MMP-Responsive 'Smart' Drug Delivery and Tumor Targeting

M1 macrophage-membrane-cloaked paclitaxel/β-elemene nanoparticles targeting cervical cancer for enhanced therapy

Cervical cancer is a leading cause of cancer-related mortality in females worldwide, necessitating urgent solutions for effective treatment. Paclitaxel (PTX), a natural diterpene alkaloid compound, has the ability to inhibit mitosis and induce programmed apoptosis in tumor cells. However, its toxicity and drug resistance limit its efficacy in certain cervical cancer patients. β-elemene (β-ELE) can reverse multidrug resistance by inhibiting ATP-binding cassette transporters, thereby enhancing chemotherapy drug retention. Therefore, we propose a combination therapy using PTX/β-ELE to improve chemotherapy sensitivity. To enhance targeted drug delivery, we developed M1-macrophage-membrane-coated nanoparticles (M1@PLGA/PTX/β-ELE) for co-delivery of PTX&β-ELE. Through both in vitro and in vivo cervical cancer models, we demonstrated that M1@PLGA/PTX/β-ELE effectively suppressed tumor progression and polarization of tumor-associated macrophages. Furthermore, H&E staining confirmed the high therapeutic biosafety of M1@PLGA/PTX/β-ELE as there was no significant damage observed in major organs throughout the entire therapeutic process. Overall, this study presents a targeted biomimetic nanoplatform and combinatorial strategy that synergistically enhances chemosensitivity in malignant tumors.

Liposomes-enabled cancer chemoimmunotherapy

Chemoimmunotherapy is an emerging paradigm in the clinic for treating several malignant diseases, such as non-small cell lung cancer, breast cancer, and large B-cell lymphoma. However, the efficacy of this strategy is still restricted by serious adverse events and a high therapeutic termination rate, presumably due to the lack of tumor-targeted distribution of both chemotherapeutic and immunotherapeutic agents. Targeted drug delivery has the potential to address this issue. Among the most promising nanocarriers in clinical translation, liposomes have drawn great attention in cancer chemoimmunotherapy in recent years. Liposomes-enabled cancer chemoimmunotherapy has made significant progress in clinics, with impressive therapeutic outcomes. This review summarizes the latest preclinical and clinical progress in liposome-enabled cancer chemoimmunotherapy and discusses the challenges and future directions of this field.

Advances in tumor stroma-based targeted delivery

The tumor stroma plays a crucial role in tumor progression, and the interactions between the extracellular matrix, tumor cells, and stromal cells collectively influence tumor progression and the efficacy of therapeutic agents. Currently, utilizing components of the tumor stroma for drug delivery is a noteworthy strategy. A number of targeted drug delivery systems designed based on tumor stromal components are entering clinical trials. Therefore, this paper provides a thorough examination of the function of tumor stroma in the advancement of targeted drug delivery systems. One approach is to use tumor stromal components for targeted drug delivery, which includes certain stromal components possessing inherent targeting capabilities like HA, laminin, along with targeting stromal cells homologously. Another method entails directly focusing on tumor stromal components to reshape the tumor stroma and facilitate drug delivery. These drug delivery systems exhibit great potential in more effective cancer therapy strategies, such as precise targeting, enhanced penetration, improved safety profile, and biocompatibility. Ultimately, the deployment of these drug delivery systems can deepen our comprehension of tumor stroma and the advanced development of corresponding drug delivery systems.

Stimuli-Responsive Polymersomes: Reshaping the Immunosuppressive Tumor Microenvironment

The progression of cancer involves mutations in normal cells, leading to uncontrolled division and tissue destruction, highlighting the complexity of tumor microenvironments (TMEs). Immunotherapy has emerged as a transformative approach, yet the balance between efficacy and safety remains a challenge. Nanoparticles such as polymersomes offer the possibility to precisely target tumors, deliver drugs in a controlled way, effectively modulate the antitumor immunity, and notably reduce side effects. Herein, stimuli-responsive polymersomes, with capabilities for carrying multiple therapeutics, are highlighted for their potential in enhancing antitumor immunity through mechanisms like inducing immunogenic cell death and activating STING (stimulator of interferon genes), etc. The recent progress of utilizing stimuli-responsive polymersomes to reshape the TME is reviewed here. The advantages and limitations to applied stimuli-responsive polymersomes are outlined. Additionally, challenges and future prospects in leveraging polymersomes for cancer therapy are discussed, emphasizing the need for future research and clinical translation.

Hydrogel-exosome system in tissue engineering: A promising therapeutic strategy

Characterized by their pivotal roles in cell-to-cell communication, cell proliferation, and immune regulation during tissue repair, exosomes have emerged as a promising avenue for "cell-free therapy" in clinical applications. Hydrogels, possessing commendable biocompatibility, degradability, adjustability, and physical properties akin to biological tissues, have also found extensive utility in tissue engineering and regenerative repair. The synergistic combination of exosomes and hydrogels holds the potential not only to enhance the efficiency of exosomes but also to collaboratively advance the tissue repair process. This review has summarized the advancements made over the past decade in the research of hydrogel-exosome systems for regenerating various tissues including skin, bone, cartilage, nerves and tendons, with a focus on the methods for encapsulating and releasing exosomes within the hydrogels. It has also critically examined the gaps and limitations in current research, whilst proposed future directions and potential applications of this innovative approach.

Biomedical applications of stimuli-responsive nanomaterials

Nanomaterials have aroused great interests in drug delivery due to their nanoscale structure, facile modifiability, and multifunctional physicochemical properties. Currently, stimuli-responsive nanomaterials that can respond to endogenous or exogenous stimulus display strong potentials in biomedical applications. In comparison with conventional nanomaterials, stimuli-responsive nanomaterials can improve therapeutic efficiency and reduce the toxicity of drugs toward normal tissues through specific targeting and on-demand drug release at pathological sites. In this review, we summarize the responsive mechanism of a variety of stimulus, including pH, redox, and enzymes within pathological microenvironment, as well as exogenous stimulus such as thermal effect, magnetic field, light, and ultrasound. After that, biomedical applications (e.g., drug delivery, imaging, and theranostics) of stimuli-responsive nanomaterials in a diverse array of common diseases, including cardiovascular diseases, cancer, neurological disorders, inflammation, and bacterial infection, are presented and discussed. Finally, the remaining challenges and outlooks of future research directions for the biomedical applications of stimuli-responsive nanomaterials are also discussed. We hope that this review can provide valuable guidance for developing stimuli-responsive nanomaterials and accelerate their biomedical applications in diseases diagnosis and treatment.

Peptide-Hitchhiking for the Development of Nanosystems in Glioblastoma

Glioblastoma (GBM) remains the epitome of aggressiveness and lethality in the spectrum of brain tumors, primarily due to the blood-brain barrier (BBB) that hinders effective treatment delivery, tumor heterogeneity, and the presence of treatment-resistant stem cells that contribute to tumor recurrence. Nanoparticles (NPs) have been used to overcome these obstacles by attaching targeting ligands to enhance therapeutic efficacy. Among these ligands, peptides stand out due to their ease of synthesis and high selectivity. This article aims to review single and multiligand strategies critically. In addition, it highlights other strategies that integrate the effects of external stimuli, biomimetic approaches, and chemical approaches as nanocatalytic medicine, revealing their significant potential in treating GBM with peptide-functionalized NPs. Alternative routes of parenteral administration, specifically nose-to-brain delivery and local treatment within the resected tumor cavity, are also discussed. Finally, an overview of the significant obstacles and potential strategies to overcome them are discussed to provide a perspective on this promising field of GBM therapy.

Stimulus-Responsive Hydrogels for Targeted Cancer Therapy

Cancer is a highly heterogeneous disease and remains a global health challenge affecting millions of human lives worldwide. Despite advancements in conventional treatments like surgery, chemotherapy, and immunotherapy, the rise of multidrug resistance, tumor recurrence, and their severe side effects and the complex nature of the tumor microenvironment (TME) necessitates innovative therapeutic approaches. Recently, stimulus-responsive nanomedicines designed to target TME characteristics (e.g., pH alterations, redox conditions, enzyme secretion) have gained attention for their potential to enhance anticancer efficacy while minimizing the adverse effects of chemotherapeutics/bioactive compounds. Among the various nanocarriers, hydrogels are intriguing due to their high-water content, adjustable mechanical characteristics, and responsiveness to external and internal stimuli, making them promising candidates for cancer therapy. These properties make hydrogels an ideal nanocarrier for controlled drug release within the TME. This review comprehensively surveys the latest advancements in the area of stimulus-responsive hydrogels for cancer therapy, exploring various stimuli-responsive mechanisms, including biological (e.g., pH, redox), chemical (e.g., enzymes, glucose), and physical (e.g., temperature, light), as well as dual- or multi-stimuli responsiveness. Furthermore, this review addresses the current developments and challenges in hydrogels in cancer treatment. Our aim is to provide readers with a comprehensive understanding of stimulus-responsive hydrogels for cancer treatment, offering novel perspectives on their development for cancer therapy and other medical applications.

MMPs-responsive silk spheres for controlled drug release within tumor microenvironment

Silk is a biocompatible and biodegradable material that enables the formation of various morphological forms, including nanospheres. The functionalization of bioengineered silk makes it possible to produce particles with specific properties. In addition to tumor cells, the tumor microenvironment (TME) includes stromal, immune, endothelial cells, signaling molecules, and the extracellular matrix (ECM). Matrix metalloproteinases (MMPs) are overexpressed in TME. We investigated bioengineered spider silks functionalized with MMP-responsive peptides to obtain targeted drug release from spheres within TME. Soluble silks MS12.2MS1, MS12.9MS1, and MS22.9MS2 and the corresponding silk spheres carrying MMP-2 or MMP-2/9 responsive peptides were produced, loaded with doxorubicin (Dox), and analyzed for their susceptibility to MMP-2/9 digestion. Although all variants of functionalized silks and spheres were specifically degraded by MMP-2/9, the MS22.9MS2 nanospheres showed the highest levels of degradation and release of Dox after enzyme treatment. Moreover, functionalized spheres were degraded in the presence of cancer cells releasing MMP-2/9. In the 2D and 3D spheroid cancer models, the MMP-2/9-responsive substrate was degraded and released from spheres when loaded into MS22.9MS2 particles but not into the control MS2 spheres. The present study demonstrated that a silk-based MMP-responsive delivery system could be used for controlled drug release within the tumor microenvironment.

Engineered protein cages with enhanced extracellular drug release for elevated antitumor efficacy

Human heavy chain ferritin (HFn) protein cage has been explored as a nanocarrier for targeted anticancer drug delivery. Here, we introduced a matrix metalloproteinases (MMPs)-cleavable sequence into the DE loop of HFn, creating an MMP-responsive variant, MR-HFn, for localized and extracellular drug release. The crystal structure of MR-HFn revealed that the addition of the MMPs recognition sequence did not affect the self-assembly of HFn but presented a surface-exposed loop susceptible to MMPs cleavage. Biochemical analysis indicated that this engineered protein cage is responsive to MMPs, enabling the targeted release of encapsulated drugs. To evaluate the therapeutic potential of this engineered protein cage, monosubstituted β-carboxy phthalocyanine zinc (CPZ), a type of photosensitizer, was loaded inside this protein cage. The prepared CPZ@MR-HFn showed higher uptake and stronger phototoxicity in MMPs overexpressed tumor cells, as well as enhanced penetration into multicellular tumor spheroids compared with its counterpart CPZ@HFn in vitro. In vivo, CPZ@MR-HFn displayed a higher tumor inhibitory rate than CPZ@HFn under illumination. These results indicated that MR-HFn is a promising nanocarrier for anticancer drug delivery and the MMP-responsive strategy here can also be adapted for other stimuli.

A review of matrix metalloproteinase-2-sensitive nanoparticles as a novel drug delivery for tumor therapy

Matrix metalloproteinase-2 (MMP-2)-responsive nanodrug vehicles have garnered significant attention as antitumor drug delivery systems due to the extensive research on matrix metalloproteinases (MMPs) within the tumor extracellular matrix (ECM). These nanodrug vehicles exhibit stable circulation in the bloodstream and accumulate specifically in tumors through various mechanisms. Upon reaching tumor tissues, their structures are degraded in response to MMP-2 within the ECM, resulting in drug release. This controlled drug release significantly increases drug concentration within tumors, thereby enhancing its antitumor efficacy while minimizing side effects on normal organs. This review provides an overview of MMP-2 characteristics, enzyme-sensitive materials, and current research progress regarding their application as MMP-2-responsive nanodrug delivery system for anti-tumor drugs, as well as considering their future research prospects. In conclusion, MMP-2-sensitive drug delivery carriers have a broad application in all kinds of nanodrug delivery systems and are expected to become one of the main means for the clinical development and application of nanodrug delivery systems in the future.

The utilization of nanotechnology in the female reproductive system and related disorders

The health of the reproductive system is intricately linked to female fertility and quality of life. There has been a growing prevalence of reproductive system disorders among women, particularly in younger age groups, resulting in significant adverse effects on their reproductive health. Consequently, there is an urgent need for effective treatment modalities. Nanotechnology, as an advanced discipline, provides innovative avenues for managing and treating diseases of the female reproductive system by enabling precise manipulation and regulation of biological molecules and cells. By utilizing nanodelivery systems, drugs can be administered with pinpoint accuracy, leading to reduced side effects and improved therapeutic efficacy. Moreover, nanomaterial imaging techniques enhance diagnostic precision and sensitivity, aiding in the assessment of disease severity and progression. Furthermore, the implementation of nanobiosensors facilitates early detection and prevention of ailments. This comprehensive review aims to summarize recent applications of nanotechnology in the treatment of female reproductive system diseases. The latest advancements in drug delivery, diagnosis, and treatment approaches will be discussed, with an emphasis on the potential of nanotechnology to improve treatment outcomes and overall quality of life.

Tumor Microenvironment-Responsive Drug Delivery Based on Polymeric Micelles for Precision Cancer Therapy: Strategies and Prospects

In clinical practice, drug therapy for cancer is still limited by its inefficiency and high toxicity. For precision therapy, various drug delivery systems, including polymeric micelles self-assembled from amphiphilic polymeric materials, have been developed to achieve tumor-targeting drug delivery. Considering the characteristics of the pathophysiological environment at the drug target site, the design, synthesis, or modification of environmentally responsive polymeric materials has become a crucial strategy for drug-targeted delivery. In comparison to the normal physiological environment, tumors possess a unique microenvironment, characterized by a low pH, high reactive oxygen species concentration, hypoxia, and distinct enzyme systems, providing various stimuli for the environmentally responsive design of polymeric micelles. Polymeric micelles with tumor microenvironment (TME)-responsive characteristics have shown significant improvement in precision therapy for cancer treatment. This review mainly outlines the most promising strategies available for exploiting the tumor microenvironment to construct internal stimulus-responsive drug delivery micelles that target tumors and achieve enhanced antitumor efficacy. In addition, the prospects of TME-responsive polymeric micelles for gene therapy and immunotherapy, the most popular current cancer treatments, are also discussed. TME-responsive drug delivery via polymeric micelles will be an efficient and robust approach for developing clinical cancer therapies in the future.

Targeted drug delivery systems for matrix metalloproteinase-responsive anoparticles in tumor cells: A review

Nanodrug delivery systems based on tumor microenvironment responses have shown excellent performance in tumor-targeted therapy, given their unique targeting and drug-release characteristics. Matrix metalloproteinases (MMPs) have been widely explored owing to their high specificity and expression in various tumor microenvironments. The design of an enzyme-sensitive nanodelivery system using MMPs as targeted receptors could markedly improve the performance of drug targeting. The current review focuses on the development and application of MMP-responsive drug carriers, and summarizes the classification of single- and multi-target nanocarriers based on their MMP responsiveness. The potential applications and challenges of this nanodrug delivery system are discussed to provide a reference for designing high-performance nanodrug delivery systems.

Biosynthesized tumor acidity and MMP dual-responsive plant toxin gelonin for robust cancer therapy

Among all kinds of anticancer agents, small molecule drugs produce an unsatisfactory therapeutic effect due to the lack of selectivity, notorious drug resistance and side effects. Therefore, researchers have begun to pay extensive attention to macromolecular drugs with high efficacy and specificity. As a plant toxin, gelonin exerts potent antitumor activity via inhibiting intracellular protein synthesis. However, gelonin lacks a translocation domain, and thus its poor cellular uptake leads to low outcomes of antitumor response. Here, tumor acidity and matrix metalloproteinase (MMP) dual-responsive functional gelonin (Trx-PVGLIG-pHLIP-gelonin, TPpG), composed of a thioredoxin (Trx) tag, a pH low insertion peptide (pHLIP), an MMP-responsive motif PVGLIG hexapeptide and gelonin, was innovatively proposed and biologically synthesized by a gene recombination technique. TPpG exhibited good thermal and serum stability, showed MMP responsiveness and could enter tumor cells under weakly acidic conditions, especially for MMP2-overexpressing HT1080 cells. Compared to low MMP2-expressing MCF-7 cells, TPpG displayed enhanced in vitro antitumor efficacy to HT1080 cells at pH 6.5 as determined by different methods. Likewise, TPpG was much more effective in triggering cell apoptosis and inhibiting protein synthesis in HT1080 cells than in MCF-7 cells. Intriguingly, with enhanced stability and pH/MMP dual responsiveness, TPpG notably inhibited subcutaneous HT1080 xenograft growth in mice and no noticeable off-target side effect was observed. This ingeniously designed strategy aims at providing new perspectives for the development of a smart platform that can intelligently respond to a tumor microenvironment for efficient protein delivery.

Matrix metalloproteinases as biomarkers and therapeutic targets in colitis-associated cancer

Colorectal cancer (CRC) remains a major cause of morbidity and mortality. Therapeutic approaches for advanced CRC are limited and rarely provide long-term benefit. Enzymes comprising the 24-member matrix metalloproteinase (MMP) family of zinc- and calcium-dependent endopeptidases are key players in extracellular matrix degradation, a requirement for colon tumor expansion, invasion, and metastasis; hence, MMPs are an important research focus. Compared to sporadic CRC, less is known regarding the molecular mechanisms and the role of MMPs in the development and progression of colitis-associated cancer (CAC) - CRC on a background of chronic inflammatory bowel disease (IBD) - primarily ulcerative colitis and Crohn's disease. Hence, the potential of MMPs as biomarkers and therapeutic targets for CAC is uncertain. Our goal was to review data regarding the role of MMPs in the development and progression of CAC. We sought to identify promising prognostic and therapeutic opportunities and novel lines of investigation. A key observation is that since MMPs may be more active in early phases of CAC, using MMPs as biomarkers of advancing neoplasia and as potential therapeutic targets for adjuvant therapy in those with advanced stage primary CAC rather than overt metastases may yield more favorable outcomes.

Smart stimuli-responsive strategies for titanium implant functionalization in bone regeneration and therapeutics

With the increasing and aging of global population, there is a dramatic rise in the demand for implants or substitutes to rehabilitate bone-related disorders which can considerably decrease quality of life and even endanger lives. Though titanium and its alloys have been applied as the mainstream material to fabricate implants for load-bearing bone defect restoration or temporary internal fixation devices for bone fractures, it is far from rare to encounter failed cases in clinical practice, particularly with pathological factors involved. In recent years, smart stimuli-responsive (SSR) strategies have been conducted to functionalize titanium implants to improve bone regeneration in pathological conditions, such as bacterial infection, chronic inflammation, tumor and diabetes mellitus, etc. SSR implants can exert on-demand therapeutic and/or pro-regenerative effects in response to externally applied stimuli (such as photostimulation, magnetic field, electrical and ultrasound stimulation) or internal pathology-related microenvironment changes (such as decreased pH value, specific enzyme secreted by bacterial and excessive production of reactive oxygen species). This review summarizes recent progress on the material design and fabrication, responsive mechanisms, and in vitro and in vivo evaluations for versatile clinical applications of SSR titanium implants. In addition, currently existing limitations and challenges and further prospective directions of these strategies are also discussed.

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.

Research progress in nano-drug delivery systems based on the characteristics of the liver cancer microenvironment

The liver cancer has microenvironmental features such as low pH, M2 tumor-associated macrophage enrichment, low oxygen, rich blood supply and susceptibility to hematotropic metastasis, high chemokine expression, enzyme overexpression, high redox level, and strong immunosuppression, which not only promotes the progression of the disease, but also seriously affects the clinical effectiveness of traditional therapeutic approaches. However, nanotechnology, due to its unique advantages of size effect and functionalized modifiability, can be utilized to develop various responsive nano-drug delivery system (NDDS) by using these characteristic signals of the liver cancer microenvironment as a source of stimulation, which in turn can realize the intelligent release of the drug under the specific microenvironment, and significantly increase the concentration of the drug at the target site. Therefore, researchers have designed a series of stimuli-responsive NDDS based on the characteristics of the liver cancer microenvironment, such as hypoxia, weak acidity, and abnormal expression of proteases, and they have been widely investigated for improving anti-tumor therapeutic efficacy and reducing the related side effects. This paper provides a review of the current application and progress of NDDS developed based on the response and regulation of the microenvironment in the treatment of liver cancer, compares the effects of the microenvironment and the NDDS, and provides a reference for building more advanced NDDS.

Smart chemistry for traceless release of anticancer therapeutics

In the design of delivery strategies for anticancer therapeutics, the controlled release of intact cargo at the destined tumor and metastasis locations is of particular importance. To this end, stimuli-responsive chemical linkers have been extensively investigated owing to their ability to respond to tumor-specific physiological stimuli, such as lowered pH, altered redox conditions, increased radical oxygen species and pathological enzymatic activities. To prevent premature action and off-target effects, anticancer therapeutics are chemically modified to be transiently inactivated, a strategy known as prodrug development. Prodrugs are reactivated upon stimuli-dependent release at the sites of interest. As most drugs and therapeutic proteins have the optimal activity when released from carriers in their native and original forms, traceless release mechanisms are increasingly investigated. In this review, we summarize the chemical toolkit for developing innovative traceless prodrug strategies for stimuli-responsive drug delivery and discuss the applications of these chemical modifications in anticancer treatment including cancer immunotherapy.

Therapeutic targeting of the pituitary tumor microenvironment

The tumor microenvironment (TME), the complex environment in which tumors develop, has been increasingly targeted for cancer treatment in recent years. Aggressive pituitary tumors and pituitary carcinomas have been so far targeted with immune-checkpoint inhibitors (28 cases, including a large cohort), and anti-angiogenic drugs (34 cases), specifically bevacizumab (30 cases), sunitinib (three cases), and apatinib (one case). Here, we reviewed all these cases, reporting tumor response, potential predictors of response, as well as adverse events. Given that the histological type could potentially influence treatment response, we present the existing data separately for each type. Briefly, under ICIs, complete response was noted in one case, partial response in a third of cases, stable disease in 10% of cases, while 54% of tumors progressed. Under BVZ monotherapy, most cases (57%) showed stable disease, while 36% of tumors progressed; partial response was reported in only one case. The three cases treated with sunitinib monotherapy progressed. Regarding predictive factors of response, the tumor type (aggressive pituitary tumor versus pituitary carcinoma) appears as the strongest predictor of response to ICIs. To date, no predictor of response to anti-angiogenic drugs in the treatment of pituitary carcinomas and aggressive pituitary tumors has been identified. The interest of BZV add-on to first- or second-line chemotherapy warrants further investigation. In addition, we discuss perspectives regarding the TME-targeting in aggressive pituitary tumors and pituitary carcinomas, including perspectives on immunotherapy, anti-angiogenic drugs, as well as on other TME components, namely stromal cells, extracellular matrix, and secreted molecules.

Injectable hydrogels for the delivery of nanomaterials for cancer combinatorial photothermal therapy

Progress in the nanotechnology field has led to the development of a new class of materials capable of producing a temperature increase triggered by near infrared light. These photothermal nanostructures have been extensively explored in the ablation of cancer cells. Nevertheless, the available data in the literature have exposed that systemically administered nanomaterials have a poor tumor-homing capacity, hindering their full therapeutic potential. This paradigm shift has propelled the development of new injectable hydrogels for the local delivery of nanomaterials aimed at cancer photothermal therapy. These hydrogels can be assembled at the tumor site after injection (in situ forming) or can undergo a gel-sol-gel transition during injection (shear-thinning/self-healing). Besides incorporating photothermal nanostructures, these injectable hydrogels can also incorporate or be combined with other agents, paving the way for an improved therapeutic outcome. This review analyses the application of injectable hydrogels for the local delivery of nanomaterials aimed at cancer photothermal therapy as well as their combination with photodynamic-, chemo-, immuno- and radio-therapies.

Progress on the pathological tissue microenvironment barrier-modulated nanomedicine

Imbalance in the tissue microenvironment is the main obstacle to drug delivery and distribution in the human body. Before penetrating the pathological tissue microenvironment to the target site, therapeutic agents are usually accompanied by three consumption steps: the first step is tissue physical barriers for prevention of their penetration, the second step is inactivation of them by biological molecules, and the third step is a cytoprotective mechanism for preventing them from functioning on specific subcellular organelles. However, recent studies in drug-hindering mainly focus on normal physiological rather than pathological microenvironment, and the repair of damaged physiological barriers is also rarely discussed. Actually, both the modulation of pathological barriers and the repair of damaged physiological barriers are essential in the disease treatment and the homeostasis maintenance. In this review, we present an overview describing the latest advances in the generality of these pathological barriers and barrier-modulated nanomedicine. Overall, this review holds considerable significance for guiding the design of nanomedicine to increase drug efficacy in the future.

Innovative Design Strategies Advance Biomedical Applications of Phthalocyanines

Owing to their long absorption wavelengths, high molar absorptivity, and tunable photosensitivity, phthalocyanines have been widely used in photodynamic therapy (PDT). However, phthalocyanines still face the drawbacks of poor targeting, "always-on" photosensitizing properties, and unsatisfactory therapeutic efficiency, which limit their wide applications in biomedical fields. Thus, new design strategies such as modification of targeting molecules, formation of nanoparticles, and activating photosensitizers are developed to improve the above defects. Notably, recent studies have shown that novel phthalocyanines are not only used in fluorescence imaging and PDT, but also in photoacoustic imaging, photothermal imaging, sonodynamic therapy, and photothermal therapy. This review focuses on recent design strategies, applications in biomedicine, and clinical development of phthalocyanines, providing ideas and references for the design and application of phthalocyanine, so as to promote their future transformation into clinical applications.

Matrix Metalloproteinase-Responsive Drug Delivery Systems

Matrix metalloproteinases (MMPs) are a class of endopeptidases that are dependent on zinc and facilitate the degradation of extracellular matrix (ECM) proteins, thereby playing pivotal parts in human physiology and pathology. MMPs regulate normal tissue and cellular functions, including tissue development, remodeling, angiogenesis, bone formation, and wound healing. Several diseases, including cancer, inflammation, cardiovascular diseases, and nervous system disorders, have been linked to dysregulated expression of specific MMP subtypes, which can promote tumor progression, metastasis, and inflammation. Various MMP-responsive drug delivery and release systems have been developed by harnessing cleavage activities and overexpression of MMPs in affected regions. Herein, we review the structure, substrates, and physiological and pathological functions of various MMPs and highlight the strategies for designing MMP-responsive nanoparticles to improve the targeting efficiency, penetration, and protection of therapeutic payloads.

Protease-Responsive Hydrogel Microparticles for Intradermal Drug Delivery

Protease-responsive multi-arm polyethylene glycol-based microparticles with biscysteine peptide crosslinkers (CGPGG↓LAGGC) were obtained for intradermal drug delivery through inverse suspension photopolymerization. The average size of the spherical hydrated microparticles was ∼40 μm after crosslinking, making them attractive as a skin depot and suitable for intradermal injections, as they are readily dispensable through 27G needles. The effects of exposure to matrix metalloproteinase 9 (MMP-9) on the microparticles were evaluated by scanning electron microscopy and atomic force microscopy, demonstrating partial network destruction and decrease in elastic moduli. Given the recurring course of many skin diseases, the microparticles were exposed to MMP-9 in a flare-up mimicking fashion (multiple-time exposure), showing a significant increase in release of tofacitinib citrate (TC) from the MMP-responsive microparticles, which was not seen for the non-responsive microparticles (polyethylene glycol dithiol crosslinker). It was found that the degree of multi-arm complexity of the polyethylene glycol building blocks can be utilized to tune not only the release profile of TC but also the elastic moduli of the hydrogel microparticles, with Young's moduli ranging from 14 to 140 kPa going from 4-arm to 8-arm MMP-responsive microparticles. Finally, cytotoxicity studies conducted with skin fibroblasts showed no reduction in metabolic activity after 24 h exposure to the microparticles. Overall, these findings demonstrate that protease-responsive microparticles exhibit the properties of interest for intradermal drug delivery.

Influence of N-arylsulfonamido d-valine N-substituents on the selectivity and potency of matrix metalloproteinase inhibitors

To develop matrix metalloproteinase inhibitors (MMPIs) for both therapy and medicinal imaging by fluorescence-based techniques or positron-emission tomography (PET), a small library of eighteen N-substituted N-arylsulfonamido d-valines were synthesized and their potency to inhibit two gelatinases (MMP-2, and MMP-9), two collagenases (MMP-8, and MMP-13) and macrophage elastase (MMP-12) was determined in a Structure-Activity-Relation study with ({4-[3-(5-methylthiophen-2-yl)-1,2,4-oxadiazol-5-yl]phenyl}sulfonyl)-d-valine (1) as a lead. All compounds were shown to be more potent MMP-2/-9 inhibitors (nanomolar range) compared to other tested MMPs. This is a remarkable result considering that a carboxylic acid group is the zinc binding moiety. The compound with a terminal fluoropropyltriazole group at the furan ring (P1' substituent) was only four times less potent in inhibiting MMP-2 activity than the lead compound 1, making this compound a promising probe for PET application (after using a prosthetic group approach to introduce fluorine-18). Compounds with a TEG spacer and a terminal azide or even a fluorescein moiety at the sulfonylamide N atom (P2' substituent) were almost as active as the lead structure 1, making the latter derivative a suitable fluorescence imaging tool.

The role of nanotherapy in head and neck squamous cell carcinoma by targeting tumor microenvironment

Head and neck squamous cell carcinomas (HNSCCs) refers to a group of highly malignant and pathogenically complex tumors. Traditional treatment methods include surgery, radiotherapy, and chemotherapy. However, with advancements in genetics, molecular medicine, and nanotherapy, more effective and safer treatments have been developed. Nanotherapy, in particular, has the potential to be an alternative therapeutic option for HNSCC patients, given its advantageous targeting capabilities, low toxicity and modifiability. Recent research has highlighted the important role of the tumor microenvironment (TME) in the development of HNSCC. The TME is composed of various cellular components, such as fibroblasts, vascular endothelial cells, and immune cells, as well as non-cellular agents such as cytokines, chemokines, growth factors, extracellular matrix (ECM), and extracellular vesicles (EVs). These components greatly influence the prognosis and therapeutic efficacy of HNSCC, making the TME a potential target for treatment using nanotherapy. By regulating angiogenesis, immune response, tumor metastasis and other factors, nanotherapy can potentially alleviate HNSCC symptoms. This review aims to summarize and discuss the application of nanotherapy that targets HNSCC's TME. We highlight the therapeutic value of nanotherapy for HNSCC patients.

Evolving strategies and application of proteins and peptide therapeutics in cancer treatment

Several proteins and peptides have therapeutic potential and can be used for cancer therapy. By binding to cell surface receptors and other indicators uniquely linked with or overexpressed on tumors compared to healthy tissue, protein biologics enhance the active targeting of cancer cells, as opposed to the passive targeting of cells by conventional small-molecule chemotherapeutics. This study focuses on peptide medications that exist to slow or stop tumor growth and the spread of cancer, demonstrating the therapeutic potential of peptides in cancer treatment. As an alternative to standard chemotherapy, peptides that selectively kill cancer cells while sparing healthy tissue are developing. A mountain of clinical evidence supports the efficacy of peptide-based cancer vaccines. Since a single treatment technique may not be sufficient to produce favourable results in the fight against cancer, combination therapy is emerging as an effective option to generate synergistic benefits. One example of this new area is the use of anticancer peptides in combination with nonpeptidic cytotoxic drugs or the combination of immunotherapy with conventional therapies like radiation and chemotherapy. This review focuses on the different natural and synthetic peptides obtained and researched. Discoveries, manufacture, and modifications of peptide drugs, as well as their contemporary applications, are summarized in this review. We also discuss the benefits and difficulties of potential advances in therapeutic peptides.

Nanotechnology-enabled gene delivery for cancer and other genetic diseases

INTRODUCTION

Despite gene therapy is ideal for genetic abnormality-related diseases, the easy degradation, poor targeting, and inefficiency in entering targeted cells are plaguing the effective delivery of gene therapy. Viral and non-viral vectors have been used for delivering gene therapeutics in vivo by safeguarding nucleic acid agents to target cells and to reach the specific intracellular location. A variety of nanotechnology-enabled safe and efficient systems have been successfully developed to improve the targeting ability for effective therapeutic delivery of genetic drugs.

AREAS COVERED

In this review, we outline the multiple biological barriers associated with gene delivery process, and highlight recent advances to gene therapy strategy in vivo, including gene correction, gene silencing, gene activation and genome editing. We point out current developments and challenges exist of non-viral and viral vector systems in association with chemical and physical gene delivery technologies and their potential for the future.

EXPERT OPINION

This review focuses on the opportunities and challenges to various gene therapy strategy, with specific emphasis on overcoming the challenges through the development of biocompatibility and smart gene vectors for potential clinical application.

Supramolecular hydrogel for programmable delivery of therapeutics to cancer multidrug resistance

Multidrug resistance (MDR) has been considered as a major adversary in oncologic chemotherapy. To simultaneously overcome drug resistance and inhibit tumor growth, it is essential to develop a drug delivery system that can carry and release multiple therapeutic agents with spatiotemporal control. In this study, we developed a hydrogel containing an enzyme-cleavable peptide motif, with a network structure formed by 4-armed polyethylene glycol (PEG) crosslinked by complementary nucleic acid sequences. Hydrogen bond formation between nucleobase pairing allows the hydrogel to be injectable, and the peptide motif grants deliberate control over hydrogel degradation and the responsive drug release. Moreover, MDR-targeted siRNAs are complexed with stearyl-octaarginine (STR-R8), while doxorubicin (Dox) is intercalated with DNA and nanoclay structures in this hydrogel to enhance therapeutic efficacy and overcome MDR. The results show a successful configuration of a hydrogel network with in situ gelation property, injectability, and degradability in the presence of tumor-associated enzyme, MMP-2. The synergistic effect by combining MDR-targeted siRNAs and Dox manifests with the enhanced anti-cancer effect on drug resistant breast cancer cells in both in vitro and in vivo tumor models. We suggest that with the tailor-designed hydrogel system, multidrug resistance in tumor cells can be significantly inhibited by the co-delivery of multiple therapeutics with spatial-temporal control release.

Matrix metalloproteinase profiling and their roles in disease

Matrix metalloproteinases (MMPs) play roles in remodelling of the extracellular matrix that occurs during morphogenesis, repair, and angiogenesis. Dysregulation of extracellular matrix remodelling can lead to cell proliferation, invasion, and tissue fibrosis. Identification of a specific MMP(s) in a disease has been challenging due to the presence of 24 closely-related human MMPs, each existing in three forms, of which only one is active and capable of catalysis. This review focuses on methods for MMP profiling, with particular emphasis on the batimastat affinity resin that binds only to the active forms of MMPs and related ADAMs (a disintegrin and metalloproteinases), which are then identified by mass spectrometry. Use of the batimastat affinity resin has identified targets for intervention in several human diseases.

Injectable MMP1-sensitive microspheres with spatiotemporally controlled exosome release promote neovascularized bone healing

Bone marrow mesenchymal stromal cell-derived exosomes (BMSC-Exos) can recruit stem cells for bone repair, with neovessels serving as the main migratory channel for stem cells to the injury site. However, existing exosome (Exo) delivery strategies cannot reach the angiogenesis phase following bone injury. To that end, an enzyme-sensitive Exo delivery material that responds to neovessel formation during the angiogenesis phase was designed in the present study to achieve spatiotemporally controlled Exo release. Herein, matrix metalloproteinase-1 (MMP1) was found to be highly expressed in neovascularized bone; as a result, we proposed an injectable MMP1-sensitive hydrogel microspheres (KGE) made using a microfluidic chip prepared by mixing self-assembling peptide (KLDL-MMP1), GelMA, and BMSC-Exos. The results revealed that KGE microspheres had a uniform diameter of 50-70 µm, ideal for minimally invasive injection and could release exosomes in response to MMP1 expression. In vitro experiments demonstrated that KGE had less cytotoxicity and could promote the migration and osteodifferentiation of BMSCs. Furthermore, in vivo experiments confirmed that KGE could promote bone repair during angiogenesis by recruiting CD90⁺ stem cells via neovessels. Collectively, our results suggest that injectable enzyme-responsive KGE microspheres could be a promising Exo-secreting material for accelerating neovascularized bone healing. STATEMENT OF SIGNIFICANCE: Exosomes can spread through blood vessels and activate stem cells to participate in bone repair, but under normal circumstances, exosomes lacking sustained-release delivery materials cannot be maintained until the angiogenesis phase. In this study, we found that MMP1 was highly expressed in neovascularized bone, then we proposed an MMP1-sensitive injectable microsphere that carries exosomes and responds temporally and spatially to neovascularization, which maximizes the ability of exosomes to recruit stem cells. Different from previous strategies that focus on promoting angiogenesis to accelerate bone healing, this is a brand new delivery strategy that is stimuli-responsive to neovessel formation. In addition, the preparation of self-assembled peptide microspheres by a microfluidic chip is also proposed for the first time.

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.

Design and characterization of matrix metalloproteinase-responsive hydrogels for the treatment of inflammatory skin diseases

Enzyme-responsive hydrogels, formed by step growth photopolymerization of biscysteine peptide linkers with alkene functionalized polyethylene glycol, provide interesting opportunities as biomaterials and drug delivery systems. In this study, we developed stimuli-responsive, specific, and cytocompatible hydrogels for delivery of anti-inflammatory drugs for the treatment of inflammatory skin diseases. We designed peptide linkers with optimized sensitivity towards matrix metalloproteinases, a family of proteolytic enzymes overexpressed in the extracellular matrix of the skin during inflammation. The peptide linkers were crosslinked with branched 4-arm and 8-arm polyethylene glycols by thiol-norbornene photopolymerization, leading to the formation of a hydrogel network, in which the anti-inflammatory Janus kinase inhibitor tofacitinib citrate was incorporated. The hydrogels were extensively characterized by physical properties, in vitro release studies, cytocompatibility with fibroblasts, and anti-inflammatory efficacy testing in both an atopic dermatitis-like keratinocyte assay and an activated T-cell assay. The drug release was studied after single and multiple-time exposure to matrix metalloproteinase 9 to mimic inflammatory flare-ups. Drug release was found to be triggered by matrix metalloproteinase 9 and to depend on type of crosslinker and of the polyethylene glycol polymer, due to differences in architecture and swelling behavior. Moreover, swollen hydrogels showed elastic properties similar to those of extracellular matrix proteins in the dermis. Cell studies revealed limited cytotoxicity when fibroblasts and keratinocytes were exposed to the hydrogels or their enzymatic cleavage products. Taken together, our results suggest multi-arm polyethylene glycol hydrogels as promising matrix metalloproteinase-responsive drug delivery systems, with potential in the treatment of inflammatory skin disease. STATEMENT OF SIGNIFICANCE: Smart responsive drug delivery systems such as matrix metalloproteinase-responsive hydrogels are excellent candidates for the treatment of inflammatory skin diseases including psoriasis. Their release profile can be optimized to correspond to the patient's individual disease state by tuning formulation parameters and disease-related stimuli, providing personalized treatment solutions. However, insufficient cross-linking efficiency, low matrix metalloproteinase sensitivity, and undesirable drug release kinetics remain major challenges in the development of such drug delivery systems. In this study, we address shortcomings of previous work by designing peptide linkers with optimized sensitivity towards matrix metalloproteinases and high cross-linking efficiencies. We further provide a proof-of-concept for the usability of the hydrogels in inflammatory skin conditions by employing a drug release set-up simulating inflammatory flare-ups.

Isoquercitrin restrains the proliferation and promotes apoptosis of human osteosarcoma cells by inhibiting the Wnt/β-catenin pathway

Currently, chemotherapeutic drugs are widely used for the treatment of osteosarcoma. However, many of these drugs exhibit shortcomings such as poor efficacy, high toxicity, and tolerance. Isoquercitrin (ISO) is a traditional Chinese medicine that has been proved to exert good therapeutic effects on various tumors; however, its role in osteosarcoma has not been reported. Here, we observed that ISO exerted a marked inhibitory effect on the occurrence and development of osteosarcoma in a time- and dose-dependent manner. First, we determined that ISO significantly inhibited proliferation, induced EMT-related migration and invasion and induced apoptosis of osteosarcoma cells in vitro. Concurrently, we also observed that both β-catenin and its downstream genes (c-Myc, CyclinD1, and Survivin) were significantly down-regulated. To verify if the anti-tumor effect of ISO was related to the Wnt/β-catenin signaling pathway, we altered the protein expression level of β-catenin using recombinant lentivirus, then we observed that the effects of ISO on the proliferation, metastasis, and apoptosis of osteosarcoma cells were significantly reversed. Additionally, we used a nude mouse xenograft model and observed that ISO significantly inhibited the growth of osteosarcoma and improved the survival rate of the animal models. In conclusion, this study demonstrates that ISO can exert anti-tumor effects in part by inhibiting the Wnt/β-catenin signaling pathway, thus providing a new potential therapeutic strategy for the treatment of osteosarcoma.

Hepatocyte-targeting and tumor microenvironment-responsive liposomes for enhanced anti-hepatocarcinoma efficacy

To increase the antitumor drug concentration in the liver tumor site and improve the therapeutic effects, a functionalized liposome (PPP-LIP) with tumor targetability and enhanced internalization after matrix metalloproteinase-2 (MMP2)-triggered cell-penetrating peptide (TATp) exposure was modified with myrcludex B (a synthetic HBV preS-derived lipopeptide endowed with compelling liver tropism) for liver tumor-specific delivery. After intravenous administration, PPP-LIP was mediated by myrcludex B to reach the hepatocyte surface. The MMP2-overexpressing tumor microenvironment deprotected PEG, exposing it to TATp, facilitating tumor penetration and subsequent efficient destruction of tumor cells. In live imaging of small animals and cellular uptake, PPP-LIP was taken up much more than typical unmodified liposomes in the ICR mouse liver and liver tumor cells. Hydroxycamptothecin (HCPT)-loaded PPP-LIP showed a better antitumor effect than commercially available HCPT injections among MTT, three-dimensional (3 D) tumor ball, and tumor-bearing nude mouse experiments. Our findings indicated that PPP-LIP nanocarriers could be a promising tumor-targeted medication delivery strategy for treating liver cancers with elevated MMP2 expression.

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.

Developments on the Smart Hydrogel-Based Drug Delivery System for Oral Tumor Therapy

At present, an oral tumor is usually treated by surgery combined with preoperative or postoperative radiotherapies and chemotherapies. However, traditional chemotherapies frequently result in substantial toxic side effects, including bone marrow suppression, malfunction of the liver and kidneys, and neurotoxicity. As a new local drug delivery system, the smart drug delivery system based on hydrogel can control drug release in time and space, and effectively alleviate or avoid these problems. Environmentally responsive hydrogels for smart drug delivery could be triggered by temperature, photoelectricity, enzyme, and pH. An overview of the most recent research on smart hydrogels and their controlled-release drug delivery systems for the treatment of oral cancer is given in this review. It is anticipated that the local drug release method and environment-responsive benefits of smart hydrogels will offer a novel technique for the low-toxicity and highly effective treatment of oral malignancy.

Design Strategies of Tumor-Targeted Delivery Systems Based on 2D Nanomaterials

Conventional chemotherapy and radiotherapy are nonselective and nonspecific for cell killing, causing serious side effects and threatening the lives of patients. It is of great significance to develop more accurate tumor-targeting therapeutic strategies. Nanotechnology is in a leading position to provide new treatment options for cancer, and it has great potential for selective targeted therapy and controlled drug release. 2D nanomaterials (2D NMs) have broad application prospects in the field of tumor-targeted delivery systems due to their special structure-based functions and excellent optical, electrical, and thermal properties. This review emphasizes the design strategies of tumor-targeted delivery systems based on 2D NMs from three aspects: passive targeting, active targeting, and tumor-microenvironment targeting, in order to promote the rational application of 2D NMs in clinical practice.

Research Progress of Antioxidant Nanomaterials for Acute Pancreatitis

Acute pancreatitis (AP) is a complex inflammatory disease caused by multiple etiologies, the pathogenesis of which has not been fully elucidated. Oxidative stress is important for the regulation of inflammation-related signaling pathways, the recruitment of inflammatory cells, the release of inflammatory factors, and other processes, and plays a key role in the occurrence and development of AP. In recent years, antioxidant therapy that suppresses oxidative stress by scavenging reactive oxygen species has become a research highlight of AP. However, traditional antioxidant drugs have problems such as poor drug stability and low delivery efficiency, which limit their clinical translation and applications. Nanomaterials bring a brand-new opportunity for the antioxidant treatment of AP. This review focuses on the multiple advantages of nanomaterials, including small size, good stability, high permeability, and long retention effect, which can be used not only as effective carriers of traditional antioxidant drugs but also directly as antioxidants. In this review, after first discussing the association between oxidative stress and AP, we focused on summarizing the literature related to antioxidant nanomaterials for the treatment of AP and highlighting the effects of these nanomaterials on the indicators related to oxidative stress in pathological states, aiming to provide references for follow-up research and promote clinical application.

Fluorescent Peptomer Substrates for Differential Degradation by Metalloproteases

Proteases, especially MMPs, are attractive biomarkers given their central role in both physiological and pathological processes. Distinguishing MMP activity with degradable substrates, however, is a difficult task due to overlapping substrate specificity profiles. Here, we developed a system of peptomers (peptide-peptoid hybrids) to probe the impact of non-natural residues on MMP specificity for an MMP peptide consensus sequence. Peptoids are non-natural, N-substituted glycines with a large side-chain diversity. Given the presence of a hallmark proline residue in the P3 position of MMP consensus sequences, we hypothesized that peptoids may offer N-substituted alternatives to generate differential interactions with MMPs. To investigate this hypothesis, peptomer substrates were exposed to five different MMPs, as well as bacterial collagenase, and monitored by fluorescence resonance energy transfer and liquid chromatography-mass spectrometry to determine the rate of cleavage and the composition of degraded fragments, respectively. We found that peptoid residues are well tolerated in the P3 and P3' substrate sites and that the identity of the peptoid in these sites displays a moderate influence on the rate of cleavage. However, peptoid residues were even better tolerated in the P1 substrate site where activity was more strongly correlated with side-chain identity than side-chain position. All MMPs explored demonstrated similar trends in specificity for the peptomers but exhibited different degrees of variability in proteolytic rate. These kinetic profiles served as "fingerprints" for the proteases and yielded separation by multivariate data analysis. To further demonstrate the practical application of this tunability in degradation kinetics, peptomer substrates were tethered into hydrogels and released over distinct timescales. Overall, this work represents a significant step toward the design of probes that maximize differential MMP behavior and presents design rules to tune degradation kinetics with peptoid substitutions, which has promising implications for diagnostic and prognostic applications using array-based sensors.

Intracellular and extracellular enzymatic responsive micelle for intelligent therapy of cancer

Recently, the incidence of cancer keeps increasing, seriously endangers human health, and has evolved into the main culprit of human death. Conventional chemotherapeutic drugs, such as paclitaxel and doxorubicin (DOX), have some disadvantages, including low therapeutic effect, poor water solubility, high toxic side effects, short blood circulation time in the body, and so on. To improve the anti-tumor effect of the drug in vivo and reduce its side effects on the body, researchers have designed and developed a variety of responsive nanocarriers. In this work, we synthesized D-α-tocopherol polyethylene glycol 3350 succinate (TPGS3350)-Gly-Pro-Leu-Gly-Val-Arg (GPLGVR)-DOX (TPD) prodrugs in response to extracellular enzymes of matrix metalloproteinase (MMP-9) in the tumor microenvironment and FA-Asp-Glu-Val-Asp (DEVD)-DOX (FPD) prodrugs responsive to intracellular enzymes of caspase-3. Then, intracellular and extracellular enzyme-responsive TPD&FPD micelles with DOX (TPD&FPD&D) were successfully prepared through dialysis method. The outer layer of TPGS3350 can prolong the blood circulation time of micelles in vivo, followed by accumulation of micelles at tumor tissue through enhanced permeability and retention (EPR) effect. The peptide of GPLGVR can be cleaved by MMP-9 enzymes to remove the outer layer of TPGS3350, exposing the targeting molecule of folate, and then the micelles are engulfed by tumor cells through folate receptor-mediated endocytosis. After entering the tumor cells, the free DOX loaded in the micelles is released, which induces tumor cell apoptosis to activate caspase-3 in the cells, cutting the peptide DEVD to accelerate the intracellular release of the DOX, which further enhances cytotoxicity to improve antitumor effect.

Electronic Supplementary Material

Supplementary material () is available in the online version of this article at 10.1007/s12274-022-4967-1.

Enhancement of anti-tumor activity in melanoma using arginine deiminase fused with 30Kc19α protein

Arginine deiminase (ADI) is a microbial-derived enzyme which catalyzes the conversion of L-arginine into L-citrulline. ADI originating from Mycoplasma has been reported to present anti-tumor activity against arginine-auxotrophic tumors, including melanoma. Melanoma cells are sensitive to arginine depletion due to reduced expression of argininosuccinate synthase 1 (ASS1), a key enzyme for arginine biosynthesis. However, clinical applications of recombinant ADI for melanoma treatment present some limitations. Since recombinant ADI is not human-derived, it shows instability, proteolytic degradation, and antigenicity in human serum. In addition, there is a problem of drug resistance issue due to the intracellular expression of once-silenced ASS1. Moreover, recombinant ADI proteins are mainly expressed as inclusion body forms in Escherichia coli and require a time-consuming refolding process to turn them back into active form. Herein, we propose fusion of recombinant ADI from Mycoplasma hominis and 30Kc19α, a cell-penetrating protein which also increases stability and soluble expression of cargo proteins, to overcome these problems. We inserted matrix metalloproteinase-2 cleavable linker between ADI and 30Kc19α to increase enzyme activity in melanoma cells. Compared to ADI, ADI-LK-30Kc19α showed enhanced solubility, stability, and cell penetration. The fusion protein demonstrated selective cytotoxicity and reduced drug resistance in melanoma cells, thus would be a promising strategy for the improved efficacy in melanoma treatment. KEY POINTS: • Fusion of ADI with 30Kc19α enhances soluble expression and productivity of recombinant ADI in E. coli • 30Kc19α protects ADI from the proteolytic degradation by shielding effect, helping ADI to remain active • Intracellular delivery of ADI by 30Kc19α overcomes ADI resistance in melanoma cells by degrading intracellularly expressed arginine.

Bioresponsive Polymers for Nanomedicine-Expectations and Reality!

Bioresponsive polymers in nanomedicine have been widely perceived to selectively activate the therapeutic function of nanomedicine at diseased or pathological sites, while sparing their healthy counterparts. This idea can be described as an advanced version of Paul Ehrlich's magic bullet concept. From that perspective, the inherent anomalies or malfunction of the pathological sites are generally targeted to allow the selective activation or sensory function of nanomedicine. Nonetheless, while the primary goals and expectations in developing bioresponsive polymers are to elicit exclusive selectivity of therapeutic action at diseased sites, this remains difficult to achieve in practice. Numerous research efforts have been undertaken, and are ongoing, to tackle this fine-tuning. This review provides a brief introduction to key stimuli with biological relevance commonly featured in the design of bioresponsive polymers, which serves as a platform for critical discussion, and identifies the gap between expectations and current reality.

Intelligent Drug Delivery by Peptide-Based Dual-Function Micelles

To endow the polymeric prodrug with smart properties through a safe and simple method, matrix metalloproteinase (MMPs) responsive peptide GPLGVRGDG was introduced into the block copolymer to prepare TPGS₃₃₅₀-GPLGVRGDG-DOX&DOX micelles, where TPGS₃₃₅₀ is D-α-tocopheryl polyethylene glycol 3350 succinate. During the doxorubicin delivery, the cleavage of the peptide chain triggers de-PEGylation, and the remaining VRGDG sequence was retained on the surface of the micelles, which can act as a ligand to facilitate cell uptake. Moreover, the cytotoxicity of TPGS₃₃₅₀-GPLGVRGDG-DOX&DOX micelles against 4T1 cells was significantly improved, compared with TPGS₃₃₅₀-GPLGVRG-DOX&DOX micelles and TPGS₃₃₅₀-DOX&DOX micelles. During in vivo studies, TPGS₃₃₅₀-GPLGVRGDG-DOX&DOX micelles exhibited good anticancer efficacy with long circulation in the body and more efficient accumulation at the tumor site. Therefore, TPGS₃₃₅₀-GPLGVRGDG-DOX&DOX micelles have improved antitumor activity and reduced toxic side effects. This work opens new potential for exploring the strategy of drug delivery in clinical applications.

Stimuli-responsive nanoformulations for CRISPR-Cas9 genome editing

The CRISPR-Cas9 technology has changed the landscape of genome editing and has demonstrated extraordinary potential for treating otherwise incurable diseases. Engineering strategies to enable efficient intracellular delivery of CRISPR-Cas9 components has been a central theme for broadening the impact of the CRISPR-Cas9 technology. Various non-viral delivery systems for CRISPR-Cas9 have been investigated given their favorable safety profiles over viral systems. Many recent efforts have been focused on the development of stimuli-responsive non-viral CRISPR-Cas9 delivery systems, with the goal of achieving efficient and precise genome editing. Stimuli-responsive nanoplatforms are capable of sensing and responding to particular triggers, such as innate biological cues and external stimuli, for controlled CRISPR-Cas9 genome editing. In this Review, we overview the recent advances in stimuli-responsive nanoformulations for CRISPR-Cas9 delivery, highlight the rationale of stimuli and formulation designs, and summarize their biomedical applications.

The tetrapartite synapse in neuropsychiatric disorders: Matrix metalloproteinases (MMPs) as promising targets for treatment and rational drug design

Inflammation and an exacerbated immune response are widely accepted contributing mechanisms to the genesis and progression of major neuropsychiatric disorders. However, despite the impressive advances in understanding the neurobiology of these disorders, there is still no approved drug directly linked to the regulation of inflammation or brain immune responses. Importantly, matrix metalloproteinases (MMPs) comprise a group of structurally related endopeptidases primarily involved in remodeling extracellular matrix (ECM). In the central nervous system (CNS), these proteases control synaptic plasticity and strength, patency of the blood-brain barrier, and glia-neuron interactions through cleaved and non-cleaved mediators. Several pieces of evidence have pointed to a complex scenario of MMPs dysregulation triggered by neuroinflammation. Furthermore, major psychiatric disorders' affective symptoms and neurocognitive abnormalities are related to MMPs-mediated ECM changes and neuroglia activation. In the past decade, research efforts have been directed to broad-spectrum MMPs inhibitors with frustrating clinical results. However, in the light of recent advances in combinatorial chemistry and drug design technologies, specific and CNS-oriented MMPs modulators have been proposed as a new frontier of therapy for regulating ECM properties in the CNS. Therefore, here we aim to discuss the state of the art of MMPs and ECM abnormalities in major neuropsychiatric disorders, namely depression, bipolar disorder, and schizophrenia, the possible neuro-immune interactions involved in this complex scenario of MMPs dysregulation and propose these endopeptidases as promising targets for rational drug design.

Immunogenic Cell Death Activates the Tumor Immune Microenvironment to Boost the Immunotherapy Efficiency

Tumor immunotherapy is only effective in a fraction of patients due to a low response rate and severe side effects, and these challenges of immunotherapy in clinics can be addressed through induction of immunogenic cell death (ICD). ICD is elicited from many antitumor therapies to release danger associated molecular patterns (DAMPs) and tumor-associated antigens to facilitate maturation of dendritic cells (DCs) and infiltration of cytotoxic T lymphocytes (CTLs). The process can reverse the tumor immunosuppressive microenvironment to improve the sensitivity of immunotherapy. Nanostructure-based drug delivery systems (NDDSs) are explored to induce ICD by incorporating therapeutic molecules for chemotherapy, photosensitizers (PSs) for photodynamic therapy (PDT), photothermal conversion agents for photothermal therapy (PTT), and radiosensitizers for radiotherapy (RT). These NDDSs can release loaded agents at a right dose in the right place at the right time, resulting in greater effectiveness and lower toxicity. Immunotherapeutic agents can also be combined with these NDDSs to achieve the synergic antitumor effect in a multi-modality therapeutic approach. In this review, NDDSs are harnessed to load multiple agents to induce ICD by chemotherapy, PDT, PTT, and RT in combination of immunotherapy to promote the therapeutic effect and reduce side effects associated with cancer treatment.