Supramolecular Core-Shell Nanoassemblies with Tumor Microenvironment-Triggered Size and Structure Switch for Improved Photothermal Therapy

Preparation of near-infrared photoacoustic imaging and photothermal treatment agent for cancer using a modifiable acid-triggered molecular platform

Ratiometric near-infrared fluorescent pH probes with various pKa values were innovatively designed and synthesized based on cyanine with a diamine moiety. The photochemical properties of these probes were thoroughly evaluated. Among the series, IR-PHA exhibited an optimal pKa value of approximately 6.40, closely matching the pH of cancerous tissues. This feature is particularly valuable for real-time pH monitoring in both living cells and living mice. Moreover, when administered intravenously to tumor-bearing mice, IR-PHA demonstrated rapid and significant enhancement of near-infrared fluorescence and photoacoustic signals within the tumor region. This outcome underscores the probe's exceptional capability for dual-modal cancer imaging utilizing near-infrared fluorescence (NIRF) and photoacoustic (PA) modalities. Concurrently, the application of a continuous-wave near-infrared laser efficiently ablated cancer cells in vivo, attributed to the photothermal effect induced by IR-PHA. The results strongly indicate that IR-PHA is well-suited for NIRF/PA dual-modality imaging and photothermal therapy of tumors. This makes it a promising candidate for theranostic applications involving small molecules.

Supramolecular Chiral Binding Affinity-Achieved Efficient Synergistic Cancer Therapy

Supramolecular chirality-mediated selective interaction among native assemblies is essential for precise disease diagnosis and treatment. Herein, to fully understand the supramolecular chiral binding affinity-achieved therapeutic efficiency, supramolecular chiral nanoparticles (WP5⊃D/L-Arg+DOX+ICG) with the chirality transfer from chiral arginine (D/L-Arg) to water-soluble pillar[5]arene (WP5) are developed through non-covalent interactions, in which an anticancer drug (DOX, doxorubicin hydrochloride) and a photothermal agent (ICG, indocyanine green) are successfully loaded. Interestingly, the WP5⊃D-Arg nanoparticles show 107 folds stronger binding capability toward phospholipid-composed liposomes compared with WP5⊃L-Arg. The enantioselective interaction further triggers the supramolecular chirality-specific drug accumulation in cancer cells. As a consequence, WP5⊃D-Arg+DOX+ICG exhibits extremely enhanced chemo-photothermal synergistic therapeutic efficacy (tumor inhibition rate of 99.4%) than that of WP5⊃L-Arg+DOX+ICG (tumor inhibition rate of 56.4%) under the same condition. This work reveals the breakthrough that supramolecular chiral assemblies can induce surprisingly large difference in cancer therapy, providing strong support for the significance of supramolecular chirality in bio-application.

Pillararene-Based Stimuli-Responsive Supramolecular Delivery Systems for Cancer Therapy

Cancer poses a significant challenge to global public health, seriously threatening human health and life. Although various therapeutic strategies, such as chemotherapy (CT), radiotherapy, phototherapy, and starvation therapy, are applied to cancer treatment, their limited therapeutic effect, severe side effects, and unsatisfactory drug release behavior need to be carefully considered. Thus, there is an urgent need to develop efficient drug delivery strategies for improving cancer treatment efficacy and realizing on-demand drug delivery. Notably, pillararenes, as an emerging class of supramolecular macrocycles, possess unique properties of highly tunable structures, superior host-guest chemistry, facile modification, and good biocompatibility, which are widely used in cancer therapy to achieve controllable drug release and reduce the toxic side effects on normal tissues under various internal/external stimuli conditions. This review summarizes the recent advance of stimuli-responsive supramolecular delivery systems (SDSs) based on pillararenes for tumor therapy from the perspectives of different assembly methods and hybrid materials, including molecular-scale SDSs, supramolecular nano self-assembly delivery systems, and nanohybrid SDSs. Moreover, the prospects and critical challenges of stimuli-responsive SDSs based on pillararenes for cancer therapy are also discussed.

Chiral cysteine-copper ion-based assemblies for improved phototherapy

Phototherapy, encompassing photothermal therapy and photodynamic therapy, is gaining attention as an appealing cancer treatment modality. To enhance its clinical implementation, a comprehensive exploration of the pivotal factors influencing phototherapy is warranted. In this study, the L/d-cysteine (Cys)-copper ion (Cu2+) chiral nanoparticles, through the assembly of L/d-Cys-Cu2+ coordination complexes, were constructed. We found that these nanoparticles interacted with chiral liposomes in a chirality-dependent manner, with d-Cys-Cu2+ nanoparticles exhibiting more than three times stronger binding affinity than l-Cys-Cu2+ nanoparticles. Furthermore, we demonstrated that the d-Cys-Cu2+ nanoparticles were more efficiently internalized by Hela cells in contrast with l-Cys-Cu2+. On this basis, indocyanine green (ICG), acting as both photothermal and photodynamic agent, was encapsulated into L/d-Cys-Cu2+ nanoparticles. Experimental results showed that the l-Cys-Cu2+-ICG and d-Cys-Cu2+-ICG nanoparticles displayed almost identical photothermal performance and singlet oxygen (1O2) generation capability in aqueous solution. However, upon laser irradiation, the d-Cys-Cu2+-ICG nanoparticles achieved enhanced anti-tumor effects compared to l-Cys-Cu2+-ICG due to their chirality-promoted higher cellular uptake efficiency. These findings highlight the crucial role of chirality in phototherapy and provide new perspectives for engineering cancer therapeutic agents.

Recent Advances in Supramolecular-Macrocycle-Based Nanomaterials in Cancer Treatment

Cancer is a severe threat to human life. Recently, various therapeutic strategies, such as chemotherapy, photodynamic therapy, and combination therapy have been extensively applied in cancer treatment. However, the clinical benefits of these therapeutics still need improvement. In recent years, supramolecular chemistry based on host-guest interactions has attracted increasing attention in biomedical applications to address these issues. In this review, we present the properties of the major macrocyclic molecules and the stimulus-response strategies used for the controlled release of therapeutic agents. Finally, the applications of supramolecular-macrocycle-based nanomaterials in cancer therapy are reviewed, and the existing challenges and prospects are discussed.

Enzyme-Triggered Size-Switchable Nanosystem for Deep Tumor Penetration and Hydrogen Therapy

The poor penetration of nanocarriers within tumor dense extracellular matrices (ECM) greatly restricts the access of anticancer drugs to the deep tumor cells, resulting in low therapeutic efficacy. Moreover, the high toxicity of the traditional chemotherapeutics inevitably causes undesirable side effects. Herein, taking the advantages of biosafe H₂ and small-sized nanoparticles in diffusion within tumor ECM, we develop a matrix metalloprotease 2 (MMP-2) responsive size-switchable nanoparticle (UAMSN@Gel-PEG) that is composed of ultrasmall amino-modified mesoporous silica nanoparticles (UAMSN) wrapped within a PEG-conjugated gelatin to deliver H₂ to the deep part of tumors for effective gas therapy. Ammonia borane (AB) is chosen as the H₂ prodrug that can be effectively loaded into UAMSN by hydrogen-bonding adsorption. Gelatin is used as the substrate of MMP-2 to trigger size change and block AB inside UAMSN during blood circulation. PEG is introduced to further increase the particle size and endow the nanoparticle with long blood circulation to achieve effective tumor accumulation via the EPR effect. After accumulation into the tumor site, MMP-2 promptly digests gelatin to expose UAMSN loading AB for deep tumor penetration. Upon stimulation by the acidic tumor microenvironment, AB decomposes into H₂ for further intratumor diffusion to achieve effective hydrogen therapy. Consequently, such a simultaneous deep tumor penetration of nanocarriers and H₂ results in an evident suppression on tumor growth in a 4T1 tumor-bearing model without any obvious toxicity on normal tissues. Our synthetic nanosystem provides a promising strategy for the development of nanomedicines with enhanced tumor permeability and good biosafety for efficient tumor treatment.