Applications of Light-Responsive Systems for Cancer Theranostics

Light- and Solvent-Responsive Bilayer Hydrogel Actuators with Reversible Bending Behaviors

Light-responsive hydrogel systems have gained significant attention due to their unique ability to undergo controlled and reversible swelling behavior in response to light stimuli. Combining light-responsive hydrogels with nonresponsive polymers offers a unique self-folding feature that can be used in soft robotic actuator designs. However, simple formulation of such systems with rapid response time is still a challenging task. Herein, we demonstrate a simple but versatile bilayer polymeric design combining light-responsive spiropyran-polyacrylamide (SP-PAAm) with polyacrylamide (PAAm) hydrogels. The photochromic spiropyran in our polymer design is a closed-ring, hydrophobic compound and turns into an open-ring, hydrophilic merocyanine isomer under light irradiation. The swelling degree of SP-PAAm and PAAm hydrogels was evaluated using LED lights with different wavelengths and solvent media (e.g., water, ethanol, DMF, and DMSO). We observed that SP-PAAm hydrogels reached a swelling ratio of ∼370% with the illumination of the blue LED in the DMF medium. By combining light-responsive SP-PAAm hydrogels with nonresponsive PAAm, a proof-of-concept demonstration was performed to demonstrate the applicability of our fabricated platforms. Although fabricated one-armed bilayer hydrogels possessed self-folding ability with a folding angle of ∼40° in 30 min, the four-armed bilayer platforms demonstrated more efficient and rapid folding behavior and reached a folding angle of ∼75° in ∼15 min. Given their simplicity and efficiency, we believe that such polymeric designs may offer new avenues for the fields of polymeric actuators and soft robotic systems.

Ultrasound-nanovesicles interplay for theranostics

Nanovesicles (NVs) are widely used in the treatment and diagnosis of diseases due to their excellent vascular permeability, good biocompatibility, high loading capacity, and easy functionalization. However, their yield and in vivo penetration depth limitations and their complex preparation processes still constrain their application and development. Ultrasound, as a fundamental external stimulus with deep tissue penetration, concentrated energy sources, and good safety, has been proven to be a patient-friendly and highly efficient strategy to overcome the restrictions of traditional clinical medicine. Recent research has shown that ultrasound can drive the generation of NVs, increase their yield, simplify their preparation process, and provide direct therapeutic effects and intelligent control to enhance the therapeutic effect of NVs. In addition, NVs, as excellent drug carriers, can enhance the targeting efficiency of ultrasound-based sonodynamic therapy or sonogenetic regulation and improve the accuracy of ultrasound imaging. This review provides a detailed introduction to the classification, generation, and modification strategies of NVs, emphasizing the impact of ultrasound on the formation of NVs and summarizing the enhanced treatment and diagnostic effects of NVs combined with ultrasound for various diseases.

Charge-Reversible Nanoparticles: Advanced Delivery Systems for Therapy and Diagnosis

The past two decades have witnessed a rapid progress in the development of surface charge-reversible nanoparticles (NPs) for drug delivery and diagnosis. These NPs are able to elegantly address the polycation dilemma. Converting their surface charge from negative/neutral to positive at the target site, they can substantially improve delivery of drugs and diagnostic agents. By specific stimuli like a shift in pH and redox potential, enzymes, or exogenous stimuli such as light or heat, charge reversal of NP surface can be achieved at the target site. The activated positive surface charge enhances the adhesion of NPs to target cells and facilitates cellular uptake, endosomal escape, and mitochondrial targeting. Because of these properties, the efficacy of incorporated drugs as well as the sensitivity of diagnostic agents can be essentially enhanced. Furthermore, charge-reversible NPs are shown to overcome the biofilm formed by pathogenic bacteria and to shuttle antibiotics directly to the cell membrane of these microorganisms. In this review, the up-to-date design of charge-reversible NPs and their emerging applications in drug delivery and diagnosis are highlighted.

Recent advances of responsive scaffolds in bone tissue engineering

The investigation of bone defect repair has been a significant focus in clinical research. The gradual progress and utilization of different scaffolds for bone repair have been facilitated by advancements in material science and tissue engineering. In recent times, the attainment of precise regulation and targeted drug release has emerged as a crucial concern in bone tissue engineering. As a result, we present a comprehensive review of recent developments in responsive scaffolds pertaining to the field of bone defect repair. The objective of this review is to provide a comprehensive summary and forecast of prospects, thereby contributing novel insights to the field of bone defect repair.

Escherichia coli Nissle 1917-driven microrobots for effective tumor targeted drug delivery and tumor regression

Potent tumor regression remains challenging due to the lack of effective targeted drug delivery into deep tumors as well as the reduced susceptibility of cancer cells to anticancer agents in hypoxic environments. Bacteria-driven drug-delivery systems are promising carriers in overcoming targeting and diffusion limits that are inaccessible for conventional antitumor drugs. In this study, probiotic facultative anaerobe Escherichia coli Nissle 1917 (EcN) was functionalized and formed self-propelled microrobots to actively deliver therapeutic drug and photosensitizer to the deep hypoxic regions of tumors. Doxorubicin (Dox) was firstly modified with cis-aconityl anhydride (CA) and terminal thiol-decorated hydrazone derivative (Hyd-SH) through dual pH-sensitive amide and imine bonds, respectively. The functionalized CA-Dox-Hyd-SH was further coordinated with photosensitizer gold nanorods (AuNRs) and then conjugated to the surface of EcN. The resulting microrobots (EcN-Dox-Au) inherited the mobility characteristics and bioactivity of native EcN. Upon the irradiation of NIR laser, the microrobots exhibited enhanced tumor accumulation and penetration into the deep hypoxia tumor site. Strikingly, after 21 days of treatment with EcN-Dox-Au formulations, complete tumor regression was achieved without relapse for at least 53 days. This self-propelled strategy utilizing bacteria-driven microrobots provides a promising paradigm for enhancing drug penetration and elevating chemosensitivity, resulting in a superior antitumor effect. STATEMENT OF SIGNIFICANCE: Self-propelled Escherichia coli Nissle 1917 (EcN) - mediated microrobots are functionalized to co-deliver therapeutic drugs and photosensitizers to the deep tumor site. Anti-tumor drug doxorubicin (Dox) was modified through dual pH-sensitive bonds on both terminals and then linked with EcN and photosensitizer gold nanorods (AuNRs) to realize tumor microenvironment acidic pH-responsive drug release. Upon irradiation with a NIR laser near the tumor site, AuNRs produced a photothermal effect which realized the superficial tumor thermal ablation and increased the permeability of the tumor cell membrane to facilitate the penetration of microrobots. Moreover, the deep penetration of microrobots also enhanced the susceptibility of the cancer cells to Dox, and realized the complete tumor regression in the established breast cancer-bearing mice without recurrence using a lower dose of drug regimen.

Photocontrolled Release of Carbendazim from Photocaged Molecule

Carbendazim (MBC) is a high-efficient and broad-spectrum fungicide, but excessive residues caused by its improper use have caused health toxicity and environmental pollution. It is an irresistible trend to find green, safe, accurate and controllable release technology of MBC. To achieve the purpose of safe and efficient use of MBC, photolabile protecting group was used to realize the controllable release. This study aimed to covalently link MBC and 6-nitropiperonyl alcohol (NP) to synthesize photocaged molecule NP-MBC. The photodegradation test showed that NP-MBC could effectively release MBC under ultraviolet light. The antifungal activity of NP-MBC showed significant difference against Rhizoctonia solani, Sclerotinia sclerotiorum and Fusarium graminearum before and after irradiation, and the effects on mycelial morphology are different. The hyphae morphology of R. solani and F. graminearum changed significantly, and mycelia were severely damaged. The hyphae surface of former was swollen and broken, and the latter was collapsed and shriveled after NP-MBC light treatment. NP-MBC could realize the light-controlled release of MBC, and the antifungal activity before and after irradiation was significantly different, which provides an effective way to release MBC.

Designing Smart Iron Oxide Nanoparticles for MR Imaging of Tumors

Iron oxide nanoparticles (IONPs) possess unique magnetism and good biocompatibility, and they have been widely applied as contrast agents (CAs) for magnetic resonance imaging (MRI). Traditional CAs typically show a fixed enhanced signal, thus exhibiting the limitations of low sensitivity and a lack of specificity. Nowadays, the progress of stimulus-responsive IONPs allows alteration of the relaxation signal in response to internal stimuli of the tumor, or external stimuli, thus providing an opportunity to overcome those limitations. This review summarizes the current status of smart IONPs as tumor imaging MRI CAs that exhibit responsiveness to endogenous stimuli, such as pH, hypoxia, glutathione, and enzymes, or exogenous stimuli, such as magnets, light, and so on. We discuss the challenges and future opportunities for IONPs as MRI CAs and comprehensively illustrate the applications of these stimuli-responsive IONPs. This review will help provide guidance for designing IONPs as MRI CAs and further promote the reasonable design of magnetic nanoparticles and achieve early and accurate tumor detection.

Pd-Based Hybrid Nanoparticles As Multimodal Theranostic Nanomedicine

A nanodelivery system based on palladium nanoparticles (PdNP) and cisplatin (CisPt) was developed by physisorption of the drug onto the PdNP synthesized via a green redox process, using d-glucose and polyvinylpyrrolidone (PVP) as reducing and stabilizing/capping agents, respectively. UV-vis analysis and H₂-evolution measurements were carried out to prove the nanoparticles' capability to act as bimodal theranostic nanomedicine, i.e., having both plasmonic and photocatalytic properties. XPS, XRD, and TEM allowed light to be shed on the chemical composition and morphology of the PdNP. The analysis of the UV-visible spectra evidenced plasmonic peak changes for the hybrid nanoparticle-drug assembly (Pd@CisPt), which pointed to a significant interaction of CisPt with the NP surface. The drug loading was quantitatively estimated by ICP-OES measurements, while DLS and AFM confirmed the strong association of the drug with the nanoparticle surface. The test of SOD-like activity in a cell-free environment proved the maintenance of the antioxidant capability of PdNP also in the Pd@CisPt systems. Finally, Pd@CisPt tested in prostate cancer cells (PC-3 line) unveiled the antitumoral action of the developed nanomedicine, related to reactive oxygen species (ROS) generation, with a condition of protein misfolding/unfolding and DNA damage, as evidenced by cytotoxicity and MitoSOX assays, as well as Raman microspectroscopy, respectively. Cell imaging by confocal microscopy evidenced cellular uptake of the nanoparticles, as well as dynamic processes of copper ion accumulation at the level of subcellular compartments. Finally, cell migration studies upon treatment with Pd@CisPt evidenced a tunable response between the inhibitory effect of CisPt and the enhanced rate of cell migration for the metal NP alone, which pointed out the promising potential of the developed theranostic nanomedicine in tissue regeneration.

Photoresponsive polymeric microneedles: An innovative way to monitor and treat diseases

Microneedles (MN) technology is an emerging technology for the transdermal delivery of therapeutics. When combined with photoresponsive (PR) materials, MNs can deliver therapeutics precisely and effectively with enhanced efficacy or synergistic effects. This review systematically summarizes the therapeutic applications of PRMNs in cancer therapy, wound healing, diabetes treatment, and diagnostics. Different PR approaches to activate and control the release of therapeutic agents from MNs are also discussed. Overall, PRMNs are a powerful tool for stimuli-responsive controlled-release therapeutic delivery to treat various diseases.

Biomaterial-assisted tumor therapy: A brief review of hydroxyapatite nanoparticles and its composites used in bone tumors therapy

Malignant bone tumors can inflict significant damage to affected bones, leaving patients to contend with issues like residual tumor cells, bone defects, and bacterial infections post-surgery. However, hydroxyapatite nanoparticles (nHAp), the principal inorganic constituent of natural bone, possess numerous advantages such as high biocompatibility, bone conduction ability, and a large surface area. Moreover, nHAp's nanoscale particle size enables it to impede the growth of various tumor cells via diverse pathways. This article presents a comprehensive review of relevant literature spanning the past 2 decades concerning nHAp and bone tumors. The primary goal is to explore the mechanisms responsible for nHAp's ability to hinder tumor initiation and progression, as well as to investigate the potential of integrating other drugs and components for bone tumor diagnosis and treatment. Lastly, the article discusses future prospects for the development of hydroxyapatite materials as a promising modality for tumor therapy.

Drug Self-Delivery Systems: Molecule Design, Construction Strategy, and Biological Application

Drug self-delivery systems (DSDSs) offer new ways to create novel drug delivery systems (DDSs). In typical DSDSs, therapeutic reagents are not considered passive cargos but active delivery agents of actionable targets. As an advanced drug delivery strategy, DSDSs with positive cooperativity of both free drugs and nanocarriers exhibit the clear merits of unprecedented drug-loading capacity, minimized systemic toxicity, and flexible preparation of nanoscale deliverables for passive targeted therapy. This review highlights the recent advances and future trends in DSDSs on the basis of two differently constructed structures: covalent and noncovalent bond-based DSDSs. Specifically, various chemical and architectural designs, fabrication strategies, and responsive and functional features are comprehensively discussed for these two types of DSDSs. In addition, additional comments on the current development status of DSDSs and the potential applications of their molecular designs are presented in the corresponding discussion. Finally, the promising potential of DSDSs in biological applications is revealed and the relationship between preliminary molecular design of DSDSs and therapeutic effects of subsequent DSDSs biological applications is clarified.

Responsive shape-shifting nanoarchitectonics and its application in tumor diagnosis and therapy

Nanodrug delivery system has a great application in the treatment of solid tumors by virtue of EPR effect, though its success in clinics is still limited by its poor extravasation, small intratumoral accumulation, and weak tumor penetration. The shape of nanoparticles (NPs) greatly affects their circulation time, flow behavior, intratumoral amassing, cell internalization as well as tumor tissue penetration. Generally, short nanorods and 100-200 nm spherical nanocarriers possess nice circulation behaviors, nanorods and nanofibers with a large aspect ratio (AR) cumulate well at tumor sites, and tiny nanospheres/disks (< 50 nm) and short nanorods with a low AR achieve a favorable tumor tissue penetration. The AR and surface evenness of NPs also tune their cell contact, cell ingestion, and drug accumulation at tumor sites. Therefore, adopting stimulus-responsive shape-switching (namely, shape-shifting nanoarchitectonics) can not only ensure a good circulation and extravasation for NPs, but also and more importantly, promote their amassing, retention, and penetration in tumor tissues to maximize therapeutic efficacy. Here we review the recently developed shape-switching nanoarchitectonics of antitumoral NPs based on stimulus-responsiveness, demonstrate how successful they are in tumor shrinking and elimination, and provide new ideas for the optimization of anticancer nanotherapeutics.

Inside-the-body light delivery system using endovascular therapy-based light illumination technology

Background

Light-based therapies are promising for treating diseases including cancer, hereditary conditions, and protein-related disorders. However, systems, methods, and devices that deliver light deep inside the body are limited. This study aimed to develop an endovascular therapy-based light illumination technology (ET-BLIT), capable of providing deep light irradiation within the body.

Methods

The ET-BLIT system consists of a catheter with a single lumen as a guidewire and diffuser, with a transparent section at the distal end for thermocouple head attachment. The optical light diffuser alters the emission direction laterally, according to the optical fibre's nose-shape angle. If necessary, after delivering the catheter to the target position in the vessel, the diffuser is inserted into the catheter and placed in the transparent section in the direction of the target lesion.

Findings

ET-BLIT was tested in an animal model. The 690-nm near-infrared (NIR) light penetrated the walls of blood vessels to reach the liver and kidneys without causing temperature increase, vessel damage, or blood component alterations. NIR light transmittance from the diffuser to the detector within the organ or vessel was approximately 30% and 65% for the renal and hepatic arteries, respectively.

Interpretation

ET-BLIT can be potentially used in clinical photo-based medicine, as a far-out technology. ET-BLIT uses a familiar method that can access the whole body, as the basic procedure is comparable to that of endovascular therapy in terms of sequence and technique. Therefore, the use of the ET-BLIT system is promising for many light-based therapies that are currently in the research phase.

Funding

Supported by Programme for Developing Next-generation Researchers (Japan Science and Technology Agency); JSPS KAKENHI (18K15923, 21K07217); JST-CREST (JPMJCR19H2); JST-FOREST-Souhatsu (JPMJFR2017); The Uehara Memorial Foundation; Yasuda Memorial Medical Foundation; Mochida Memorial Foundation for Medical and Pharmaceutical Research; Takeda Science Foundation; The Japan Health Foundation; Takahashi Industrial and Economic Research Foundation; AICHI Health Promotion Foundation; and Princess Takamatsu Cancer Research Fund.

Advances in nanobiotechnology-propelled multidrug resistance circumvention of cancer

Multidrug resistance (MDR) is one of the main reasons for the failure of tumor chemotherapy and has a negative influence on the therapeutic effect. MDR is primarily attributable to two mechanisms: the activation of efflux pumps for drugs, which can transport intracellular drug molecules from cells, and other mechanisms not related to efflux pumps, e.g., apoptosis prevention, strengthened DNA repair, and strong oxidation resistance. Nanodrug-delivery systems have recently attracted much attention, showing some unparalleled advantages such as drug targeting and reduced drug efflux, drug toxicity and side effects in reversing MDR. Notably, in drug-delivery platforms based on nanotechnology, multiple therapeutic strategies are integrated into one system, which can compensate for the limitations of individual strategies. In this review, the mechanisms of tumor MDR as well as common vectors and nanocarrier-combined therapy strategies to reverse MDR were summarized to promote the understanding of the latest progress in improving the efficiency of chemotherapy and synergistic strategies. In particular, the adoption of nanotechnology has been highlighted and the principles underlying this phenomenon have been elucidated, which may provide guidance for the development of more effective anticancer strategies.

Progress in Stimuli-Responsive Biomaterials for Treating Cardiovascular and Cerebrovascular Diseases

Cardiovascular and cerebrovascular diseases (CCVDs) describe abnormal vascular system conditions affecting the brain and heart. Among these, ischemic heart disease and ischemic stroke are the leading causes of death worldwide, resulting in 16% and 11% of deaths globally. Although several therapeutic approaches are presented over the years, the continuously increasing mortality rates suggest the need for more advanced strategies for their treatment. One of these strategies lies in the use of stimuli-responsive biomaterials. These "smart" biomaterials can specifically target the diseased tissue, and after "reading" the altered environmental cues, they can respond by altering their physicochemical properties and/or their morphology. In this review, the progress in the field of stimuli-responsive biomaterials for CCVDs in the last five years, aiming at highlighting their potential as early-stage therapeutics in the preclinical scenery, is described.

One stone, many birds: Recent advances in functional nanogels for cancer nanotheranostics

Inspired by the development of nanomedicine and nanotechnology, more and more possibilities in cancer theranostic have been provided in the last few years. Emerging therapeutic modalities like starvation therapy, chemodynamic therapy, and tumor oxygenation have been integrated with diagnosis, giving a plethora of theranostic nanoagents. Among all of them, nanogels (NGs) show superiority benefiting from their unique attributes: high stability, high water-absorption, large specific surface area, mechanical strength, controlled responsiveness, and high encapsulation capacity. There have been a vast number of investigations supporting various NGs combining drug delivery and multiple bioimaging techniques, encompassing photothermal imaging, photoacoustic imaging, fluorescent imaging, ultrasound imaging, magnetic resonance imaging, and computed tomography. This review summarizes recent advances in functional NGs for theranostic nanomedicine and discusses the challenges and future perspectives of this fast-growing field. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Water-soluble thienoviologen derivatives for imaging bacteria and antimicrobial photodynamic therapy

A series of water-soluble cationic thienoviologen derivative photosensitizers (nTPy-Rs) for photodynamic therapy (PDT) is reported. Cationic pyridine groups were introduced into the thiophene framework to enhance solubility and bacteria-binding ability, which effectively improved bacteriological imaging and antibacterial activity. The optoelectronic properties of nTPy-Rs were regulated by adjusting the number of thiophene groups, and the differences in antibacterial activity due to the functional scaffolds were compared. The results showed that nTPy-Rs could generate reactive oxygen species (ROS, including macroscopic free radicals), efficiently inhibit bacterial growth, and achieve the minimum inhibitory concentration (MIC) to the ng mL^-1 level. Remarkably, 2TPyC6, containing two thiophene groups and modified by alkyl side chains, showed the best bacteriostatic performance, with the MIC of 20 ng mL^-1 and 4.5 ng mL^-1 for E. coli and S. aureus, respectively, which are the lowest photosensitizer concentrations used in PDT to date. The low cell cytotoxicity and excellent antibacterial performance give nTPy-Rs great potential as PDT agents in vivo.

Application of "smart" multifunctional nanoprobes in tumor diagnosis and treatment

Cancer is one of the major diseases that pose a threat to human health and life, especially because it is difficult to diagnose and cure, and recurs easily. In recent years, the development of nanotechnology has provided researchers with new tools for cancer treatment. In particular, nanoprobes that facilitate integrated diagnosis and treatment, high-resolution imaging, and accurate tumor targeting provide new avenues for the early detection and treatment of cancer. This review focuses on the preparations and applications of two kinds of "smart" multifunctional nanoprobes: "Off-On" nanoprobes and "Charge-Reversal" nanoprobes. This review also briefly discusses their mechanisms of action, as they could provide new ideas for the further development of this field.

Multifunctional high-Z nanoradiosensitizers for multimodal synergistic cancer therapy

Radiotherapy (RT) is one of the most common and effective clinical therapies for malignant tumors. However, there are several limitations that undermine the clinical efficacy of cancer RT, including the low X-ray attenuation coefficient of organs, serious damage to normal tissues, and radioresistance in hypoxic tumors. With the rapid development of nanotechnology and nanomedicine, high-Z nanoradiosensitizers provide novel opportunities to overcome radioresistance and improve the efficacy of RT by deposition of radiation energy through photoelectric effects. To date, several types of nanoradiosensitizers have entered clinical trials. Nevertheless, the limitation of the single treatment mode and the unclear mechanism of nanoparticle radiosensitization have hindered the further development of nanoradiosensitizers. In this review, we systematically describe the interaction mechanisms between X-rays and nanomaterials and summarize recent advances in multifunctional high-Z nanomaterials for radiotherapeutic-based multimodal synergistic cancer therapy. Finally, the challenges and prospects are discussed to stimulate the development of nanomedicine-based cancer RT.

A pH-sensitive supramolecular nanosystem with chlorin e6 and triptolide co-delivery for chemo-photodynamic combination therapy

The combination of Ce6, an acknowledged photosensitizer, and TPL, a natural anticancer agent, has been demonstrated as a useful strategy to reinforce the tumor growth suppression, as well as decrease the systemic side effects compared with their monotherapy. However, in view of the optimal chemo-photodynamic combination efficiency, there is still short of the feasible nanovehicle to steadily co-deliver Ce6 and TPL, and stimuli-responsively burst release drugs in tumor site. Herein, we described the synergistic antitumor performance of a pH-sensitive supramolecular nanosystem, mediated by the host–guest complexing between β-CD and acid pH-responsive amphiphilic co-polymer mPEG-PBAE-mPEG, showing the shell–core structural micelles with the tight β-CD layer coating. Both Ce6 and TPL were facilely co-loaded into the spherical supramolecular NPs (TPL+Ce6/NPs) by one-step nanoprecipitation method, with an ideal particle size (156.0 nm), acid pH-responsive drug release profile, and enhanced cellular internalization capacity. In view of the combination benefit of photodynamic therapy and chemotherapy, as well as co-encapsulation in the fabricated pH-sensitive supramolecular NPs, TPL+Ce6/NPs exhibited significant efficacy to suppress cellular proliferation, boost ROS level, lower MMP, and promote cellular apoptosis in vitro. Particularly, fluorescence imaging revealed that TPL+Ce6/NPs preferentially accumulated in the tumor tissue area, with higher intensity than that of free Ce6. As expected, upon 650-nm laser irradiation, TPL+Ce6/NPs exhibited a cascade of amplified synergistic chemo-photodynamic therapeutic benefits to suppress tumor progression in both hepatoma H22 tumor-bearing mice and B16 tumor-bearing mice. More importantly, lower systemic toxicity was found in the tumor-bearing mice treated with TPL+Ce6/NPs. Overall, the designed supramolecular TPL+Ce6/NPs provided a promising alternative approach for chemo-photodynamic therapy in tumor treatment.

Near-Infrared Light-Responsive SERS Tags Enable Positioning and Monitoring of the Drug Release of Photothermal Nanomedicines In Vivo

Understanding the in vivo behavior of photothermal nanomedicines (PTNMs) is important for drug development and evaluation. However, it is still very challenging. Herein, two key parameters, i.e., the depth of PTNMs under biological tissue and the drug release ratio of PTNMs in vivo, can be revealed by a near-infrared (NIR) light-responsive surface-enhanced Raman scattering (SERS) strategy. The fabricated PTNMs were composed of waxberry-like gold nanoparticles, model drug curcumin, and an elaborately selected NIR light-responsive Raman reporter (3,3'-diethylthiatricarbocyanine iodide, DTTC). The response mechanism of DTTC to NIR light was investigated as photodegradation. NIR light irradiation heated the gold nanoparticles, triggered the release of a model drug, and simultaneously decreased the SERS intensity of the PTNMs. In vitro experiment results revealed that the SERS intensity decrease could well reflect the depth of PTNMs with a correlation coefficient of more than 0.99. On this basis, after in situ SERS detection, the depth of PTNMs in a tumor could be revealed with satisfactory accuracy. Moreover, the decrease in the SERS intensity of PTNMs showed a highly similar trend to the increase in the drug release, suggesting that it could be used for real-time monitoring of drug release of PTNMs. This study not only opens a new avenue for the release study of many inactive fluorescent and Raman drugs of PTNMs but also provides an effective way for reporting the depth, which greatly promotes the application of PTNMs in vivo.

Nanomedicine from amphiphilizedprodrugs: Concept and clinical translation

Nanomedicines generally consisting of carrier materials with small fractions of active pharmaceutical ingredients (API) have long been used to improve the pharmacokinetics and biodistributions, augment the therapeutic efficacies and mitigate the side effects. Amphiphilizing hydrophobic/hydrophilic drugs to prodrugs capable of self-assembly into well-defined nanostructures has emerged as a facile approach to fabricating nanomedicines because this amphiphilized prodrug (APD) strategy presents many advantages, including minimized use of inert carrier materials, well-characterized prodrug structures, fixed and high drug loading contents, 100% loading efficiency, and burst-free but controlled drug release. This review comprehensively summarizes recent advances in APDs and their nanomedicines, from the rationale and the stimuli-responsive linker chemistry for on-demand drug release to their progress to the clinics, clinical performance of APDs, as well as the challenges and perspective on future development.

Hydrogen Sulfide-Responsive Bicontinuous Nanospheres

Block copolymers (BCPs) that can self-assemble into particles and be triggered by disease-specific molecules such as hydrogen sulfide (H₂S) have the potential to impact on drug delivery, decreasing off-target toxicities while increasing drug efficacy. However, the incorporation of H₂S-responsive aryl azides into BCPs for self-assembly has been limited by heat, light, and radical sensitivities. In this study, a robust activator regenerated by the electron-transfer atom-transfer radical polymerization reaction was used to synthesize aryl-azide-containing BCPs under ambient conditions. Conditions controlling self-assembly of the BCPs into 150-200 nm particles and the physicochemical properties of the particles were investigated. The use of nanoprecipitation with tetrahydrofuran to promote self-assembly of the BCPs resulted in vesicle structures, while dimethylformamide or dimethylsulfoxide resulted in polymeric bicontinuous nanospheres (BCNs). Triggering of the BCPs and particles (vesicles or BCNs) via exposure to H₂S revealed that unsubstituted aryl azides were readily reduced (by HS^-), resulting in particle disruption or cross-linking. The relative polar nature of the particle bilayers containing unsubstituted aryl azides and the open structure of the BCNs did however limit encapsulation of small hydrophilic and hydrophobic payloads. Incorporation of a benzylamide substituent onto the aryl azide group increased the hydrophobicity of the particles and encapsulation of hydrophilic cargo but reduced sensitivity to H₂S, likely due to the reduced penetration of HS^- into the bilayer.

Sequential drug delivery by injectable macroporous hydrogels for combined photodynamic-chemotherapy

With hollow mesoporous silica (hMSN) and injectable macroporous hydrogel (Gel) used as the internal and external drug-loading material respectively, a sequential drug delivery system DOX-CA4P@Gel was constructed, in which combretastatin A4 phosphate (CA4P) and doxorubicin (DOX) were both loaded. The anti-angiogenic drug, CA4P was initially released due to the degradation of Gel, followed by the anti-cell proliferative drug, DOX, released from hMSN in tumor microenvironment. Results showed that CA4P was mainly released at the early stage. At 48 h, CA4P release reached 71.08%, while DOX was only 24.39%. At 144 h, CA4P was 78.20%, while DOX release significantly increased to 61.60%, showing an obvious sequential release behavior. Photodynamic properties of porphyrin endow hydrogel (ϕΔ(Gel) = 0.91) with enhanced tumor therapy effect. In vitro and in vivo experiments showed that dual drugs treated groups have better tumor inhibition than solo drug under near infrared laser irradiation, indicating the effectivity of combined photodynamic-chemotherapy.

Stimuli-Responsive Nanofibers Containing Gold Nanorods for On-Demand Drug Delivery Platforms

On-demand drug delivery systems using nanofibers have attracted significant attention owing to their controllable properties for drug release through external stimuli. Near-infrared (NIR)-responsive nanofibers provide a platform where the drug release profile can be achieved by the on-demand supply of drugs at a desired dose for cancer therapy. Nanomaterials such as gold nanorods (GNRs) exhibit absorbance in the NIR range, and in response to NIR irradiation, they generate heat as a result of a plasmon resonance effect. In this study, we designed poly (N-isopropylacrylamide) (PNIPAM) composite nanofibers containing GNRs. PNIPAM is a heat-reactive polymer that provides a swelling and deswelling property to the nanofibers. Electrospun nanofibers have a large surface-area-to-volume ratio, which is used to effectively deliver large quantities of drugs. In this platform, both hydrophilic and hydrophobic drugs can be introduced and manipulated. On-demand drug delivery systems were obtained through stimuli-responsive nanofibers containing GNRs and PNIPAM. Upon NIR irradiation, the heat generated by the GNRs ensures shrinking of the nanofibers owing to the thermal response of PNIPAM, thereby resulting in a controlled drug release. The versatility of the light-responsive nanofibers as a drug delivery platform was confirmed in cell studies, indicating the advantages of the swelling and deswelling property of the nanofibers and on-off drug release behavior with good biocompatibility. In addition, the system has potential for the combination of chemotherapy with multiple drugs to enhance the effectiveness of complex cancer treatments.

The pH responsive upconversion fluorescence and photothermal conversion properties of NaYF4:Yb3+/Er3+@NaYF4@MnO2@Au

While photothermal therapy is widely applied in phototherapy, there are still challenges in developing new generation phototherapy materials with precise diagnostic functions. Here we report the construction of a pH responsive upconversion fluorescence imaging precisely guided photothermal therapy system, namely NaYF4:Yb3+/Er3+@NaYF4@MnO2@Au nanocomposites, which can effectively avoid light damage to non-target tissues. Owing to the fluorescence resonance energy transfer between the upconversion nanocrystal donor and MnO2 and Au acceptor, the upconversion fluorescence is completely quenched. However, in pH 5.3 PBS buffer, MnO2 is gradually broken down, and the upconversion fluorescence is partially recovered, which could be used for upconversion fluorescence imaging to precisely guide photothermal therapy under 980 nm excitation. Simultaneously, due to the absorption of 980 nm excitation light and the emission bands of Er3+ (2H11/2→4I15/2 and 4S3/2→4I15/2 transition), temperature increment of core@shell@MnO2@Au could reach 35.5 °C under 980 nm excitation at 0.8 W cm-2. The core@shell@MnO2@Au nanocomposites are supposed to contribute significantly in the biological applications of photoluminescence imaging and photothermal therapy.

Intramolecular Charge Transfer-Based Conjugated Oligomer with Fluorescence, Efficient Photodynamics, and Photothermal Activities

To develop efficient photoactive agents with satisfactory fluorescence, photodynamic, and photothermal effects is crucial for a phototherapeutic strategy to combat cancer diseases and pathogenic microbes. Herein, a water-soluble donor-acceptor-donor (D-A-D) structured conjugated oligomer was designed and synthesized, consisting of two cyclopenta-dithiophene (CDT) units as the electron donor and boron dipyrromethene (BODIPY) as the electron acceptor. Upon excitation, dual emission was observed for CDT-BODIPY with blue and red fluorescence peaks at 463 nm and at 730 nm, respectively, which was ascribed to intramolecular charge transfer (ICT). Due to the ICT effect, the singlet-to-triplet intersystem crossing rate of CDT-BODIPY was also enhanced, leading to an outstanding photodynamic behavior to produce reactive oxygen species (ROS). Meanwhile, its low bandgap also enabled it a moderate photothermal capability with a conversion efficiency of 33.1%. Taking advantage of its phototriggered activities, this conjugated oligomer exhibited an effective inhibition behavior on the pathogenic growth of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans), which can be guided by dual-wavelength fluorescence imaging. This D-A-D type conjugated oligomer with balanced photophysical characteristics provides a promising strategy to imaging-guided photoactive therapy.

Competition between the Photothermal Effect and Emission in Potential Phototherapy Agents

Planar donor-acceptor-donor (D-A-D) organic molecules have been highlighted as promising photothermal agents due to their good light-to-heat conversion ratio, easy degradation, and chemical tunability. Very recently, it has been demonstrated that their photothermal conversion can be boosted by appending rather long alkyl chains. Despite this behavior being tentatively associated with the population of a nonradiative twisted intramolecular charge transfer (TICT) state driven by an intramolecular motion, the precise mechanisms and the role played by the environment, and most notably aggregation, still remain elusive. In this context, we carried out a series of time-dependent density functional theory (TD-DFT) calculations combined with molecular dynamics (MD) simulations to achieve a realistic description of the isolated and aggregated systems. Our theoretical models unambiguously evidence that the population of CT states is very unlikely in both cases, whereas the light-triggered heat dissipation can be ascribed to the activation of specific vibrational degrees of freedom related to the relative motion of the peripheral chains. Overall, our results clearly corroborate the active role played by the alkyl substituents in the photothermal conversion through vibrational motion, while breaking from the conventional picture, which invokes the formation of dark TICT states in loosely packed aggregates.

Smart magnetic resonance imaging-based theranostics for cancer

Smart theranostics are dynamic platforms that integrate multiple functions, including at least imaging, therapy, and responsiveness, in a single agent. This review showcases a variety of responsive theranostic agents developed specifically for magnetic resonance imaging (MRI), due to the privileged position this non-invasive, non-ionising imaging modality continues to hold within the clinical imaging field. Different MRI smart theranostic designs have been devised in the search for more efficient cancer therapy, and improved diagnostic efficiency, through the increase of the local concentration of therapeutic effectors and MRI signal intensity in pathological tissues. This review explores novel small-molecule and nanosized MRI theranostic agents for cancer that exhibit responsiveness to endogenous (change in pH, redox environment, or enzymes) or exogenous (temperature, ultrasound, or light) stimuli. The challenges and obstacles in the design and in vivo application of responsive theranostics are also discussed to guide future research in this interdisciplinary field towards more controllable, efficient, and diagnostically relevant smart theranostics agents.

Intelligent optical diagnosis and treatment system for automated image-guided laser ablation of tumors

PURPOSE

For tumor resections near critical structures, accurate identification of tumor boundaries and maximum removal are the keys to improve surgical outcome and patient survival rate, especially in neurosurgery. In this paper, we propose an intelligent optical diagnosis and treatment system for tumor removal, with automated lesion localization and laser ablation.

METHODS

The proposed system contains a laser ablation module, an optical coherence tomography (OCT) unit, and a robotic arm along with a stereo camera. The robotic arm can move the OCT sample arm and the laser ablation front-end to the suspected lesion area. The corresponding diagnosis and treatment procedures include computer-aided lesion segmentation using OCT, automated ablation planning, and laser control. The ablation process is controlled by a deflectable mirror, and a non-common-path ablation planning algorithm based on the transformation from lesion positions to mirror deflection angles is presented.

RESULTS

Phantom and animal experiments are carried out for system verification. The robot could reach the planned position with high precision, which is approximately 1.16 mm. Tissue classification with OCT images achieves 91.7% accuracy. The error of OCT-guided automated laser ablation is approximately 0.74 mm. Experiments on mouse brain tumors show that the proposed system is capable of clearing lesions efficiently and precisely. We also conducted an ex vivo porcine brain experiment to verify the whole process of the system.

CONCLUSION

An intelligent optical diagnosis and treatment system is proposed for tumor removal. Experimental results show that the proposed system and method are promising for precise and intelligent theranostics. Compared to conventional cancer diagnosis and treatment, the proposed system allows for automated operations monitored in real-time, with higher precision and efficiency.

Theranostic Applications of Nanoparticle-Mediated Photoactivated Therapies

Nanoparticle-mediated light-activated therapies, such as photodynamic therapy and photothermal therapy, are earnestly being viewed as efficient interventional strategies against several cancer types. Theranostics is a key hallmark of cancer nanomedicine since it allows diagnosis and therapy of both primary and metastatic cancer using a single nanoprobe. Advanced in vivo diagnostic imaging using theranostic nanoparticles not only provides precise information about the location of tumor/s but also outlines the narrow time window corresponding to the maximum tumor-specific drug accumulation. Such information plays a critical role in guiding light-activated therapies with high spatio-temporal accuracy. Furthermore, theranostics facilitates monitoring the progression of therapy in real time. Herein, we provide a general review of the application of theranostic nanoparticles for in vivo image-guided light-activated therapy in cancer. The imaging modalities considered here include fluorescence imaging, photoacoustic imaging, thermal imaging, magnetic resonance imaging, X-ray computed tomography, positron emission tomography, and single-photon emission computed tomography. The review concludes with a brief discussion about the broad scope of theranostic light-activated nanomedicine.

Nanoparticles as therapeutic options for treating multidrug-resistant bacteria: research progress, challenges, and prospects

Resistance to antimicrobial agents has been alarming in recent years and poses a huge public health threat globally according to the WHO. The increase in morbidity and mortality resulting from microbial infections has been attributed to the emergence of multidrug-resistant microbes. Associated with the increase in multidrug resistance is the lack of new and effective antimicrobials. This has led to global initiatives to identify novel and more effective antimicrobial agents in addition to discovering novel and effective drug delivery and targeting methods. The use of nanoparticles as novel biomaterials to fully achieve this feat is currently gaining global attention. Nanoparticles could become an indispensable viable therapeutic option for treating drug-resistant infections. Of all the nanoparticles, the metals and metal oxide nanoparticles appear to offer the most promise and have attracted tremendous interest from many researchers. Moreover, the use of nanomaterials in photothermal therapy has received considerable attention over the years. This review provides current insight on antimicrobial resistance as well as the mechanisms of nanoparticle antibacterial activity. It offers an in-depth review of all the recent findings in the use of nanomaterials as agents against multi-resistant pathogenic bacteria. Also, nanomaterials that can respond to light stimuli (photothermal therapy) to kill microbes and facilitate enhanced drug delivery and release are discussed. Moreover, the synergistic interactions of nanoparticles with antibiotics and other nanomaterials, microbial adaptation strategies to nanoparticles, current challenges, and future prospects were extensively discussed.

IR780-based nanomaterials for cancer imaging and therapy

IR780, a small molecule with a strong optical property and excellent photoconversion efficiency following near infrared (NIR) irradiation, has attracted increasing attention in the field of cancer treatment and imaging. This review is focused on different IR780-based nanoplatforms and the application of IR780-based nanomaterials for cancer bioimaging and therapy. Thus, this review summarizes the overall aspects of IR780-based nanomaterials that positively impact cancer biomedical applications.

Platinum-Containing Supramolecular Drug Self-Delivery Nanomicelles for Efficient Synergistic Combination Chemotherapy

Supramolecular drug self-delivery systems (SDSDSs) involving active drugs as building blocks linked by supramolecular interactions have been well defined as an advanced chemotherapy strategy. However, the lack of detecting release of drugs from SDSDSs at specific tumor sites inevitably leads to unsatisfactory therapeutic effects, owing to the lack of information regarding the administration of these drugs. In this work, predesigned platinum-containing supramolecular drug self-delivery nanomicelles (SDSDNMs) were employed to synchronously realize drug monitoring by computed tomography imaging, immediately reflecting the evolution of drug release and real-time treatment at the tumor site. The appropriate administration dosage (1.2 mg mL^-1,100 μL) and the injection interval (once every 3 days) needed to guide the antitumor activity of SDSDNMs were then defined, thereby attaining the aim of efficient synergistic combination chemotherapy. In vivo tumor inhibition and histological analyses showed that SDSDNMs exhibited a strong tumor inhibition effect and good safety with respect to normal organs. Such a supramolecular drug self-delivery strategy with monitored functions may offer new potential opportunities for application in the field of synergistic combination chemotherapy.

Polymeric Nanosystems for Immunogenic Cell Death-Based Cancer Immunotherapy

Immunotherapy has pointed out a scientific and promising direction for cancer treatment through the rouse of immunosurveillance and the decrease of possible side effects in recent years. In immunotherapy, immunogenic cancer cell death (ICD) plays a critical role in regulating anti-cancer immune system in vivo via the release of damage-associated molecular patterns. ICD can not only induce in situ cancer cells apoptosis, but also arouse the immune response against metastatic tumors, which is of great clinical significance to eradicate tumors. In cancer immunotherapy, polymer nanoparticles have drawn increasing attention as an important component of ICD-based immunotherapy attributing to their controllable size, excellent biocompatibility, promising ability of protecting cargo from surrounding environment, which delivers the antigens or immune inducers to antigen-presenting cells, and further triggers sinnvoll T cell response. In this review, the recent advances in the development of polymeric material-based nanosystems for ICD-mediated cancer immunotherapy are summarized. The mechanism of ICD and some current restrictions inhibiting the efficiency of immunotherapy and future prospects are also discussed.

A Near-Infrared Laser-Triggered Size-Shrinkable Nanosystem with In Situ Drug Release for Deep Tumor Penetration

The development of smart size-tunable drug delivery nanoplatform enables the solving of the paradox of inconsistent size-dependence of high tumor accumulation and deep penetration during its delivery process, thus achieving superior cancer treatment efficacy. Herein, we report a size-shrinkable nanomicelle complex system with an initial size of 101 nm enabling effective retention around the tumor periphery and could destruct to ultrasmall nanomicelles triggered by a near-infrared (NIR) laser to realize the deep tumor penetration. The nanomicelle system is consisted of an upper critical solution temperature (UCST)-type block copolymer poly(acrylamide-acrylonitrile)-polyethylene glycol-lipoic acid (p(AAm-co-AN)-g-PEG-LA) encapsulating gold nanorods. Upon the irradiation of the NIR laser at the tumor site, gold nanorods could convert the light energy to heat energy, realizing the photothermal ablation of superficial tumor tissue. Concurrently, the large micelles split into a cascade of ultrasmall micelles (∼7 nm), which could easily penetrate into the deep site of the tumor and achieve the in situ "on-demand" release of the loaded drug to exert superior combined photothermal-chemotherapy of cancer. By the precise manipulation of laser, the micelle complex system realized the hierarchical killing from the superficial-to-deep tumor and achieved almost complete tumor growth inhibition on the established xenograft liver tumor mice model.

Metal-organic complex-based chemodynamic therapy agents for cancer therapy

In recent years, many inorganic nanoparticle-based chemodynamic therapy (CDT) agents have been employed in cancer therapy; however, the relatively lower catalytic activity compared to that of other CDT agents and long-term toxicity owing to low biodegradability present significant challenges for their future clinical application. In light of this, metal-organic complex-based agents have been attracting attention as potential alternatives/complements to traditional CDT agents. During the past few years, many reports of agents with improved therapeutic potential have been published; however, no comprehensive review regarding metal-organic complex-based CDT agents has appeared to date. In this feature article, we present the different types and characteristics of metal-organic CDT agents and the potential future therapeutic applications associated with each of these. Representative agents that have been used in the field of CDT over the past 5 years are summarized, and recent advances aimed at improving the therapeutic efficacy in various tumors are highlighted. This framework allows us to discuss recent trends in the field of CDT. We also provide views as to where the field is moving and discuss how the potential of CDT agents can be broadened to include a range of clinical applications that go beyond standard CDT-based treatment strategies.

One Robust Microporous TmIII-Organic Framework for Highly Catalytic Activity on Chemical CO2 Fixation and Knoevenagel Condensation

In terms of documented references, multifunctional MOFs with high catalytic performance could be constructed from the combination of metal cations and polycarboxyl-pyridine ligands, which could efficiently endow crystallized porous frameworks with the coexisting Lewis acid-base properties. Thus, by employing a ligand-directed synthetic strategy, the exquisite combination of wave-like inorganic chains of [Tm(CO₂)₃(OH₂)]_n and mononuclear units of [Tm(CO₂)₄(OH₂)₂] with the aid of the specially designed ligand of 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H₅BDCP) generates one highly robust microporous framework of {(Me₂NH₂)[Tm₃(BDCP)₂)(H₂O)₃]·4DMF·H₂O}_n (simplified as NUC-25), which contains near-rectangular nanochannels and large solvent-residing voids. Furthermore, the activated state of NUC-25 with the removal of associated water molecules is a rarely reported bifunctional heterogeneous catalyst due to the coexistence of Lewis acid-base sites including 6-coordinated Tm³⁺ ions, uncoordinated carboxyl oxygen atoms, and N_pyridine atoms. Just as expected, NUC-25 exhibits greatly high catalytic activity for the cycloaddition reaction of epoxides with CO₂ into alkyl cyclic carbonates under bland solvent-free conditions, which should be ascribed to the polarity of nitrogen-containing pyridine heterocycles as Lewis base sites on the inner surface of nano-caged voids except for recognized Lewis acid sites of rare earth cations. Moreover, the excellent pore-size-dependent catalytic property for Knoevenagel condensation reactions confirms that NUC-25 can be viewed as a recyclable bifunctional heterogeneous catalyst. Therefore, these results strongly demonstrate that microporous MOFs assembled from pre-designed polycarboxyl-heterocyclic ligands display better catalytic performance not only for chemical CO₂ fixation but also for Knoevenagel condensation reactions.

Current update on nanoplatforms as therapeutic and diagnostic tools: A review for the materials used as nanotheranostics and imaging modalities

In the last decade, the use of nanotheranostics as emerging diagnostic and therapeutic tools for various diseases, especially cancer, is held great attention. Up to date, several approaches have been employed in order to develop smart nanotheranostics, which combine bioactive targeting on specific tissues as well as diagnostic properties. The nanotheranostics can deliver therapeutic agents by concomitantly monitor the therapy response in real-time. Consequently, the possibility of over- or under-dosing is decreased. Various non-invasive imaging techniques have been used to quantitatively monitor the drug delivery processes. Radiolabeling of nanomaterials is widely used as powerful diagnostic approach on nuclear medicine imaging. In fact, various radiolabeled nanomaterials have been designed and developed for imaging tumors and other lesions due to their efficient characteristics. Inorganic nanoparticles as gold, silver, silica based nanomaterials or organic nanoparticles as polymers, carbon based nanomaterials, liposomes have been reported as multifunctional nanotheranostics. In this review, the imaging modalities according to their use in various diseases are summarized, providing special details for radiolabeling. In further, the most current nanotheranostics categorized via the used nanomaterials are also summed up. To conclude, this review can be beneficial for medical and pharmaceutical society as well as material scientists who work in the field of nanotheranostics since they can use this research as guide for producing newer and more efficient nanotheranostics.

Smart Responsive Nanoformulation for Targeted Delivery of Active Compounds From Traditional Chinese Medicine

Traditional Chinese medicine (TCM) has been used to treat disorders in China for ~1,000 years. Growing evidence has shown that the active ingredients from TCM have antibacterial, antiproliferative, antioxidant, and apoptosis-inducing features. However, poor solubility and low bioavailability limit clinical application of active compounds from TCM. “Nanoformulations” (NFs) are novel and advanced drug-delivery systems. They show promise for improving the solubility and bioavailability of drugs. In particular, “smart responsive NFs” can respond to the special external and internal stimuli in targeted sites to release loaded drugs, which enables them to control the release of drug within target tissues. Recent studies have demonstrated that smart responsive NFs can achieve targeted release of active compounds from TCM at disease sites to increase their concentrations in diseased tissues and reduce the number of adverse effects. Here, we review “internal stimulus–responsive NFs” (based on pH and redox status) and “external stimulus–responsive NFs” (based on light and magnetic fields) and focus on their application for active compounds from TCM against tumors and infectious diseases, to further boost the development of TCM in modern medicine.

Highly Robust 3s-3d {CaZn}-Organic Framework for Excellent Catalytic Performance on Chemical Fixation of CO2 and Knoevenagel Condensation Reaction

In terms of ligand-directed synthetic strategy, multifunctional metal-organic frameworks (MOFs) could be assembled by employing organic ligands with nitrogen-containing heterocycles, which could serve as Lewis base sites in crystallized porous frameworks. Here, the acidic one-pot hydrothermal reaction of CaCl₂, Zn(NO₃)₂, and 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (H₆TDP) generates one robust honeycomb-shaped double-walled material of {[(CH₃)₂NH₂]₂[CaZn(TDP)(H₂O)]·3DMF·3H₂O}_n (NUC-21), which has the excellent physicochemical characteristics of nanoscopic channels, high porosity (58.3%), large specific surface area, and high heat/water-resisting property. To the best of our knowledge, this is the first 3s-3d dinuclear [CaZn(CO₂)₆(OH₂)]-based nanoporous host framework, whose activated state possesses the coexistence of Lewis acid-base sites including four-coordinated Zn²⁺ ions, four-coordinated Ca²⁺ ions, uncoordinated carboxyl oxygen atoms, and N_pyridine atoms. As expected, because of the coexistence of Lewis acid-base nature, desolvated NUC-21 displays satisfactory catalytic activity on the chemical cycloaddition of various epoxides with CO₂ into the corresponding alkyl carbonates under comparatively mild conditions. Furthermore, the efficient conversion of benzaldehydes and malononitrile confirms that NUC-21 is simultaneously a bifunctional heterogeneous catalyst for Knoevenagel condensation reactions. Hence, the achievements broaden the way for assembling nanoporous multifunctional MOFs by employing ligand-directed synthetic strategy, which can accelerate the transformation from simple structural research to socially demanding applications.

Modified nanoscale metal organic framework-based nanoplatforms in photodynamic therapy and further applications

Photodynamic therapy (PDT) has emerged as a modality in cancer treatment because it is less invasive and highly selective compared with conventional chemotherapy and radiation therapy. Nanoscale metal organic frameworks (nMOFs) have exhibited great potential for use in constructing nanoplatforms for improved PDT because of their unique structural advantages such as large surface areas, high porosities, tunable compositions and various other modifications. The large majority of current nMOF-based systems employ specific modifying groups to overcome the deficiencies previously observed when using older nMOFs in PDT. In this review, we summarize modifications to these systems such as enhancing singlet oxygen generation by introducing photoactive agents, alleviating tumor hypoxia and engineering active targeting abilities. The applications of MOF-based nanoparticles in synergistic cancer therapies that include PDT, as well as in theranostics are also discussed. Finally, we discuss some of the challenges faced in this field and the future prospects for the use of nMOFs in PDT.