Challenges and opportunities of poly(amino acid) nanomedicines in cancer therapy.

Poly(amino acid) nanomedicines hold significant promise for cancer therapy. However, their clinical translation has not matched the extensive efforts of scientists or the burgeoning body of research. The therapeutic outcomes with most nanomedicines often fall short of the promising results observed in animal experiments. This review explores the challenges faced in cancer therapy using poly(amino acid) nanomedicines, particularly addressing the controversies surrounding the enhanced permeability and retention effect and the lack of methods for controlled and reproducible mass production of poly(amino acid) nanomedicines. Furthermore, this review examines the opportunities emerging in this field due to the rapid advancements in artificial intelligence.

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Dual Stimuli-Responsive Nanoprecursor of Ascorbic Acid and Quinone Methide Disrupting Redox Homeostasis for Cancer Treatment.

Disrupting the redox balance through reactive oxygen species (ROS) generation and intracellular glutathione (GSH) depletion presents a promising strategy for cancer therapy. Megadoses of ascorbic acid (AA) can induce oxidative stress in cancer cells, leading to cell death. However, achieving enhanced oxidative stress using ultrahigh doses of AA is challenging because of the intricate delivery of high-concentration AA to the targeted sites while the cancer cells could also re-establish more robust redox homeostasis by upregulating antioxidants such as GSH. Recently, quinone methide and its analogues (QMs) have been recognized as effective GSH scavengers, offering a new dimension to accelerate oxidative stress. In this study, we formulated a dual stimuli-responsive nanoprecursor of AA and QM using gold nanoparticles. The nanoprecursor can release AA in response to the intracellular acidic pH in tumor cells, elevating the intracellular ROS levels and triggering the production of ample QMs to quench excessive GSH. This positive feedback mechanism significantly amplifies oxidative stress and disrupts redox homeostasis in cancer cells at a relatively low concentration of AA, leading to selective apoptosis without affecting normal cells. These results highlight the potential of the nanoprecursor as an effective anticancer therapeutic.

Cascade-amplified self-immolative polymeric prodrug for cancer therapy by disrupting redox homeostasis.

The amplification of reactive oxygen species (ROS) generation and glutathione (GSH) depletion in cancer cells represents a promising strategy to disrupt redox homeostasis for cancer therapy. Quinone methide and its analogs (QM) have recently been recognized as potential GSH scavengers for anticancer applications; however, an effective QM prodrug is yet to be developed. In this study, we prepare a self-immolative polymeric prodrug (SPP), which could be selectively degraded to generate large quantities of QMs in cancer cells during the spontaneous stepwise head-to-tail degradation of SPP. The amphiphilic SPP is self-assembled into nano-sized micelles, allowing for encapsulating 2-methoxy-ß-estradiol (2ME), an anticancer drug that produces a large amount of intracellular ROS. When SPP@2ME, as the cascade-amplified prodrug, is treated on the cancer cells, 2ME is rapidly released at the ROS-rich intracellular environment by degradation of SPP, thus generating more ROS that triggers the degradation of more SPP chains. Such a domino-like cascade-amplified feedback loop significantly amplifies oxidative stress and disrupts the redox homeostasis in cancer cells. This unique strategy provides synergistic anticancer therapeutic efficacy and demonstrates an important perception in innovative and precise nanomedicine.

Self-immolative polymer-based immunogenic cell death inducer for regulation of redox homeostasis.

Doxorubicin (DOX), widely used as an anticancer drug, is considered an immunogenic cell death (ICD) inducer that enhances cancer immunotherapy. However, its extended application as an ICD inducer has been limited owing to poor antigenicity and inefficient adjuvanticity. To enhance the immunogenicity of DOX, we prepare a reactive oxygen species (ROS)-responsive self-immolative polymer (R-SIP) that can efficiently destroy redox homeostasis via self-immolation-mediated glutathione depletion in cancer cells. Owing to its amphiphilic nature, R-SIP self-assemble into nano-sized particles under aqueous conditions, and DOX is efficiently encapsulated inside the nanoparticles by a simple dialysis method. Interestingly, when treated with 4T1 cancer cells, DOX-encapsulated R-SIP (DR-SIP) induces the phosphorylation of eukaryotic translation initiation factor 2α and overexpression of ecto-calreticulin, resulting in endoplasmic reticulum-associated ICD. In addition, DR-SIP contributes to the maturation of dendritic cells by promoting the release of damage-associated molecular patterns (DAMPs) from cancer cells. When intravenously administered to tumor-bearing mice, DR-SIP remarkably inhibits tumor growth compared with DOX alone. Overall, DR-SIP may have the potential to elicit an immune response as an ICD inducer.

Recent progress in nitric oxide-generating nanomedicine for cancer therapy.

Nitric oxide (NO) is an endogenous, multipotent biological signaling molecule that participates in several physiological processes. Recently, exogenous supplementation of tumor tissues with NO has emerged as a potential anticancer therapy. In particular, it induces synergistic effects with other conventional therapies (such as chemo-, radio-, and photodynamic therapies) by regulating the activity of P-glycoprotein, acting as a vascular relaxant to relieve tumor hypoxia, and participating in the metabolism of reactive oxygen species. However, NO is highly reactive, and its half-life is relatively short after generation. Meanwhile, NO-induced anticancer activity is dose-dependent. Therefore, the targeted delivery of NO to the tumor is required for better therapeutic effects. In the past decade, NO-generating nanomedicines (NONs), which enable sustained and specific NO release in tumor tissues, have been developed for enhanced cancer therapy. This review describes the recent efforts and preclinical achievements in the development of NON-based cancer therapies. The chemical structures employed in the fabrication of NONs are summarized, and the strategies involved in NON-based cancer therapies are elaborated.

A Tissue-Tended Mycophenolate-Modified Nanoparticle Alleviates Systemic Lupus Erythematosus in MRL/Lpr Mouse Model Mainly by Promoting Local M2-Like Macrophagocytes Polarization.

Background: Mycophenolate mofetil (MMF), for which the bioactive metabolite is mycophenolic acid (MPA), is a frequently used immunosuppressant for systemic lupus erythematosus (SLE). However, its short half-life and poor biodistribution into cells and tissues hinder its clinical efficacy. Our dextran mycophenolate-based nanoparticles (MPA@Dex-MPA NPs) have greatly improved the pharmacokinetics of MMF/MPA. We here tested the therapeutic efficacy of MPA@Dex-MPA NPs against SLE and investigated the underlying mechanism. Methods: The tissue and immune cell biodistributions of MPA@Dex-MPA NPs were traced using live fluorescence imaging system and flow cytometry, respectively. Serological proinflammatory mediators and kidney damage were detected to assess the efficacy of MPA@Dex-MPA NPs treatments of MRL/lpr lupus-prone mice. Immune cell changes in the kidney and spleen were further analyzed post-treatment via flow cytometry. Bone marrow-derived macrophages were used to investigate the potential mechanism. Results: MPA@Dex-MPA NPs exhibited superior therapeutic efficacy and safety in the MRL/lpr mice using significantly lower administration dosage (one-fifth) and frequency (once/3 days) compared to MMF/MPA used in ordinary practice. The overall prognosis of the mice was improved as they showed lower levels of serological proinflammatory mediators. Moreover, kidney injury was alleviated with reduced pathological signs and decreased urine protein-creatinine ratio. Further investigations of the underlying mechanism revealed a preferential penetration and persistent retention of MPA@Dex-MPA NPs in the spleen and kidney, where they were mostly phagocytosed by macrophages. The macrophages were found to be polarized towards a CD206+ M2-like phenotype, with a downregulation of surface CD80 and CD40, and reduced TNF-α production in the spleen and kidney and in vitro. The expansion of T cells was also significantly inhibited in these two organs. Conclusion: Our research improved the efficacy of MPA for MRL/lpr mice through synthesizing MPA@Dex-MPA NPs to enhance its tissue biodistribution and explored the possible mechanism, providing a promising strategy for SLE therapy.

Dissolving microneedles for long-term storage and transdermal delivery of extracellular vesicles.

Extracellular vesicles (EVs) have shown great potential in disease diagnosis and treatment; however, their clinical applications remain challenging due to their unsatisfactory long-term stability and the lack of effective delivery strategies. In this study, we prepared human adipose stem cell-derived EV (hASC-EV)-loaded hyaluronic acid dissolving microneedles (EV@MN) to investigate the feasibility of EVs for their clinical applications. The biological activities of the EVs in this formulation were maintained for more than six months under mild storage conditions, especially at temperatures lower than 4 °C. Moreover, the EV@MN enabled precise and convenient intradermal delivery for sustained release of EVs in the dermis layer. Therefore, EV@MN significantly improved the biological functions of hASC-EVs on dermal fibroblasts by promoting syntheses of proteins for the extracellular matrix such as collagen and elastin, enhancing fibroblast proliferation, and regulating the phenotype of fibroblast, compared with other administration methods. This research revealed a possible and feasible formulation for the clinical application of EVs.

Polysaccharide mycophenolate-based nanoparticles for enhanced immunosuppression and treatment of immune-mediated inflammatory diseases.

Immune-mediated inflammatory diseases (IMIDs) are characterized by immune dysregulation and severe inflammation caused by the aberrant and overactive host immunological response. Mycophenolic acid (MPA)-based immunosuppressive drugs are potential treatments for IMIDs because of their mild side-effect profile; however, their therapeutic effects are limited by the high albumin binding rate, unsatisfactory pharmacokinetics, and undefined cellular uptake selectivity. Methods: Polysaccharide mycophenolate was synthesized by conjugating MPA molecules to dextran (a typical polysaccharide widely used in drug delivery) and encapsulated extra free MPA molecules to fabricate MPA@Dex-MPA nanoparticles (NPs). The efficacy of these NPs for mediating immunosuppression and treatment of IMIDs was evaluated in imiquimod-induced psoriasis-like skin inflammation in Balb/c mice, a representative IMID model. Results: The MPA@Dex-MPA NPs exhibited high MPA loading efficiency, low albumin binding rates, and sustained MPA release, resulting in improved pharmacokinetics in vivo. Compared to free MPA, MPA@Dex-MPA NPs induced more robust therapeutic effects on IMIDs. Mechanistic studies indicated that MPA@Dex-MPA NPs were primarily distributed in dendritic cells (DCs) and significantly suppressed the overactivated DCs in vivo and in vitro. Furthermore, the recovered DCs rehabilitated the IL-23/Th17 axis function and significantly ameliorated imiquimod-induced psoriasis-like skin inflammation. Importantly, MPA@Dex-MPA NPs showed favorable safety and biocompatibility in vivo. Conclusion: Our results indicated the polysaccharide mycophenolate-based NPs to be highly promising for IMID treatment.

Gold nanoparticle-guarded large-pore mesoporous silica nanocomposites for delivery and controlled release of cytochrome c.

Efficient delivery of active proteins to specific cells and organs is one of the most important issues in medical applications. However, in most cases, proteins without appropriate carriers face numerous barriers when delivered to the target, due to their unsatisfied properties, such as poor stability, short half-life, and low membrane permeability. Herein, we have presented a large-pore mesoporous silica nanoparticle (LPMSN)-based protein delivery system. LPMSNs were obtained with ethyl acetate as a pore expander. A 2,3-dimethylmaleamic acid-containing silane coupling agent was modified on LPMSNs to provide pH-triggered charge reversal. After Cytochrome c (CC) was encapsulated in the large pores of LPMSNs, amino-terminated polyethylene glycol-modified gold nanoparticles (AuNPs) served as gateguards to cap the tunnels of LPMSNs and to avoid the leakage of CC. Above nanocomposites exhibited the capability to deliver active CC into cancer cells, charge reversal-induced protein release, as well as to initiate the apoptosis machinery of cancer cells in vitro. Importantly, the nanocomposites significantly inhibited tumor growth and extended survival rate without obvious side effects. This study provides a smart and efficient protein delivery platform with good safety profiles for efficacious tumor protein therapy in vivo.

Acitretin-Conjugated Dextran Nanoparticles Ameliorate Psoriasis-like Skin Disease at Low Dosages.

Psoriasis is a common chronic inflammatory skin disease mainly characterized by keratinocyte hyperproliferation and massive infiltration of inflammatory immune cells. Acitretin (ACT), an FDA-approved first-line systemic drug for psoriasis treatment, could suppress the proliferation of keratinocytes and downregulate the expression of inflammatory cytokines by modulating signal transducer and activator of transcription (STAT) signaling pathways. However, dose-dependent side effects of ACT limit its long-term administration in the clinic. Therefore, improving the therapeutic efficacy of ACT to reduce clinical dosage will benefit the patients. Here, we develop ACT-conjugated dextran nanoparticles (ACT-Dex NPs) and evaluated the potential for psoriasis treatment. Our results indicate that ACT-Dex NPs ameliorate psoriasis-like skin disease significantly at a low dosage which does not cause side effects, while neat ACT drugs at an equivalent dosage provide much less benefit. Moreover, we demonstrate that ACT-Dex NPs suppress keratinocyte proliferation more efficiently than neat ACT by enhancing the inhibitory effect on STAT3 phosphorylation. Thus, the proposed ACT-Dex NPs provide an effective and safe option for psoriasis treatment.

NIR-Light-Activated Ratiometric Fluorescent Hybrid Micelles for High Spatiotemporally Controlled Biological Imaging and Chemotherapy.

Intelligent-responsive imaging-therapy strategy has shown great significance for biomedicine. However, it is still a challenge to construct spatiotemporally controlled imaging-therapy systems triggered by near infrared (NIR) light. In this work, NIR-light-activated ratiometric fluorescent hybrid micelles (RFHM) are prepared via the co-assembly of upconversion nanoparticles (UCNPs), doxorubicin (DOX), and UV-light-responsive amphiphilic block copolymer for the spatiotemporally controlled imaging and chemotherapy. Upon NIR light irradiation, UCNPs can convert NIR light to UV light. The emitted UV light induces the photoreaction of copolymer to further trigger ratiometric fluorescence imaging and degradation of hybrid micelles, resulting in rapid DOX release from hybrid micelles for antitumor therapy. The animal experiments reveal that NIR light can not only remotely regulate the ratiometric fluorescence imaging of RFHM in tumor tissue, but also trigger DOX release from RFHM to inhibit tumor growth. Therefore, this study provides a new strategy to achieve high spatial-temporal-controlled biological imaging and chemotherapy.

Kinetic Control of Length and Morphology of Segmented Polymeric Nanofibers in Microfluidic Chips.

In this work, we report an approach to prepare segmented polymer nanofibers (SPNFs) composed of rodlike subunits by kinetically controlled self-assembly of polystyrene-b-poly(4-vinylpyridine)-based supramolecules in microfluidic chips. The length and morphology of the SPNFs could be effectively adjusted by changing the total flow rate (Vtotal) and the molar ratio (x) of 4-vinylpyridine (4VP) unit to a hydrogen-bonding molecule, 3-n-pentadecyphenol. Moreover, the subunits of SPNFs could transform from short rods to spheres when the interfacial tension between PS core and solvent increased. On the contrary, the SPNFs elongated along the major axis when the interfacial tension decreased. This work not only offers mechanism insights into the hierarchical self-assembly of block copolymer-based supramolecules but also provides a versatile and effective method for kinetically controlling the hierarchical structures of assemblies.

Hypoxia-responsive nanoparticles for tumor-targeted drug delivery.

Hypoxia is a negative prognostic indicator of solid tumors. Increasing evidence indicates that the intratumoral hypoxic microenvironment is strongly related to enhanced tumor aggressiveness, decreased therapeutic effect and poor prognosis of chemotherapy, radiotherapy (RT), and photodynamic therapy (PDT). However, due to an unusual gene expression profile and abnormal metabolism, enzymes responsible for reduction reactions or electron donation are highly reactive in hypoxic tumor cells and provide the possibility of exploiting targeted drug delivery systems for cancer therapy. Taking advantage of the specific bioreductive microenvironments in hypoxic tumors, researchers have recently developed several hypoxia-responsive nanoparticles (HR-NPs) for targeted cancer therapy. In this review, the hypoxia-responsive molecular structures that were employed to construct HR-NPs are presented. Furthermore, the strategies to make use of these HR-NPs, and the recent advances in HR-NPs for efficient tumor-targeted drug delivery and cancer therapy are highlighted.

Flow-Induced Micellar Morphological Transformation in Microfluidic Chips under Nonequilibrium State: From Aggregates to Spherical Micelles.

Self-assembly of block copolymers (BCPs) in microfluidic chips is a versatile yet effective route to produce micellar aggregates with various controllable sizes and morphologies. In this study, the morphological transformation of the BCP of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) assemblies from irregular aggregates to multicompartment micelles and ultimately to ordered spherical micelles is demonstrated in microfluidic chips. Our experimental and computational simulation results indicate that the transverse diffusion of solvents plays an important role in the morphological transformation of PS-b-P4VP assemblies in the confined flow condition. We find that the mixing time (tmix) between a BCP/tetrahydrofuran (THF) solution and water affects the morphological transformation. Micellar morphologies are intended to transform from aggregates to ordered spherical structures under a relatively long mixing time (tmix). In addition, it is observed that the size of the micelles decreases with the increase of the flow velocity ratio by tuning the hydrodynamic conditions of the flows. Moreover, by adjusting the initial polymer solution concentration, temperature, and weight fraction of the introduced homopolystyrene (hPS), which can affect the viscosity of the BCP solution, the flow diffusion in the microfluidic chip and the resulted micellar structures can also be readily adjusted. The current study provides a new flow-driven method to adjust the micellar ordered structural transformation under the nonequilibrium state.

Transdermal delivery of rapamycin with poor water-solubility by dissolving polymeric microneedles for anti-angiogenesis.

Angiogenesis plays an important role in the occurrence and development of skin tumors and vascular anomalies (VAs). Many drugs have been adopted for the inhibition of angiogenesis, among which rapamycin (RAPA) possesses good application prospects. However, the clinical potential of RAPA for VAs is limited by its poor solubility, low bioavailability, and high cytotoxicity. To extend its application prospect for VAs treatment, in this study, we develop RAPA-loaded dissolving polymeric microneedles (RAPA DMNs) made of polyvinylpyrrolidone (PVP) due to its excellent solubilizing ability. RAPA DMNs are shown to have sufficient mechanical strength to overcome the skin barrier of the stratum corneum and could deliver RAPA to a depth of 200 µm. The microneedle shafts completely dissolve and 80% of the drug could be released within 10 min after insertion ex vivo. The DMNs-penetrated mice skin could repair itself within 4 h after the application of RAPA DMNs. RAPA DMNs also show good anti-angiogenic effect by inhibiting the growth of human umbilical vein endothelial cells (HUVECs) and decreasing the secretion of vascular endothelial growth factor (VEGF). Therefore, RAPA DMNs promisingly provide a safe and efficient approach for VAs treatment.

Hyaluronidase-Functionalized Silica Nanocarrier for Enhanced Chemo-Immunotherapy through Inducing Immunogenic Cell Death.

The chemo-immunotherapy has become a highly prospective method for cancer treatment, and it has been known that chemotherapeutic drugs [e.g., doxorubicin (DOX)] could trigger antitumor immune responses. Yet, insufficient tumor penetrability and weak immunogenic cell death (ICD) severely limits the therapeutic effect of chemo-immunotherapy against cancer. Herein, we report the design of DOX-loaded silica nanocarriers (DOX@HMSPHs) with hyaluronidase functionalization, which could increase the permeability of drug and induce enhanced ICD effect through the degradation of hyaluronic acid (HA) in the extracellular matrix (ECM). Interestingly, the controlled release of DOX from DOX@HMSPHs in the acidic microenvironment induced ICD of tumor cells to release tumor antigens and damage-associated molecular patterns, promoting the antigen-presentation of dendritic cells (DCs) and the activation of specific tumor immunity. Moreover, HMSPHs could be used as an immune adjuvant to promote maturation of DCs, thereby promoting the activation of tumor infiltrating cytotoxic T lymphocytes. This strategy presents a concept to improve the efficacy of chemo-immunotherapy through degradation of HA in the ECM.

5-Aminolevulinic Acid-Loaded Hyaluronic Acid Dissolving Microneedles for Effective Photodynamic Therapy of Superficial Tumors with Enhanced Long-Term Stability.

5-Aminolevulinic acid (5-ALA) is one of the most widely used prodrug in clinical photodynamic therapy of dermatological diseases and cancers; yet, its clinical application is still limited by the shallow skin penetration and unsatisfied stability in any existed formulations. Here, 5-ALA-loaded hyaluronic acid dissolving microneedles (5-ALA@HAMNs) are prepared for photodynamic therapy of superficial tumors. The HAMNs can not only assist the loaded 5-ALA to effectively penetrate the stratum corneum but also provide 5-ALA with an acidic and oxygen-free environment to reduce the dimerization of 5-ALA molecules via Schiff-base bonds and formation of inactive pyrazine derivatives, thus maintaining its chemical structure and biological activity. The chemical stability of 5-ALA in HAMNs is confirmed by UV-vis spectra and mass spectra measurements. The 5-ALA@HAMNs display remarkable tumor elimination both in vitro and in vivo, even after storage at room temperature for nine months, making it a highly potential device for effective delivery of 5-ALA in cancer photodynamic therapy.

Enhanced in vitro efficacy for inhibiting hypertrophic scar by bleomycin-loaded dissolving hyaluronic acid microneedles.

Hypertrophic scarring is a widespread skin disorder that affects a patient's confidence and quality of life. Intralesional injection of bleomycin is one of the most commonly employed treatments for hypertrophic scars, which, however, always brings pain and requires long-term treatment. To overcome these limitations, new methods for bleomycin delivery enabling painlessness, self-administration, the fast onset of action, and good bioavailability are urgently needed. In this study, we developed bleomycin-loaded dissolving microneedles (BMN) made up of hyaluronic acid (HA) with excellent aqueous solubility and enhanced efficacy for inhibiting hypertrophic scars. The as-obtained BMN possesses sufficient mechanical strength to pierce porcine skin ex vivo with an insertion depth of over 300 µm. Moreover, BMN can dissolve rapidly and release 20% of loaded bleomycin within 1 min and 52% within 10 min, and the BMN-treated skin could recover to its original status within 3 h, demonstrating good biocompatibility. Besides, the HA matrix also maintains the stability and activity of bleomycin. Furthermore, we show that BMN consisting of HA and bleomycin can inhibit the proliferation of human hypertrophic scar fibroblasts (hHSFs) and the secretion of transforming growth factor-ß (TGF-ß1) in vitro. Therefore, bleomycin-loaded dissolving HA microneedles provide a potential route to treat hypertrophic scars in a convenient, efficient, and minimally invasive manner.