Multimodal-Imaging-Guided Cancer Phototherapy by Versatile Biomimetic Theranostics with UV and γ-Irradiation Protection

PL-W18O49-TPZ Nanoparticles for Simultaneous Hypoxia-Activated Chemotherapy and Photothermal Therapy

The combination of W₁₈O₄₉ and tirapazamine (TPZ) core has been first introduced into the preparation of poly(ε-caprolactone)-poly(ethylene glycol) (PL) surrounded nanoparticles (NPs). The aim of using W₁₈O₄₉ is employing its capability of reacting with the absorbed O₂ to generate reactive oxygen species (ROS) when exposed to a long-wavelength laser at 808 nm to increase skin penetration and body tolerance. In this work, we have demonstrated that W₁₈O₄₉ unit gives rise to more hypoxic tumor microenvironment and activates the prodrug TPZ to achieve hypoxia-activated chemotherapy, which could be monitored by the intracellular ROS/hypoxia detection and in vivo positron emission tomography imaging. In addition, the successful introduction of W₁₈O₄₉ into PL-W₁₈O₄₉-TPZ NPs could render the photothermal therapy under the irradiation of an 808 nm laser. As a result, in vivo antitumor results have clearly shown that PL-W₁₈O₄₉-TPZ NPs could efficiently erase the solid tumor tissues by means of simultaneous hypoxia-activated chemotherapy and photothermal therapy. In comparison to the costly small-molecule photosensitizer chlorine e6 used in hypoxia-activated chemotherapy, W₁₈O₄₉ NPs have two advantages of large-scale preparation and additional photothermal therapy effect, which could provide new insight into future clinical applications.

Photosensitizer-loaded biomimetic platform for multimodal imaging-guided synergistic phototherapy

Photodynamic therapy (PDT) has attracted much attention as a strategy for tumor therapy. However, the insolubility and poor tumor-targeting ability of most photosensitizers (PSs) hinder PDT from further development. Therefore, it is necessary to explore new carriers with good water solubility and biocompatibility to deliver PSs to tumors. Melanin nanoparticles are novel biomimetic nanocarriers with excellent biocompatibility, loading capacity, photothermal therapy (PTT) and magnetic resonance (MR)/photoacoustic (PA) imaging properties. Here we designed polydopamine melanin nanoparticles (PDMNs) as a delivery platform for the photosensitizer Chlorin e6 (PDMN–Ce6) and realized its application as a theranostic agent for tumor therapy. The PDMN–Ce6 exhibited excellent biocompatibility, good water solubility and high loading capability (35.2 wt%) for Ce6. Compared with the free Ce6, PDMN–Ce6 showed higher cellular internalization and superior synergistic phototherapy effects in an in vitro study. An in vivo study indicated that the accumulation of PDMN–Ce6 at tumor sites was 2.8-fold higher than that of free Ce6 at 24 h post-injection, which was beneficial for MR/PA imaging. Moreover, the synergetic therapy significantly inhibited tumor growth, causing tumor necrosis and tumor angiogenesis suppression. These results suggest that our biomimetic and biocompatible platform could improve the delivery of Ce6 to tumors and realize multimodal imaging-guided tumor synergetic phototherapy.

Photodynamic therapy (PDT) has attracted much attention as a strategy for tumor therapy.

Janus Gold Nanoplatform for Synergetic Chemoradiotherapy and Computed Tomography Imaging of Hepatocellular Carcinoma

There is a pressing need to develop nanoplatforms that integrate multimodal therapeutics to improve treatment responses and prolong the survival of patients with unresectable hepatocellular carcinoma (HCC). Mesoporous silica-coated gold nanomaterials have emerged as a novel multifunctional platform combining tunable surface plasmon resonance and mesoporous properties that exhibit multimodality properties in cancer theranostics. However, their reduced radiation-absorption efficiency and limited surface area hinder their further radiochemotherapeutic applications. To address these issues, we designed Janus-structured gold-mesoporous silica nanoparticles using a modified sol-gel method. This multifunctional theranostic nanoplatform was subsequently modified via the conjugation of folic acid for enhanced HCC targeting and internalization. The loaded anticancer agent doxorubicin can be released from the mesopores in a pH-responsive manner, facilitating selective and safe chemotherapy. Additionally, the combination of chemotherapy and radiotherapy induced synergistic anticancer effects in vitro and exhibited remarkable inhibition of tumor growth in vivo along with significantly reduced systematic toxicity. Additionally, the Janus NPs acted as targeted computed tomography (CT)-imaging agents for HCC diagnosis. Given their better performance in chemoradiotherapy and CT imaging as compared with that of their core-shell counterparts, this new nanoplatform designed with dual functionalities provides a promising strategy for unresectable HCC theranostics.

Injectable thermosensitive magnetic nanoemulsion hydrogel for multimodal-imaging-guided accurate thermoablative cancer therapy

Ferrofluid-based magnetic hyperthermia of cancers has gained significant attention in recent years due to its excellent efficacy, few deleterious side effects and unlimited tissue penetration capacity. However, the high tumor osmotic pressure causes injection leakage and thus position imprecision because of the fluidity of the ferrofluid and the absence of multimodal imaging guidance, which create tremendous challenges for clinical application. Here, a body temperature-induced gelation strategy is constructed for accurate localized magnetic tumor regression based on the unique behaviors of a magnetic nanoemulsion hydrogel (MNH) within tumors. The rapid intra-tumor gelation can securely restrict the MNH in tumor tissue without diffusion and leakage. The magnetically induced nanoparticle assembly-enhanced heating in the hydrogel and the heat accumulation caused by crosslinking among the nanoemulsion droplets further increased the heating efficiency. Meanwhile, US/MR/NIR multimodal imaging can guide the whole therapeutic process, achieving excellent magnetic hyperthermia therapeutic efficiency. This work highlights the great promise for improving the magnetic hyperthermia efficiency and the precision of the injection site for localized tumor therapy.

Iron oxide nanoparticles - In vivo/in vitro biomedical applications and in silico studies

The review presents a broad overview of the biomedical applications of surface functionalized iron oxide nanoparticles (IONPs) as magnetic resonance imaging (MRI) agents for sensitive and precise diagnosis tool and synergistic combination with other imaging modalities. Then, the recent progress in therapeutic applications, such as hyperthermia is discussed and the available toxicity data of magnetic nanoparticles concerning in vitro and in vivo biomedical applications are addressed. This review also presents the available computer models using molecular dynamics (MD), Monte Carlo (MC) and density functional theory (DFT), as a basis for a complete understanding of the behaviour and morphology of functionalized IONPs, for improving NPs surface design and expanding the potential applications in nanomedicine.

A Laser-Activated Biocompatible Theranostic Nanoagent for Targeted Multimodal Imaging and Photothermal Therapy

Multifunctional nanoparticles have been reported for cancer detection and treatment currently. However, the accurate diagnosis and efficient treatment for tumors are still not satisfied. Here we report on the development of targeted phase change multimodal polymeric nanoparticles for the imaging and treatment of HER2-positive breast cancer.

Methods: We evaluated the multimodal imaging capabilities of the prepared nanoparticles in vitro using agar-based phantoms. The targeting performance and cytotoxicity of the nanoparticles were examined in cell culture using SKBR3 (over-expressing HER2) and MDA-MB-231 (HER2 negative) cells. We then tested the magnetic resonance (MR)/ photoacoustic (PA)/ ultrasound (US)/ near-infrared fluorescence (NIRF) multimodal imaging properties and photothermal effect of the nanoparticles in vivo using a SKBR3 breast xenograft model in nude mice. Tissue histopathology and immunofluorescence were also conducted.

Results: Both in vitro and in vivo systematical studies validated that the hybrid nanoparticles can be used as a superb MR/US/PA/NIRF contrast agent to simultaneously diagnose and guide tumor photothermal therapy (PTT). When irradiated by a near infrared laser, the liquid PFP vaporizes to a gas, rapidly expelling the contents and damaging surrounding tissues. The resulting micro-sized bubbles provide treatment validation through ultrasound imaging. Localization of DIR and SPIO in the tumor region facilitate photothermal therapy for targeted tumor destruction. The mice treated with HER2 targeted nanoparticles had a nearly complete response to treatment, while the controls showed continued tumor growth.

Conclusion: This novel theranostic agent may provide better diagnostic imaging and therapeutic potential than current methods for treating HER2-positive breast cancer.

Biopolymer-Drug Conjugate Nanotheranostics for Multimodal Imaging-Guided Synergistic Cancer Photothermal-Chemotherapy

Some of the biomedical polymer-drug conjugates are being translated into clinical trials; however, they intrinsically lack photothermal and multi-imaging capabilities, hindering them from imaging-guided precision cancer therapy and complete tumor regression. We introduce a new concept of all-in-one biopolymer-drug conjugate nanotheranostics and prepare a kind of intracellular pH-sensitive polydopamine-doxorubicin (DOX) conjugate nanoparticles (PDCNs) under mild conditions. Significantly, this strategy integrates polymeric prodrug-induced chemotherapy (CT), near-infrared (NIR) light-mediated photothermal therapy (PT), and triple modalities including DOX self-fluorescence, photothermal, and photoacoustic (PA) imaging into one conjugate nanoparticle. The PDCNs present excellent photothermal property, dual stimuli-triggered drug release behavior, and about 12.4-fold blood circulation time compared to free DOX. Small animal fluorescent imaging technique confirms that PDCNs have preferential tumor accumulation effect in vivo, giving a 12.8-fold DOX higher than the control at 12 h postinjection. Upon NIR laser irradiation (5 min, 808 nm, and 2 W·cm^-2), the PDCN-mediated photothermal effect can quickly elevate the tumor over 50 °C, exhibiting good photothermal and PA imaging functions, of which the PA amplitude is 3.6-fold greater than the control. In vitro and in vivo assays persuasively verify that intravenous photothermal-CT of PDCNs produces synergistic antitumor activity compared to single PT or CT, achieving complete tumor ablation during the evaluation period.

"One-Pot" Fabrication of Highly Versatile and Biocompatible Poly(vinyl alcohol)-porphyrin-based Nanotheranostics

Nanoparticle-based theranostic agents have emerged as a new paradigm in nanomedicine field for integration of multimodal imaging and therapeutic functions within a single platform. However, the clinical translation of these agents is severely limited by the complexity of fabrication, long-term toxicity of the materials, and unfavorable biodistributions. Here we report an extremely simple and robust approach to develop highly versatile and biocompatible theranostic poly(vinyl alcohol)-porphyrin nanoparticles (PPNs). Through a “one-pot” fabrication process, including the chelation of metal ions and encapsulation of hydrophobic drugs, monodispersenanoparticle could be formed by self-assembly of a very simple and biocompatible building block (poly(vinyl alcohol)-porphyrin conjugate). Using this approach, we could conveniently produce multifunctional PPNs that integrate optical imaging, positron emission tomography (PET), photodynamic therapy (PDT), photothermal therapy (PTT) and drug delivery functions in one formulation. PPNs exhibited unique architecture-dependent fluorescence self-quenching, as well as photodynamic- and photothermal- properties. Near-infrared fluorescence could be amplified upon PPN dissociation, providing feasibility of low-background fluorescence imaging. Doxorubicin (DOX)-loaded PPNs achieved 53 times longer half-life in blood circulation than free DOX. Upon irradiation by near infrared light at a single excitation wavelength, PPNs could be activated to release reactive oxygen species, heat and drugs simultaneously at the tumor sites in mice bearing tumor xenograft, resulting in complete eradication of tumors. Due to their organic compositions, PPNs showed no obvious cytotoxicity in mice via intravenous administration during therapeutic studies. This highly versatile and multifunctional PPN theranostic nanoplatform showed great potential for the integration of multimodal imaging and therapeutic functions towards personalized nanomedicine against cancers.

New Application of Old Material: Chinese Traditional Ink for Photothermal Therapy of Metastatic Lymph Nodes

Finding a simple and effective strategy to eliminate tumor metastatic lymph nodes is highly desired in clinical tumor treatment. Herein, we reported a Chinese traditional ink (Hu-ink)-based treatment for photothermal therapy (PTT) of tumor metastatic lymph nodes. By simple dilution, stable Chinese traditional ink dispersion was obtained, which presents excellent photothermal effect because of its high absorption in near-infrared (NIR) region. Meanwhile, as revealed by staining and photoacoustic imaging, Hu-ink could transfer to nearby lymph nodes after directly injected into the primary tumors. Under the guidance of dual-modality mapping, the metastatic sentinel lymph nodes could be subsequently eliminated by NIR irradiation. The good biocompatibility of Hu-ink has also been verified by a series of experiments. Therefore, the Hu-ink-based treatment exhibits great potential for PTT of tumor metastatic lymph nodes in future clinical practice.

Emerging Nanotechnology and Advanced Materials for Cancer Radiation Therapy

Radiation therapy (RT) including external beam radiotherapy (EBRT) and internal radioisotope therapy (RIT) has been widely used for clinical cancer treatment. However, owing to the low radiation absorption of tumors, high doses of ionizing radiations are often needed during RT, leading to severe damages to normal tissues adjacent to tumors. Meanwhile, the RT efficacies are limited by different mechanisms, among which the tumor hypoxia-associated radiation resistance is a well-known one, as there exists hypoxia inside most solid tumors while oxygen is essential to enhance radiation-induced DNA damages. With the development in nanotechnology, there have been great interests in using nanomedicine strategies to enhance radiation responses of tumors. Nanomaterials containing high-Z elements to absorb radiation rays (e.g. X-ray) can act as radio-sensitizers to deposit radiation energy within tumors and promote treatment efficacy. Nanoscale carriers are able to deliver therapeutic radioisotopes into tumors for internal RIT, or chemotherapeutic drugs for synergistically combined chemo-radiotherapy. As uncovered in recent studies, the tumor microenvironment could be modulated by various nanomedicine approaches to overcome hypoxia-associated radiation resistance. Herein, the authors will summarize the applications of nanomedicine for RT cancer treatment, and pay particular attention to the latest development of 'advanced materials' for enhanced cancer RT.

Synthesis and Optimization of MoS2@Fe3O4-ICG/Pt(IV) Nanoflowers for MR/IR/PA Bioimaging and Combined PTT/PDT/Chemotherapy Triggered by 808 nm Laser

Elaborately designed biocompatible nanoplatforms simultaneously achieving multimodal bioimaging and therapeutic functions are highly desirable for modern biomedical applications. Herein, uniform MoS2 nanoflowers with a broad size range of 80-180 nm have been synthesized through a facile, controllable, and scalable hydrothermal method. The strong absorbance of MoS2 nanoflowers at 808 nm imparts them with high efficiency and stability of photothermal conversion. Then a novel multifunctional composite of MoS2@Fe3O4-ICG/Pt(IV) (labeled as Mo@Fe-ICG/Pt) is designed by covalently grafting Fe3O4 nanoparticles with polyethylenimine (PEI) functionalized MoS2, and then loading indocyanine green molecules (ICG, photosensitizers) and platinum (IV) prodrugs (labeled as Pt(IV) prodrugs) on the surface of MoS2@Fe3O4. The resulting Mo@Fe-ICG/Pt nanocomposites can achieve excellent magnetic resonance/infrared thermal/photoacoustic trimodal biomaging as well as remarkably enhanced antitumor efficacy of combined photothermal therapy, photodynamic therapy, and chemotherapy triggered by a single 808 nm NIR laser, thus leading to an ideal nanoplatform for cancer diagnosis and treatment in future.

Marriage of Albumin-Gadolinium Complexes and MoS2 Nanoflakes as Cancer Theranostics for Dual-Modality Magnetic Resonance/Photoacoustic Imaging and Photothermal Therapy

The construction of safe and stable theranostics is beneficial to realize simultaneous cancer diagnosis and treatment. In this study, bovine serum albumin-gadolinium (BSA-Gd) complexes and MoS₂ nanoflakes (MoS₂-Gd-BSA) were successfully married as cancer theranostics for dual-modality magnetic resonance (MR)/photoacoustic (PA) imaging and photothermal therapy (PTT). BSA-Gd complexes were prepared by the biomineralization method and then conjugated with MoS₂ nanoflakes via an amide bond. The as-prepared MoS₂-Gd-BSA possessed a good photostability and photothermal effect. The cytotoxicity assessment and hemolysis assay suggested the excellent biocompatibility of MoS₂-Gd-BSA. Meanwhile, MoS₂-Gd-BSA could not only achieve in vivo MR/PA dual-modality imaging of xenograft tumors, but also effectively kill cancer cells in vitro and ablate the xenograft tumors in vivo upon 808 nm laser illumination. The biodistribution and histological evaluations indicated the negligible toxicity of MoS₂-Gd-BSA both in vitro and in vivo. Thus, our results substantiated the potential of MoS₂-Gd-BSA for cancer theranostics.

Black Phosphorus Nanosheets for Mild Hyperthermia-Enhanced Chemotherapy and Chemo-Photothermal Combination Therapy

Near-infrared (NIR) light triggered photothermally enhanced cellular internalization strategy shows great potential to improve antitumor effect to fight against cancer. In this work, a black phosphorus (BP) nanosheet-based nanomedicine, which is composed of BP nanosheet, human serum albumin (HSA) and paclitaxel (PTX), was developed for mild hyperthermia-enhanced intracellular drug delivery and chemo-photothermal combination therapy. BP nanosheet was successfully synthesized by a one-pot biomimetic synthesis method using HSA as exfoliating agent and capping agent. Meanwhile, PTX can be efficiently loaded by HSA via hydrophobic interactions. The PTX-loaded HSA functionalized BP (BP-HSA-PTX) exhibits great photothermal performance, excellent biodegradability/biocompatibility, and effective drug loading. Upon NIR laser illumination, mild hyperthermia (~43 °C) or photothermal effect can be achieved to improve the intracellular drug delivery efficiency and antitumor effect of BP-HSA-PTX. Our results indicate that HSA-functionalized BP has great potential for the loading, delivery, cellular uptake enhancement of chemotherapeutics and chemo-photothermal combination antitumor effect.

Rethinking cancer nanotheranostics

Advances in nanoparticle synthesis and engineering have produced nanoscale agents affording both therapeutic and diagnostic functions that are often referred to by the portmanteau 'nanotheranostics'. The field is associated with many applications in the clinic, especially in cancer management. These include patient stratification, drug-release monitoring, imaging-guided focal therapy and post-treatment response monitoring. Recent advances in nanotheranostics have expanded this notion and enabled the characterization of individual tumours, the prediction of nanoparticle-tumour interactions, and the creation of tailor-designed nanomedicines for individualized treatment. Some of these applications require breaking the dogma that a nanotheranostic must combine both therapeutic and diagnostic agents within a single, physical entity; instead, it can be a general approach in which diagnosis and therapy are interwoven to solve clinical issues and improve treatment outcomes. In this Review, we describe the evolution and state of the art of cancer nanotheranostics, with an emphasis on clinical impact and translation.

Ratiometric Photoacoustic Molecular Imaging for Methylmercury Detection in Living Subjects

Photoacoustic molecular imaging is an emerging and promising diagnostic tool for heavy metal ions detection. Methylmercury (MeHg+ ) is one of the most potent neurotoxins, which damages the brain and nervous system of human beings through fish consumption. The development of a selective and sensitive method for MeHg+ detection is highly desirable. In this Communication, we develope a chemoselective photoacoustic sensor (LP-hCy7) composed of the liposome (LP) and MeHg+ -responsive near-infrared (NIR) cyanine dye (hCy7) for MeHg+ detection within living subjects, such as zebrafish and mouse. The as-prepared LP-hCy7 nanoprobe displays unique dual-shift NIR absorbance peaks and produces a normalized turn-on response after the reaction of MeHg+ and hCy7 through a mercury-promoted cyclization reaction. The absorbance intensities of LP-hCy7 nanoprobe at 690 and 860 nm are decreased and increased, respectively. The ratiometric photoacoustic signal (PA860/PA690) is noticeably increased in the presence of MeHg+ . These findings not only provide a ratiometric photoacoustic molecular imaging probe for the detection of metal ions in vivo, but also provides a tool for spectroscopic photoacoustic molecular imaging.

Two-dimensional Pd-based nanomaterials for bioapplications

Noble metal nanomaterials have been extensively explored in cancer diagnostic and therapeutic applications owing to their unique physical and chemical properties, such as facile synthesis, straightforward surface functionalization, strong photothermal effect, and excellent biocompatibility. Herein, we summarize the recent development of two-dimensional (2D) Pd-based nanomaterials and their applications in cancer diagnosis and therapy. Different synthetic strategies for Pd nanosheets and the related nanostructures, including Pd@Au, Pd@Ag nanoplates and mesocrystalline Pd nanocorolla, are first discussed. Together with their unique properties, the potential bioapplications of these 2D Pd nanomaterials are then demonstrated. With strong absorption in near-infrared (NIR) region, these nanomaterials have great potentials in cancer photothermal therapy (PTT). They also readily act as contrast agents in photoacoustic (PA) imaging or X-ray computed tomography (CT) to achieve image-guided cancer therapy. Moreover, significant efforts have been devoted to studying the combination of PTT and other treatment modalities (e.g., chemotherapy or photodynamic therapy) based on Pd nanomaterials. The remarkable synergistic or collaborative effects to achieve better therapeutic efficacy are discussed as well. Additionally, the biosafety of 2D Pd-based nanomaterials in vitro and in vivo was evaluated. Finally, challenges for the applications of Pd-based nanomaterials in cancer diagnosis and therapy, and future research prospects are highlighted.

Positron emission tomography and nanotechnology: A dynamic duo for cancer theranostics

Development of novel imaging probes for cancer diagnosis is critical for early disease detection and management. The past two decades have witnessed a surge in the development and evolution of radiolabeled nanoparticles as a new frontier in personalized cancer nanomedicine. The dynamic synergism of positron emission tomography (PET) and nanotechnology combines the sensitivity and quantitative nature of PET with the multifunctionality and tunability of nanomaterials, which can help overcome certain key challenges in the field. In this review, we discuss the recent advances in radionanomedicine, exemplifying the ability to tailor the physicochemical properties of nanomaterials to achieve optimal in vivo pharmacokinetics and targeted molecular imaging in living subjects. Innovations in development of facile and robust radiolabeling strategies and biomedical applications of such radionanoprobes in cancer theranostics are highlighted. Imminent issues in clinical translation of radiolabeled nanomaterials are also discussed, with emphasis on multidisciplinary efforts needed to quickly move these promising agents from bench to bedside.

Polymer nanoparticles with high photothermal conversion efficiency as robust photoacoustic and thermal theranostics

Synthesis of photothermal agents with absorption in the near-infrared (NIR) region and featuring excellent photostability, high photothermal conversion efficiency, and good biocompatibility is necessary for the application of photothermal therapy (PTT). In this work, a low band gap thiophene-benzene-diketopyrrolopyrrole (TBD)-based polymer was synthesized and used to fabricate TBD polymer nanoparticles (TBDPNPs) through a one-step nanoprecipitation method. The obtained near-infrared-absorbing TBDPNPs presented good water dispersibility, high photothermal stability, and low toxicity. Significantly, the TBDPNPs exhibited an ultrahigh photothermal conversion efficiency of approximately 68.1% under 671 nm laser irradiation. In addition, photoacoustic (PA) imaging, with high spatial resolution and deep tissue penetration, showed that the TBDPNPs targeted tumor sites through the enhanced permeability and retention effect. Therefore, the robust TBDPNPs with a photothermal conversion efficiency of 68.1% can serve as an excellent therapeutic agent for PA-imaging-guided PTT.

Dual-Stimuli Responsive Nanotheranostics for Multimodal Imaging Guided Trimodal Synergistic Therapy

Multimodal imaging guided synergistic therapy promises more accurate diagnosis than any single imaging modality, and higher therapeutic efficiency than any single one or their simple "mechanical" combination. Herein, we report a dual-stimuli responsive nanotheranostic based on a hierarchical nanoplatform, composed of mesoporous silica-coated gold nanorods (GNR@SiO2), Indocyanine Green (ICG), and 5-fluorouracil (5-FU), for in vivo multimodal imaging guided synergistic therapy. The 5-FU loaded ICG-conjugated silica-coated gold nanorods (GNR@SiO2-5-FU-ICG) was able to response specifically to the two stimuli of pH change and near-infrared (NIR) light irradiation. Both the NIR light irradiation and acidic environment accelerated the 5-FU release. Meanwhile, the heat generation and singlet oxygen production can be induced by GNR@SiO2-5-FU-ICG upon light irradiation. Most intriguingly, the nanoplatform also promises multimodal imaging such as two-photon luminescence, fluorescence, photoacoustic, photothermal imaging, as well as trimodal synergistic therapy such as photothermal therapy (PTT), photodynamic therapy (PDT), and chemotherapy. The cancer theranostic capability of GNR@SiO2-5-FU-ICG was evaluated both in vitro and in vivo. The trimodal synergistic therapy with the guidance of multimodal imaging exhibited remarkably enhanced treatment efficacy. This concept of a hierarchical nanoplatform integrates multiple diagnostic/therapeutic modalities into one platform, which can potentially be applied as personalized nanomedicine with drug delivery, diagnosis, and treatment.

Synthetic strategies and biomedical applications of I–III–VI ternary quantum dots

In this review, we discuss recent advances of I–III–VI QDs with a major focus on synthesis and biomedical applications; advantages include low toxicity and fluorescent tuning in the biological window.

Targeted CT/MR dual mode imaging of human hepatocellular carcinoma using lactobionic acid-modified polyethyleneimine-entrapped gold nanoparticles

Multifunctional PEI-entrapped gold nanoparticles modified with lactobionic acid enable efficient targeted dual mode CT/MR imaging of human hepatocellular carcinoma.

Facile fabrication of a magnetically smart PTX-loaded Cys–Fe3O4/CuS@BSA nano-drug for imaging-guided chemo-photothermal therapy

A PTX-loaded Cys-Fe₃O₄/CuS@BSA nano-drug was synthesized for MR and NIR imaging-guided chemo-photothermal combination therapy of cancer via a facile fabrication method.

Targeted Nanomaterials for Phototherapy

Phototherapies involve the irradiation of target tissues with light. To further enhance selectivity and potency, numerous molecularly targeted photosensitizers and photoactive nanoparticles have been developed. Active targeting typically involves harnessing the affinity between a ligand and a cell surface receptor for improved accumulation in the targeted tissue. Targeting ligands including peptides, proteins, aptamers and small molecules have been explored for phototherapy. In this review, recent examples of targeted nanomaterials used in phototherapy are summarized.

Ultrasmall Biocompatible Bi2Se3 Nanodots for Multimodal Imaging-Guided Synergistic Radiophotothermal Therapy against Cancer

Sub-3 nm ultrasmall Bi₂Se₃ nanodots stabilized with bovine serum albumin were successfully synthesized through a reaction of hydroxyethylthioselenide with bismuth chloride in aqueous solution under ambient conditions. These nanodots exhibit a high photothermal conversion efficiency (η = 50.7%) due to their strong broad absorbance in the near-infrared (NIR) window and serve as a nanotheranostic agent for photoacoustic imaging and photothermal cancer therapy. In addition, they also display radioenhancement with a ratio of 6% due to their sensitivity to X-rays, which makes them a potential sensitizer for radiotherapy. These nanodots were also labled with radioactive ^99mTc for quantification of their biodistribution by single-photon-emission computed tomography (SPECT)/computed tomography (CT) imaging. Our work demonstrates the potential of ultrasmall Bi₂Se₃ nanodots in multimodal imaging-guided synergetic radiophotothermal therapy of cancer.

Near-Infrared Emission CuInS/ZnS Quantum Dots: All-in-One Theranostic Nanomedicines with Intrinsic Fluorescence/Photoacoustic Imaging for Tumor Phototherapy

Many theranostic nanomedicines (NMs) have been fabricated by packaging imaging and therapeutic moieties together. However, concerns about their potential architecture instability and pharmacokinetic complexity remain major obstacles to their clinical translation. Herein, we demonstrated the use of CuInS/ZnS quantum dots (ZCIS QDs) as "all-in-one" theranostic nanomedicines that possess intrinsic imaging and therapeutic capabilities within a well-defined nanostructure. ZCIS QDs were exploited for multispectral optical tomography (MSOT) imaging and synergistic PTT/PDT therapy. Due to the intrinsic fluorescence/MSOT imaging ability of the ZCIS QDs, their size-dependent distribution profiles were successfully visualized at tumor sites in vivo. Our results showed that the smaller nanomedicines (ZCIS NMs-25) have longer tumor retention times, higher tumor uptake, and deeper tumor penetration than the larger nanomedicines (ZCIS NMs-80). The ability of ZCIS QDs to mediate photoinduced tumor ablation was also explored. Our results verified that under a single 660 nm laser irradiation, the ZCIS NMs had simultaneous inherent photothermal and photodynamic effects, resulting in high therapy efficacy against tumors. In summary, the ZCIS QDs as "all-in-one" versatile nanomedicines allow high therapeutic efficacy as well as noninvasively monitoring tumor site localization profiles by imaging techniques and thus hold great potential as precision theranostic nanomedicines.

Optimization of Bi3+ in Upconversion Nanoparticles Induced Simultaneous Enhancement of Near-Infrared Optical and X-ray Computed Tomography Imaging Capability

Bioimaging probes have been extensive studied for many years, while it is still a challenge to further improve the image quality for precise diagnosis in clinical medicine. Here, monodisperse NaGdF₄:Yb³⁺,Tm³⁺,x% Bi³⁺ (abbreviated as GYT-x% Bi³⁺, x = 0, 5, 10, 15, 20, 25, 30) upconversion nanoparticles (UCNPs) have been prepared through the solvothermal method. The near-infrared upconversion emission intensity of GYT-25% Bi³⁺ has been enhanced remarkably than that of NaGdF₄:Yb³⁺,Tm³⁺ (GYT) with a factor of ∼60. Especially, the near-infrared upconversion emission band centered at 802 nm is 150 times stronger than the blue emission band of GYT-25% Bi³⁺ UCNPs. Such high ratio of NIR/blue UCL intensity could reduce the damage to tissues in the bioimaging process. The possibility of using GYT-25% Bi³⁺ UCNPs with strong near-infrared upconversion emission for optical imaging in vitro and in vivo was performed. Encouragingly, the UCL imaging penetration depth can be achieved as deep as 20 mm. Importantly, GYT-25% Bi³⁺ UCNPs exhibit a much higher X-ray computed tomography (CT) contrast efficiency than GYT and iodine-based contrast agent under the same clinical conditions, due to the high X-ray attenuation coefficient of bismuth. Hence, simultaneous remarkable enhancement of NIR emission and X-ray CT signal in upconversion nanoparticles could be achieved by optimizing the doping concentration of Bi³⁺ ions. Additionally, Gd³⁺ ions in the UCNPs endow GYT-25% Bi³⁺ UCNPs with T₁-weighted magnetic resonance (MR) imaging capability.

Recent Advances of Light-Mediated Theranostics

Currently, precision theranostics have been extensively demanded for the effective treatment of various human diseases. Currently, efficient therapy at the targeted disease areas still remains challenging since most available drug molecules lack of selectivity to the pathological sites. Among different approaches, light-mediated therapeutic strategy has recently emerged as a promising and powerful tool to precisely control the activation of therapeutic reagents and imaging probes in vitro and in vivo, mostly attributed to its unique properties including minimally invasive capability and highly spatiotemporal resolution. Although it has achieved initial success, the conventional strategies for light-mediated theranostics are mostly based on the light with short wavelength (e.g., UV or visible light), which may usually suffer from several undesired drawbacks, such as limited tissue penetration depth, unavoidable light absorption/scattering and potential phototoxicity to healthy tissues, etc. Therefore, a near-infrared (NIR) light-mediated approach on the basis of long-wavelength light (700-1000 nm) irradiation, which displays deep-tissue penetration, minimized photo-damage and low autofluoresence in living systems, has been proposed as an inspiring alternative for precisely phototherapeutic applications in the last decades. Despite numerous NIR light-responsive molecules have been currently proposed for clinical applications, several inherent drawbacks, such as troublesome synthetic procedures, low water solubility and limited accumulation abilities in targeted areas, heavily restrict their applications in deep-tissue therapeutic and imaging studies. Thanks to the amazing properties of several nanomaterials with large extinction coefficient in the NIR region, the construction of NIR light responsive nanoplatforms with multifunctions have become promising approaches for deep-seated diseases diagnosis and therapy. In this review, we summarized various light-triggered theranostic strategies and introduced their great advances in biomedical applications in recent years. Moreover, some other promising light-assisted techniques, such as photoacoustic and Cerenkov radiation, were also systemically discussed. Finally, the potential challenges and future perspectives for light-mediated deep-tissue diagnosis and therapeutics were proposed.

Recent Advances in Photoacoustic Imaging for Deep-Tissue Biomedical Applications

Photoacoustic imaging (PAI), a novel imaging modality based on photoacoustic effect, shows great promise in biomedical applications. By converting pulsed laser excitation into ultrasonic emission, PAI combines the advantages of optical imaging and ultrasound imaging, which benefits rich contrast, high resolution and deep tissue penetration. In this paper, we introduced recent advances of contrast agents, applications, and signal enhancement strategies for PAI. The PA contrast agents were categorized by their components, mainly including inorganic and organic PA contrast agents. The applications of PAI were summarized as follows: deep tumor imaging, therapeutic responses monitoring, metabolic imaging, pH detection, enzyme detection, reactive oxygen species (ROS) detection, metal ions detection, and so on. The enhancement strategies of PA signals were highlighted. In the end, we elaborated on the challenges and provided perspectives of PAI for deep-tissue biomedical applications.

Surfactant-Stripped Frozen Pheophytin Micelles for Multimodal Gut Imaging

Edible, surfactant-stripped, frozen micelles are formed from pheophytin (demetallated chlorophyll), a pigment that is naturally consumed in human diets. Pheophytin nanoparticles pass completely and safely through the gastrointestinal tract and enable trimodal gut contrast imaging via photoacoustic, fluorescence, and positron emission tomography techniques.

Effective tracking of bone mesenchymal stem cells in vivo by magnetic resonance imaging using melanin-based gadolinium3+ nanoparticles

Tracking transplanted stem cells is necessary to clarify cellular properties and improve transplantation success. In this study, we designed and synthesized melanin-based gadolinium³⁺ (Gd³⁺ )-chelate nanoparticles (MNP-Gd³⁺ ) of ∼7 nm for stem cell tracking in vivo. MNP-Gd³⁺ possesses many beneficial properties, such as its high stability and sensitivity, shorter T1 relaxation time, higher cell labeling efficiency, and lower cytotoxicity compared with commercial imaging agents. We found that the T1 relaxivity (r₁ ) of MNP-Gd³⁺ was significantly higher than that of Gd-DTPA; the nanoparticles were taken up by bone mesenchymal stem cells (BMSCs) via endocytosis and were broadly distributed in the cytoplasm. Based on an in vitro MTT assay, no cytotoxicity of labeled stem cells was observed for MNP-Gd³⁺ concentrations of less than 800 µg/mL. Furthermore, we tracked MNP-Gd³⁺ -labeled BMSCs in vivo using 3.0T MRI equipment. After intramuscular injection, MNP-Gd³⁺ -labeled BMSCs were detected, even after four weeks, by 3T MRI. We concluded that MNP-Gd³⁺ nanoparticles at appropriate concentrations can be used to effectively monitor and track BMSCs in vivo. MNP-Gd³⁺ nanoparticles have potential as a new positive MRI contrast agent in clinical applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 131-137, 2017.

A polypeptide micelle template method to prepare polydopamine composite nanoparticles for synergistic photothermal–chemotherapy

A polypeptide micelle template method was, for the first time, developed to fabricate polydopamine nanocomposites for the synergistic photothermal–chemotherapy of cancer.

Overcoming the Achilles' heel of photodynamic therapy

This review summarizes the latest progress in deep photodynamic therapy (PDT), which overcomes the Achilles' heel of PDT.

Facile one-pot synthesis of Fe3O4@chitosan nanospheres for MRI and fluorescence imaging guided chemo-photothermal combinational cancer therapy

Fe₃O₄@chitosan nanospheres were fabricated by a facile one-step method for MRI and fluorescence imaging guided chemo-photothermal combinational cancer therapy.