Insights into Theranostic Properties of Titanium Dioxide for Nanomedicine

Glutathione and acid dual-responsive bismuth-based nanosensitizer for chemo-mediated cancer sonodynamic therapy

Chemotherapeutic agents hold significant clinical potential in combating tumors. However, delivering these drugs to the tumor site for controlled release remains a crucial challenge. In this study, we synthesize and construct a glutathione (GSH) and acid dual-responsive bismuth-based nano-delivery platform (BOD), aiming for sonodynamic enhancement of docetaxel (DTX)-mediated tumor therapy. The bismuth nanomaterial can generate multiple reactive oxygen species under ultrasound stimulation. Furthermore, the loading of DTX to form BOD effectively reduces the toxicity of DTX in the bloodstream, ensuring its cytotoxic effect is predominantly exerted at the tumor site. DTX can be well released in high expression of GSH and acidic tumor microenvironment. Meanwhile, ultrasound can also promote the release of DTX. Results from bothin vitroandin vivoexperiments substantiate that the synergistic therapy involving chemotherapy and sonodynamic therapy significantly inhibits the growth and proliferation of tumor cells. This study provides a favorable paradigm for developing a synergistic tumor treatment platform for tumor microenvironment response and ultrasound-promoted drug release.

Functional nanomaterials as photosensitizers or delivery systems for antibacterial photodynamic therapy

Bacterial infection is a global health problem that closely related to various diseases threatening human life. Although antibiotic therapy has been the mainstream treatment method for various bacterial infectious diseases for decades, the increasing emergence of bacterial drug resistance has brought enormous challenges to the application of antibiotics. Therefore, developing novel antibacterial strategies is of great importance. By producing reactive oxygen species (ROS) with photosensitizers (PSs) under light irradiation, antibacterial photodynamic therapy (aPDT) has emerged as a non-invasive and promising approach for treating bacterial infections without causing drug resistance. However, the insufficient therapeutic penetration, poor hydrophilicity, and poor biocompatibility of traditional PSs greatly limit the efficacy of aPDT. Recently, studies have found that nanomaterials with characteristics of favorable photocatalytic activity, surface plasmonic resonance, easy modification, and high drug loading capacity can improve the therapeutic efficacy of aPDT. In this review, we aim to provide a comprehensive understanding of the mechanism of nanomaterials-mediated aPDT and summarize the representative nanomaterials in aPDT, either as PSs or carriers for PSs. In addition, the combination of advanced nanomaterials-mediated aPDT with other therapies, including targeted therapy, gas therapy, and multidrug resistance (MDR) therapy, is reviewed. Also, the concerns and possible solutions of nanomaterials-based aPDT are discussed. Overall, this review may provide theoretical basis and inspiration for the development of nanomaterials-based aPDT.

Brucine Entrapped Titanium Oxide Nanoparticle for Anticancer Treatment: An In Vitro Study

Backgroundand Objective. The public's health has been seriously threatened by cervical cancer during recent times. In terms of newly diagnosed cases worldwide, it ranks as the ninth most prevalent malignancy. Multiple investigations have proven that nanoparticles can effectively combat cancer due to their small dimensions and extensive surface area. In the meantime, bioactive compounds which are biocompatible are being loaded onto nanoparticles to promote cancer therapy. The current study investigates the anticancerous potential of Brucine-entrapped titanium oxide nanoparticles (TiO2 NPs) in cervical cancer cell line (HeLa). Materials and Methods. The physiochemical, structural, and morphological aspects of Brucine-entrapped TiO2 NPs were evaluated by UV-visible spectrophotometer, Fourier transform-infrared spectroscopy (FT-IR), dynamic light scattering (DLS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDAX). The cytotoxic effect against the HeLa cell line was assessed using a tetrazolium-based colorimetric assay (MTT), a trypan blue exclusion (TBE) assay, phase contrast microscopic analysis, and a fluorescence assay including ROS and DAPI staining. Furthermore, estimation of antioxidant markers includes catalase (CAT), glutathione (GSH), and superoxide dismutase (SOD). Results. The UV spectrum at 266 nm revealed the formation of TiO NPs. The FT-IR peaks confirmed the effective entrapment of brucine with TiO2 NPs. The average size (100.0 nm) of Brucine-entrapped TiO2 NPs was revealed in DLS analysis. The micrograph of the SEM revealed the formation of ellipsoidal to tetragonal-shaped NPs. The Ti, O, and C signals were observed in EDAX. In MTT assay, Brucine-entrapped TiO2 NPs showed inhibition of cell proliferation in a dose-wise manner and IC50 was noticed at the concentration of 30 µg/mL. The percentage of viable cells gradually reduced in the trypan blue exclusion assay. The phase contrast microscopic analysis of Brucine-entrapped TiO2 NP-treated cells showed cell shrinkage, cell wall deterioration, and cell blebbing. The intracellular ROS level was increased in a dose-wise manner when compared to control cells in ROS staining. The condensed nuclei and apoptotic cells were increased in treated cells, as noted in DAPI staining. In treated cells, the antioxidant markers such as CAT, GSH, and SOD levels were substantially lower compared to the control cells. Conclusion. The synthesized Brucine entrapped TiO2 NPs exhibited remarkable anticancer activity against the HeLa cell line.

A simulation study on the radiosensitization properties of gold nanorods

Objective. Gold nanorods (GNRs) have emerged as versatile nanoparticles with unique properties, holding promise in various modalities of cancer treatment through drug delivery and photothermal therapy. In the rapidly evolving field of nanoparticle radiosensitization (NPRS) for cancer therapy, this study assessed the potential of gold nanorods as radiosensitizing agents by quantifying the key features of NPRS, such as secondary electron emission and dose enhancement, using Monte Carlo simulations.Approach. Employing the TOPAS track structure code, we conducted a comprehensive evaluation of the radiosensitization behavior of spherical gold nanoparticles and gold nanorods. We systematically explored the impact of nanorod geometry (in particular size and aspect ratio) and orientation on secondary electron emission and deposited energy ratio, providing validated results against previously published simulations.Main results. Our findings demonstrate that gold nanorods exhibit comparable secondary electron emission to their spherical counterparts. Notably, nanorods with smaller surface-area-to-volume ratios (SA:V) and alignment with the incident photon beam proved to be more efficient radiosensitizing agents, showing superiority in emitted electron fluence. However, in the microscale, the deposited energy ratio (DER) was not markedly influenced by the SA:V of the nanorod. Additionally, our findings revealed that the geometry of gold nanoparticles has a more significant impact on the emission of M-shell Auger electrons (with energies below 3.5 keV) than on higher-energy electrons.Significance. This research investigated the radiosensitization properties of gold nanorods, positioning them as promising alternatives to the more conventionally studied spherical gold nanoparticles in the context of cancer research. With increasing interest in multimodal cancer therapy, our findings have the potential to contribute valuable insights into the perspective of gold nanorods as effective multipurpose agents for synergistic photothermal therapy and radiotherapy. Future directions may involve exploring alternative metallic nanorods as well as further optimizing the geometry and coating materials, opening new possibilities for more effective cancer treatments.

Nanomaterials-based precision sonodynamic therapy enhancing immune checkpoint blockade: A promising strategy targeting solid tumor

Burgeoning is an evolution from conventional photodynamic therapy (PDT). Thus, sonodynamic therapy (SDT) regulated by nanoparticles (NPs) possesses multiple advantages, including stronger penetration ability, better biological safety, and not reactive oxygen species (ROS)-dependent tumor-killing effect. However, the limitation to tumor inhibition instead of shrinkage and the incapability of eliminating metastatic tumors hinder the clinical potential for SDT. Fortunately, immune checkpoint blockade (ICB) can revive immunological function and induce a long-term immune memory against tumor rechallenges. Hence, synergizing NPs-based SDT with ICB can provide a promising therapeutic outcome for solid tumors. Herein, we briefly reviewed the progress in NPs-based SDT and ICB therapy. We highlighted the synergistic anti-tumor mechanisms and summarized the representative preclinical trials on SDT-assisted immunotherapy. Compared to other reviews, we provided comprehensive and unique perspectives on the innovative sonosensitizers in each trial. Moreover, we also discussed the current challenges and future corresponding solutions.

Targeted delivery of temozolomide by nanocarriers based on folic acid-hollow TiO2 -nanospheres for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is a highly malignant brain tumor. Its standard treatment includes a combination of surgery, radiation, and chemotherapy. The last involves the oral delivery of free drug molecules to GBM such as Temozolomide (TMZ). However, this treatment has limited effectiveness owing to the drugs premature degradation, lack of cell selectivity, and poor control of pharmacokinetics. In this work, the development of a nanocarrier based on hollow titanium dioxide (HT) nanospheres functionalized with folic acid (HT-FA) for the targeted delivery of temozolomide (HT-TMZ-FA) is reported. This approach has the potential benefits of prolonging TMZ degradation, targeting GBM cells, and increasing TMZ circulation time. The HT surface properties were studied, and the nanocarrier surface was functionalized with folic acid as a potential targeting agent against GBM. The loading capacity, protection from degradation, and drug retention time were investigated. Cell viability was performed to assess the cytotoxicity of HT against LN18, U87, U251, and M059K GBM cell lines. The cell internalization of HT configurations (HT, HT-FA, HT-TMZ-FA) was evaluated to study targeting capabilities against GBM cancer. Results show that HT nanocarriers have a high loading capacity, retain and protect TMZ for at least 48 h. Folic acid-functionalized HT nanocarriers successfully delivered and internalized TMZ to glioblastoma cancer cells with high cytotoxicity through autophagic and apoptotic cellular mechanisms. Thus, HT-FA nanocarriers could be a promising targeted delivery platform for chemotherapeutic drugs for the treatment of GBM cancer.

Improved Simulated-Daylight Photodynamic Therapy and Possible Mechanism of Ag-Modified TiO2 on Melanoma

Simulated-daylight photodynamic therapy (SD-PDT) may be an efficacious strategy for treating melanoma because it can overcome the severe stinging pain, erythema, and edema experienced during conventional PDT. However, the poor daylight response of existing common photosensitizers leads to unsatisfactory anti-tumor therapeutic effects and limits the development of daylight PDT. Hence, in this study, we utilized Ag nanoparticles to adjust the daylight response of TiO₂, acquire efficient photochemical activity, and then enhance the anti-tumor therapeutic effect of SD-PDT on melanoma. The synthesized Ag-doped TiO₂ showed an optimal enhanced effect compared to Ag-core TiO₂. Doping Ag into TiO₂ produced a new shallow acceptor impurity level in the energy band structure, which expanded optical absorption in the range of 400-800 nm, and finally improved the photodamage effect of TiO₂ under SD irradiation. Plasmonic near-field distributions were enhanced due to the high refractive index of TiO₂ at the Ag-TiO₂ interface, and then the amount of light captured by TiO₂ was increased to induce the enhanced SD-PDT effect of Ag-core TiO₂. Hence, Ag could effectively improve the photochemical activity and SD-PDT effect of TiO₂ through the change in the energy band structure. Generally, Ag-doped TiO₂ is a promising photosensitizer agent for treating melanoma via SD-PDT.

3D-printed polyether-ether-ketone/n-TiO2 composite enhances the cytocompatibility and osteogenic differentiation of MC3T3-E1 cells by downregulating miR-154-5p

The object was to enhance the bioactivity of pure polyether-ether-ketone (PEEK) by incorporating nano-TiO₂ (n-TiO₂) and investigate its potential mechanism. PEEK/n-TiO₂ composite was manufactured using a 3D PEEK printer and characterized by scanning electron microscopy (SEM), 3D profiler, energy-dispersive spectroscopy, and Fourier-transform infrared (FT-IR) analyses. Cytocompatibility was tested using SEM, fluorescence, and cell counting kit-8 assays. Osteogenic differentiation was evaluated by osteogenic gene and mineralized nodule levels. The expression of the candidate miRNAs were detected in composite group, and its role in osteogenic differentiation was studied. As a results the 3D-printed PEEK/n-TiO₂ composite (Φ = 25 mm, H = 2 mm) was successfully fabricated, and the TiO₂ nanoparticles were well distributed and retained the nanoscale size of the powder. The Ra value of the composite surface was 2.69 ± 0.29, and Ti accounted for 22.29 ± 12.09% (in weight), and FT-IR analysis confirmed the characteristic peaks of TiO₂. The cells in the composite group possessed better proliferation and osteogenic differentiation abilities than those in the PEEK group. miR-154-5p expression was decreased in the composite group, and the inhibition of miR-154-5p significantly enhanced the proliferation and osteogenic differentiation abilities. In conclusion, 3D-printed PEEK/n-TiO₂ composite enhanced cytocompatibility and osteogenic induction ability by downregulating miR-154-5p, which provides a promising solution for improving the osteointegration of PEEK.

Macrophage-Targeted Sonodynamic/Photothermal Synergistic Therapy for Preventing Atherosclerotic Plaque Progression Using CuS/TiO2 Heterostructured Nanosheets

Sonodynamic therapy (SDT) and photothermal therapy (PTT) are two effective strategies for the treatment of atherosclerotic plaques. However, the low yield of reactive oxygen species (ROS) of conventional organic sonosensitizers and the low biosafety of hyperthermia limit the therapeutic efficacy of SDT and PTT. Herein, we report copper sulfide/titanium oxide heterostructure nanosheets modified with hyaluronic acid (HA) and PEG (HA-HNSs) for low-intensity sonodynamic and mild-photothermal synergistic therapy for early atherosclerotic plaques. CuS/TiO₂ heterostructure nanosheets (HNSs) show high electron-hole separation efficiency and superior sonodynamic performance, because it has high surface energy crystal facets as well as a narrow band. Moreover, HNSs exhibit intense absorbance in the NIR-II region, which endows the nanosheets with excellent photothermal performance. With a further modification of HA, HA-HNSs can selectively target intraplaque proinflammatory macrophages through CD44-HA interaction. Because SDT reduces the expression of heat shock protein 90 and PTT facilitates the sonocatalytic process, the combination of SDT and PTT based on HA-HNSs could synergistically induce proinflammatory macrophage apoptosis. More importantly, the synergistic therapy prevents the progression of early atherosclerotic plaque by removing lesional macrophages and mitigating inflammation. Taken together, this work provides a macrophage-targeting sonodynamic/photothermal synergistic therapy, which is an effective translational clinical intervention for early atherosclerotic plaques.

Influence of Parameters on Photodynamic Therapy of Au@TiO2-HMME Core-Shell Nanostructures

Photodynamic therapy (PDT) is a promising tumor therapy and has been proven to be an effective, safe and minimally invasive technique. Hematoporphyrin monomethyl ether (HMME) mediated PDT has been used in clinical treatment of port wine stain (PWS) due to its single component, high yield of singlet oxygen and short light-sensitive period. However, as an amphiphilic photosensitizer, HMME is easy to aggregate due to the presence of a hydrophobic group, which undesirably reduced its generation of singlet oxygen and bioavailability. In this study, we synthesized the stable conjugate of Au@TiO₂ core-shell nanostructure with HMME, and the influence of different factors on PTD efficiency were studied. The results showed that the nanostructure had higher PTD efficiency for KB cells than that of HMME. The irradiation wavelength, gold nanoparticle shape and the shell thickness are all important factors for KB cell PDT.

Influence of Anodized Titanium Surfaces on the Behavior of Gingival Cells in Contact with: A Systematic Review of In Vitro Studies

Electrochemically anodized (EA) surfaces promise enhanced biological properties and may be a solution to ensure a seal between peri-implant soft tissues and dental transmucosal components. However, the interaction between the modified nano-structured surface and the gingival cells needs further investigation. The aim of this systematic review is to analyze the biological response of gingival cells to EA titanium surfaces in in vitro studies with a score-based reliability assessment. A protocol aimed at answering the following focused question was developed: “How does the surface integrity (e.g., topography and chemistry) of EA titanium influence gingival cell response in in vitro studies?”. A search in three computer databases was performed using keywords. A quality assessment of the studies selected was performed using the SciRAP method. A total of 14 articles were selected from the 216 eligible papers. The mean reporting and the mean methodologic quality SciRAP scores were 87.7 ± 7.7/100 and 77.8 ± 7.8/100, respectively. Within the limitation of this review based on in vitro studies, it can be safely speculated that EA surfaces with optimal chemical and morphological characteristics enhance gingival fibroblast response compared to conventional titanium surfaces. When EA is combined with functionalization, it also positively influences gingival epithelial cell behavior.

A state-of-the-art review of the fabrication and characteristics of titanium and its alloys for biomedical applications

Abstract

Commercially pure titanium and titanium alloys have been among the most commonly used materials for biomedical applications since the 1950s. Due to the excellent mechanical tribological properties, corrosion resistance, biocompatibility, and antibacterial properties of titanium, it is getting much attention as a biomaterial for implants. Furthermore, titanium promotes osseointegration without any additional adhesives by physically bonding with the living bone at the implant site. These properties are crucial for producing high-strength metallic alloys for biomedical applications. Titanium alloys are manufactured into the three types of α, β, and α + β. The scientific and clinical understanding of titanium and its potential applications, especially in the biomedical field, are still in the early stages. This review aims to establish a credible platform for the current and future roles of titanium in biomedicine. We first explore the developmental history of titanium. Then, we review the recent advancement of the utility of titanium in diverse biomedical areas, its functional properties, mechanisms of biocompatibility, host tissue responses, and various relevant antimicrobial strategies. Future research will be directed toward advanced manufacturing technologies, such as powder-based additive manufacturing, electron beam melting and laser melting deposition, as well as analyzing the effects of alloying elements on the biocompatibility, corrosion resistance, and mechanical properties of titanium. Moreover, the role of titania nanotubes in regenerative medicine and nanomedicine applications, such as localized drug delivery system, immunomodulatory agents, antibacterial agents, and hemocompatibility, is investigated, and the paper concludes with the future outlook of titanium alloys as biomaterials.

Graphic abstract

Biosensitive and antibacterial coatings on metallic material for medical applications

Metallic materials are commonly used for load-bearing implants and as internal fixation devices. It is customary to use austenitic stainless steel, especially surgical grade type 316L SS as temporary and Ti alloys as permanent implants. However, long-term, poor bonding with bone, corrosion, and release of metal ions, such as chromium and nickel occur. These ions are powerful allergens and carcinogens and their uncontrolled leaching may be avoided by surface coatings. Therefore, bioactive glasses (BGs) became a vital biomedical material, which can form a biologically active phase of hydroxycarbonate apatite on their surface when in contact with physiological fluids. To reduce the high coefficient of friction and the brittle nature of BGs, polymers are normally incorporated to avoid the high-temperature sintering/densification of ceramic-only coatings. For medical application, electrophoretic deposition (EPD) is now used for polymer (organic) and ceramic (inorganic) components at room temperature due to its simplicity, control of coating thickness and uniformity, low cost of equipment, ability to coat substrates of intricate shape and to supply thick films in composite form, high purity of deposits as well as no phase transformation during coating. Although extensive research has been conducted on polymer/inorganic composite coatings, only some studies have reported multifunctional properties, such as biological antibacterial activity, enhanced cell adhesion, controlled drug release ability, and mechanical properties. This review will focus on biodegradable coatings, including zien, chitosan, gelatin, cellulose loaded with antibacterial drugs/metallic ions/natural herbs on biostable substrates (PEEK/PMMA/PCL/PLLA layers), which have the potential of multifunctional coating for metallic implants.

Inorganic chemoreactive nanosonosensitzers with unique physiochemical properties and structural features for versatile sonodynamic nanotherapies

The fast development of nanomedicine and nanobiotechnology has enabled the emerging of versatile therapeutic modalities with high therapeutic efficiency and biosafety, among which nanosonosensitizer-involved sonodynamic therapy (SDT) employs ultrasound (US) as the exogenous activation source for inducing the production of reactive oxygen species (ROS) and disease therapy. The chemoreactive nanosonosensitizers are the critical components participating in the SDT process, which generally determine the SDT efficiency and therapeutic outcome. Compared to the traditional and mostly explored organic sonosensitizers, the recently developed inorganic chemoreactive nanosonosensitizers feature the distinct high stability, multifunctionality and significantly different SDT mechanism. This review dominantly discusses and highlights two types of inorganic nanosensitizers in sonodynamic treatments of various diseases and their underlying therapeutic mechanism, including US-activated generation of electrons (e^-) and holes (h⁺) for facilitating the following ROS production and delivery of organic molecular sonosensitizers. Especially, this review proposes four strategies aiming for augmenting the SDT efficiency on antitumor and antibacterial applications based on inorganic sonosensitizers, including defect engineering, novel metal coupling, increasing electric conductivity and alleviating tumor hypoxia. The encountered challenges and critical issues facing these inorganic nanosonosensitzers are also highlighted and discussed for advancing their clinical translations.

Color Centers on Hydrogenated TiO2 Facets Unlock Fluorescence Imaging

Hydrogenation of TiO₂ provides a promising strategy to realize fluorescence imaging. The fluorescence of hydrogenated TiO₂ arises from photoluminescence (PL) from the color centers. Color centers changed the surface electronic states to shorten fluorescence lifetimes, to unlock the intrinsic fluorescence of hydrogenated TiO₂. Specifically, the formation of color centers and their role in determining electronic states are highly facet-dependent. Color centers corresponding to surface oxygen vacancies (Vo) on {201} and {101} facets, surface Ti³⁺ on {001} facets, and subsurface Vo on {100} facets were discerned, following distinct Vo formation pathways and diffusion behaviors, as well as electron localization. The electronic states in the color centers are contributed by Ti 3d orbitals with different energy levels. Distinct electronic states on each facet give rise to TiO₂ coloration from white to dark gray, and the energy levels in color centers trigger unique PL emissions, enabling dark-gray hydrogenated {201} TiO₂ to emit bright intrinsic fluorescence.

Using C-doped TiO2 Nanoparticles as a Novel Sonosensitizer for Cancer Treatment

Sonodynamic therapy is an effective treatment for eliminating tumor cells by irradiating sonosentitizer in a patient's body with higher penetration ultrasound and inducing the free radicals. Titanium dioxide has attracted the most attention due to its properties among many nanosensitizers. Hence, in this study, carbon doped titanium dioxide, one of inorganic materials, is applied to avoid the foregoing, and furthermore, carbon doped titanium dioxide is used to generate ROS under ultrasound irradiation to eliminate tumor cells. Spherical carbon doped titanium dioxide nanoparticles are synthesized by the sol-gel process. The forming of C-Ti-O bond may also induce defects in lattice which would be beneficial for the phenomenon of sonoluminescence to improve the effectiveness of sonodynamic therapy. By dint of DCFDA, WST-1, LDH and the Live/Dead test, carbon doped titanium dioxide nanoparticles are shown to be a biocompatible material which may induce ROS radicals to suppress the proliferation of 4T1 breast cancer cells under ultrasound treatment. From in vivo study, carbon doped titanium dioxide nanoparticles activated by ultrasound may inhibit the growth of the 4T1 tumor, and it showed a significant difference between sonodynamic therapy (SDT) and the other groups on the seventh day of the treatment.