Tumor Microenvironment-Mediated Construction and Deconstruction of Extracellular Drug-Delivery Depots

Mechanistic Underpinnings of Epigenetic Enzyme-Responsive Nanoparticles

Epigenetic enzyme-responsive nanoparticles (ERPs), which destabilize under the influence of histone deacetylase 8 (HDAC8), have been characterized in terms of their physicochemical, nanomechanical, and in vitro attributes. These nanoparticles were synthesized from amphiphilic block copolymers composed of poly(acetyl l-lysine) as the hydrophobic and poly(ethylene glycol) as the hydrophilic block. Upon optimizing the particle assembly process, we demonstrated that the nanoscale properties of ERPs, including hydrodynamic diameter (DH), size distribution, and stiffness, are selectively influenced by the HDAC8 enzyme. Using 1H NMR and circular dichroism spectroscopy, we identified that deacetylation of the lysine residues located within the hydrophobic block acts as a molecular driver for the enzyme-induced destabilization of ERPs. Comprehensive in vitro studies demonstrated that ERPs are biocompatible and noncytotoxic and can accumulate in perinuclear and several cellular organelles, including lysosomes and mitochondria. Collectively, this study attempts to establish the mechanistic background of ERP functions, providing the baseline for designing epigenetic-enzyme-sensitive nanoscale platforms.

Heat-guided drug delivery via thermally induced crosslinking of polymeric micelles

Targeted drug delivery in response to external stimuli is therapeutically desirable, but long-term drug retention at the target site after stimulation is turned off remains a challenge. Herein, we present a targeted-delivery strategy via irreversible aggregation of drug carriers in response to mild external heating. We constructed two types of polymeric micelles, DBCO-TRM and Az-TRM, having a thermo-responsive polymer shell based on N-isopropylacrylamide (NIPAAm) and incorporating alkyne and azide moieties, respectively. Upon heating at 42 °C, the micelles aggregated through hydrophobic interaction between their dehydrated shells. Further, the azide moieties of Az-TRM become exposed on the surface due to the thermally shrinkage of the shells, thereby enabling crosslinking between the two types of micelles via azide-alkyne click chemistry to form irreversible aggregates. These aggregates were efficiently accumulated at tumor sites in mice by local heating after intravenous administration of a mixture of the micelles, and were well retained after cessation of heating due to their increased size. As proof of concept, we show that delivery of doxorubicin in this heat-guided drug delivery system dramatically improved the anti-tumor effect in a mouse model after a single treatment. Our results suggest that this platform could be an efficient tool for on-demand drug delivery.

Design and evaluation of nanoscale materials with programmed responsivity towards epigenetic enzymes

Self-assembled materials capable of modulating their assembly properties in response to specific enzymes play a pivotal role in advancing 'intelligent' encapsulation platforms for biotechnological applications. Here, we introduce a previously unreported class of synthetic nanomaterials that programmatically interact with histone deacetylase (HDAC) as the triggering stimulus for disassembly. These nanomaterials consist of co-polypeptides comprising poly(acetyl L-lysine) and poly(ethylene glycol) blocks. Under neutral pH conditions, they self-assemble into particles. The hydrodynamic diameters of particles were typically withing the range of 108-190 nm, depending on degree of acetylation of the hydrophobic block. However, their stability is compromised upon exposure to HDACs, depending on enzyme concentration and exposure time. Our investigation, utilizing HDAC8 as the model enzyme, revealed that the primary mechanism behind disassembly involves a decrease in amphiphilicity within the block copolymer due to the deacetylation of lysine residues within the particles' hydrophobic domains. To elucidate the response mechanism, we encapsulated a fluorescent dye within these nanoparticles. Upon incubation with HDAC, the nanoparticle structure collapsed, leading to controlled release of the dye over time. Notably, this release was not triggered by denatured HDAC8, other proteolytic enzymes like trypsin, or the co-presence of HDAC8 and its inhibitor. We also demonstrated the biocompatibility and cellular effects of these materials in the context of drug delivery in different types of anticancer cell lines, such as MIA PaCa-2, PANC-1, cancer like stem cells (CSCs), and non-cancerous HPNE cells. We observed that the release of a model drug (such as a STAT3 pathway inhibitor, Napabucasin) can be loaded into these nanoparticles, with >90% of the dosage can be released over 3 h under the influence of HDAC8 enzyme in a controlled fashion. Further, we conducted a comprehensive computational study to unveil the possible interaction mechanism between enzymes and particles. By drawing parallels to the mechanism of naturally occurring histone proteins, this research represents a pioneering step toward developing functional materials capable of harnessing the activity of epigenetic enzymes such as HDACs.

Deformable nanocarriers for enhanced drug delivery and cancer therapy

Recently, the field of nanomedicine has witnessed substantial advancements in the development of nanocarriers for targeted drug delivery, emerges as promising platforms to enhance therapeutic efficacy and minimize adverse effects associated with conventional chemotherapy. Notably, deformable nanocarriers have garnered considerable attention due to their unique capabilities of size changeable, tumor-specific aggregation, stimuli-triggered disintegration, and morphological transformations. These deformable nanocarriers present significant opportunities for revolutionizing drug delivery strategies, by responding to specific stimuli or environmental cues, enabling achieved various functions at the tumor site, including size-shrinkage nanocarriers enhance drug penetration, aggregative nanocarriers enhance retention effect, disintegrating nanocarriers enable controlled drug release, and shape-changing nanocarriers improve cellular uptake, allowing for personalized treatment approaches and combination therapies. This review provides an overview of recent developments and applications of deformable nanocarriers for enhancing tumor therapy, underscores the diverse design strategies employed to create deformable nanocarriers and elucidates their remarkable potential in targeted tumor therapy.

Biomaterials with cancer cell-specific cytotoxicity: challenges and perspectives

Significant advances have been made in materials for biomedical applications, including tissue engineering, bioimaging, cancer treatment, etc. In the past few decades, nanostructure-mediated therapeutic strategies have been developed to improve drug delivery, targeted therapy, and diagnosis, maximizing therapeutic effectiveness while reducing systemic toxicity and side effects by exploiting the complicated interactions between the materials and the cell and tissue microenvironments. This review briefly introduces the differences between the cells and tissues of tumour or normal cells. We summarize recent advances in tumour microenvironment-mediated therapeutic strategies using nanostructured materials. We then comprehensively discuss strategies for fabricating nanostructures with cancer cell-specific cytotoxicity by precisely controlling their composition, particle size, shape, structure, surface functionalization, and external energy stimulation. Finally, we present perspectives on the challenges and future opportunities of nanotechnology-based toxicity strategies in tumour therapy.

Tumor microenvironment-regulated drug delivery system combined with sonodynamic therapy for the synergistic treatment of breast cancer

Co-loading of sonosensitizers and chemotherapeutic drugs into nanocarriers can improve the biocompatibilities, stabilities, and targeting of drugs and reduce the adverse reactions of drugs, providing a robust platform to orchestrate the synergistic interplay between chemotherapy and sonodynamic therapy (SDT) in cancer treatment. In this regard, biodegradable manganese dioxide (MnO2) has attracted widespread attention because of its unique properties in the tumor microenvironment (TME). Accordingly, herein, MnO2 nanoshells with hollow mesoporous structures (H-MnO2) were etched to co-load hematoporphyrin monomethyl ether (HMME) and doxorubicin (DOX), and DOX/HMME-HMnO2@bovine serum albumin (BSA) obtained after simple BSA modification of DOX/HMME-HMnO2 exhibited excellent hydrophilicity and dispersibility. H-MnO2 rapidly degraded in the weakly acidic TME, releasing loaded HMME and DOX, and catalysed the decomposition of H2O2 abundantly present in TME, producing oxygen (O2) in situ, significantly increasing O2 concentration and downregulating the hypoxia-inducible factor 1α (HIF-1α). After irradiation of the tumor area with low-frequency ultrasound, the drug delivery efficiency of DOX/HMME-HMnO2@BSA substantially increased, and the excited HMME generated a large amount of reactive oxygen species (ROS), which caused irreversible damage to tumor cells. Moreover, the cell death rate exceeded 60% after synergistic SDT-chemotherapy. Therefore, the pH-responsive nanoshells designed in this study can realize drug accumulation in tumor regions by responding to TME and augment SDT-chemotherapy potency for breast cancer treatment by improving hypoxia in tumors. Thus, this study provides theoretical support for the development of multifunctional nanocarriers and scientific evidence for further exploration of safer and more efficient breast cancer treatments.

Design and Evaluation of Nanoscale Materials with Programmed Responsivity towards Epigenetic Enzymes

Self-assembled materials capable of modulating their assembly properties in response to specific enzymes play a pivotal role in advancing 'intelligent' encapsulation platforms for biotechnological applications. Here, we introduce a previously unreported class of synthetic nanomaterials that programmatically interact with histone deacetylase (HDAC) as the triggering stimulus for disassembly. These nanomaterials consist of co-polypeptides comprising poly (acetyl L-lysine) and poly(ethylene glycol) blocks. Under neutral pH conditions, they self-assemble into particles. However, their stability is compromised upon exposure to HDACs, depending on enzyme concentration and exposure time. Our investigation, utilizing HDAC8 as the model enzyme, revealed that the primary mechanism behind disassembly involves a decrease in amphiphilicity within the block copolymer due to the deacetylation of lysine residues within the particles' hydrophobic domains. To elucidate the response mechanism, we encapsulated a fluorescent dye within these nanoparticles. Upon incubation with HDAC, the nanoparticle structure collapsed, leading to controlled release of the dye over time. Notably, this release was not triggered by denatured HDAC8, other proteolytic enzymes like trypsin, or the co-presence of HDAC8 and its inhibitor. We further demonstrated the biocompatibility and cellular effects of these materials and conducted a comprehensive computational study to unveil the possible interaction mechanism between enzymes and particles. By drawing parallels to the mechanism of naturally occurring histone proteins, this research represents a pioneering step toward developing functional materials capable of harnessing the activity of epigenetic enzymes such as HDACs.

Poly-β-thioester-Based Cross-Linked Nanocarrier for Cancer Cell Selectivity over Normal Cells and Cellular Apoptosis by Triggered Release of Parthenolide, an Anticancer Drug

Breast cancer is the most prevalent and aggressive type of cancer, causing high mortality rates in women globally. Many drawbacks and side effects of the current chemotherapy force us to develop a robust chemotherapeutic system that can deal with off-target hazards and selectively combat cancer growth, invasiveness, and cancer-initiating cells. Here, a pH-responsive cross-linked nanocarrier (140-160 nm) endowed with poly-β-thioester functionality (CBAPTL) has been sketched and fabricated for noncovalent firm encapsulation of anticancer drug, parthenolide (PTL) at physiological pH (7.4), which enables sustain release of PTL at relevant endosomal pH (∼5.0-5.3). For this, a bolaamphiphilic molecule integrated with β-thioester and acrylate functionality was synthesized to fabricate the pH-responsive poly-β-thioester-based cross-linked nanocarrier via Michael addition click reactions in water. The poly-β-thioester functionality of CBAPTL hydrolyzes at endosomal acidic conditions, thus leading to the selective release of PTL inside the cancer cell. Cross-linked nanocarriers exhibit high serum stability, dilution insensitivity, and targeted cellular uptake at tumor microenvironment (TME), contrasting normal cells. In vitro study using human MCF-7 breast cancer cells demonstrated that CBAPTL exhibited selective cytotoxicity, reduced clonogenic potential, increased reactive oxygen species (ROS) generation, and arrested the progression of the cell cycle at the G0/G1 phase efficiently. CBAPTL induced apoptosis via downregulating pro-proliferative protein Bcl-2 and upregulating proapoptotic proteins p53, BAD, p21, and cleaved PARP-1. CBAPTL inhibited proliferating signaling by suppressing AKT phosphorylation and p38 expression. CBAPTL also blocked the invasion and migration of MCF-7 cells. CBAPTL effectively inhibits primary and secondary mammosphere formation, thereby preventing cancer-initiating cells' growth. Conversely, CBAPTL has negligible effect on human red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs). These findings highlight the superior efficacy of CBAPTL compared to PTL alone in suppressing cancer cell growth, inducing apoptosis, and preventing invasiveness of MCF-7 cells. Thus, CBAPTL could be considered a possible selective chemotherapeutic cargo against breast cancer without affecting normal cells.

Aptamer-Based Smart Targeting and Spatial Trigger-Response Drug-Delivery Systems for Anticancer Therapy

In recent years, the field of drug delivery has witnessed remarkable progress, driven by the quest for more effective and precise therapeutic interventions. Among the myriad strategies employed, the integration of aptamers as targeting moieties and stimuli-responsive systems has emerged as a promising avenue, particularly in the context of anticancer therapy. This review explores cutting-edge advancements in targeted drug-delivery systems, focusing on the integration of aptamers and stimuli-responsive platforms for enhanced spatial anticancer therapy. In the aptamer-based drug-delivery systems, we delve into the versatile applications of aptamers, examining their conjugation with gold, silica, and carbon materials. The synergistic interplay between aptamers and these materials is discussed, emphasizing their potential in achieving precise and targeted drug delivery. Additionally, we explore stimuli-responsive drug-delivery systems with an emphasis on spatial anticancer therapy. Tumor microenvironment-responsive nanoparticles are elucidated, and their capacity to exploit the dynamic conditions within cancerous tissues for controlled drug release is detailed. External stimuli-responsive strategies, including ultrasound-mediated, photo-responsive, and magnetic-guided drug-delivery systems, are examined for their role in achieving synergistic anticancer effects. This review integrates diverse approaches in the quest for precision medicine, showcasing the potential of aptamers and stimuli-responsive systems to revolutionize drug-delivery strategies for enhanced anticancer therapy.

Size-tunable nanogels for cascaded release of metronidazole and chemotherapeutic agents to combat Fusobacterium nucleatum-infected colorectal cancer

Bacteria play important roles in tumor formation, growth and metastasis through downregulating immune response and initiating drug resistance. Herein, size-tunable nanogels (NGs) have been developed to address the existing size paradox in tumor accumulation, intratumoral penetration and intracellular release of therapeutics for the treatment of Fusobacterium nucleatum (F. nucleatum)-infected colorectal cancer. Zinc-imidazolate frameworks with doxorubicin (DOX) loading and folate grafting (f-ZIFD) were mixed with metronidazole (MET) and encapsulated in NGs through thiol-ene click crosslinking of sulfhydryl hyaluronan, sulfhydryl alginate and 4-arm poly(ethylene glycol) acrylate. Hyaluronidase-initiated matrix degradation causes NG swelling to release sufficient MET and maintains a large size for an extended time period, and the gradually discharged f-ZIFD nanoparticles (NPs) from NGs exhibit acid-responsive intracellular release of DOX after folate-mediated internalization into tumor cells. The encapsulation into NGs significantly enhances the bioavailability and increases half-lives of MET and DOX by around 20 times. In the F. nucleatum-infected tumor model, the extended retention of swollen NGs and the efficient tumor infiltration and cellular uptake of the discharged f-ZIFD NPs cause 6 times higher DOX levels in tumors than that of free DOX administration. F. nucleatum promotes tumor cell proliferation and tumor growth, and the cascaded releases of MET and f-ZIFD NPs eliminate F. nucleatum to effectively inhibit tumor growth with a significant extension of animal survival. Thus, the hyaluronidase-mediated NG expansion and dual-responsive cascaded drug release have overcome challenges in the release regimen and size paradox of drug delivery carriers to combat bacteria-infected cancer.

Tiny titans- unravelling the potential of polysaccharides and proteins based dissolving microneedles in drug delivery and theranostics: A comprehensive review

In recent years, microneedles (MNs) have emerged as a promising alternative to traditional drug delivery systems in transdermal drug delivery. The use of MNs has demonstrated significant potential in improving patient acceptance and convenience while avoiding the invasiveness of traditional injections. Dissolving, solid, hollow, coated, and hydrogel microneedles are among the various types studied for drug delivery. Dissolving microneedles (DMNs), in particular, have gained attention for their safety, painlessness, patient convenience, and high delivery efficiency. This comprehensive review primarily focuses on different types of microneedles, fabrication methods, and materials used in fabrication of DMNs such as hyaluronic acid, chitosan, alginate, gelatin, collagen, silk fibroin, albumin, cellulose and starch, to list a few. The review also provides an exhaustive discussion on the applications of DMNs, including the delivery of vaccines, cosmetic agents, contraceptives, hormone and genes, and other therapeutic applications like for treating cancer, skin diseases, and diabetes, among others, are covered in this review. Additionally, this review highlights some of the DMN systems that are presently undergoing clinical trials. Finally, the review discusses current advances and trends in DMNs, as well as future prospective directions for this ground-breaking technology in drug delivery.

Synthesizing biomaterials in living organisms

Living organisms fabricate biomacromolecules such as DNA, RNA, and proteins by the self-assembly process. The research on the mechanism of biomacromolecule formation also inspires the exploration of in vivo synthesized biomaterials. By elaborate design, artificial building blocks or precursors can self-assemble or polymerize into functional biomaterials within living organisms. In recent decades, these so-called in vivo synthesized biomaterials have achieved extensive applications in cell-fate manipulation, disease theranostics, bioanalysis, cellular surface engineering, and tissue regeneration. In this review, we classify strategies for in vivo synthesis into non-covalent, covalent, and genetic types. The development of these approaches is based on the chemical principles of supramolecular chemistry and synthetic chemistry, biological cues such as enzymes and microenvironments, and the means of synthetic biology. By summarizing the design principles in detail, some insights into the challenges and opportunities in this field are provided to  enlighten further research.

Developing and scaling up captopril-loaded electrospun ethyl cellulose fibers for sustained-release floating drug delivery

In this work ethyl cellulose (EC) was used as the matrix polymer and loaded with captopril, with the goal to fabricate electrospun fibers as potential sustained-release floating gastro-retentive drug delivery systems. Fibers were prepared with monoaxial and coaxial electrospinning, and both bench-top and scaled-up (needle-based) methods were explored. With monoaxial electrospinning, EC-based fibers in the shape of cylinders and with smooth surfaces were obtained both at 1 and 20 mL/h. For coaxial electrospinning, the drug was encapsulated in the core end fibers generated with core/shell feeding rates of 0.5/1 and 5/10 mL/h. The fibers were cylindrical in shape with a wrinkled surface, and confocal microscopy suggested them to have a core/shell structure. X-ray diffraction and differential scanning calorimetry results showed that all the fibers were amorphous. The encapsulation efficiency of all the formulations was almost 100%. Release studies in simulated gastric fluid indicated that the monoaxial electrospun fibers gave slower release profiles compared with a physical mixture of captopril and EC, but there was still an initial "burst" of release at the start of the experiment. Fibers with low drug-loading (9.09% w/w) showed a slower release than fibers with high loading (23.08% w/w). The coaxial fibers exhibited sustained release profiles with reduced initial burst release. Both monoaxial and coaxial fibers could float on the surface of simulated gastric fluid for over 24 hours at 37 °C. After storage under ambient conditions (19-21°C, relative humidity 30-40%) for 8 weeks, all the fibers remained amorphous and the release profiles had no significant changes compared with fresh fibers. This work thus highlights the potential of coaxial electrospinning for fabricating a sustained-release floating gastro-retentive drug delivery system for captopril.

Remodeling Tumor Immune Microenvironment by Using Polymer-Lipid-Manganese Dioxide Nanoparticles with Radiation Therapy to Boost Immune Response of Castration-Resistant Prostate Cancer

Despite substantial progress in the treatment of castration-resistant prostate cancer (CRPC), including radiation therapy and immunotherapy alone or in combination, the response to treatment remains poor due to the hypoxic and immunosuppressive nature of the tumor microenvironment. Herein, we exploited the bioreactivity of novel polymer-lipid manganese dioxide nanoparticles (PLMDs) to remodel the tumor immune microenvironment (TIME) by increasing the local oxygen levels and extracellular pH and enhancing radiation-induced immunogenic cell death. This study demonstrated that PLMD treatment sensitized hypoxic human and murine CRPC cells to radiation, significantly increasing radiation-induced DNA double-strand breaks and ultimately cell death, which enhanced the secretion of damage-associated molecular patterns, attributable to the induction of autophagy and endoplasmic reticulum stress. Reoxygenation via PLMDs also polarized hypoxic murine RAW264.7 macrophages toward the M1 phenotype, enhancing tumor necrosis factor alpha release, and thus reducing the viability of murine CRPC TRAMP-C2 cells. In a syngeneic TRAMP-C2 tumor model, intravenous injection of PLMDs suppressed, while radiation alone enhanced recruitment of regulatory T cells and myeloid-derived suppressor cells. Pretreatment with PLMDs followed by radiation down-regulated programmed death-ligand 1 and promoted the infiltration of antitumor CD8+ T cells and M1 macrophages to tumor sites. Taken together, TIME modulation by PLMDs plus radiation profoundly delayed tumor growth and prolonged median survival compared with radiation alone. These results suggest that PLMDs plus radiation is a promising treatment modality for improving therapeutic efficacy in radioresistant and immunosuppressive solid tumors.

In situ stimulus-responsive self-assembled nanomaterials for drug delivery and disease treatment

The individual motifs that respond to specific stimuli for the self-assembly of nanomaterials play important roles. In situ constructed nanomaterials are formed spontaneously without human intervention and have promising applications in bioscience. However, due to the complex physiological environment of the human body, designing stimulus-responsive self-assembled nanomaterials in vivo is a challenging problem for researchers. In this article, we discuss the self-assembly principles of various nanomaterials in response to the tissue microenvironment, cell membrane, and intracellular stimuli. We propose the applications and advantages of in situ self-assembly in drug delivery and disease diagnosis and treatment, with a focus on in situ self-assembly at the lesion site, especially in cancer. Additionally, we introduce the significance of introducing exogenous stimulation to construct self-assembly in vivo. Based on this foundation, we put forward the prospects and possible challenges in the field of in situ self-assembly. This review uncovers the relationship between the structure and properties of in situ self-assembled nanomaterials and provides new ideas for innovative drug molecular design and development to solve the problems in the targeted delivery and precision medicine.

Tumor acidity-induced surface charge modulation in covalent nanonetworks for activated cellular uptake: targeted delivery of anticancer drugs and selective cancer cell death

A β-thioester and tertiary amine based covalently cross-linked nanoassembly coined as a nanonetwork (NN) endowed with dual pH responsive features (tumor acidity induced surface charge modulation and endosomal pH triggered controlled degradation) has been designed and synthesized for stable sequestration and sustained release of drug molecules in response to endosomal pH. An amphiphile integrated with tertiary amine and acrylate (ATA) functionalities was synthesized to fabricate the nanonetwork. This amphiphile showed entropically driven self-assembly and micellar nanostructures (nanoassemblies), which can sequester hydrophobic drug molecules at neutral pH. To further stabilize the nanoassemblies and the sequestered drug molecules even below its critical aggregation concentration (CAC), the micellar core was cross-linked via the thiol-acrylate Michael addition click reaction to generate multiple copies of acid labile β-thioester functionalities in the core, which undergo slow hydrolysis at endosomal pH (∼5.0), thus enabling sustained release of the anti-cancer drug doxorubicin at endosomal pH. The nanonetworks showed a significant decrease in drug leakage compared to the nanoassemblies (NAs), which was also justified by a low leakage coefficient calculated from the fluorescence resonance energy transfer experiment. The NN also exhibited dilution insensitivity and high serum stability, whereas the NA disassembled upon dilution and during serum treatment. The biological evaluation revealed tumor extracellular matrix pH (∼6.4-6.8) induced surface charge modulation and cancer cell (HeLa) selective activated cellular uptake of the doxorubicin loaded nanonetwork (NN-DOX). In contrast, the benign nature of NN-DOX towards normal cells (H9c2) suggests excellent cell specificity. Thus, we believe that the ease of synthesis, nanonetwork fabrication reproducibility, robust stability, smart nature of tumor microenvironment sensitive surface charge modulation, boosted tumoral-cell uptake, and triggered drug release will make this system a potential nanomedicine for chemotherapeutic treatments.

Smart Nanosystems for Overcoming Multiple Biological Barriers in Cancer Nanomedicines Transport: Design Principles, Progress, and Challenges

The development of smart nanosystems, which could overcome diverse biological barriers of nanomedicine transport, has received intense scientific interest in improving the therapeutic efficacies of traditional nanomedicines. However, the reported nanosystems generally hold disparate structures and functions, and the knowledge of involved biological barriers is usually scattered. There is an imperative need for a summary of biological barriers and how these smart nanosystems conquer biological barriers, to guide the rational design of the new-generation nanomedicines. This review starts from the discussion of major biological barriers existing in nanomedicine transport, including blood circulation, tumoral accumulation and penetration, cellular uptake, drug release, and response. Design principles and recent progress of smart nanosystems in overcoming the biological barriers are overviewed. The designated physicochemical properties of nanosystems can dictate their functions in biological environments, such as protein absorption inhibition, tumor accumulation, penetration, cellular internalization, endosomal escape, and controlled release, as well as modulation of tumor cells and their resident tumor microenvironment. The challenges facing smart nanosystems on the road heading to clinical approval are discussed, followed by the proposals that could further advance the nanomedicine field. It is expected that this review will provide guidelines for the rational design of the new-generation nanomedicines for clinical use.

Transformable nanodrugs for overcoming the biological barriers in the tumor environment during drug delivery

Drug delivery systems have been studied massively with explosive growth in the last few decades. However, challenges such as biological barriers are still obstructing the delivery efficiency of nanomedicines. Reports have shown that the physicochemical properties, such as the morphologies of nanodrugs, could highly affect their biodistribution and bioavailability. Therefore, transformable nanodrugs that take advantage of different sizes and shapes allow for overcoming multiple biological barriers, providing promising prospects for drug delivery. This review aims to present an overview of the most recent developments of transformable nanodrugs in this emerging field. First, the design principles and transformation mechanisms which serve as guidelines for smart nanodrugs are summarized. Afterward, their applications in overcoming biological barriers, including the bloodstream, intratumoral pressure, cellular membrane, endosomal wrapping, and nuclear membrane, are highlighted. Finally, discussions on the current developments and future perspectives of transformable nanodrugs are given.

Pt(II)-PLGA Hybrid in a pH-Responsive Nanoparticle System Targeting Ovarian Cancer

Platinum-based agents are the main treatment option in ovarian cancer (OC). Herein, we report a poly(lactic-co-glycolic acid) (PLGA) nanoparticle (NP) encapsulating platinum (II), which is targeted to a cell-spanning protein overexpressed in above 90% of late-stage OC, mucin 1 (MUC1). The NP is coated with phospholipid-DNA aptamers against MUC1 and a pH-sensitive PEG derivative containing an acid-labile hydrazone linkage. The pH-sensitive PEG serves as an off-on switch that provides shielding effects at the physiological pH and is shed at lower pH, thus exposing the MUC1 ligands. The pH-MUC1-Pt NPs are stable in the serum and display pH-dependent PEG cleavage and drug release. Moreover, the NPs effectively internalize in OC cells with higher accumulation at lower pH. The Pt (II) loading into the NP was accomplished via PLGA-Pt (II) coordination chemistry and was found to be 1.62 wt.%. In vitro screening using a panel of OC cell lines revealed that pH-MUC1-Pt NP has a greater effect in reducing cellular viability than carboplatin, a clinically relevant drug analogue. Biodistribution studies have demonstrated NP accumulation at tumor sites with effective Pt (II) delivery. Together, these results demonstrate a potential for pH-MUC1-Pt NP for the enhanced Pt (II) therapy of OC and other solid tumors currently treated with platinum agents.

Photodynamic therapy: Innovative approaches for antibacterial and anticancer treatments

Photodynamic therapy is an alternative treatment mainly for cancer but also for bacterial infections. This treatment dates back to 1900 when a German medical school graduate Oscar Raab found a photodynamic effect while doing research for his doctoral dissertation with Professor Hermann von Tappeiner. Unexpectedly, Raab revealed that the toxicity of acridine on paramecium depends on the intensity of light in his laboratory. Photodynamic therapy is therefore based on the administration of a photosensitizer with subsequent light irradiation within the absorption maxima of this substance followed by reactive oxygen species formation and finally cell death. Although this treatment is not a novelty, there is an endeavor for various modifications to the therapy. For example, selectivity and efficiency of the photosensitizer, as well as irradiation with various types of light sources are still being modified to improve final results of the photodynamic therapy. The main aim of this review is to summarize anticancer and antibacterial modifications, namely various compounds, approaches, and techniques, to enhance the effectiveness of photodynamic therapy.

Acid-switchable nanoparticles induce self-adaptive aggregation for enhancing antitumor immunity of natural killer cells

Deficiency of natural killer (NK) cells shows a significant impact on tumor progression and failure of immunotherapy. It is highly desirable to boost NK cell immunity by upregulating active receptors and relieving the immunosuppressive tumor microenvironment. Unfortunately, mobilization of NK cells is hampered by poor accumulation and short retention of drugs in tumors, thus declining antitumor efficiency. Herein, we develop an acid-switchable nanoparticle with self-adaptive aggregation property for co-delivering galunisertib and interleukin 15 (IL-15). The nanoparticles induce morphology switch by a decomposition-metal coordination cascade reaction, which provides a new methodology to trigger aggregation. It shows self-adaptive size-enlargement upon acidity, thus improving drug retention in tumor to over 120 h. The diameter of agglomerates is increased and drug release is effectively promoted following reduced pH values. The nanoparticles activate both NK cell and CD8⁺ T cell immunity in vivo. It significantly suppresses CT26 tumor in immune-deficient BALB/c mice, and the efficiency is further improved in immunocompetent mice, indicating that the nanoparticles can not only boost innate NK cell immunity but also adaptive T cell immunity. The approach reported here provides an innovative strategy to improve drug retention in tumors, which will enhance cancer immunotherapy by boosting NK cells.

Transformable nanoparticles to bypass biological barriers in cancer treatment

Nanomedicine based drug delivery platforms provide an interesting avenue to explore for the future of cancer treatment. Here we discuss the barriers for drug delivery in cancer therapeutics and how nanomaterials have been designed to bypass these blockades through stimuli responsive transformation in the most recent update. Nanomaterials that address the challenges of each step provide a promising solution for new cancer therapeutics.

Recent advancements in enzyme-incorporated nanomaterials: Synthesis, mechanistic formation, and applications

Over the past decade, nanotechnology has been developed and employed across various entities. Among the numerous nanostructured material types, enzyme-incorporated nanomaterials have shown great potential in various fields, as an alternative to biologically derived as well as synthetically developed hybrid structures. The mechanism of incorporating enzyme onto a nanostructure depends on several factors including the method of immobilization, type of nanomaterial, as well as operational and environmental conditions. The prospects of enzyme-incorporated nanomaterials have shown promising results across various applications, such as biocatalysts, biosensors, drug therapy, and wastewater treatment. This is due to their excellent ability to exhibit chemical and physical properties such as high surface-to-volume ratio, recovery and/or reusability rates, sensitivity, response scale, and stable catalytic activity across wide operating conditions. In this review, the evolution of enzyme-incorporated nanomaterials along with their impact on our society due to its state-of-the-art properties, and its significance across different industrial applications are discussed. In addition, the weakness and future prospects of enzyme-incorporated nanomaterials were also discussed to guide scientists for futuristic research and development in this field.

Intratumoral synthesis of transformable metal-phenolic nanoaggregates with enhanced tumor penetration and retention for photothermal immunotherapy

Rationale: Effective photothermal therapy (PTT) remains a great challenge due to the difficulties of delivering photothermal agents with both deep penetration and prolonged retention at tumor lesion spatiotemporally. Methods: Here, we report an intratumoral self-assembled nanostructured aggregate named FerH, composed of a natural polyphenol and a commercial iron supplement. FerH assemblies possess size-increasing dynamic kinetics as a pseudo-stepwise polymerization from discrete nanocomplexes to microscale aggregates. Results: The nanocomplex can penetrate deeply into solid tumors, followed by prolonged retention (> 6 days) due to the in vivo growth into nanoaggregates in the tumor microenvironment. FerH performs a targeting ablation of tumors with a high photothermal conversion efficiency (60.2%). Importantly, an enhanced immunotherapeutic effect on the distant tumor can be triggered when co-administrated with checkpoint-blockade PD-L1 antibody. Conclusions: Such a therapeutic approach by intratumoral synthesis of metal-phenolic nanoaggregates can be instructive to address the challenges associated with malignant tumors.

An update on dual targeting strategy for cancer treatment

The key issue in the treatment of solid tumors is the lack of efficient strategies for the targeted delivery and accumulation of therapeutic cargoes in the tumor microenvironment (TME). Targeting approaches are designed for more efficient delivery of therapeutic agents to cancer cells while minimizing drug toxicity to normal cells and off-targeting effects, while maximizing the eradication of cancer cells. The highly complicated interrelationship between the physicochemical properties of nanoparticles, and the physiological and pathological barriers that are required to cross, dictates the need for the success of targeting strategies. Dual targeting is an approach that uses both purely biological strategies and physicochemical responsive smart delivery strategies to increase the accumulation of nanoparticles within the TME and improve targeting efficiency towards cancer cells. In both approaches, either one single ligand is used for targeting a single receptor on different cells, or two different ligands for targeting two different receptors on the same or different cells. Smart delivery strategies are able to respond to triggers that are typical of specific disease sites, such as pH, certain specific enzymes, or redox conditions. These strategies are expected to lead to more precise targeting and better accumulation of nano-therapeutics. This review describes the classification and principles of dual targeting approaches and critically reviews the efficiency of dual targeting strategies, and the rationale behind the choice of ligands. We focus on new approaches for smart drug delivery in which synthetic and/or biological moieties are attached to nanoparticles by TME-specific responsive linkers and advanced camouflaged nanoparticles.

Strategies of engineering nanomedicines for tumor retention

The retention of therapeutic agents in solid tumors at sufficient concentration and duration is crucial for their antitumor effects. Given the important contribution of nanomedicines to oncology, we herein summarized two major strategies of nanomedicines for tumor retention, such as transformation- and interactions-mediated strategies. The transformation-mediated retention strategy was achieved by enlarging particle size of nanomedicines or modulating the morphology into fibrous structures, while the interactions-mediated retention strategy was accomplished by modulating nanomedicines to promote their interactions with versatile cells or components in tumors. Moreover, we provide some considerations and perspectives of tumor-retaining nanomedicines for effective cancer therapy.

Polymeric Fibers as Scaffolds for Spinal Cord Injury: A Systematic Review

Spinal cord injury (SCI) is a complex neurological condition caused by trauma, inflammation, and other diseases, which often leads to permanent changes in strength and sensory function below the injured site. Changes in the microenvironment and secondary injuries continue to pose challenges for nerve repair and recovery after SCI. Recently, there has been progress in the treatment of SCI with the use of scaffolds for neural tissue engineering. Polymeric fibers fabricated by electrospinning have been increasingly used in SCI therapy owing to their biocompatibility, complex porous structure, high porosity, and large specific surface area. Polymer fibers simulate natural extracellular matrix of the nerve fiber and guide axon growth. Moreover, multiple channels of polymer fiber simulate the bundle of nerves. Polymer fibers with porous structure can be used as carriers loaded with drugs, nerve growth factors and cells. As conductive fibers, polymer fibers have electrical stimulation of nerve function. This paper reviews the fabrication, characterization, and application in SCI therapy of polymeric fibers, as well as potential challenges and future perspectives regarding their application.

Tumor microenvironment-responsive size-switchable drug delivery nanosystems

INTRODUCTION

Compared with ordinary chemotherapeutic drugs, the variable-size nanoparticles (NPs) have better therapeutic effects and fewer side effects.

AREAS COVERED

This review mainly summarizes the strategies used to construct smart, size-tunable nanocarriers based on characteristic factors of tumor microenvironment (TME) to dramatically increase the penetration and retention of drugs within tumors.

EXPERT OPINION

Nanosystems with changeable sizes based on the TME have been extensively studied in the past decade, and their permeability and retention have been greatly improved, making them a very promising treatment for tumors.

Stimuli-Responsive Nanoparticles for Controlled Drug Delivery in Synergistic Cancer Immunotherapy

Cancer immunotherapy has achieved promising clinical progress over the recent years for its potential to treat metastatic tumors and inhibit their recurrences effectively. However, low patient response rates and dose-limiting toxicity remain as major dilemmas for immunotherapy. Stimuli-responsive nanoparticles (srNPs) combined with immunotherapy offer the possibility to amplify anti-tumor immune responses, where the weak acidity, high concentration of glutathione, overexpressions of enzymes, and reactive oxygen species, and external stimuli in tumors act as triggers for controlled drug release. This review highlights the design of srNPs based on tumor microenvironment and/or external stimuli to combine with different anti-tumor drugs, especially the immunoregulatory agents, which eventually realize synergistic immunotherapy of malignant primary or metastatic tumors and acquire a long-term immune memory to prevent tumor recurrence. The authors hope that this review can provide theoretical guidance for the construction and clinical transformation of smart srNPs for controlled drug delivery in synergistic cancer immunotherapy.

Tumor-penetrating iron oxide nanoclusters for T1/T2 dual mode MR imaging-guided combination therapy

A hyaluronic acid (HA)-stabilized iron oxide nanocluster (Fe2O3@PFDH NC) was developed as an intelligent tumor-penetrating theranostic nanoagent for dual-mode MRI guided chemo-photothermal therapy.

Triple cascade nanocatalyst with laser-activatable O2 supply and photothermal enhancement for effective catalytic therapy against hypoxic tumor

Nanozymes have been combined with glucose oxidase (GOx) for dual-enzyme cascade catalytic therapy. However, their catalysis efficiency is restricted because of the hypoxia tumor microenvironment (TME). Although many methods are developed for O₂ supply, the O₂ leakage and consumption of H₂O₂ compromised their practical application. Herein, a biocompatible carbon nitride (C₃N₄)/nanozyme/GOx triple cascade nanocatalyst was designed with laser-activatable O₂ self-supply via water splitting to relieve tumor hypoxia and thus improve the catalysis efficiency. To this end, polydopamine (PDA) nanosphere was prepared and attached with C₃N₄ nanosheet to improve water splitting efficiency and realize photothermal-enhanced catalysis, simultaneously. The PDA@C₃N₄ composite was then coated with MIL-100 (Fe), where GOx was loaded, to form C₃N₄/MIL-100/GOx triple cascade nanocatalyst. The triple cascade catalysis was realized with laser-activatable O₂ supply from PDA@C₃N₄, H₂O₂ generation with GOx, and •OH production from peroxidase-like MIL-100 (Fe) for tumor therapy. Upon 808 nm irradiation, PDA, as a photothermal agent, realized photothermal therapy and enhanced the catalytic therapy. Thus, the synergy of laser-activatable O₂ supply and photothermal enhancement in our triple cascade nanocatalyst improved the performance of catalytic therapy without drug resistance and toxicity to normal tissues.

Strategic Design of Intelligent-Responsive Nanogel Carriers for Cancer Therapy

Owing to the distinctive constituents of tumor tissue from those healthy organs, nanomedicine strategies show significant potentials in smart drug delivery. Nowadays, stimuli-responsive nanogels are playing increasingly important roles in the application of cancer therapy because of their sensitivity to various internal or external physicochemical stimuli, which exhibit site-specific and markedly enhanced drug release. Besides, nanogels are promising as drug carriers because of their porous structures, good biocompatibility, large surface area, and excellent capability with drugs. Taking advantage of multiresponsiveness, recent years have witnessed the rapid evolution of stimulus-responsive nanogels from monoresponsive to multiresponsive systems; however, there lacks a comprehensive review summarizing these reports. In this Review, we discuss the properties, synthesis, and characterization of nanogels. Moreover, tumor microenvironment and corresponding designing strategies for stimuli-response nanogels, both exogenous (temperature, magnetic field, light) and endogenous (pH, biomolecular, redox, ROS, pressure, hypoxia) are summarized on the basis of the recent advances in multistimuli-responsive nanogel systems. Nanogel and two-dimensional material composites show excellent performance in the field of constructing multistimulus-responsive nanoparticles and precise intelligent drug release integrated system for multimodal cancer diagnosis and therapy. Finally, potential progresses and suggestions are provided for the further design of hybrid nanogels based on emerging two-dimensional materials.

Size-Adjustable Nano-Drug Delivery Systems for Enhanced Tumor Retention and Penetration

Over the past decades, nano-drug delivery systems have shown great potential in improving tumor treatment. And the controllability and design flexibility of nanoparticles endow them a broad development space. The particle size is one of the most important factors affecting the potency of nano-drug delivery systems. Large-size (100–200 nm) nanoparticles are more conducive to long circulation and tumor retention, but have poor tumor penetration; small-size (<50 nm) nanoparticles can deeply penetrate tumor but are easily cleared. Most of the current fixed-size nanoparticles are difficult to balance the retention and penetration, while the proposal of size-adjustable nano-drug delivery systems offers a solution to this paradox. Many endogenous and exogenous stimuli, such as acidic pH, upregulated enzymes, temperature, light, catalysts, redox conditions, and reactive oxygen species, can trigger the in situ transformation of nanoparticles based on protonation, hydrolysis, click reaction, phase transition, photoisomerization, redox reaction, etc. In this review, we summarize the principles and applications of stimuli-responsive size-adjustable strategies, including size-enlargement strategies and size-shrinkage strategies. We also propose the challenges faced by size-adjustable nano-drug delivery systems, hoping to promote the development of this strategy.

Smart Nanogatekeepers for Tumor Theranostics

Nanoparticulate drug delivery systems (nano-DDSs) are required to reliably arrive and persistently reside at the tumor site with minimal off-target side effects for clinical theranostics. However, due to the complicated environment and high interstitial pressure in tumor tissue, they can return to the bloodstream and cause secondary side effects in normal organs. Recently, a number of nanogatekeepers have been engineered via structure-transformable/stable strategies to overcome this undesirable dilemma. The emerging structure-transformable nanogatekeepers for tumor imaging and therapy are first overviewed here, particularly for nanogatekeepers undergoing structural transformation in tumor microenvironments, cell membranes, and organelles. Thereafter, intelligent structure-stable nanogatekeepers through reversible activation and artificial individualization receptors are overviewed. Finally, the ongoing challenges and prospects of nanogatekeepers for clinical translation are briefly discussed.

Multimodal obstruction of tumorigenic energy supply via bionic nanocarriers for effective tumor therapy

Sufficient energy generation based on effective transport of nutrient via abundant blood vessels in tumor tissue and subsequent oxidative metabolism in mitochondria is critical for growth, proliferation and migration of tumor. Thus the strategy to cut off this transport pathway (blood vessels) and simultaneously close the power house (mitochondria) is highly desired for tumor treatment. Herein, we fabricated a bionic nanocarrier with core-shell-corona structure to give selective and effective tumor therapy via stepwise destruction of existed tumor vessel, inhibition of tumor angiogenesis and dysfunction of tumor mitochondria. The core of this bionic nanocarrier consists of combretastatin A4 phosphate (CA4P) and vitamin K₂ (VK₂) co-loaded mesoporous silica nanoparticle (MSNs), which is in charge of the vasculature destruction and mitochondrial dysfunction after cargos release. The N-tert-butylacrylamide (TBAM) and tri-sulfated N-acetylglucosamine (TSAG) shell served as artificial affinity reagent against vascular endothelial growth factor (VEGF) for angiogenesis inhibition. As to guarantee that these actions only happened in tumor, the hyaluronic acid (HA) corona was introduced to endow the nanocarrier with tumor targeting property and stimuli-responsiveness for accurate therapy. Both in vitro and in vivo results indicated that the CA4P/VK₂-MSNs-TBAM/TSAG-HA (CVM_MGH for short) nanocarrier combined well-controllable manipulation of tumor vasculature and tumor mitochondria to effectivly cut off the tumorigenic energy supply, which performed significant inhibition of tumor growth, demonstrating the great candidate of our strategy for effective tumor therapy.

Bioresponsive micro-to-nano albumin-based systems for targeted drug delivery against complex fungal infections

As a typical human pathogenic fungus, Cryptococcus neoformans is a life-threatening invasive fungal pathogen with a worldwide distribution causing ∼700,000 deaths annually. Cryptococcosis is not just an infection with multi-organ involvement, intracellular survival and extracellular multiplication of the fungus also play important roles in the pathogenesis of C. neoformans infections. Because adequate accumulation of drugs at target organs and cells is still difficult to achieve, an effective delivery strategy is desperately required to treat these infections. Here, we report a bioresponsive micro-to-nano (MTN) system that effectively clears the C. neoformans in vivo. This strategy is based on our in-depth study of the overexpression of matrix metalloproteinase 3 (MMP-3) in infectious microenvironments (IMEs) and secreted protein acidic and rich in cysteine (SPARC) in several associated target cells. In this MTN system, bovine serum albumin (BSA, a natural ligand of SPARC) was used for the preparation of nanoparticles (NPs), and then microspheres were constructed by conjugation with a special linker, which mainly consisted of a BSA-binding peptide and an MMP-3-responsive peptide. This MTN system was mechanically captured by the smallest capillaries of the lungs after intravenous injection, and then hydrolyzed into BSA NPs by MMP-3 in the IMEs. The NPs further targeted the lung tissue, brain and infected macrophages based on the overexpression of SPARC, reaching multiple targets and achieving efficient treatment. We have developed a size-tunable strategy where microspheres "shrink" to NPs in IMEs, which effectively combines active and passive targeting and may be especially powerful in the fight against complex fungal infections.

Phototriggered Self-Adaptive Functionalized MOC-Based Drug Delivery Platform Promises High Antitumor Efficacy

Due to their great stability and special cavities, metal-organic cages (MOCs) are increasingly considered as promising nanocarriers for drug delivery. However, the size and surface dilemmas restrict their further biomedical applications. The ultrasmall size of MOCs facilitates tumor penetration but suffers from quick clearance and poor accumulation at the tumor site. Hydrophobicity of MOC surfaces improves internalization into tumor cells while causing low blood circulation time as well as poor biocompatibility. Therefore, it remains challenging for the MOC-based drug delivery nanoplatform to realize high therapeutic efficacy because it requires different or even opposite dimensions and surface characteristics in different steps of circulation, penetration, accumulation, and internalization processes. In this study, an unprecedented phototriggered self-adaptive platform (ZnPc@polySCage) is developed by integrating functionalized MOCs and a photodynamic therapy based reactive oxygen species responsive strategy to realize high-efficiency tumor-specific therapy. ZnPc@polySCage remains hydrophilic and stealthy during circulation, and retains its small original size for tumor penetration, while transforming to a larger size for effective accumulation and hydrophobic for enhanced internalization under laser irradiation in tumor tissue. With these essential transitions, ZnPc@polySCage demonstrates prominent antitumor effects. Overall, the work provides an advantageous strategy for functional MOC-based platforms and biomedical applications.

Time-programmed activation of dual polyprodrugs for synergistic cascade oxidation-chemotherapy

Combination therapy using multiple drugs with time-programmed administration is promising for enhanced cancer treatment. However, it is still challenging to achieve time-programmed drug release from a single nanocarrier. Here, dual polyprodrugs of hemicyanine dye (CyNH₂) and doxorubicin (DOX) are developed to achieve time-programmed prodrug activation for synergistic cascade oxidation therapy and chemotherapy. The polyprodrug NP_DOX/Cy, composed of CyNH₂, is modified with a glutathione (GSH)-responsive disulfate group, while DOX is modified with a reactive oxygen species (ROS)-response thioketal (TK) group. Upon uptake by cancer cells overexpressing GSH, CyNH₂ can be activated quickly and accumulate in the mitochondria to induce mitochondrial damage and ROS upregulation, thus achieving subsequent burst activation of DOX through the ROS-triggered cleavage of the TK linker. The early activation of CyNH₂ makes the cancer cells more sensitive to subsequent DOX treatment for a synergistic effect of from oxidation therapy and chemotherapy. Therefore, the polyprodrug with time-programmed drug activation developed in this work provides a promising strategy for synergistic cancer therapy.

Near-infrared light-controllable MXene hydrogel for tunable on-demand release of therapeutic proteins

Precise delivery of therapeutic protein drugs that specifically modulate desired cellular responses is critical in clinical practice. However, the spatiotemporal regulation of protein drugs release to manipulate the target cell population in vivo remains a huge challenge. Herein, we have rationally developed an injectable and Near-infrared (NIR) light-responsive MXene-hydrogel composed of Ti₃C₂, agarose, and protein that enables flexibly and precisely control the release profile of protein drugs to modulate cellular behaviors with high spatiotemporal precision remotely. As a proof-of-concept study, we preloaded hepatic growth factor (HGF) into the MXene@hydrogel (MXene@agarose/HGF) to activate the c-Met-mediated signaling by NIR light. We demonstrated NIR light-instructed cell diffusion, migration, and proliferation at the user-defined localization, further promoting angiogenesis and wound healing in vivo. Our approach's versatility was validated by preloading tumor necrotic factor-α (TNF-α) into the composite hydrogel (MXene@agarose/TNF-α) to promote the pro-apoptotic signaling pathway, achieving the NIR light-induced programmed cell deaths (PCD) of tumor spheroids. Taking advantage of the deep-tissue penetrative NIR light, we could eradicate the deep-seated tumors in a xenograft model exogenously. Therefore, the proposed MXene-hydrogel provides the impetus for developing therapeutic synthetic materials for light-controlled drug release under thick tissue, which will find promising applications in regenerative medicine and tumor therapy. STATEMENT OF SIGNIFICANCE: Current stimuli-responsive hydrogels for therapeutic proteins delivery mainly depend on self-degradation, passive diffusion, or the responsiveness to cues relevant to diseases. However, it remains challenging to spatiotemporally deliver protein-based drugs to manipulate the target cell population in vivo in an "on-demand" manner. Therefore, we have rationally constructed an injectable and Near-infrared (NIR) light-responsive composite hydrogel by embedding Ti₃C₂ MXene and protein drugs within an agarose hydrogel to enable the remote control of protein drugs delivery with high spatiotemporal precision. The NIR light-controlled release of the growth factor or cytokine has been carried out to regulate receptor-mediated cellular behaviors under deep tissue for skin wound healing or cancer therapy. This system will provide the potential for precision medicine through the development of intelligent drug delivery systems.

Smart Cargo Delivery System based on Mesoporous Nanoparticles for Bone Disease Diagnosis and Treatment

Bone diseases constitute a major issue for modern societies as a consequence of progressive aging. Advantages such as open mesoporous channel, high specific surface area, ease of surface modification, and multifunctional integration are the driving forces for the application of mesoporous nanoparticles (MNs) in bone disease diagnosis and treatment. To achieve better therapeutic effects, it is necessary to understand the properties of MNs and cargo delivery mechanisms, which are the foundation and key in the design of MNs. The main types and characteristics of MNs for bone regeneration, such as mesoporous silica (mSiO2 ), mesoporous hydroxyapatite (mHAP), mesoporous calcium phosphates (mCaPs) are introduced. Additionally, the relationship between the cargo release mechanisms and bone regeneration of MNs-based nanocarriers is elucidated in detail. Particularly, MNs-based smart cargo transport strategies such as sustained cargo release, stimuli-responsive (e.g., pH, photo, ultrasound, and multi-stimuli) controllable delivery, and specific bone-targeted therapy for bone disease diagnosis and treatment are analyzed and discussed in depth. Lastly, the conclusions and outlook about the design and development of MNs-based cargo delivery systems in diagnosis and treatment for bone tissue engineering are provided to inspire new ideas and attract researchers' attention from multidisciplinary areas spanning chemistry, materials science, and biomedicine.

Biomaterials-Based Delivery of Therapeutic Antibodies for Cancer Therapy

Considerable breakthroughs in the treatment of malignant tumors using antibody drugs, especially immunomodulating monoclonal antibodies (mAbs), have been made in the past decade. Despite technological advancements in antibody design and manufacture, multiple challenges face antibody-mediated cancer therapy, such as instability in vivo, poor tumor penetration, limited response rate, and undesirable off-target cytotoxicity. In recent years, an increasing number of biomaterials-based delivery systems have been reported to enhance the antitumor efficacy of antibody drugs. This review summarizes the advances and breakthroughs in integrating biomaterials with therapeutic antibodies for enhanced cancer therapy. A brief introduction to the principal mechanism of antibody-based cancer therapy is first established, and then various antibody immobilization strategies are provided. Finally, the current state-of-the-art in biomaterials-based antibody delivery systems and their applications in cancer treatment are summarized, highlighting how the delivery systems augment the therapeutic efficacy of antibody drugs. The outlook and perspective on biomaterials-based delivery of antitumor antibodies are also discussed.

Protein-Based Nanomedicine for Therapeutic Benefits of Cancer

Proteins, a type of natural biopolymer that possess many prominent merits, have been widely utilized to engineer nanomedicine for fighting against cancer. Motivated by their ever-increasing attention in the scientific community, this review aims to provide a comprehensive showcase on the current landscape of protein-based nanomedicine for cancer therapy. On the basis of role differences of proteins in nanomedicine, protein-based nanomedicine engineered with protein therapeutics, protein carriers, enzymes, and composite proteins is introduced. The cancer therapeutic benefits of the protein-based nanomedicine are also discussed, including small-molecular therapeutics-mediated therapy, macromolecular therapeutics-mediated therapy, radiation-mediated therapy, reactive oxygen species-mediated therapy, and thermal effect-mediated therapy. Lastly, future developments and potential challenges of protein-based nanomedicine are elucidated toward clinical translation. It is believed that protein-based nanomedicine will play a vital role in the battle against cancer. We hope that this review will inspire extensive research interests from diverse disciplines to further push the developments of protein-based nanomedicine in the biomedical frontier, contributing to ever-greater medical advances.

Synthesis and biological evaluation of fluorescent hyaluronic acid modified amorphous calcium phosphate drug carriers for tumor-targeting

Cancer is becoming a major threat to national public health security. The integration of disease diagnosis and monitoring with treatment has become a hot spot for researchers. The amorphous calcium phosphate (ACP) nanoparticles prepared by the group in the previous stage could not precisely treat the lesion without tumor targeting and imaging characteristics. In this paper, water-soluble hyaluronic acid fluorescent carbon nanoparticles (HA-FCNs) were prepared and co-interacting with ACP nanoparticles to form hyaluronic acid fluorescent carbon/amorphous calcium phosphate (HA-FCNs/ACP) nanoparticles. The basic characteristics were characterized and the biological characteristics before and after drug loading were evaluated. HA-FCNs/ACP nanoparticles have good hemocompatibility, pH responsiveness, and enzymatic release. HA-FCNs and HA-FCNs/ACP nanoparticles are dispersed in the cytoplasm through the overexpressed CD44 receptors, which are actively targeted into A549 cells. Besides, the migration of A549 cells would be inhibited after cells were treated with drug-loaded nanomaterials. Therefore, the as-prepared nanoparticles can be used to monitor and treat focal sites through tumor-targeting bioimaging, pH-responsive, and enzymatic drug release properties, thus enabling integrated diagnosis and treatment.

Quadruple-responsive nanoparticle-mediated targeted combination chemotherapy for metastatic breast cancer

The synergism of combination chemotherapy can only be achieved under specific drug ratios. Herein, hyaluronic acid (HA)-functionalized regenerated silk fibroin-based nanoparticles (NPs) were used to concurrently deliver curcumin (CUR) and 5-fluorouracil (5-FU) at various weight ratios (3.3 : 1, 1.6 : 1, 1.1 : 1, 1 : 1, and 1 : 1.2) to breast tumor cells. The generated HA-CUR/5-FU-NPs were found to have desirable particle sizes (around 200 nm), narrow size distributions, and negative zeta potentials (about -26.0 mV). Interestingly, these NPs showed accelerated drug release rates when they were exposed to buffers that mimicked the multi-hallmarks in the tumor microenvironment (pH/hydrogen peroxide/glutathione/hyaluronidase). The surface functionalization of NPs with HA endowed them with in vitro and in vivo breast tumor-targeting properties. Furthermore, we found that the co-loading of CUR and 5-FU in HA-functionalized NPs exhibited obvious synergistic anti-cancer, pro-apoptotic, and anti-migration effects, and the strongest synergism was found at the CUR/5-FU weight ratio of 1 : 1.2. Most importantly, mice experiments revealed that HA-CUR/5-FU-NPs (1 : 1.2) showed a superior anti-cancer activity against metastatic breast cancer compared to the single drug-loaded NPs and non-functionalized CUR/5-FU-NPs (1 : 1.2). Collectively, these results demonstrate that HA-CUR/5-FU-NPs (1 : 1.2) can be exploited as a robust nanococktail for the treatment of breast cancer and its lung metastasis.

Smart transformable nanomedicines for cancer therapy

Despite that great progression has been made in nanoparticulate drug delivery systems (nano-DDS), multiple drug delivery dilemmas still impair the delivery efficiency of nanomedicines. Rational design of smart transformable nano-DDS based on the in vivo drug delivery process represents a promising strategy for overcoming delivery obstacle of nano-DDS. In recent years, tremendous efforts have been devoted to developing smart transformable anticancer nanomedicines. Herein, we provide a review to outline the advances in this emerging field. First, smart size-reducible nanoparticles (NPs) for deep tumor penetration are summarized, including carrier degradation-induced, protonation-triggered and photobleaching-induced size reduction. Second, emerging transformable nanostructures for various therapeutic applications are discussed, including prolonging tumor retention, reversing drug-resistance, inhibiting tumor metastasis, preventing tumor recurrence and non-pharmaceutical therapy. Third, shell-detachable nanocarriers are introduced, focusing on chemical bonds breaking-initiated, charge repulsion-mediated and exogenous stimuli-triggered shell detachment approaches. Finally, the future perspectives and challenges of transformable nanomedicines in clinical cancer therapy are highlighted.