NIR‐Light‐Activated Combination Therapy with a Precise Ratio of Photosensitizer and Prodrug Using a Host–Guest Strategy

Development of stimuli responsive polymeric nanomedicines modulating tumor microenvironment for improved cancer therapy

The complexity of the tumor microenvironment (TME) severely hinders the therapeutic effects of various cancer treatment modalities. The TME differs from normal tissues owing to the presence of hypoxia, low pH, and immune-suppressive characteristics. Modulation of the TME to reverse tumor growth equilibrium is considered an effective way to treat tumors. Recently, polymeric nanomedicines have been widely used in cancer therapy, because their synthesis can be controlled and they are highly modifiable, and have demonstrated great potential to remodel the TME. In this review, we outline the application of various stimuli responsive polymeric nanomedicines to modulate the TME, aiming to provide insights for the design of the next generation of polymeric nanomedicines and promote the development of polymeric nanomedicines for cancer therapy.

A Hybrid Supramolecular Polymeric Nanomedicine for Cascade-Amplified Synergetic Cancer Therapy

Supramolecular nanomedicines have shown great merits in cancer therapy, but their clinical translation is hampered by monotonous therapeutic modality and unsatisfactory antitumor performance. Herein, a hybrid supramolecular polymeric nanomedicine (SNPs) is developed based on β-cyclodextrin/camptothecin (CPT) host-guest molecular recognition and iron-carboxylate coordination. Iron ions stabilizing SNPs catalyze the conversion of intracellular hydrogen peroxide into highly toxic hydroxyl radical through a Fenton reaction, which further cleaves the thioketal linker of the supramolecular monomer to release potent CPT, thus amplifying the therapeutic efficacy by combining chemodynamic therapy and chemotherapy. The combination therapy stimulates antitumor immunity and promotes intratumoral infiltration of cytotoxic T lymphocytes by triggering immunogenic cell death. In synergy with PD-L1 checkpoint blockade, SNPs enables enhanced immune therapy and a long-term tumor remission.

Chemiexcitation-Triggered Prodrug Activation for Targeted Carbon Monoxide Delivery

Photolysis-based prodrug strategy can address some critical drug delivery issues, which otherwise are very challenging to tackle with traditional prodrug strategy. However, the need for external light irradiation significantly hampers its in vivo application due to the poor light accessibility of deep tissue. Herein, we propose a new strategy of chemiexcitation-triggered prodrug activation, wherein a photoresponsive prodrug is excited for drug payload release by chemiexcitation instead of photoirradiation. As such, the bond-cleavage power of photolysis can be employed to address some critical drug delivery issues while obviating the need for external light irradiation. We have established the proof of concept by the successful development of a chemiexcitation responsive carbon monoxide delivery platform, which exhibited specific CO release at the tumor site and pronounced tumor suppression effects. We anticipate that such a concept of chemiexcitation-triggered prodrug activation can be leveraged for the targeted delivery of other small molecule-based drug payloads.

Coordinating the mechanism of actions of ferroptosis and photothermal effect for cancer theranostics

Combination therapy based on different mechanisms of cell death has shown promises in tumor therapy. However, design considerations for integrating different modalities are often lack of rationale to synergize the therapeutic effects to the maximal extent. Here, we report a cancer theranostic nanomedicine formula by attentively considering the mechanisms of action of ferroptosis and photothermal effect in combination therapy. We applied the croconaine molecule as both a photothermal converter and an iron-chelating agent which could be readily encapsulated with BSA thus attaining biocompatible and stable Cro-Fe@BSA nanoparticles. The Cro-Fe@BSA nanoprticles in the tumor milieu showed an activated photothermal effect which could enhance the radical formation due to the temperature-dependent Fenton reaction kinetics, while the radical formation during ferroptosis could in turn destruct the heat-induced formation of heat shock proteins, thus preventing the self-protection mechanism of cancer cells in response to heat. This mutually beneficial strategy led to an efficient anticancer effect both in vitro and in a subcutaneous mouse tumor model. Furthermore, the activatable photoacoustic and magnetic resonance imaging performance of the Cro-Fe@BSA nanoparticles provided an intelligent paradigm for safe and reliable cancer theranostics. This study may open up new avenues in designing nanomedicines from a vantage point of synergizing different therapeutic modalities.

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.

Β-Cyclodextrin-graft-poly(amidoamine) dendrons as the nitric oxide deliver system for the chronic rhinosinusitis therapy

Chronic rhinosinusitis (CRS) is a rather prevalent condition with a chronic inflammatory process, which is hard to cure. Herein, a new antibacterial drug, nitric oxide (NO), was used for the attempt on CRS therapy. To achieve this, a star copolymer (β-CD-PAMAM) consisting of the β-cyclodextrin (β-CD) core and seven PAMAM-G3 arms, which was designed as a low-cytotoxicity and high NO loading carrier, were synthesized and characterizied. The obtained β-CD-PAMAM/NONOate showed the effect in inhibiting and dispersing the biofilm of S. aureus, as well as the effective antibacterial performance, implying the promising application in CRS treatment. The in vivo assay confirmed that β-CD-PAMAM/NONOate displayed excellent therapy effect on CRS and significantly improved the symptoms of the experimental rats, which was no significant different in therapy effect with the clinical Rhinocort. Incorporated with its little toxicity in vitro and in vivo, the β-CD-PAMAM/NONOate was suggested a promising application in CRS therapy.

Recent Progress of Alkyl Radicals Generation-Based Agents for Biomedical Applications

Photodynamic therapy (PDT) is extensively explored for anticancer and antibacterial applications. It typically relies on oxygen-dependent generation of reactive oxygen species (ROS) to realize its killing effect. This type of therapy modality shows compromised therapeutic results for treating hypoxic tumors or bacteria-infected wounds. Recently, alkyl radicals attracted much attention as they can be generated from some azo-based initiators only under mild heat stimulus without oxygen participation. Many nanocarriers or hydrogel systems have been developed to load and deliver these radical initiators to lesion sites for theranostics. These systems show good anticancer or antimicrobial effect in hypoxic environment and some of them possess specific imaging abilities providing precise guidance for treatment. This review summarizes the developed materials that aim at treating hypoxic cancer and bacteria-infected wound by using this kind of oxygen-irrelevant alkyl radicals. Based on the carrier components, these agents are divided into three groups: inorganic, organic, as well as inorganic and organic hybrid carrier-based therapeutic systems. The construction of these agents and their specific advantages in biomedical field are highlighted. Finally, the existing problems and future promising development directions are discussed.

Controlling the Stacking Modes of Metal-Organic Framework Nanosheets through Host-Guest Noncovalent Interactions

The tuning of metal-organic framework (MOF) nanosheet stacking modes from molecular level was rarely explored although it significantly affected the properties and applications of nanosheets. Here, the different stacking modes of Zr-1, 3, 5-(4-carboxylphenyl)-benzene framework nanosheets were synthesized through the induction of different host-guest noncovalent interactions. The solvents of methyl benzene and ethyl acetate induced twisted stacking of nanosheets with the specific rotation angles of 12°, 18°, 24° and 6°, 18°, 24°, 30°, respectively, which was in agreement with theoretical calculations. Meanwhile, the alkanes were likely to vertically enter the pores of Zr-BTB nanosheets because of steric hindrance and hydrophobic interactions, resulting in the untwisted stacking of nanosheets. The untwisted ordered nanopores showed the excellent gas chromatographic separations of benzene derivative isomers, which was better than twisted nanosheets stacking and commercial columns. This work uncovers a rational strategy to control the stacking of two-dimensional MOF nanosheets.

Recent Advancements in Stimuli Responsive Drug Delivery Platforms for Active and Passive Cancer Targeting

The tumor-specific targeting of chemotherapeutic agents for specific necrosis of cancer cells without affecting the normal cells poses a great challenge for researchers and scientists. Though extensive research has been carried out to investigate chemotherapy-based targeted drug delivery, the identification of the most promising strategy capable of bypassing non-specific cytotoxicity is still a major concern. Recent advancements in the arena of onco-targeted therapies have enabled safe and effective tumor-specific localization through stimuli-responsive drug delivery systems. Owing to their promising characteristic features, stimuli-responsive drug delivery platforms have revolutionized the chemotherapy-based treatments with added benefits of enhanced bioavailability and selective cytotoxicity of cancer cells compared to the conventional modalities. The insensitivity of stimuli-responsive drug delivery platforms when exposed to normal cells prevents the release of cytotoxic drugs into the normal cells and therefore alleviates the off-target events associated with chemotherapy. Contrastingly, they showed amplified sensitivity and triggered release of chemotherapeutic payload when internalized into the tumor microenvironment causing maximum cytotoxic responses and the induction of cancer cell necrosis. This review focuses on the physical stimuli-responsive drug delivery systems and chemical stimuli-responsive drug delivery systems for triggered cancer chemotherapy through active and/or passive targeting. Moreover, the review also provided a brief insight into the molecular dynamic simulations associated with stimuli-based tumor targeting.

High-Efficiency Synergistic Effect of Supramolecular Nanoparticles Based on Cyclodextrin Prodrug on Cancer Therapy

Novel cyclodextrin-prodrug supramolecular nanoparticles (NPs) with cooperative-enhancing cancer therapy were constructed from a reduction-sensitive disulfide bond-linked permethyl-β-cyclodextrin-camptothecin prodrug, water-soluble adamantane-porphyrin photosensitizer, and hyaluronic acid grafted by triphenylphosphine and β-cyclodextrin through an orthogonal host-guest recognition strategy, displaying uniform nanoparticles with a diameter around 100 nm as revealed by dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Compared with 293T normal cells, the supramolecular NPs could be easily taken up by mitochondria of A549 cancer cells, then release the active anticancer drug camptothecin (CPT) in situ via the cleavage of the disulfide bond by the overexpressed glutathione, and could initiate the effective singlet oxygen (¹O₂) generation by porphyrin under light irradiation, ultimately resulting in severe mitochondrial dysfunction and a rising cell death rate with increasing micromolar concentration of NPs. These multicomponent supramolecular nanoassemblies effectively combined the two-step synergistic chemo-photodynamic therapy of reduction-release of CPT and light-triggered ¹O₂ generation within cancer cells presenting the synergistic effect of supramolecular nanoparticles on cancer therapy, which provide a new approach for efficient step-by-step cancer therapy.

Amphiphilic block polymer-based self-assembly of high payload nanoparticles for efficient combinatorial chemo-photodynamic therapy

Combinatorial chemo-photodynamic therapy is regared as effective cancer therapy strategy, which could be realized via multiple nano-drug delivery system. Herein, novel high payload nanoparticles stabilized by amphiphilic block polymer cholesterol-b-poly(ethylene glycol) (PEG)₂₀₀₀ (Chol-PEG₂₀₀₀) were fabricated for loading chemotherapeutic drug 10-hydroxycamptothecin (HCPT) and photosensitizer chlorin e6 (Ce6). The obtained HCPT/Ce6 NPs showed uniform rod-like morphology with a hydration diameter of 178.9 ± 4.0 nm and excellent stability in aqueous solution. HCPT and Ce6 in the NPs displayed differential release profile, which was benefit for preferentially exerting the photodynamic effect and subsequently enhancing the sensitivity of the cells to HCPT. Under laser irradiation, the NPs demonstrated fantastic in vitro and in vivo anticancer efficiency due to combinational chemo-photodynamic therapy, enhanced cellular uptake effectiveness, and superb intracellular ROS productivity. Besides, the NPs were proved as absent of systemic toxicity. In summary, this nanoparticle delivery system could be hopefully utilized as effective cancer therapy strategy for synergistically exerting combined chemo-photodynamic therapy in clinic.

Biodegradable magnesium alloy with eddy thermal effect for effective and accurate magnetic hyperthermia ablation of tumors

Magnetic hyperthermia therapy (MHT) is able to ablate tumors using an alternating magnetic field (AMF) to heat up magnetocaloric agents (e.g. magnetic nanoparticles) administered into the tumors. For clinical applications, there is still a demand to find new magnetocaloric agents with strong AMF-induced heating performance and excellent biocompatibility. As a kind of biocompatible and biodegradable material, magnesium (Mg) and its alloys have been extensively used in the clinic as an implant metal. Herein, we discovered that the eddy thermal effect of the magnesium alloy (MgA) could be employed for MHT to effectively ablate tumors. Under low-field-intensity AMFs, MgA rods could be rapidly heated, resulting in a temperature increase in nearby tissues. Such AMF-induced eddy thermal heating of MgA could not only be used to kill tumor cells in vitro, but also be employed for effective and accurate ablation of tumors in vivo. In addition to killing tumors in mice, we further demonstrated that VX₂ tumors of much larger sizes growing in rabbits after implantation of MgA rods could also be eliminated after exposure to an AMF, illustrating the ability of MgA-based MHT to kill large-sized tumors. Moreover, the implanted MgA rods showed excellent biocompatibility and ∼20% of their mass was degraded within three months. Our work thus discovered for the first time that non-magnetic biodegradable MgA, an extensively used implant metal in clinic, could be used for effective magnetic thermal ablation of tumors under a low-field-intensity AMF. Such a strategy could be readily translated into clinical use.

Iridium(III) Complex-Derived Polymeric Micelles with Low Dark Toxicity and Strong NIR Excitation for Phototherapy and Chemotherapy

Iridium(III) complexes are potent candidates for photodynamic therapy. However, their clinical usage is impeded by their poor water solubility, high dark toxicity, and negligible absorption in near-infrared region (NIR region). Here, it is proposed to solve these challenges by developing an iridium(III) complexe-based polymeric micelle system. This system is self-assembled using an iridium(III) complex-containing amphiphilic block polymer. The upconversion nanoparticles are included in the polymeric micelles to permit NIR excitation. Compared with the nonformulated iridium(III) complexes, under NIR stimulation, this polymeric micelle system exhibits higher ¹ O₂ generation efficiency, negligible dark toxicity, excellent tumor-targeting ability, and synergistic phototherapy-chemotherapy effect both in vitro and in vivo.

Novel carrier-free nanoparticles composed of 7-ethyl-10-hydroxycamptothecin and chlorin e6: Self-assembly mechanism investigation and in vitro/in vivo evaluation

The combination therapy strategy based on both chemotherapy and photodynamic therapy (PDT) exhibits great potential for advanced cancer treatment. Multimodal nanodrug delivery systems based on both chemotherapeutic drug and photodynamic agent have been proven to possess excellent synergistic efficacy. In this study, 7-ethyl-10-hydroxycamptothecin (SN38) and chlorin e6 (Ce6) were co-assembled into novel carrier-free nanoparticles (SN38/Ce6 NPs) via simple antisolvent precipitation method. As expected, SN38/Ce6 NPs exhibited uniform morphology with a particle size of around 150 nm and a zeta potential of about -30 mV, good stability in aqueous solution/at lyophilized state and high cellular uptake efficiency against murine mammary carcinoma (4T1) cell lines. Besides, enhanced singlet oxygen generation capacity of the nanoparticles was both observed in test-tube and in 4T1 cell lines in contrast with Ce6 injection. Moreover, a ∼85 % inhibition rate of SN38/Ce6 NPs with laser was detected, which was significantly higher (P < 0.05) than those without laser (∼65 %) and injections (less than 20 %), verified the excellent synergistic antitumor efficacy of the nanoparticles due to combined chemo-photodynamic therapy, enhanced tumor accumulation and higher cellular internalization. Notably, chemical thermodynamic method and molecular dynamics (MD) simulations supplied solid data and visual images to estimate the driving forces for the self-assembly process of the carrier-free nanoparticles as primary hydrophobic interactions (π-π stacking) and subordinate hydrogen bonds. Conclusively, the above self-assembled carrier-free nanoparticles represented a promising synergistic anticancer strategy capable of maximal therapeutic efficacy and minimal systemic toxicity. Moreover, the application of thermodynamic method together with MD simulations in the investigation of NPs self-assembly process also provided new ideas for the assembly mechanism exploration of more complicated nanodrug delivery system.