Near-infrared-driven upconversion nanoparticles with photocatalysts through water-splitting towards cancer treatment

Water splitting is promising, especially for energy and environmental applications; however, there are limited studies on the link between water splitting and cancer treatment. Upconversion nanoparticles (UCNPs) can be used to convert near-infrared (NIR) light to ultraviolet (UV) or visible (Vis) light and have great potential for biomedical applications because of their profound penetration ability, theranostic approaches, low self-fluorescence background, reduced damage to biological tissue, and low toxicity. UCNPs with photocatalytic materials can enhance the photocatalytic activities that generate a shorter wavelength to increase the tissue penetration depth in the biological microenvironment under NIR light irradiation. Moreover, UCNPs with a photosensitizer can absorb NIR light and convert it into UV/vis light and emit upconverted photons, which excite the photoinitiator to create H2, O2, and/or OH˙ via water splitting processes when exposed to NIR irradiation. Therefore, combining UCNPs with intensified photocatalytic and photoinitiator materials may be a promising therapeutic approach for cancer treatment. This review provides a novel strategy for explaining the principles and mechanisms of UCNPs and NIR-driven UCNPs with photocatalytic materials through water splitting to achieve therapeutic outcomes for clinical applications. Moreover, the challenges and future perspectives of UCNP-based photocatalytic materials for water splitting for cancer treatment are discussed in this review.

Ferrocene-Containing Nucleic Acid-Based Energy-Storage Nanoagent for Continuously Photo-Induced Oxidative Stress Amplification

Regulation of cellular oxidative stress plays a critical role in revealing the molecular mechanisms of cellular activities and thus is a potential strategy for tumor treatment. Optical methods have been employed for intelligent regulation of oxidative stress in tumor regions. However, long-time continuous irradiation inevitably causes damage to normal tissues. Herein, a ferrocene-containing nucleic acid-based energy-storage nanoagent was designed to achieve the continuous photo-regulation of cellular oxidative stress in the dark. Specifically, the photoenergy stored in the agent could convert effectively and accelerate Fenton-like reaction continuously, augmenting cellular oxidative stress. This nanoagent could also silence oxidative damage repair genes to further amplify oxidative stress. This strategy not only provides oxidative stress regulation for studying the molecular mechanisms of biological activities, but also offers a promising step toward tumor microenvironment modulation.

Advances in Photodynamic Therapy Based on Nanotechnology and Its Application in Skin Cancer

Comprehensive cancer treatments have been widely studied. Traditional treatment methods (e.g., radiotherapy, chemotherapy), despite ablating tumors, inevitably damage normal cells and cause serious complications. Photodynamic therapy (PDT), with its low rate of trauma, accurate targeting, synergism, repeatability, has displayed great advantages in the treatment of tumors. In recent years, nanotech-based PDT has provided a new modality for cancer treatment. Direct modification of PSs by nanotechnology or the delivery of PSs by nanocarriers can improve their targeting, specificity, and PDT efficacy for tumors. In this review, we strive to provide the reader with a comprehensive overview, on various aspects of the types, characteristics, and research progress of photosensitizers and nanomaterials used in PDT. And the application progress and relative limitations of nanotech-PDT in non-melanoma skin cancer and melanoma are also summarized.

Advances with metal oxide-based nanoparticles as MDR metastatic breast cancer therapeutics and diagnostics

Metal oxide nanoparticles have attracted increased attention due to their emerging applications in cancer detection and therapy. This study envisioned to highlight the great potential of metal oxide NPs due to their interesting properties including high payload, response to magnetic field, affluence of surface modification to overcome biological barriers, and biocompatibility. Mammogram, ultrasound, X-ray computed tomography (CT), MRI, positron emission tomography (PET), optical or fluorescence imaging are used for breast imaging. Drug-loaded metal oxide nanoparticle delivered to the breast cancer cells leads to higher drug uptake. Thus, enhanced the cytotoxicity to target cells compared to free drug. The drug loaded metal oxide nanoparticle formulations hold great promise to enhance efficacy of breast cancer therapy including multidrug resistant (MDR) and metastatic breast cancers. Various metal oxides including magnetic metal oxides and magnetosomes are of current interests to explore cancer drug delivery and diagnostic efficacy especially for metastatic breast cancer. Metal oxide-based nanocarrier formulations are promising for their usage in drug delivery and release to breast cancer cells, cancer diagnosis and their clinical translations.

Biomarker targeted therapy approaches for TNBC using metal oxide-based NPs are highly effective and promising.

Recent advances in functionalized upconversion nanoparticles for light-activated tumor therapy

Upconversion nanoparticles (UCNPs) are a class of optical nanocrystals doped with lanthanide ions that offer great promise for applications in controllable tumor therapy. In recent years, UCNPs have become an important tool for studying the treatment of various malignant and nonmalignant cutaneous diseases. UCNPs convert near-infrared (NIR) radiation into shorter-wavelength visible and ultraviolet (UV) radiation, which is much better than conventional UV activated tumor therapy as strong UV-light can be damaging to healthy surrounding tissue. Moreover, UV light generally does not penetrate deeply into the skin, an issue that UCNPs can now address. However, the current studies are still in the early stage of research, with a long way to go before clinical implementation. In this paper, we systematically analysed recent advances in light-activated tumor therapy using functionalized UCNPs. We summarized the purpose and mechanism of UCNP-based photodynamic therapy (PDT), gene therapy, immunotherapy, chemo-therapy and integrated therapy. We believe the creation of functional materials based on UCNPs will offer superior performance and enable innovative applications, increasing the scope and opportunities for cancer therapy in the future.

Recent Advances in Magnetic Upconversion Nanocomposites for Bioapplications

The combination of magnetism and upconversion luminescent property into one single nanostructure is fascinating for biological fields, such as multimodal bioimaging, targeted drug delivery, and imaging-guided therapy. In this review, we will provide the state-of-the-art advances on magnetic upconversion nanocomposites towards their bioapplications. Their structure design, synthesis methods, surface engineering and applications in bioimaging, drug delivery, therapy as well as biodetection will be covered.

Nanoheterostructures (NHS) and Their Applications in Nanomedicine: Focusing on In Vivo Studies

Inorganic nanoparticles have great potential for application in many fields, including nanomedicine. Within this class of materials, inorganic nanoheterostructures (NHS) look particularly promising as they can be formulated as the combination of different domains; this can lead to nanosystems with different functional properties, which, therefore, can perform different functions at the same time. This review reports on the latest development in the synthesis of advanced NHS for biomedicine and on the tests of their functional properties in in vivo studies. The literature discussed here focuses on the diagnostic and therapeutic applications with special emphasis on cancer. Considering the diagnostics, a description of the NHS for cancer imaging and multimodal imaging is reported; more specifically, NHS for magnetic resonance, computed tomography and luminescence imaging are considered. As for the therapeutics, NHS employed in magnetic hyperthermia or photothermal therapies are reported. Examples of NHS for cancer theranostics are also presented, emphasizing their dual usability in vivo, as imaging and therapeutic tools. Overall, NHS show a great potential for biomedicine application; further studies, however, are necessary regarding the safety associated to their use.

Advances in the application of upconversion nanoparticles for detecting and treating cancers

The detection and treatment of cancer cells at an early stage are crucial for prolonging the survival time and improving the quality of life of patients. Upconversion nanoparticles (UCNPs) have unique physical and chemical advantages and likely provide a platform for detecting and treating cancer cells at an early stage. In this paper, the principle of UCNPs as chemical sensors based on fluorescence resonance energy transfer (FRET) has been briefly introduced. Research progress in such chemical sensors for detecting and analyzing bioactive substances and heavy metal ions at the subcellular level has been summarized. The principle of UCNP-based nanoprobe-targeting of cancer cells has been described. The research progress in using nanocomposites for cancer cell detection, namely cancer cell targeted imaging and tissue staining, has been discussed. In the field of cancer treatment, the principles and research progress of UCNPs in photodynamic therapy and photothermal therapy of cancer cells are systematically discussed. Finally, the prospects for UCNPs and remaining challenges to UCNP application in the field of cancer diagnosis and treatment are briefly described. This review provides powerful theoretical guidance and useful practical information for the research and application of UCNPs in the field of cancer.

Therapeutic applications of iron oxide based nanoparticles in cancer: basic concepts and recent advances

Nanotechnology has introduced new techniques and phototherapy approaches to fabricate and utilize nanoparticles for cancer therapy. These phototherapy approaches, such as photothermal therapy (PTT) and photodynamic therapy (PDT), hold great promise to overcome the limitations of traditional treatment methods. In phototherapy, magnetic iron oxide nanoparticles (IONPs) are of paramount importance due to their wide range of biomedical applications. This review discusses the basic concepts, various therapy approaches (PTT, PDT, magnetic hyperthermia therapy (MHT), chemotherapy and immunotherapy), intrinsic properties, and mechanisms of cell death of IONPs; it also provides a brief overview of recent developments in IONPs, with focus on their therapeutic applications. Much attention is devoted to elaborating the various parameters, intracellular behaviors and limitations of MHT. Bimodal therapies which act alone or in combination with other modalities are also discussed. The review highlights some limitations in the explored research areas and suggests future directions to overcome these limitations.

Role of Mn2+ Doping in the Preparation of Core-Shell Structured Fe₃O₄@upconversion Nanoparticles and Their Applications in T₁/T₂-Weighted Magnetic Resonance Imaging, Upconversion Luminescent Imaging and Near-Infrared Activated Photodynamic Therapy

Core-shell (C/S) structured upconversion coated Fe₃O₄ nanoparticles (NPs) are of great interest due to their potential as magnetic resonance imaging (MRI) and upconversion luminescent (UCL) imaging agents, as well as near-infrared activated photodynamic therapy (PDT) platforms. When C/S structured Fe₃O₄@Mn²⁺-doped NaYF₄:Yb/Er NPs were prepared previously, well-defined C/S-NPs could not be formed without the doping of Mn²⁺ during synthesis. Here, the role of Mn²⁺ doping on the synthesis of core-shell structured magnetic-upconversion nanoparticles (MUCNPs) is investigated in detail. Core-shell-shell nanoparticles (C/S/S-MUCNPs) with Fe₃O₄ as the core, an inert layer of Mn²⁺-doped NaYF₄ and an outer shell consisting of Mn²⁺-doped NaYF₄:Yb/Er were prepared. To further develop C/S/S-MUCNPs applications in the biological field, amphiphilic poly(maleic anhydride-alt-1-octadecene) (C₁₈PMH) modified with amine functionalized methoxy poly(ethylene glycol) (C₁₈PMH-mPEG) was used as a capping ligand to modify the surface of C/S/S-MUCNPs to improve biocompatibility. UCL imaging, T₁-weighted MRI ascribed to the Mn²⁺ ions and T₂-weighted MRI ascribed to the Fe₃O₄ core of C/S/S-MUCNPs were then evaluated. Finally, chlorine e6 (Ce6) was loaded on the C/S/S-MUCNPs and the PDT performance of these NPs was explored. Mn²⁺ doping is an effective method to control the formation of core-shell structured MUCNPs, which would be potential candidate as multifunctional nanoprobes for future T₁/T₂-weighted MR/UCL imaging and PDT platforms.

Applications of functionalized nanomaterials in photodynamic therapy

Specially designed functionalized nanomaterials such as superparamagnetic iron oxide, gold, quantum dots and up- and down-conversion lanthanide series nanoparticles have consistently and completely revolutionized the biomedical environment over the past few years due to their specially inferring properties, such as specific drug delivery, plasmonic effect, optical and imaging properties, therapeutic thermal energy productionand excellent irresistible cellular penetration. These properties have been used to improve many existing disease treatment modalities and have led to the development of better therapeutic approaches for the advancement of the treatment of critical human diseases, such as cancers and related malaise. In photodynamic therapy, for example, where the delivery of therapeutic agents should ideally avoid toxicity on nearby healthy cells, superparamagnetic iron oxide nanoparticles have been shown to be capable of making photodynamic therapy (PDT) prodrugs and their associative targeting moieties tumor-specific via their unique response to an external magnetic fields. In this review, the nanomaterials commonly employed for the enhancement of photodynamic therapy are discussed. The review further describes the various methods of synthesis and characterization of these nanomaterials and highlights challenges for improving the efficacy of PDT in the future.

Novel Magnetic-Luminescent Janus Nanoparticles for Cell Labeling and Tumor Photothermal Therapy

Magnetic-luminescent nanocomposites have multiple uses including multimodal imaging, magnetic targeted drug delivery, and cancer imaging-guided therapies. In this work, dumbbell-like MnFe₂ O₄ -NaYF₄ Janus nanoparticles are synthesized via a two-step thermolysis approach. These synthesized nanoparticles exhibit stability in aqueous solutions and very low cytotoxicity after poly(acryl amide) modification. High cellular uptake efficiency is observed for the folic acid-conjugated MnFe₂ O₄ -NaYF₄ in human esophagus carcinoma cells (Eca-109) due to the upconversion luminescence properties as well as the folate targeting potential. The MnFe₂ O₄ -NaYF₄ also strongly absorbs light in the near-infrared range and rapidly converts to heat energy. It is demonstrated that Eca-109 cells incubated with MnFe₂ O₄ -NaYF₄ are killed with high efficiency after 808 nm laser irradiation. Furthermore, the growth of tumors in mice (grown from Eca-109 cells) is highly inhibited by the photothermal effects of MnFe₂ O₄ -NaYF₄ efficiently. Histological analysis reveals no pathological change and inflammatory response in heart, liver, spleen, lung, or kidney. The low toxicity, excellent luminescence, and highly efficient photothermal therapy properties of MnFe₂ O₄ -NaYF₄ Janus nanoparticles illustrated in this work support their vast potential for nanomedicine and cancer therapy.

Iron Oxide Nanoparticle Based Contrast Agents for Magnetic Resonance Imaging

Magnetic iron oxide nanoparticles (MIONs) have attracted enormous attention due to their wide applications, including for magnetic separation, for magnetic hyperthermia, and as contrast agents for magnetic resonance imaging (MRI). This review article introduces the methods of synthesizing MIONs, and their application as MRI contrast agents. Currently, many methods have been reported for the synthesis of MIONs. Herein, we only focus on the liquid-based synthesis methods including aqueous phase methods and organic phase methods. In addition, the MIONs larger than 10 nm can be used as negative contrast agents and the recently emerged extremely small MIONs (ES-MIONs) smaller than 5 nm are potential positive contrast agents. In this review, we focus on the ES-MIONs because ES-MIONs avoid the disadvantages of MION-based T₂- and gadolinium chelate-based T₁-weighted contrast agents.

Multimodal imaging-guided, dual-targeted photothermal therapy for cancer

The multimodal imaging-guided, dual-targeted photothermal therapy.

Novel electrospun bilayered composite fibrous membrane endowed with tunable and simultaneous quadrifunctionality of electricity–magnetism at one layer and upconversion luminescence–photocatalysis at the other layer

A novel [PANI/Fe₃O₄/PAN]/[Bi₂WO₆:Yb³⁺,Er³⁺/PAN] bilayered composite, fibrous membrane with tunable quadrifunctionality of electricity, magnetism, upconversion luminescence and photocatalysis has been successfully synthesized.

Multifunctional FePt–Au heterodimers: promising nanotheranostic agents for dual-modality MR/CT imaging diagnosis and in situ cancer therapy

We report the synthesis of multifunctional FePt–Au hybrid nanoparticles via a simple hydrothermal approach and their potential application in cancer dual-modality MR/CT imaging diagnosis and simultaneous in situ therapy.

β-NaGdF4:Eu3+ nanocrystal markers for melanoma tumor imaging

Europium doped nanocrystals can be optimized to be successfully used as visualization markers for i.e. melanoma tumor.

Near-infrared light activated delivery platform for cancer therapy

Cancer treatment using conventional drug delivery platforms may lead to fatal damage to normal cells. Among various intelligent delivery platforms, photoresponsive delivery platforms are becoming popular, as light can be easily focused and tuned in terms of power intensity, wavelength, and irradiation time, allowing remote and precise control over therapeutic payload release both spatially and temporally. This unprecedented controlled delivery manner is important to improve therapeutic efficacy while minimizing side effects. However, most of the existing photoactive delivery platforms require UV/visible excitation to initiate their function, which suffers from phototoxicity and low level of tissue penetration limiting their practical applications in biomedicine. With the advanced optical property of converting near infrared (NIR) excitation to localized UV/visible emission, upconversion nanoparticles (UCNPs) have emerged as a promising photoactive delivery platform that provides practical applications for remote spatially and temporally controlled release of therapeutic payload molecules using low phototoxic and high tissue penetration NIR light as the excitation source. This article reviews the state-of-the-art design, synthesis and therapeutic molecular payload encapsulation strategies of UCNP-based photoactive delivery platforms for cancer therapy. Challenges and promises for engineering of advanced delivery platforms are also highlighted.

In vitro photodynamic therapy based on magnetic-luminescent Gd2O3:Yb,Er nanoparticles with bright three-photon up-conversion fluorescence under near-infrared light

Yb(3+) and Er(3+) co-doped Gd2O3 nanoparticles were synthesized via a simple homogeneous precipitation method followed by subsequent heat treatment. Morphology characterization results showed that these nanoparticles were almost spherical in shape with diameters of 200-400 nm. The particles were further modified by polyethylene glycol (PEG) to improve their suspensibility in water. The sintering temperature was found to greatly influence the fluorescent properties of the products. After calcination at 700-1200 °C, the Gd2O3:Yb,Er nanoparticles could emit bright up-conversion fluorescence under 980 nm near-infrared (NIR) laser light excitation. The mechanism of up-conversion fluorescence was studied in detail and a three-photon process was observed for both green and red up-conversion fluorescence of the Gd2O3:Yb,Er nanoparticles. Different from many other Yb(3+),Er(3+) co-doped up-conversion materials, the prepared Gd2O3:Yb,Er nanoparticles emitted much stronger red light than green light. The reason was investigated and ascribed to the presence of abundant hydroxyl groups on the surface of the nanoparticles as a result of PEGylation. The nanoparticles could be taken up by the human cervical cancer (HeLa) cells and presented low toxicity. Well-selected photodynamic therapy (PDT) drugs, methylene blue (MB) with a UV/Vis absorption maximum (λmax) of 665 nm and 5-aminolevulinic acid (5ALA) which is a precursor of the natural photosensitizer photoporphyrin IX (PpIX) with a λmax of 635 nm, were loaded onto the nanoparticles respectively to obtain Gd2O3:Yb,Er-MB and Gd2O3:Yb,Er-5ALA nanoparticles. Being up-conversion nanoparticles (UCNPs), the taken up Gd2O3:Yb,Er nanoparticles exposed to 980 nm laser light emitted red fluorescence which activated the loaded MB and PpIX, and then killed the HeLa cells via a PDT mechanism. In vitro therapeutic investigation evidenced the prominent PDT effects of Gd2O3:Yb,Er-MB and Gd2O3:Yb,Er-5ALA upon NIR light irradiation. In magnetic resonance imaging (MRI) studies, the relaxivity values obtained for Gd2O3:Yb,Er were r1 = 2.2705 M(-1) s(-1) and r2 = 3.0675 M(-1) s(-1) with a r2/r1 ratio close to 1, suggesting that it would be a good candidate as a positive MRI agent. It is expected that these particles have applications in magnetic-fluorescent bimodal imaging and NIR light-triggered PDT.

In vivo targeted magnetic resonance imaging and visualized photodynamic therapy in deep-tissue cancers using folic acid-functionalized superparamagnetic-upconversion nanocomposites

Multifunctional nanoprobes used in magnetic resonance imaging (MRI) and photodynamic therapy (PDT) also have potential applications in diagnosis and visualized therapy of cancers, and hence it is important to investigate the active-targeting ability and in vivo reliability of these nanoprobes. In this work, folic acid (FA)-targeted, photosensitizer (PS)-loaded Fe3O4@NaYF4:Yb/Er (FA-NPs-PS) nanocomposites were synthesized for in vivo T2-weighted MRI and visualized PDT of cancers by modeling MCF-7 tumor-bearing nude mice. By measuring the upconversion luminescence (UCL) and fluorescence emission spectra, the as-prepared FA-NPs-PS nanocomposites showed near-infrared (NIR)-triggered PDT performance due to the production of a singlet oxygen species. Moreover, by tracing PS fluorescence in MCF-7, HeLa cells and in MCF-7 tumors, the FA-targeted nanocomposites demonstrated good targeting ability both in vitro and in vivo. Under the irradiation of a 980 nm laser, the viabilities of MCF-7 and HeLa cells incubated with FA-NPs-PS nanocomposites could decrease to about 18.4% and 30.7%, respectively, and the inhibition of MCF-7 tumors could reach about 94.9%. The transverse MR relaxivity of 63.79 mM(-1) s(-1) (r2 value) and in vivo MR imaging of MCF-7 tumors indicated an excellent T2-weighted MR performance. This work demonstrated that FA-targeted MRI/PDT nanoprobes are effective for in vivo diagnosis and visualized therapy of breast cancers.

Hydrothermal synthesis of core-shell structured TbPO4:Ce(3+)@TbPO4:Gd(3+) nanocomposites for magnetic resonance and optical imaging

Multi-modal imaging based on multifunctional nanoparticles provides deep, non-invasive and highly sensitive imaging and is a promising alternative approach that can improve the sensitivity of early cancer diagnosis. In this study, two nanoparticles, TbPO4:Ce(3+) and TbPO4:Ce(3+)@TbPO4:Gd(3+), were synthesized via the citric-acid-mediated hydrothermal route, and then systematically characterized by means of microstructure, photoluminescence, magnetic resonance imaging (MRI), biocompatibility, and bioimaging. The results of energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) line scans indicated that TbPO4:Gd(3+) nanoshells about 5 nm in thickness were successfully coated on the TbPO4:Ce(3+) nanocores. X-ray diffraction (XRD) and Fourier transforms of high-resolution transmission electron microscopy (TEM) images indicated that the core-shell nanocomposites had a single crystal structure. The photoluminescence of the TbPO4:Ce(3+)@TbPO4:Gd(3+) and TbPO4:Ce(3+) nanoparticles was greatly intensified by 200 times and 100 times, respectively, compared with pure TbPO4 nanoparticles. In vitro cytotoxicity tests based on the methyl thiazolyl tetrazolium (MTT) assay demonstrated that the monodispersed nanoparticles of TbPO4:Ce(3+)@TbPO4:Gd(3+) had low toxicity. The intracellular luminescence of the nanoparticles after being internalized by HeLa cells was also observed using confocal fluorescence microscopes. MRI showed that the nanoshells of Gd-doped TbPO4 possessed a longitudinal relaxivity of 4.067 s(-1) mM(-1), which is comparable to that of the commercial MRI contrast Gd-TDPA. As a result, the core-shell structured TbPO4:Ce(3+)@TbPO4:Gd(3+) nanoparticles can potentially serve as multifunctional nanoprobes for both optical biolabels and MRI contrast agents.

Upconversion nanoparticles as versatile light nanotransducers for photoactivation applications

Upconversion nanoparticles enable use of near infrared light for spatially and temporally controlled activation of therapeutic compounds in deeper tissues.

Stimuli responsive upconversion luminescence nanomaterials and films for various applications

This review highlights recent advances in upconversion luminescence materials in response to various stimuli for a broad spectrum of applications.

Light upconverting core–shell nanostructures: nanophotonic control for emerging applications

Nanophotonic control of light upconversion in the hierarchical core–shell nanostructures, their biomedical, solar energy and security encoding applications were reviewed.