Metabolizable Semiconducting Polymer Nanoparticles for Second Near-Infrared Photoacoustic Imaging

Photoactivatable Protherapeutic Nanomedicine for Cancer

Therapeutic systems with site-specific pharmaceutical activation hold great promise to enhance therapeutic efficacy while reducing systemic toxicity in cancer therapy. With operational flexibility, noninvasiveness, and high spatiotemporal resolution, photoactivatable nanomedicines have drawn growing attention. Distinct from traditional controlled release systems relying on the difference of biomarker concentrations between disease and healthy tissues, photoactivatable nanomedicines capitalize on the interaction between nanotransducers and light to either trigger photochemical reactions or generate reactive oxygen species (ROS) or heat effect to remotely induce pharmaceutical actions in living subjects. Herein, the recent advances in the development of photoactivatable protherapeutic nanoagents for oncology are summarized. The design strategies and therapeutic applications of these nanoagents are described. Representative examples of each type are discussed in terms of structure, photoactivation mechanism, and preclinical models. Last, potential challenges and perspectives to further develop photoactivatable protherapeutic nanoagents in cancer nanomedicine are discussed.

Colloidal Porous AuAg Alloyed Nanoparticles for Enhanced Photoacoustic Imaging

Colloidal porous AuAg alloyed nanoparticles (pAuAgNPs) were synthesized by galvanic replacement reaction from Ag nanocubes. pAuAgNPs have a 50 nm exterior diameter and half of their inner space consists of voids that have a bimodal size distribution with peaks at 21 and 8.3 nm. pAuAgNPs showed a plasmonic peak at 750 nm, which was exploited for photoacoustic (PA) imaging. Gold nanorods (AuNRs) were prepared and used as the control; they have a strong plasmonic peak at 720 nm. In in vitro experiments at respective plasmonic peak excitations, pAuAgNPs gave stronger PA signals than AuNRs by 8.9 times per particle and 11.7 times per dosage by exogenous atom. The high surface area per volume as a result of the inner voids amplified the PA signals by efficient thermoacoustic conversion. In experiments of chicken-tissue phantoms, pAuAgNPs showed PA signals through 4.5 cm thick tissue, whereas AuNRs gave no detectable signal. In whole-body in vivo experiments, pAuAgNPs injected into the body showed 2.7 times stronger PA signals than AuNRs. Coating the pAuAgNPs with a silica layer additionally increased their PA signal by 1.8 times when compared to the uncoated ones.

Dual-targeted photothermal agents for enhanced cancer therapy

Photothermal therapy, in which light is converted into heat and triggers local hyperthermia to ablate tumors, presents an inherently specific and noninvasive treatment for tumor tissues. In this area, the development of efficient photothermal agents (PTAs) has always been a central topic. Although many efforts have been made on the investigation of novel molecular architectures and photothermal materials over the past decades, PTAs can cause severe damage to normal tissues because of the poor tumor aggregate ability and high irradiation density. Recently, dual-targeted photothermal agents (DTPTAs) provide an attractive strategy to overcome these problems and enhance cancer therapy. DTPTAs are functionalized with two classes of targeting units, including tumor environment targeting sites, tumor targeting sites and organelle targeting sites. In this perspective, typical targeted ligands and representative examples of photothermal therapeutic agents with dual-targeted properties are systematically summarized and recent advances using DTPTAs in tumor therapy are highlighted.

Grafted semiconducting polymer amphiphiles for multimodal optical imaging and combination phototherapy

Semiconducting polymer nanoparticles (SPNs) have gained growing attention in biomedical applications. However, the preparation of SPNs is usually limited to nanoprecipitation in the presence of amphiphilic copolymers, which encounters the issue of dissociation. As an alternative to SPNs, grafted semiconducting polymer amphiphiles (SPAs) composed of a semiconducting polymer (SP) backbone and hydrophilic side chains show increased physiological stability and improved optical properties. This review summarizes recent advances in SPAs for cancer imaging and combination phototherapy. The applications of SPAs in optical imaging including fluorescence, photoacoustic, multimodal and activatable imaging are first described, followed by the discussion of applications in imaging-guided phototherapy and combination therapy, light-triggered drug delivery and gene regulation. At last, the conclusion and future prospects in this field are discussed.

Photothermal Fenton Nanocatalysts for Synergetic Cancer Therapy in the Second Near-Infrared Window

Chemodynamic therapy (CDT) that utilizes endogenous hydrogen peroxide (H₂O₂) to produce reactive oxygen species (ROS) to kill cancer cells has shown a promising strategy for malignant tumor treatment. Nevertheless, limited H₂O₂ levels in the tumor microenvironment often compromise the therapeutic benefits of CDT, leading to cancer recurrence and metastasis. Herein, a second near-infrared (NIR-II) photothermal Fenton nanocatalyst (PFN) was developed for activatable magnetic resonance imaging (MRI)-guided synergetic photothermal therapy (PTT) and CDT of pancreatic carcinoma. Such a PFN consists of manganese dioxide (MnO₂), copper sulfide (CuS), and human serum albumin (HSA), which serve as the activatable imaging contrast agent, the NIR-II photothermal agent and Fenton catalyst, and the stabilizer, respectively. The acidic tumor microenvironment increased the relaxivity of PFN by 2.1-fold, allowing for improved imaging performance and monitoring of nanoparticle accumulation in tumors. Under NIR-II laser irradiation at 1064 nm, PFN generates local heat, which not only permits PTT but also enhances the nanocatalyst-mediated Fenton-like reaction. As such, PFN exerts a synergetic action to completely ablate xenografted tumor models in living animals, while the sole CDT fails to do so. This study thus provides an NIR-II photothermal nanocatalyst for potential treatment of deep-seated tumors.

Mitochondria-Targeting Organic Nanoparticles for Enhanced Photodynamic/Photothermal Therapy

Organelle-targeting techniques have been proved to be promising approaches for enhanced cancer treatment, especially phototherapy, because it can greatly improve the efficiency of photosensitizers. In this work, we designed and synthesized a mitochondria-targeting diketopyrrolopyrrole-based photosensitizer (DPP2+) for synergistic photodynamic/photothermal therapy upon irradiation. The obtained mitochondria-targeting nanoparticles (DPP2+ NPs) could produce thermal energy and singlet oxygen under 635 nm laser irradiation with ideal cytocompatibility. Importantly, DPP2+ NPs are more likely to enter the cells and target mitochondria. In in vitro and in vivo antitumor experiments, DPP2+ NPs showed highly effective antitumor effects, suggesting that mitochondria-targeting photosensitizers have potential for cancer treatment. The present work provides an alternative strategy to mitochondria-targeting molecular engineering and highlights the potential of organic nanomaterials in biomedical fields and cancer treatment.

SWIR Photodetection and Visualization Realized by Incorporating an Organic SWIR Sensitive Bulk Heterojunction

Short-wavelength infrared (SWIR) photodetection and visualization has profound impacts on different applications. In this work, a large-area organic SWIR photodetector (PD) that is sensitive to SWIR light over a wavelength range from 1000 to 1600 nm and a SWIR visualization device that is capable of upconverting SWIR to visible light are developed. The organic SWIR PD, comprising an organic SWIR sensitive blend of a near-infrared polymer and a nonfullerene n-type small molecule SWIR dye, demonstrates an excellent capability for real-time heart rate monitoring, offering an attractive opportunity for portable and wearable healthcare gadgets. The SWIR-to-visible upconversion device is also demonstrated by monolithic integration of an organic SWIR PD and a perovskite light-emitting diode, converting SWIR (1050 nm) to visible light (516 nm). The most important attribute of the SWIR visualizing device is its solution fabrication capability for large-area SWIR detection and visualization at a low cost. The results are very encouraging, revealing the exciting large-area SWIR photodetection and visualization for a plethora of applications in environmental pollution, surveillance, bioimaging, medical, automotive, food, and wellness monitoring.

Instantaneous In Vivo Imaging of Acute Myocardial Infarct by NIR-II Luminescent Nanodots

Fast and precise localization of ischemic tissues in the myocardium after an acute infarct is required by clinicians as the first step toward accurate and efficient treatment. Nowadays, diagnosis of a heart attack at early times is based on biochemical blood analysis (detection of cardiac enzymes) or by ultrasound-assisted imaging. Alternative approaches are investigated to overcome the limitations of these classical techniques (time-consuming procedures or low spatial resolution). As occurs in many other fields of biomedicine, cardiological preclinical imaging can also benefit from the fast development of nanotechnology. Indeed, bio-functionalized near-infrared-emitting nanoparticles are herein used for in vivo imaging of the heart after an acute myocardial infarct. Taking advantage of the superior acquisition speed of near-infrared fluorescence imaging, and of the efficient selective targeting of the near-infrared-emitting nanoparticles, in vivo images of the infarcted heart are obtained only a few minutes after the acute infarction event. This work opens an avenue toward cost-effective, fast, and accurate in vivo imaging of the ischemic myocardium after an acute infarct.

Tracking Osteoarthritis Progress through Cationic Nanoprobe-Enhanced Photoacoustic Imaging of Cartilage

A major obstacle in osteoarthritis (OA) theranostics is the lack of a timely and accurate monitoring method. It is hypothesized that the loss of anionic glycosaminoglycans (GAGs) in articular cartilage reflects the progression of OA. Thus, this study investigated the feasibility of photoacoustic imaging (PAI) applied for monitoring the in vivo course of OA progression via GAG-targeted cationic nanoprobes. The nanoprobes were synthesized through electrostatic attraction between poly-l-Lysine and melanin (PLL-MNPs). Cartilage explants with different concentrations of GAGs incubated with PLL-MNPs to test the relationship between GAGs content and PA signal intensity. GAG activity was then evaluated in vivo in destabilization of the medial meniscus (DMM) surgically-induced mouse model. To track OA progression over time, mice were imaged consistently for 10 weeks after OA-inducing surgery. X-ray was used to verify the superiority of PAI in detecting OA. The correlation between PAI data and histologic results was also analyzed. In vitro study demonstrated the ability of PLL-MNPs in sensitively detecting different GAGs concentrations. In vivo PAI exhibited significantly lower signal intensity from OA knees compared to normal knees. More importantly, PA signal intensity showed serial reduction over the course of OA, while X-ray showed visible joint destruction until 6 weeks. A decrease in GAGs content was confirmed by histologic examinations; moreover, histologic findings were well correlated with PAI results. Therefore, using cationic nanoprobe-enhanced PAI to detect the changes in GAG contents provides sensitive and consistent visualization of OA development. This approach will further facilitate OA theranostics and clinical translation. STATEMENT OF SIGNIFICANCE: The study of in vivo monitoring osteoarthritis (OA) is of high significance to tracking the trajectory of OA development and therapeutic monitoring. Here, we developed a cartilage-targeted cationic nanoprobe, poly-l-Lysine-melanin nanoparticles (PLL-MNPs), enhancing photoacoustic imaging (PAI) to monitor the progression of OA. The in vitro study demonstrated the ability of PLL-MNPs to detect different concentrations of GAGs with high sensitivity. We found that the contents of GAGs in vivo steadily decreased from the development of OA initial-stage to the end-point of our investigation via PAI; it reflected the course of OA in living subjects with high sensitivity. These results allow for further development in various aspects of OA research. It has potential for clinical translation and has a great impact on personalized medicine.

Programmable NIR-II Photothermal-Enhanced Starvation-Primed Chemodynamic Therapy using Glucose Oxidase-Functionalized Ancient Pigment Nanosheets

Chemodynamic therapy (CDT) has attracted considerable attention recently, but the poor reaction kinetics restrict its practical utility in clinic. Herein, glucose oxidase (GOx) functionalized ancient pigment nanosheets (SrCuSi₄ O₁₀ , SC) for programmable near-infrared II (NIR-II) photothermal-enhanced starvation primed CDT is developed. The SC nanosheets (SC NSs) are readily exfoliated from SC bulk suspension in water and subsequently functionalized with GOx to form the nanocatalyst (denoted as SC@G NSs). Upon laser irradiation, the photothermal effect of SC NSs can enhance the catalytic activity of GOx for NIR-II photothermal-enhanced starvation therapy, which effectively eliminates intratumoral glucose and produces abundant hydrogen peroxide (H₂ O₂ ). Importantly, the high photothermal-conversion efficiency (46.3%) of SC@G NSs in second biological window permits photothermal therapy of deep-seated tumors under the guidance of NIR-II photoacoustic imaging. Moreover, the acidity amplification due to gluconic acid generation will in turn accelerate the degradation of SC NSs, facilitating the release of strontium (Sr) and copper (Cu) ions. Both the elevated H₂ O₂ and the released ions will prime the Cu²⁺ /Sr²⁺ -H₂ O₂ reaction for enhanced CDT. Thus, a programmable NIR-II photothermal-enhanced starvation primed CDT is established to combat cancer with minimal side effects.

A two-dimensional MXene potentiates a therapeutic microneedle patch for photonic implantable medicine in the second NIR biowindow

Due to the refractory nature and recurrence of cancer, the related treatments are continuously updated and improved. Here, we designed a soluble polyvinylpyrrolidone (PVP) microneedle system loaded with a two-dimensional (2D) MXene (Nb2C nanosheets) for medical implantation and photothermal ablation of superficial tumors in the second near infrared biological window (NIR-II). In this system, 2D Nb2C nanosheets acted as high-performance photothermal nanoagents, and biocompatible PVP functioned as matrix material to maintain the structure of the needles. The microneedle system exhibited sufficient skin-penetration ability and distinctive dissolution behavior. After being inserted into the skin of the tumor site, it can be dissolved within a short period to release the loaded 2D Nb2C nanosheets. The temperature of the tumor site increased rapidly to almost 70 °C under the irradiation of a 1064 nm laser at a power density of 1 W cm-2, and this could provide sufficient conditions for photonic tumor ablation. After two weeks of treatment, the tumor growth was significantly suppressed, compared to that of the control group, and the survival rate of mice was clearly improved. In addition, the biocompatibility of the microneedle system was tested on mice, in which no significant toxicity or side effects were observed. Therefore, this kind of microneedle system with minimally invasive, safe and effective features is expected to be developed as an intriguing strategy for localized superficial cancer treatment.

NIR-emitting semiconducting polymer nanoparticles for in vivo two-photon vascular imaging

Two-photon fluorescence (TPF) imaging holds great promise for real-time monitoring of cerebral ischemia-reperfusion injury, which is important for the clinical diagnosis of stroke. However, biocompatible and photostable NIR-emitting probes for TPF imaging of ischemic stroke are lacking. Herein, we report the first NIR-emitting TPF probe (named NESPN) prepared using semiconducting polymers for TPF imaging of cerebral ischemia. By virtue of its excellent biocompatibility with the nervous system and bright fluorescence NIR emission, NESPN enables the real-time imaging of mouse brain vasculature with micrometer-scale spatial resolution, realizing clear visualization of ultrafine capillaries (∼3.16 μm). Moreover, NESPN can be utilized in the dynamic monitoring of cerebral blood flow velocity. Microangiography using NESPN was successfully used to indicate the openness of the penumbra area in the mouse brain stroke model. More importantly, this technique allows us to continuously monitor the whole process of ischemic stroke and subsequent reperfusion. This work provides a new and versatile tool for vascular research and diagnosis of vascular diseases.

Activatable NIR-II photoacoustic imaging and photochemical synergistic therapy of MRSA infections using miniature Au/Ag nanorods

Multidrug-resistant Staphylococcus aureus (MRSA) seriously endanger human health. The development of efficient methods to eliminate the infections and monitor the treatment process are of great significance. Near-infrared-II (NIR-II) photoacoustic (PA) imaging and photothermal therapy (PTT) are highly integrated theranostic platforms with superior performance including a low imaging background, increased tissue penetration depth, and high photothermal threshold. Herein, we report an activatable near-infrared II (NIR-II) phototheranostic strategy using miniature Au/Ag nanorods (NRs) for the photochemical synergistic therapy of MRSA infections and in situ monitoring of the treatment progress. Au/Ag NRs were efficiently activated by ferricyanide solution and allowed to continuously release free Ag+ to eliminate MRSA, triggering NIR-II photothermal and PA performance enhancement. The activated NIR-II photothermal effect in turn accelerated the release of free Ag+ from Au/Ag NRs for the synergistic elimination of gram-positive Staphylococcus aureus and promoted wound healing. No photothermal damages or free Ag+-induced side effects were observed in treated mice. After synergistic treatment, a 20-fold NIR-II PA signal increase with a maximum signal-to-noise measurement of 9.5 was observed between the implanted site and normal tissue, enabling sensitive monitoring of Ag+ release process. The prepared Au/Ag NRs were stable and biocompatible, showing great potential for activatable NIR-II phototheranostic application.

Alginate mediated functional aggregation of gold nanoclusters for systemic photothermal therapy and efficient renal clearance

For renal clearable nanoagents, it is challenging to delay the renal clearance to acquire efficient tumor accumulation. Herein, we report sodium alginate (SA) stabilized gold (Au) NCs. The Au NCs are of high biocompatibility and renal clearable. Contributed from the ligands of SA, the half-life (t_1/2) of Au NCs is prolonged to ∼9.3 h, enhancing the tumor accumulation rate to 10.4 %ID/g. In tumor microenvironment (TME), the Au NCs are stimulated to functionally aggregate, which switches on the photothermal effect. Animal experiments prove that Au NCs aggregates are efficient photothermal therapy (PTT) agents for both local treatment of single tumors and systemic treatment of double-tumor models without causing noticeable side effects, confirming the biosecurity of Au NCs and systemic PTT. The switchable strategy of PTT may signify the establishment of a new systemic therapeutic methodology.

Transformable hybrid semiconducting polymer nanozyme for second near-infrared photothermal ferrotherapy

Despite its growing promise in cancer treatment, ferrotherapy has low therapeutic efficacy due to compromised Fenton catalytic efficiency in tumor milieu. We herein report a hybrid semiconducting nanozyme (HSN) with high photothermal conversion efficiency for photoacoustic (PA) imaging-guided second near-infrared photothermal ferrotherapy. HSN comprises an amphiphilic semiconducting polymer as photothermal converter, PA emitter and iron-chelating Fenton catalyst. Upon photoirradiation, HSN generates heat not only to induce cytotoxicity but also to enhance Fenton reaction. The increased ·OH generation promotes both ferroptosis and apoptosis, oxidizes HSN (42 nm) and transforms it into tiny segments (1.7 nm) with elevated intratumoral permeability. The non-invasive seamless synergism leads to amplified therapeutic effects including a deep ablation depth (9 mm), reduced expression of metastasis-related proteins and inhibition of metastasis from primary tumor to distant organs. Thereby, our study provides a generalized nanozyme strategy to compensate both ferrotherapy and phototherapeutics for complete tumor regression.

Due to tumour microenvironment, Fenton reactions have low therapeutic efficiency. Here the authors report on the application of NIR-II hybrid semiconducting nanozymes for combined photothermal therapy and enhanced ferrotherapy with photoacoustic imaging and show application in vivo in tumour models.

Fluoro-Photoacoustic Polymeric Renal Reporter for Real-Time Dual Imaging of Acute Kidney Injury

Photoacoustic (PA) imaging agents detect disease tissues and biomarkers with increased penetration depth and enhanced spatial resolution relative to traditional optical imaging, and thus hold great promise for clinical applications. However, existing PA imaging agents often encounter the issues of slow body excretion and low-signal specificity, which compromise their capability for in vivo detection. Herein, a fluoro-photoacoustic polymeric renal reporter (FPRR) is synthesized for real-time imaging of drug-induced acute kidney injury (AKI). FPRR simultaneously turns on both near-infrared fluorescence (NIRF) and PA signals in response to an AKI biomarker (γ-glutamyl transferase) with high sensitivity and specificity. In association with its high renal clearance efficiency (78% at 24 h post-injection), FPRR can detect cisplatin-induced AKI at 24 h post-drug treatment through both real-time imaging and optical urinalysis, which is 48 h earlier than serum biomarker elevation and histological changes. More importantly, the deep-tissue penetration capability of PA imaging results in a signal-to-background ratio that is 2.3-fold higher than NIRF imaging. Thus, the study not only demonstrates the first activatable PA probe for real-time sensitive imaging of kidney function at molecular level, but also highlights the polymeric probe structure with high renal clearance.

Nanoparticles from Ancient Ink Endowing a Green and Effective Strategy for Cancer Photothermal Therapy in the Second Near-Infrared Window

Photothermal therapy (PTT) in the second near-infrared window (NIR-II, 1000-1350 nm) has presented great superiority in cancer treatment recently. However, it is generally limited to a few photothermal agents and most of them often suffer from intricate design and complicated synthesis. Herein, by subtly extracting nanoparticles from ancient ink (AINPs), a versatile AINP dispersion with definite ingredients, good biosafety, and excellent photothermal effect in the NIR-II window was obtained. In vivo trials demonstrated that the obtained AINP dispersion provides a promising alternative for tumor sentinel lymph node (SLN) mapping. Besides, under the guidance of photoacoustic imaging, the metastatic SLNs could be accurately eliminated by NIR-II laser irradiation. The preliminary biosafety of AINP dispersion has also been systematically confirmed. Therefore, we believe this work would provide a green and effective strategy for PTT of tumor in the NIR-II window.

Semiconducting Polymer Nanoparticles as Theranostic System for Near-Infrared-II Fluorescence Imaging and Photothermal Therapy under Safe Laser Fluence

Theranostic systems combining fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) and photothermal therapy (PTT) under safe laser fluence have great potential in preclinical research and clinical practice, but the development of such systems with sufficient effective NIR-II brightness and excellent photothermal properties is still challenging. Here we report a theranostic system based on semiconducting polymer nanoparticles (L1057 NPs) for NIR-II fluorescence imaging and PTT under a 980 nm laser irradiation, with low (25 mW/cm²) and high (720 mW/cm²) laser fluence, respectively. Taking into consideration multiple parameters including the extinction coefficient, the quantum yield, and the portion of emission in the NIR-II region, L1057 NPs have much higher effective NIR-II brightness than most reported organic NIR-II fluorophores. The high brightness, together with good stability and excellent biocompatibility, allows for real-time visualization of the whole body and brain vessels and the detection of cerebral ischemic stroke and tumors with high clarity. The excellent photothermal properties and high maximal permissible exposure limit at 980 nm allow L1057 NPs for PTT of tumors under safe laser fluence. This study demonstrates that L1057 NPs behave as an excellent theranostic system for NIR-II imaging and PTT under safe laser fluence and have great potential for a wide range of biomedical applications.

Conjugated polymer nano-systems for hyperthermia, imaging and drug delivery

Hyperthermia has shown tremendous therapeutic efficiency in the treatment of cancer due to its controllability, minimal invasiveness and limited side effects compared to the conventional treatment techniques like surgery, radiotherapy and chemotherapy. To improve the precision of hyperthermia specifically to a tumor location, near infra-red (NIR) light activatable inorganic metal nanoparticles have served as effective photothermal therapy materials, but toxicity and non-biodegradability have limited their clinical applications. Conjugated polymer nanoparticles have overcome these limitations and are emerging as superior photothermal materials owing to their excellent light harvesting nature, biocompatibility and tunable absorption properties. In this review we focus on the development of organic conjugated polymers (polyaniline, polypyrrole, polydopamine etc.) and their nanoparticles, which have broad NIR absorption. Such materials elicit photothermal effects upon NIR stimulation and may also serve as carriers for delivery of therapeutic and contrast agents for combined therapy. Subsequently, the emergence of donor-acceptor based semiconducting polymer nanoparticles with strong absorbance that is tunable across the NIR have been shown to eradicate tumors by either hyperthermia alone or combined with other therapies. The design of multifunctional polymer nanoparticles that absorb near- or mid- infrared light for heat generation, as well as their diagnostic abilities for precise biomedical applications are highlighted.

Red fluorescent pyrazoline-BODIPY nanoparticles for ultrafast and long-term bioimaging

Fluorescence bioimaging is very significant in studying biological processes. Fluorescent nanoparticles (NPs) manufactured from aggregation-induced emission (AIE) materials, as promising candidates, have attracted more attention. However, it is still a challenge to explore suitable AIE NPs for bioimaging. Herein, we synthesized pyrazoline-BODIPY (PZL-BDP) with a donor and acceptor (D-A) structure by a condensation reaction, cultured its single crystal, and studied its twisted intramolecular charge transfer (TICT) and AIE effects. PZL-BDP could self-assemble to form red fluorescent nanoparticles (PZL-BDP NPs) which showed a good fluorescence quantum yield of 15.8% in water. PZL-BDP NPs with excellent stability and biocompatibility exhibited a large Stokes shift (Δλ = 111 nm) which resulted in the reduction of external interference and enhancement of the fluorescence contrast. Furthermore, these nanoparticles could be readily internalized by HeLa cells and they stain the cells in just five seconds, indicating an ultrafast bioimaging protocol. Moreover, long-term tracking fluorescence signals in vivo for about 12 days were obtained. The bright red fluorescence, ultrafast cell staining ability, and long-term in vivo tracking competence outline the great potential of rational design nanomaterials with AIE characteristics for monitoring biological processes.

Deep-Tissue Photothermal Therapy Using Laser Illumination at NIR-IIa Window

Photothermal therapy (PTT) using near-infrared (NIR) light for tumor treatment has triggered extensive attentions because of its advantages of noninvasion and convenience. The current research on PTT usually uses lasers in the first NIR window (NIR-I; 700-900 nm) as irradiation source. However, the second NIR window (NIR-II; 1000-1700 nm) especially NIR-IIa window (1300-1400 nm) is considered much more promising in diagnosis and treatment as its superiority in penetration depth and maximum permissible exposure over NIR-I window. Hereby, we propose the use of laser excitation at 1275 nm, which is approved by Food and Drug Administration for physical therapy, as an attractive technique for PTT to balance of tissue absorption and scattering with water absorption. Specifically, CuS-PEG nanoparticles with similar absorption values at 1275 and 808 nm, a conventional NIR-I window for PTT, were synthesized as PTT agents and a comparison platform, to explore the potential of 1275 and 808 nm lasers for PTT, especially in deep-tissue settings. The results showed that 1275 nm laser was practicable in PTT. It exhibited much more desirable outcomes in cell ablation in vitro and deep-tissue antitumor capabilities in vivo compared to that of 808 nm laser. NIR-IIa laser illumination is superior to NIR-I laser for deep-tissue PTT, and shows high potential to improve the PTT outcome.

Deep tissue photoacoustic imaging of nickel(II) dithiolene-containing polymeric nanoparticles in the second near-infrared window

Photoacoustic imaging is gaining great attention in the medical world due to its significant potential for clinical translation. Light excitation in the second near-infrared (NIR-II) window (1000-1350 nm) has resolution and penetration depth suitable for several clinical applications. However, the significant challenge exists for clinical translation because of the absence of notable intrinsic chromophores in this clinically significant optical range to generate diagnostic images. Methods: We present newly developed a biocompatible nickel dithiolene-based polymeric nanoparticle (NiPNP), which have a strong and sharp absorption peak at 1064 nm, as a photoacoustic contrast agent to boost specific absorbance in the NIR-II window for in vivo deep tissue imaging. Results: We confirm the enhanced PA signal by NiPNP's strong light absorption in the NIR-II window (287% higher than that of NIR-I) and deep tissue imaging capability (~5.1 cm) through in vitro experiment. We have successfully acquired diagnostic-quality in vivo photoacoustic images in deep tissue (~3.4 cm) of sentinel lymph nodes, gastrointestinal tracts, and bladders of live rats by using clinically viable imaging system. Conclusions: Our results prove that with strong absorption in the NIR-II window and with deeper imaging depth, the clinical translation of photoacoustic imaging with NiPNP is feasible for preclinical studies and thus would facilitate further clinical investigations.

Near-infrared optogenetic engineering of photothermal nanoCRISPR for programmable genome editing

We herein report an optogenetically activatable CRISPR-Cas9 nanosystem for programmable genome editing in the second near-infrared (NIR-II) optical window. The nanosystem, termed nanoCRISPR, is composed of a cationic polymer-coated Au nanorod (APC) and Cas9 plasmid driven by a heat-inducible promoter. The APC not only serves as a carrier for intracellular plasmid delivery but also can harvest external NIR-II photonic energy and convert it into local heat to induce the gene expression of the Cas9 endonuclease. Due to high transfection activity, the APC shows strong ability to induce a significant level of disruption in different genomic loci upon optogenetic activation. Moreover, the precise control of genome-editing activity can be simply programmed by finely tuning exposure time and irradiation time in vitro and in vivo and also enables editing at multiple time points, thus proving the sensitivity and inducibility of such an editing modality. The NIR-II optical feature of nanoCRISPR enables therapeutic genome editing at deep tissue, by which treatment of deep tumor and rescue of fulminant hepatic failure are demonstrated as proof-of-concept therapeutic examples. Importantly, this modality of optogenetic genome editing can significantly minimize the off-target effect of CRISPR-Cas9 in most potential off-target sites. The optogenetically activatable CRISPR-Cas9 nanosystem we have developed offers a useful tool to expand the current applications of CRISPR-Cas9, and also defines a programmable genome-editing strategy toward high precision and spatial specificity.

Nanoparticle-based Cell Trackers for Biomedical Applications

The continuous or real-time tracking of biological processes using biocompatible contrast agents over a certain period of time is vital for precise diagnosis and treatment, such as monitoring tissue regeneration after stem cell transplantation, understanding the genesis, development, invasion and metastasis of cancer and so on. The rationally designed nanoparticles, including aggregation-induced emission (AIE) dots, inorganic quantum dots (QDs), nanodiamonds, superparamagnetic iron oxide nanoparticles (SPIONs), and semiconducting polymer nanoparticles (SPNs), have been explored to meet this urgent need. In this review, the development and application of these nanoparticle-based cell trackers for a variety of imaging technologies, including fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, magnetic particle imaging, positron emission tomography and single photon emission computing tomography are discussed in detail. Moreover, the further therapeutic treatments using multi-functional trackers endowed with photodynamic and photothermal modalities are also introduced to provide a comprehensive perspective in this promising research field.

Multifunctional phototheranostic nanomedicine for cancer imaging and treatment

Cancer, as one of the most life-threatening diseases, shows a high fatality rate around the world. When improving the therapeutic efficacy of conventional cancer treatments, researchers also conduct extensive studies into alternative therapeutic approaches, which are safe, valid, and economical. Phototherapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), are tumor-ablative and function-reserving oncologic interventions, showing strong potential in clinical cancer treatment. During phototherapies, the non-toxic phototherapeutic agents can be activated upon light irradiation to induce cell death without causing much damage to normal tissues. Besides, with the rapid development of nanotechnology in the past decades, phototheranostic nanomedicine also has attracted tremendous interests aiming to continuously refine their performance. Herein, we reviewed the recent progress of phototheranostic nanomedicine for improved cancer therapy. After a brief introduction of the therapeutic principles and related phototherapeutic agents for PDT and PTT, the existing works on developing of phototheranostic nanomedicine by mainly focusing on their categories and applications, particularly on phototherapy-synergized cancer immunotherapy, are comprehensively reviewed. More importantly, a brief conclusion and future challenges of phototheranostic nanomedicine from our point of view are delivered in the last part of this article.

Core-Shell-Heterostructured Magnetic-Plasmonic Nanoassemblies with Highly Retained Magnetic-Plasmonic Activities for Ultrasensitive Bioanalysis in Complex Matrix

Herein, a facile self-assembly strategy for coassembling oleic acid-coated iron oxide nanoparticles (OC-IONPs) with oleylamine-coated gold nanoparticles (OA-AuNPs) to form colloidal magnetic-plasmonic nanoassemblies (MPNAs) is reported. The resultant MPNAs exhibit a typical core-shell heterostructure comprising aggregated OA-AuNPs as a plasmonic core surrounded by an assembled magnetic shell of OC-IONPs. Owing to the high loading of OA-AuNPs and reasonable spatial distribution of OC-IONPs, the resultant MPNAs exhibit highly retained magnetic-plasmonic activities simultaneously. Using the intrinsic dual functionality of MPNAs as a magnetic separator and a plasmonic signal transducer, it is demonstrated that the assembled MPNAs can achieve the simultaneous magnetic manipulation and optical detection on the lateral flow immunoassay platform after surface functionalization with recognition molecules. In conclusion, the core-shell-heterostructured MPNAs can serve as a nanoanalytical platform for the separation and concentration of target compounds from complex biological samples using magnetic properties and simultaneous optical sensing using plasmonic properties.

Rational design of near-infrared platinum(ii)-acetylide conjugated polymers for photoacoustic imaging-guided synergistic phototherapy under 808 nm irradiation

We have developed a novel near-infrared Pt-acetylide conjugated polymer CP3 with highly efficient photoconversion behaviors for synergistic cancer phototherapy.

Full-spectrum responsive ZrO2-based phototheranostic agent for NIR-II photoacoustic imaging-guided cancer phototherapy

A second near-infrared window (NIR-II) responsive, cancer targeting ZrO₂-based phototheranostic agent has been fabricated for imaging-guided precise synergetic phototherapy.

Emerging combination strategies with phototherapy in cancer nanomedicine

Based on the challenges in single-mode phototherapy, this review summarizes the significant research progress in combinatorial strategies with phototherapy.

An Ultrasound Activated Vesicle of Janus Au-MnO Nanoparticles for Promoted Tumor Penetration and Sono-Chemodynamic Therapy of Orthotopic Liver Cancer

Sonodynamic therapy (SDT) has the advantages of high penetration, non-invasiveness, and controllability, and it is suitable for deep-seated tumors. However, there is still a lack of effective sonosensitizers with high sensitivity, safety, and penetration. Now, ultrasound (US) and glutathione (GSH) dual responsive vesicles of Janus Au-MnO nanoparticles (JNPs) were coated with PEG and a ROS-sensitive polymer. Upon US irradiation, the vesicles were disassembled into small Janus Au-MnO nanoparticles (NPs) with promoted penetration ability. Subsequently, GSH-triggered MnO degradation simultaneously released smaller Au NPs as numerous cavitation nucleation sites and Mn²⁺ for chemodynamic therapy (CDT), resulting in enhanced reactive oxygen species (ROS) generation. This also allowed dual-modality photoacoustic imaging in the second near-infrared (NIR) window and T₁ -MR imaging due to the released Mn²⁺ , and inhibited orthotopic liver tumor growth via synergistic SDT/CDT.

Advanced Nanotechnology Leading the Way to Multimodal Imaging-Guided Precision Surgical Therapy

Surgical resection is the primary and most effective treatment for most patients with solid tumors. However, patients suffer from postoperative recurrence and metastasis. In the past years, emerging nanotechnology has led the way to minimally invasive, precision and intelligent oncological surgery after the rapid development of minimally invasive surgical technology. Advanced nanotechnology in the construction of nanomaterials (NMs) for precision imaging-guided surgery (IGS) as well as surgery-assisted synergistic therapy is summarized, thereby unlocking the advantages of nanotechnology in multimodal IGS-assisted precision synergistic cancer therapy. First, mechanisms and principles of NMs to surgical targets are briefly introduced. Multimodal imaging based on molecular imaging technologies provides a practical method to achieve intraoperative visualization with high resolution and deep tissue penetration. Moreover, multifunctional NMs synergize surgery with adjuvant therapy (e.g., chemotherapy, immunotherapy, phototherapy) to eliminate residual lesions. Finally, key issues in the development of ideal theranostic NMs associated with surgical applications and challenges of clinical transformation are discussed to push forward further development of NMs for multimodal IGS-assisted precision synergistic cancer therapy.

Biodegradable π-Conjugated Oligomer Nanoparticles with High Photothermal Conversion Efficiency for Cancer Theranostics

We developed a biodegradable photothermal therapeutic (PTT) agent, π-conjugated oligomer nanoparticles (F8-PEG NPs), for highly efficient cancer theranostics. By exploiting an oligomer with excellent near-infrared (NIR) absorption, the nanoparticles show a high photothermal conversion efficiency (PCE) up to 82%, surpassing those of reported inorganic and organic PTT agents. In addition, the oligomer nanoparticles show excellent photostability and good biodegradability. The F8-PEG NPs are also demonstrated to have excellent biosafety and PTT efficacy both in vitro and in vivo. This contribution not only proposes a promising oligomer-based PTT agent but also provides insight into developing highly efficient nanomaterials for cancer theranostics.

Optically Active Nanomaterials for Bioimaging and Targeted Therapy

Non-invasive tracking for monitoring the selective delivery and transplantation of biotargeted agents in vivo has been employed as one of the most effective tools in the field of nanomedicine. Different nanoprobes have been developed and applied to bioimaging tissues and the treatment of diseases ranging from inflammatory and cardiovascular diseases to cancer. Herein, we will review the recent advances in the development of optics-responsive nanomaterials, including organic and inorganic nanoparticles, for multimodal bioimaging and targeted therapy. The main focus is placed on nanoprobe fabrication, mechanistic illustrations, and diagnostic, or therapeutical applications. These nanomedicine strategies have promoted a better understanding of the biological events underlying diverse disease etiologies, thereby facilitating diagnosis, illness evaluation, therapeutic effect, and drug discovery.