ZnO based 0-3D diverse nano-architectures, films and coatings for biomedical applications

Thin-film nano-architecting is a promising approach that controls the properties of nanoscale surfaces to increase their interdisciplinary applications in a variety of fields. In this context, zinc oxide (ZnO)-based various nano-architectures (0-3D) such as quantum dots, nanorods/nanotubes, nanothin films, tetrapods, nanoflowers, hollow structures, etc. have been extensively researched by the scientific community in the past decade. Owing to its unique surface charge transport properties, optoelectronic properties and reported biomedical applications, ZnO has been considered as one of the most important futuristic bio-nanomaterials. This review is focused on the design/synthesis and engineering of 0-3D nano-architecture ZnO-based thin films and coatings with tunable characteristics for multifunctional biomedical applications. Although ZnO has been extensively researched, ZnO thin films composed of 0-3D nanoarchitectures with promising thin film device bio-nanotechnology applications have rarely been reviewed. The current review focuses on important details about the technologies used to make ZnO-based thin films, as well as the customization of properties related to bioactivities, characterization, and device fabrication for modern biomedical uses that are relevant. It features biosensing, tissue engineering/wound healing, antibacterial, antiviral, and anticancer activity, as well as biomedical diagnosis and therapy with an emphasis on a better understanding of the mechanisms of action. Eventually, key issues, experimental parameters and factors, open challenges, etc. in thin film device fabrications and applications, and future prospects will be discussed, followed by a summary and conclusion.

Supramolecular catalyst with [FeCl4] unit boosting photoelectrochemical seawater splitting via water nucleophilic attack pathway

Propelled by the structure of water oxidation co-catalysts in natural photosynthesis, molecular co-catalysts have long been believed to possess the developable potential in artificial photosynthesis. However, the interfacial complexity between light absorber and molecular co-catalyst limits its structural stability and charge transfer efficiency. To overcome the challenge, a supramolecular scaffold with the [FeCl4] catalytic units is reported, which undergo a water-nucleophilic attack of the water oxidation reaction, while the supramolecular matrix can be in-situ grown on the surface of photoelectrode through a simple chemical polymerization to be a strongly coupled interface. A well-defined BiVO4 photoanode hybridized with [FeCl4] units in polythiophene reaches 4.72 mA cm-2 at 1.23 VRHE, which also exhibits great stability for photoelectrochemical seawater splitting due to the restraint on chlorine evolution reaction by [FeCl4] units and polythiophene. This work provides a novel solution to the challenge of the interface charge transfer of molecular co-catalyst hybridized photoelectrode.

Nanomaterials-mediated photodynamic therapy and its applications in treating oral diseases

Oral diseases, such as dental caries, periodontitis and oral cancer, have a very high morbidity over the world. Basically, many oral diseases are commonly related to bacterial infections or cell malignant proliferation, and usually located on the superficial positions. These features allow the convenient and efficient application of photodynamic therapy (PDT) for oral diseases, since PDT is ideally suitable for the diseases on superficial sites and has been widely used for antimicrobial and anticancer therapy. Photosensitizers (PSs) are an essential element in PDT, which induce the generation of a large number of reactive oxygen species (ROS) upon absorption of specific lights. Almost all the PSs are small molecules and commonly suffered from various problems in the PDT environment, such as low solubility and poor stability. Recently, reports on the nanomedicine-based PDT have been well documented. Various functionalized nanomaterials can serve either as the PSs carriers or the direct PSs, thus enhancing the PDT efficacy. Herein, we aim to provide a comprehensive understanding of the features of different oral diseases and discuss the potential applications of nanomedicine-based PDT in the treatment of some common oral diseases. Also, the concerns and possible solutions for nanomaterials-mediated PDT are discussed.

Construction of a matchstick-shaped Au@ZnO@SiO2-ICG Janus nanomotor for light-triggered synergistic antibacterial therapy

The drug-resistance of bacteria poses a serious threat to public health, so the exploration of new antibacterial materials has attracted extensive attention. Here, we report Au@ZnO@SiO₂-ICG nanomotors as an antibacterial candidate. Firstly, we prepared the Janus structure Au@ZnO loaded with indocyanine green (ICG) and constructed a synergistic antibacterial platform with photothermal and photodynamic properties triggered by dual light sources. Specifically, the metal/semiconductor heterostructure of Au@ZnO has a synergistic effect under ultraviolet (UV) irradiation, which can adjust the transfer of interface electrons, so as to greatly improve the generation of cytotoxic ROS for photodynamic sterilization. The loaded ICG is an effective photosensitizer, and can induce a stronger photothermal effect in collaboration with Au under near-infrared light (NIR). In addition, the asymmetric structures of nanomotors have autonomous movement with the help of generated temperature gradient when exposed to NIR light, conducive to breaking through the bacterial membrane and improving the membrane insertion ability of antibacterial therapeutic agents. The results indicate that the prepared Au@ZnO@SiO₂-ICG nanomotors show excellent light responses and synergistic sterilization ability to Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). This study will provide a new idea for the application of metal-semiconductor nanocomposites in the treatment of bacterial infection.

Magnetic-targeted capacitive heterostructure of polypyrrole for hypoxia-tolerant synergistic photodynamic/photothermal therapy under near infrared excitation

Dual/Multi-modal photonanomedicines with the maximized antitumor efficacy has attracted extensive concerning. In this contribution, through photovoltaic engineering of photothermal conjugated polymer, a facile magnetic-targeted capacitive heterostructure of polypyrrole (upconversion nanoparticles (UCNPs)@SiO₂-Fe₃O₄ @polypyrrole (USFP)), capable of photodynamic therapy (PDT) and photothermal therapy (PTT) upon near infrared (NIR) excitation is purposefully developed. Owing to the optimized regulation of photoreaction pathway via photoinduced capacitance effect, the yield of reactive oxygen species (ROS) including ¹O₂ in polypyrrole can be significantly promoted. Notably, the external layers (porous silica and polypyrrole) of USFP allow the encounter and subsequent Fenton reaction between Fe₃O₄ and H₂O₂ in tumor site, thereby further enhancing the photodynamic effect via an effective O₂ supply. Upon intravenous injection into tumor-bearing mice, USFP can accumulate in tumors through a magnetic guidance, ablation experiments in vitro and in vivo confirmed the enhanced synergistic therapeutic effect and desirable biocompatibility of USFP.

A UCMPs@MIL-100 based thermo-sensitive molecularly imprinted fluorescence sensor for effective detection of β-lactoglobulin allergen in milk products

In this study, a thermo-sensitive molecularly imprinted fluorescence sensor was developed for the specific detection of β-Lactoglobulin (β-LG) allergen in milk products. The metal–organic frameworks (MIL-100) with a high specific surface area was coated on the surface of upconversion micro-particles (UCMPs). As the core, an imprinted polymer layer allowing for swelling and shrinking with response to temperature was prepared, which exhibited high adsorption and mass transfer capabilities for β-LG allergen. The fluorescence intensity of UCMPs@MIL-100@MIP decreased linearly with the concentration of β-LG in the range of 0.1–0.8 mg mL⁻¹, and the limit of detection was 0.043 mg mL⁻¹. The imprinting factor reached 3.415, which indicated that excellent specificity of the UCMPs@MIL-100@MIP for β-LG allergen. In the analysis of β-LG allergen in actual milk samples, the proposed UCMPs@MIL-100@MIP fluorescence sensor produced reliable and accurate results (recovery: 86.0–98.4%, RSD: 2.8–6.8%), closely related to the results of standard HPLC method (correlation coefficient: 0.9949), indicating that its feasibility in the detection of β-LG allergen.

Preparation and synergistic chemo-photothermal therapy of redox-responsive carboxymethyl cellulose/chitosan complex nanoparticles

Chemo-photothermal combination therapy has great promise for enhanced tumor treatment. Hereby, we developed a complex nanoparticle using electrostatic absorption method, in which the inner chitosan (CS) NPs loaded polypyrrole (PPy) nanoparticles and 5-fluorouracil (5Fu), the outer shell was carboxymethyl cellulose (CMC) crosslinked with disulfide. The drug loaded polysaccharide complex nanoparticles displayed good photothermal effects, and the drug release would be triggered by multi-model response of NIR irradiation, high glutathione (GSH) and weak acidity in tumor environment. In vitro biological studies indicated the nanopartiles could be effectively internalized by HepG2 cancer cells. Moreover, the remarkable inhibition of the CMC complex PPy and 5Fu loaded CS nanoparticles (CMC/CS@PPy + 5Fu NPs) against tumor growth was achieved in HepG2-bearing mice model, suggesting its great potential for synergetic chemo-photothermal therapy.

Water-soluble PANI:PSS designed for spontaneous non-disruptive membrane penetration and direct intracellular photothermal damage on bacteria

The major challenge in the field of antibacterial agents is to overcome the low-permeability of bacteria cell membranes that protects the cells against diverse drugs. In this work, water-soluble polyaniline (PANI)-poly (p-styrenesulfonic acid) (PSS) (PANI:PSS) is found to spontaneously penetrate bacteria cellular membranes in a non-disruptive way, leaving no evidence of membrane poration/disturbance or cell death, thus avoiding side effects caused by cationic ammonia groups in traditional ammonia-containing antibacterial agents. For aqueous synthesis, which is important for biocompatibility, the polymer is synthesized via an enzyme-mimetic route relying on the catalysis of a nanozyme. Owing to its fluorescent properties, the localization of as-prepared PANI:PSS is determined by the confocal microscope, and the results confirm its rapid entry into bacteria. Under 808 nm near-infrared (NIR) irradiation, the internalized PANI:PSS generates local hyperthermia and destroys bacteria highly efficiently from inside the cells due to its excellent photothermal effects. Staphylococcus aureus (S. aureus), M ethicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) could be effectively eliminated as well as the corresponding bacterial biofilms. Results of in vivo antibacterial experiments demonstrate excellent antibacterial activities of the water-soluble PANI:PSS without side effects. Therefore, the prepared water-soluble polymer in this study has great potential in the treatment of various bacterial infections.

Current trends in smart mesoporous silica-based nanovehicles for photoactivated cancer therapy

Photoactivated therapeutic strategies (photothermal therapy and photodynamic therapy), due to the adjusted therapeutic area, time and light dosage, have prevailed for the fight against tumors. Currently, the monotherapy with limited treatment effect and undesired side effects is gradually replaced by multimodal and multifunctional nanosystems. Mesoporous silica nanoparticles (MSNs) with unique physicochemical advantages, such as huge specific surface area, controllable pore size and morphology, functionalized modification, satisfying biocompatibility and biodegradability, are considered as promising candidates for multimodal photoactivated cancer therapy. Excitingly, the innovative nanoplatforms based on the mesoporous silica nanoparticles provide more and more effective treatment strategies and display excellent antitumor potential. Given the rapid development of antitumor strategies based on MSNs, this review summarizes the current progress in MSNs-based photoactivated cancer therapy, mainly consists of (1) photothermal therapy-related theranostics; (2) photodynamic therapy-related theranostics; (3) multimodal synergistic therapy, such as chemo-photothermal-photodynamic therapy, phototherapy-immunotherapy and phototherapy-radio therapy. Based on the limited penetration of irradiation light in photoactivated therapy, the challenges faced by deep-seated tumor therapy are fully discussed, and future clinical translation of MSNs-based photoactivated cancer therapy are highlighted.

Energy transfer facilitated near infrared fluorescence imaging and photodynamic therapy of tumors

Near infrared (NIR) light activated fluorescence imaging and photodynamic therapy hold great potential for tumor treatment in deep tissues. Development of effective theranostic nanosystems to integrate both functions is becoming an attractive route for tumor diagnosis and therapy. Herein, nitrogen (N), sulfur (S) co-doped graphene quantum dots (GQDs) were engineered on the surface of upconversion nanoparticles (UCNPs) to form GUCNP nanosystems, where fluorescence resonance energy transfer (FRET) from UCNPs to GQDs could significantly facilitate the NIR fluorescence enhancement and NIR light activated singlet oxygen (¹O₂) generation. Under 980 nm laser irradiation, UCNPs could emit green and NIR fluorescence, where the wavelength of green fluorescence matched the excitation band of GQDs to activate ¹O₂ generation and produce additional NIR fluorescence. Both NIR fluorescence from UCNPs and GQDs could be used for cell and animal fluorescence imaging, and the generated ¹O₂ enhanced ROS production, phase II enzyme expression, apoptosis and cell death in 4T1 cells, as a result of tumor growth inhibition in 4T1 tumor-bearing mice. GUCNP nanosystems may pave a new way for cancer therapy.

A full-spectrum responsive B-TiO2@SiO2–HA nanotheranostic system for NIR-II photoacoustic imaging-guided cancer phototherapy

A full-spectrum responsive B-TiO₂@SiO₂–HA nanotheranostic system has been successfully fabricated for second near-infrared photoacoustic imaging-guided synergistic cancer targeting phototherapy.

A smart theranostic agent based on Fe-HPPy@Au/DOX for CT imaging and PTT/chemotherapy/CDT combined anticancer therapy

We herein explored a smart Fe-HPPy@Au/DOX theranostic agent for CT diagnosis and PTT/chemotherapy/CDT synergistic treatment of cancer. When the Fe-HPPy@Au/DOX theranostic agent entered the tumor, the tumor environment accelerated the trapped Fe ions release to catalyze the production of ˙OH for CDT. NIR irradiation drove the PTT, and at the same time improved the CDT by increasing the production of ˙OH and triggered DOX release for chemotherapy. In addition, the Au nanoparticles on the surface of Fe-HPPy@Au nanocomposites could be used as a CT imaging agent and catalyzer to produce H₂O₂ for enhanced CDT.

Quantum-Sized Zinc Oxide Nanoparticles Synthesised within Mesoporous Silica (SBA-11) by Humid Thermal Decomposition of Zinc Acetate

A modified facile method is presented to synthesise quantum-sized zinc oxide nanoparticles within the pores of a mesoporous silica host (SBA-11). This method eliminates the 3 h alcohol reflux and the basic solution reaction steps of zinc acetate. The mesoporous structure and the ZnO nanoparticles were analysed by X-ray diffractometry, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, nitrogen sorption analysis and UV–VIS spectroscopy. These tests confirm the synthesis of ~1 nm sized ZnO within the pores of SBA-11 and that the porous structure remained intact after ZnO synthesis.

The investigation of unique water-soluble heptamethine cyanine dye for use as NIR photosensitizer in photodynamic therapy of cancer cells

In this paper, a unique water-soluble heptamethine cyanine dye as NIR photosensitizer was synthesized to explore its properties associated with potential applications in photodynamic therapy (PDT). In the strategy of designing this photosensitizer, a sulfonic acid was used as a water soluble functional group and linked to the fluorophore through alkyl chains. 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl(Tempo) moiety was used as the a nitroxide spin label in obtaining biochemical reaction information in vivo due to it could greatly increase the inter-system crossing (ISC) process for triplet-state photosensitizers and low toxicity. As expected, the photosensitizers performed well in vitro photodynamic therapy. There were a remarkable absorbance band located at 692 nm and emission peaks falls at 762 nm, the quantum yield (Φ_f) was calculated to be 12.12% in pure aqueous solution using ICG as standards. The photosensitizer also has high singlet oxygen quantum yield (Φ_△) for 16.96% with NIR LED irradiation. This photosensitizer can rapidly produce singlet oxygen and exhibit high phototoxicity under NIR light irradiation. It has excellent cellular uptake ability and better cell compatibility. It was also successfully applied in Near-infrared fluorescence imaging and AO/EB staining. In a whole, the organic dye based on Heptamethine cyanine used as photosensitizer has great potential in vivo cancer treatment.

Nanoscale ZnO-based photosensitizers for photodynamic therapy

Due to the ability to induce the generation of reactive oxygen species (ROS) under light irradiation, ZnO nanoparticles show great potential in photodynamic therapy (PDT). Photo-triggered ROS production by ZnO nanoparticles and the resulting phototoxicity are efficient in killing cancer cells. This review highlights the recent exciting progress on the nanoscale ZnO-based photosensitizers (PSs) for PDT. Both the semplice ZnO nanoparticles as the PSs and the various chemicals (organic PS, dopant, metal and chemotherapeutic drugs) modified ZnO nanoparticles as the PSs show good ROS generation efficiency. The productive rate of ROS, the wavelength of exciting lights, and the therapeutic effect can be altered by doping different chemicals into ZnO nanoparticles at will. Additionally, we give some outlook on the design and functionalization of next-generation ZnO nanoparticles for more effective anti-cancer applications.

Facile synthesis of polypyrrole-rhodamine B nanoparticles for self-monitored photothermal therapy of cancer cells

Photothermal therapy following microscopic temperature detection can avoid overheating effects or insufficient heating, and thus improve therapeutic efficacy. In this study, biocompatible dual-functional nanoparticles (NPs) are constructed from polypyrrole (PPy) and rhodamine B (RB) by a one-step modified polymerization method. The polypyrrole serves as a photothemal agent, and rhodamine B acts as a temperature-sensing probe. The polypyrrole-rhodamine B (PPy-RB) NPs possess a high photothermal effect on irradiation by 808 nm laser, and a competent temperature sensitivity for the real-time temperature monitoring based on the emission intensity response of rhodamine B. After acting on HepG2 cells, the PPy-RB NPs can effectively induce cancer cell death, and the microscopic temperature is monitored by fluorescence feedback from rhodamine B during PTT by laser confocal microscopy. Hence, the proposed approach can supply a facile and promising way for the fabrication of effective theranostic nanoplatforms assisted by self-monitoring of cancer therapeutic processes.

Recent progress in the augmentation of reactive species with nanoplatforms for cancer therapy

Reactive species (RS), mainly including reactive oxygen species (ROS) and reactive nitrogen species (RNS), are indispensable in a wide variety of biological processes. RS often have elevated levels in cancer cells and tumor microenvironments. They also have a dual effect on cancer: on the one hand, they promote pro-tumorigenic signaling to facilitate tumor survival and on the other hand, they promote antitumorigenic pathways to induce cell death. Excessive RS would disrupt the cellular redox homeostasis balance and show partiality as oxidants, which would cause irreversible damage to the adjacent biomolecules such as lipids, proteins and nucleic acids. The altered redox environment and the corresponding increased antioxidant capacity in cancer cells render the cells susceptible to RS-manipulated therapies, especially the augmentation of RS. With the rapid development of nanotechnology and nanomedicine, a large number of cancer therapeutic nanoplatforms have been developed to trigger RS overproduction by exogenous and/or endogenous stimulation. In this review, we highlighted the latest progress in the nanoplatforms designed for the augmentation of RS in cancer therapy. Nanoplatforms based on strategies including disabling the antioxidant defense system, photodynamic therapy (PDT), sonodynamic therapy (SDT), and chemodynamic therapy (CDT) were introduced. The crucial obstacles involved in these strategies, such as the light penetration limitation of PDT, relatively low RS release by SDT, and strict conditions of Fenton reaction-mediated CDT, were also discussed, and feasible solutions for improvement were proposed. Furthermore, synergistic therapies among individual therapeutic modalities such as chemotherapy, photothermal therapy, and RS-based dynamic therapies were overviewed, which contributed to achieving more optimal anticancer efficacy than linear addition. This review sheds light on the development of non-invasive cancer therapy based on RS manipulation and provides guidance for establishing promising cancer therapeutic platforms in clinical settings.

Nanotechnology based therapeutic application in cancer diagnosis and therapy

Due to the lack of early diagnosis, cancer remains as one of the leading cause of human mortality. Inability to translate research into clinical trials and also inability of chemotherapeutics delivery to targeted tumor sites are major drawbacks in cancer therapeutics. With the emergence of nanomedicine, several nanoprobes (conjugated with targeting ligands and chemotherapeutic drugs) are developed. It can interact with biological system and thus sense and monitor the biological events with high efficiency and accuracy along with therapy application. Nanoparticles like gold and iron oxide are frequently used in the computed tomography and magnetic resonance imaging applications, respectively. Moreover, enzymatic activity of gold and iron oxide nanoparticles enables the visible colorimetric diagnostic of cancer cells, whereas, fluorescence property of quantum dots and upconversion nanoparticles helps in in vivo imaging application. Other than this, drug conjugation with nanoparticles also reduces the systemic toxic effect of chemotherapeutic drugs. Due to their several unique intrinsic properties, nanoparticles itself can also be employed as therapeutics in cancer treatment by photothermal therapy (PTT) and photodynamic therapy (PDT). Thus, the main focus of this review is to emphasize on current progress in diagnostic and therapeutic application of nanoprobes in cancer.

A facile method for the synthesis of copper–cysteamine nanoparticles and study of ROS production for cancer treatment

A facile synthesis method of copper–cysteamine nanoparticles is reported and their application for cancer treatment through ROS-mediated mechanisms is explored.

Self-destructive PEG–BODIPY nanomaterials for photodynamic and photothermal therapy

Amphiphilic photosensitizers are made from boron dipyrromethene and poly(ethylene glycol) by using a thioketal linker, which is reactive oxygen species-responsive for photodynamic and photothermal therapy.