the effects of silanization parameters on biocompatibility and biofunctionality of the silane adhesion layers. Accordingly, the present study successfully fabricated the silane adhesion layers with different thickness, intactness, and surface morphologies by introducing 3-aminopropyltriethoxysilane on the alkali-treated titanium surface in time-varied processing of silanization. The regulatory effects of the silane adhesion layers on angiogenesis and osteogenesis were assessed in vitro. Results showed that the prolonged silanization processing time increased the thickness and intactness of the silane adhesion layer and significantly improved its biocompatibility. Notably, the silane adhesion layer prepared after 12 h of silanization exhibited a brain-like surface morphology and benefited the adhesion and proliferation of endothelial cells (ECs) and osteoblasts (OBs). Moreover, the layer promoted angiogenesis via stimulating vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production of ECs. Simultaneously, it improved osteogenesis by enhancing alkaline phosphatase (ALP) activity, collagen secretion, and extracellular matrix mineralization of OBs. This work systematically investigated the biocompatibility and biofunctionality of the modified silane adhesion layers, thus providing valuable references for their application in covalently grafting biomolecules on the titanium implant surface.

Nanostructured Cu-doped TiO2 with photothermal effect for prevention of implant-associated infection

Bacterial infection of titanium (Ti) dental implants is still a major clinical complication. In this study, a combination of copper (Cu) ions and photothermal therapy is used to combat implant-associated infection. Cu doped TiO₂ (TiO₂-Cu) films were prepared on Ti by magnetron sputtering and subsequently annealing. TiO₂-Cu films had efficient photothermal conversion ability due to the generated nanostructure during the annealing process. Under the irradiation of 808 near infrared light, the combined actions of hyperthermia and Cu ions gave rise to excellent antibacterial activity against Streptococcus mutans on Ti as demonstrated by the experiments conducted in vitro and in vivo. The TiO₂-Cu films also exhibited excellent biocompatibility. In addition, the surface hardness and corrosion resistance of TiO₂-Cu films were greatly improved.

Ti3 C2 TX MXene Modified with ZnTCPP with Bacteria Capturing Capability and Enhanced Visible Light Photocatalytic Antibacterial Activity

Light-assisted antibacterial therapy is a promising alternative to antibiotic therapy due to the high antibacterial efficacy without bacterial resistance. Recent research has mainly focused on the use of near-infrared light irradiation to kill bacteria by taking advantage of the synergistic effects rendered by hyperthermia and radical oxygen species. However, photocatalytic antibacterial therapy excited by visible light is more convenient and practical, especially for wounds. Herein, a visible light responsive organic-inorganic hybrid of ZnTCPP/Ti₃ C₂ T_X is designed and fabricated to treat bacterial infection with antibacterial efficiency of 99.86% and 99.92% within 10 min against Staphylococcus aureus and Escherichia coli, respectively. The porphyrin-metal complex, ZnTCPP, is assembled on the surface of Ti₃ C₂ T_X MXene to capture bacteria electrostatically and the Schottky junction formed between Ti₃ C₂ T_X and ZnTCPP promotes visible light utilization, accelerates charge separation, and enhances the mobility of photogenerated charges, and finally increases the photocatalytic activity. As a result of the excellent bacteria capturing ability and photocatalytic antibacterial effects, ZnTCPP/Ti₃ C₂ T_X exposed to visible light has excellent antibacterial properties in vitro and in vivo. Therefore, organic-inorganic materials that have been demonstrated to possess good biocompatibility and enhance wound healing have large potential in bio-photocatalysis, antibacterial therapy, as well as antibiotics-free treatment of wounds.

Fast Cross-Linked Hydrogel as a Green Light-Activated Photocatalyst for Localized Biofilm Disruption and Brush-Free Tooth Whitening

Biofilm-driven caries and tooth discoloration are two major problems in oral health care. The current methods have the disadvantages of insufficient biofilm targeting and irreversible enamel damage. Herein, an injectable sodium alginate hydrogel membrane doped with bismuth oxychloride (Bi₁₂O₁₇Cl₂) and cubic cuprous oxide (Cu₂O) nanoparticles was designed to simultaneously achieve local tooth whitening and biofilm removal through a photodynamic dental therapy process. This fast cross-linked hydrogel could form a biofilm removal coating on the target tooth surface precisely. Afterward, reactive oxygen species was effectively released on demand under green light, which could not only eradicate the biofilm but also whiten the tooth non-destructively in a facile manner without significant damage to both the enamel and biological cells. After the usage, the removal of this hydrogel can also enhance the effect of biofilm destruction and caries prevention.

Ti3C2Tx MXene loaded with indocyanine green for synergistic photothermal and photodynamic therapy for drug-resistant bacterium

Infections caused by antibiotic-resistant bacteria are a critical threat to human health. Considering the difficulties and time-consuming nature of synthesizing new antibiotics, it is of great significance and importance to develop the antibiotic-independent antibacterial approaches against drug-resistant bacteria. Nanomaterials-based photothermal therapy (PTT) and photodynamic therapy (PDT) have attracted much attention due to their broad-spectrum bactericidal activity, low toxicity, and drug-free feature. In this work, we loaded indocyanine green (ICG) on the Ti₃C₂T_x MXene nanosheets (454 nm) so as to combine the photothermal effect of MXene with the photodynamic effect of ICG. Without near-infrared (NIR) irradiation, MXene (20 μg/mL), ICG (5 μg/mL) or ICG-loaded MXene (ICG-MXene) showed no significant antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Under NIR, however, the viability loss of MRSA remarkably increased to 45% for MXene, 66% for ICG and 100% for ICG-MXene. We further found that the great anti-MRSA activity of ICG-MXene under NIR was attributed to the combination of photothermal effect of MXene (high temperature) and photodynamic effect of ICG (high level of reactive oxygen species). Our findings indicate that MXene can be used as both the photothermal agent and the carrier of photosensitizers to achieve the synergistic PTT/PDT therapy for bacterial infections.

Multifunctional mesoporous silica nanoparticles for pH-response and photothermy enhanced osteosarcoma therapy

The recurrence and bone defect of malignant osteosarcoma postsurgical treatment have gained remarkable attention. Therefore, the development of multifunctional treatment platform is urgently desirable to achieve efficient tumor treatment and bone regeneration. In this paper, a multifunctional nanomaterial using mesoporous silica (MSN) as platform modified with quercetin (Qr), collagen (Col) and dopamine (PDA) was developed. Our findings demonstrated that the nanoparticles designed in this work had excellent photothermal properties and pH responsiveness. In addition, the nanoparticles had outstanding anti-tumor ability and could killed Saos-2 cells within 10 min under 808 nm laser irradiation owing to the synergistic effect of hyperthermia and Qr. Besides, the modification of PDA and Col endows the nanoparticles with excellent osteogenic activity.

Recent Research on Hybrid Hydrogels for Infection Treatment and Bone Repair

The repair of infected bone defects (IBDs) is still a great challenge in clinic. A successful treatment for IBDs should simultaneously resolve both infection control and bone defect repair. Hydrogels are water-swollen hydrophilic materials that maintain a distinct three-dimensional structure, helping load various antibacterial drugs and biomolecules. Hybrid hydrogels may potentially possess antibacterial ability and osteogenic activity. This review summarizes the recent progress of different kinds of antibacterial agents (including inorganic, organic, and natural) encapsulated in hydrogels. Several representative hydrogels of each category and their antibacterial mechanism and effect on bone repair are presented. Moreover, the advantages and disadvantages of antibacterial agent hybrid hydrogels are discussed. The challenge and future research directions are further prospected.

Nanostructured Titanium Implant Surface Facilitating Osseointegration from Protein Adsorption to Osteogenesis: The Example of TiO2 NTAs

Titanium implants have been widely applied in dentistry and orthopedics due to their biocompatibility and resistance to mechanical fatigue. TiO₂ nanotube arrays (TiO₂ NTAs) on titanium implant surfaces have exhibited excellent biocompatibility, bioactivity, and adjustability, which can significantly promote osseointegration and participate in its entire path. In this review, to give a comprehensive understanding of the osseointegration process, four stages have been divided according to pivotal biological processes, including protein adsorption, inflammatory cell adhesion/inflammatory response, additional relevant cell adhesion and angiogenesis/osteogenesis. The impact of TiO₂ NTAs on osseointegration is clarified in detail from the four stages. The nanotubular layer can manipulate the quantity, the species and the conformation of adsorbed protein. For inflammatory cells adhesion and inflammatory response, TiO₂ NTAs improve macrophage adhesion on the surface and induce M2-polarization. TiO₂ NTAs also facilitate the repairment-related cells adhesion and filopodia formation for additional relevant cells adhesion. In the angiogenesis and osteogenesis stage, TiO₂ NTAs show the ability to induce osteogenic differentiation and the potential for blood vessel formation. In the end, we propose the multi-dimensional regulation of TiO₂ NTAs on titanium implants to achieve highly efficient manipulation of osseointegration, which may provide views on the rational design and development of titanium implants.

Graphene oxide and mineralized collagen-functionalized dental implant abutment with effective soft tissue seal and romotely repeatable photodisinfection

Grasping the boundary of antibacterial function may be better for the sealing of soft tissue around dental implant abutment. Inspired by ‘overdone is worse than undone’, we prepared a sandwich-structured dental implant coating on the percutaneous part using graphene oxide (GO) wrapped under mineralized collagen. Our unique coating structure ensured the high photothermal conversion capability and good photothermal stability of GO. The prepared coating not only achieved suitable inhibition on colonizing bacteria growth of Streptococcus sanguinis, Fusobacterium nucleatum and Porphyromonas gingivalis but also disrupted the wall/membrane permeability of free bacteria. Further enhancements on the antibacterial property were generally observed through the additional incorporation of dimethylaminododecyl methacrylate. Additionally, the coating with sandwich structure significantly enhanced the adhesion, cytoskeleton organization and proliferation of human gingival fibroblasts, which was effective to improve soft tissue sealing. Furthermore, cell viability was preserved when cells and bacteria were cultivated in the same environment by a coculture assay. This was attributed to the sandwich structure and mineralized collagen as the outmost layer, which would protect tissue cells from photothermal therapy and GO, as well as accelerate the recovery of cell activity. Overall, the coating design would provide a useful alternative method for dental implant abutment surface modification and functionalization.

Biocompatible mechano-bactericidal nanopatterned surfaces with salt-responsive bacterial release

Bio-inspired nanostructures have demonstrated highly efficient mechano-bactericidal performances with no risk of bacterial resistance; however, they are prone to become contaminated with the killed bacterial debris. Herein, a biocompatible mechano-bactericidal nanopatterned surface with salt-responsive bacterial releasing behavior is developed by grafting salt-responsive polyzwitterionic (polyDVBAPS) brushes on a bio-inspired nanopattern surface. Benefiting from the salt-triggered configuration change of the grafted polymer brushes, this dual-functional surface shows high mechano-bactericidal efficiency in water (low ionic strength condition), while the dead bacterial residuals can be easily lifted by the extended polymer chains and removed from the surface in 1 M NaCl solution (high ionic strength conditions). Notably, this functionalized nanopatterned surface shows selective biocidal activity between bacterial cells sand eukaryotic cells. The biocompatibility with red blood cells (RBCs) and mammalian cells was tested in vitro. The histocompatibility and prevention of perioperative contamination activity were verified by in vivo evaluation in a rat subcutaneous implant model. This nanopatterned surface with bacterial killing and releasing activities may open new avenues for designing bio-inspired mechano-bactericidal platforms with long-term efficacy, thus presenting a facile alternative in combating perioperative-related bacterial infection. STATEMENT OF SIGNIFICANCE: Bioinspired nanostructured surfaces with noticeable mechano-bactericidal activity showed great potential in moderating drug-resistance. However, the nanopatterned surfaces are prone to be contaminated by the killed bacterial debris and compromised the bactericidal performance. In this study, we provide a dual-functional antibacterial conception with both mechano-bactericidal and bacterial releasing performances not requiring external chemical bactericidal agents. Additionally, this functionalized antibacterial surface also shows selective biocidal activity between bacteria and eukaryotic cells, and the excellent biocompatibility was tested in vitro and in vivo. The new concept for the functionalized mechano-bactericidal surface here illustrated presents a facile antibiotic-free alternative in combating perioperative related bacterial infection in practical application.

A bone implant with NIR-responsiveness for eliminating osteosarcoma cells and promoting osteogenic differentiation of BMSCs

Incomplete removal of tumor cells and insufficient osseointegration are the main causes of bone tumor recurrence and implantation failure. In the present study, a multifunctional titanium-based bioactive implant for near-infrared-triggered synergy therapy to overcome these hurdles is engineered, composed of titanium dioxide (TiO₂) nanoparticles doped with fluorine (F)/dopamine (PDA)/collagen. The TiO₂ nanoparticles designed in this work can simultaneously exhibit excellent near-infrared-activated photothermal and photocatalytic properties. Besides, the layer designed in this work show excellent anti-tumor activity under irradiation with 808 nm light due to the synergetic effect of hyperthermia and reactive oxygen species (ROS), and Saos-2 cells can be eradicated within 10 min. Moreover, modification of PDA and collagen endue the Ti alloy excellent osteogenic activity.

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).

Photonic Crystal Effects on Upconversion Enhancement of LiErF4:0.5%Tm3+@LiYF4 for Noncontact Cholesterol Detection

Cholesterol is a vital compound in maintenance for human health, and its concentration levels are tightly associated with various diseases. Therefore, accurate monitoring of cholesterol is of great significance in clinical diagnosis. Herein, we fabricated a noncontact biosensor based on photonic crystal-enhanced upconversion nanoparticles (UCNPs) for highly sensitive and interference-free cholesterol detection. By compounding LiErF₄:0.5%Tm³⁺@LiYF₄ UCNPs with poly(methyl methacrylate) (PMMA) photonic crystals (OPCs), we were able to selectively tune the coupling of the photonic band gap to the excitation field and modulate the upconversion (UC) luminescence intensity, given the unique multi-wavelength excitation property of LiErF₄:0.5%Tm³⁺@LiYF₄. A 48.5-fold enhancement of the monochromatic red UC emission was ultimately achieved at 980 nm excitation, ensuring improved detection sensitivity. Based on the principle of quenching of the intense monochromic red UC emission by the oxidation products of 3,3',5,5'-tetramethylbenzidine (TMB) yielded from the cholesterol cascade reactions, the biosensor has a detection limit of 1.6 μM for cholesterol with excellent specificity and stability. In addition, the testing results of the as-designed biosensor in patients are highly consistent with clinical diagnostic data, providing a sensitive, reliable, reusable, interference-free, and alternative strategy for clinical cholesterol detection.

pH-switchable nanozyme cascade catalysis: a strategy for spatial-temporal modulation of pathological wound microenvironment to rescue stalled healing in diabetic ulcer

The management of diabetic ulcer (DU) to rescue stalled wound healing remains a paramount clinical challenge due to the spatially and temporally coupled pathological wound microenvironment that features hyperglycemia, biofilm infection, hypoxia and excessive oxidative stress. Here we present a pH-switchable nanozyme cascade catalysis (PNCC) strategy for spatial–temporal modulation of pathological wound microenvironment to rescue stalled healing in DU. The PNCC is demonstrated by employing the nanozyme of clinically approved iron oxide nanoparticles coated with a shell of glucose oxidase (Fe₃O₄-GOx). The Fe₃O₄-GOx possesses intrinsic glucose oxidase (GOx), catalase (CAT) and peroxidase (POD)-like activities, and can catalyze pH-switchable glucose-initiated GOx/POD and GOx/CAT cascade reaction in acidic and neutral environment, respectively. Specifically, the GOx/POD cascade reaction generating consecutive fluxes of toxic hydroxyl radical spatially targets the acidic biofilm (pH ~ 5.5), and eradicates biofilm to shorten the inflammatory phase and initiate normal wound healing processes. Furthermore, the GOx/CAT cascade reaction producing consecutive fluxes of oxygen spatially targets the neutral wound tissue, and accelerates the proliferation and remodeling phases of wound healing by addressing the issues of hyperglycemia, hypoxia, and excessive oxidative stress. The shortened inflammatory phase temporally coupled with accelerated proliferation and remodeling phases significantly speed up the normal orchestrated wound-healing cascades. Remarkably, this Fe₃O₄-GOx-instructed spatial–temporal remodeling of DU microenvironment enables complete re-epithelialization of biofilm-infected wound in diabetic mice within 15 days while minimizing toxicity to normal tissues, exerting great transformation potential in clinical DU management. The proposed PNCC concept offers a new perspective for complex pathological microenvironment remodeling, and may provide a powerful modality for the treatment of microenvironment-associated diseases.

Metal-Organic-Framework-Based Hydrogen-Release Platform for Multieffective Helicobacter Pylori Targeting Therapy and Intestinal Flora Protective Capabilities

Helicobacter pylori (H. pylori) infection is the leading cause of chronic gastritis, peptic ulcer, and gastric cancer. Antibiotics, as traditional method for eliminating H. pylori, have no targeting effect, which causes serious bacterial resistance and gut dysbacteriosis. Moreover, antibiotics can hardly address hyperactive inflammatory response or damaged gastric mucosal barrier caused by H. pylori infection. Here, a pH-responsive metal-organic framework hydrogen-generation nanoparticle (Pd(H) @ ZIF-8) is reported, which is encapsulated with ascorbate palmitate (AP) hydrogel. Both in vitro and in vivo experiments demonstrate that the outer AP hydrogel can target and adhere to the inflammatory site through electrostatic interactions, and is then hydrolyzed by matrix metalloproteinase (MMP) enriching in inflammatory sites. The released Pd(H) @ ZIF-8 nanoparticles are further decomposed by gastric acid to generate zinc ions (Zn²⁺ ) and hydrogen, thus effectively killing H. pylori, alleviating inflammation and restoring impaired gastric mucosa simultaneously. Unexpectedly, this metal-organic framework hydrogen-generation platform (Pd(H) @ ZIF-8 @ AP) also has an effect toward avoiding the imbalance of intestinal flora, which thus provides a more precise, effective, and healthy strategy for the treatment of H. pylori infection.

Near-infrared light-triggered nano-prodrug for cancer gas therapy

Gas therapy (GT) has attracted increasing attention in recent years as a new cancer treatment method with favorable therapeutic efficacy and reduced side effects. Several gas molecules, such as nitric oxide (NO), carbon monoxide (CO), hydrogen (H2), hydrogen sulfide (H2S) and sulfur dioxide (SO2), have been employed to treat cancers by directly killing tumor cells, enhancing drug accumulation in tumors or sensitizing tumor cells to chemotherapy, photodynamic therapy or radiotherapy. Despite the great progress of gas therapy, most gas molecules are prone to nonspecific distribution when administered systemically, resulting in strong toxicity to normal tissues. Therefore, how to deliver and release gas molecules to targeted tissues on demand is the main issue to be considered before clinical applications of gas therapy. As a specific and noninvasive stimulus with deep penetration, near-infrared (NIR) light has been widely used to trigger the cleavage and release of gas from nano-prodrugs via photothermal or photodynamic effects, achieving the on-demand release of gas molecules with high controllability. In this review, we will summarize the recent progress in cancer gas therapy triggered by NIR light. Furthermore, the prospects and challenges in this field are presented, with the hope for ongoing development.

Versatile Types of Inorganic/Organic NIR-IIa/IIb Fluorophores: From Strategic Design toward Molecular Imaging and Theranostics

In vivo imaging in the second near-infrared window (NIR-II, 1000-1700 nm), which enables us to look deeply into living subjects, is producing marvelous opportunities for biomedical research and clinical applications. Very recently, there has been an upsurge of interdisciplinary studies focusing on developing versatile types of inorganic/organic fluorophores that can be used for noninvasive NIR-IIa/IIb imaging (NIR-IIa, 1300-1400 nm; NIR-IIb, 1500-1700 nm) with near-zero tissue autofluorescence and deeper tissue penetration. This review provides an overview of the reports published to date on the design, properties, molecular imaging, and theranostics of inorganic/organic NIR-IIa/IIb fluorophores. First, we summarize the design concepts of the up-to-date functional NIR-IIa/IIb biomaterials, in the order of single-walled carbon nanotubes (SWCNTs), quantum dots (QDs), rare-earth-doped nanoparticles (RENPs), and organic fluorophores (OFs). Then, these novel imaging modalities and versatile biomedical applications brought by these superior fluorescent properties are reviewed. Finally, challenges and perspectives for future clinical translation, aiming at boosting the clinical application progress of NIR-IIa and NIR-IIb imaging technology are highlighted.

Construction of a TiO2/MoSe2/CHI coating on dental implants for combating Streptococcus mutans infection

Infection and inflammation are the main causes resulting in the failure of dental implants. In this work, molybdenum diselenide (MoSe₂) was synthesized hydrothermally on the surface of porous TiO₂ coating prepared by micro-arc oxidation on titanium (Ti) implants to render the coating excellent in situ antibacterial activity under the irradiation of near-infrared (NIR) light. Chitosan (CHI) was adsorbed on the surface of MoSe₂ nanosheets by electrostatic bonding to improve the biocompatibility. The introduction of MoSe₂ significantly improved the photothermal and photodynamic ability of TiO₂ coating and made the implants possess excellent in vitro and in vivo antibacterial property against Streptococcus mutans (S. mutans) under the irradiation of 808 nm NIR light for 15 min because of the synergistic of hyperthermia and reactive oxygen species (ROS). The immobilization of CHI improved the hydrophilicity and biocompatibility of MoSe₂, and the hybrid coating (TiO₂/MoSe₂/CHI) promoted osseointegration even in the presence of infection in vivo under 808 nm light irradiation. The light - assisted antibacterial coating described here has large clinical potential in dental implants applications.

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

Killing bacteria, eliminating biofilm and building soft tissue integration are very important for percutaneous implants which service in a complicated environment. In order to endow Ti implants with above abilities, multifunctional coatings consisted of Fe₂O₃–FeOOH nanograins as an outer layer and Zn doped microporous TiO₂ as an inner layer were fabricated by micro-arc oxidation, hydrothermal treatment and annealing treatment. The microstructures, physicochemical properties and photothermal response of the coatings were observed; their antibacterial efficiencies and cell response in vitro as well as biofilm elimination and soft tissue integration in vivo were evaluated. The results show that with the increased annealing temperature, coating morphologies didn't change obviously, but lattices of β-FeOOH gradually disorganized into amorphous state and rearranged to form Fe₂O_3. The coating annealed at 450 °C (MA450) had nanocrystallized Fe₂O₃ and β-FeOOH. With a proper NIR irradiation strategy, MA450 killed adhered bacteria efficiently and increased fibroblast behaviors via up-regulating fibrogenic-related genes in vitro; in an infected model, MA450 eliminated biofilm, reduced inflammatory response and improved biointegration with soft tissue. The good performance of MA450 was due to a synergic effect of photothermal response and released ions (Zn²⁺ and Fe³⁺).

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Nanocrystallized Fe₂O₃–FeOOH layer endows Ti with good photothermal response.

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With NIR irradiation, Fe₂O₃–FeOOH layer improves biointegration in an infected model.

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Photothermal response combined with released ions gives implants good performance.

In Situ Coatings of Silver Nanoparticles for Biofilm Treatment in Implant-Retention Surgeries: Antimicrobial Activities in Monoculture and Coculture

Bacterial biofilms are indicated in most medical device-associated infections. Treating these biofilms is challenging yet critically important for applications such as in device-retention surgeries, which can have reinfection rates of up to 80%. This in vitro study centered around our new method of treating biofilm and preventing reinfection. Ionic silver (Ag, in the form of silver nitrate) combined with dopamine and a biofilm-lysing enzyme (α-amylase) were applied to model 4-day-old Staphylococcus aureus biofilms on titanium substrates to degrade the extracellular matrix of the biofilm and kill the biofilm bacteria. In this process, the oxidative self-polymerization of dopamine converted Ag ions into Ag nanoparticles that, together with the resultant self-adhering polydopamine (PDA), formed coatings that strongly bound to the treated substrates. Surprisingly, although these Ag/PDA coatings significantly reduced S. aureus growth in standard bacterial monoculture, they showed much lower antimicrobial activity in coculture of the bacteria and osteoblastic MC3T3-E1 cells in which the bacteria were also found attached to the osteoblasts. This S. aureus- osteoblast interaction was also linked to bacterial survival against gentamicin treatment observed in coculture. Our study thus provided clear evidence suggesting that bacteria's interactions with tissue cells surrounding implants may significantly contribute to their resistance to antimicrobial treatment.

Light-Triggered Antibacterial Hydrogels Containing Recombinant Growth Factor for Treatment of Bacterial Infections and Improved Wound Healing

Microbial infection and the limitation of tissue regeneration are main obstacles to chronic wound healing. Herein, a biofunctional hydrogel is prepared to simultaneously kill bacteria efficiently and promote would healing. First, a rose bengal/polypyrrole hybrid poly(vinyl alcohol) hydrogel (RB/PPy PVA HD) is synthesized and its antibacterial property is investigated under coirradiation of 550 nm visible light and 808 near-infrared light. The hydrogel exhibits excellent antibacterial activity within 10 min below 45 °C in vitro due to the synergistic effect of photothermal and photodynamic antibacterial therapy. Next, the recombined human epidermal growth factor (rhEGF) is physically absorbed on the surface of the porous hydrogel to form a RB/PPy/rhEGF hybrid PVA HD (rhEGF/RB/PPy PVA HD). The introduction of rhEGF enables the hydrogel to promote fibroblast proliferation and collagen secretion. Furthermore, the in vivo results indicate that the rhEGF/RB/PPy PVA HD can control infection effectively and promote wound healing significantly.