Hierarchically stimuli-responsive nanovectors for improved tumor penetration and programed tumor therapy

pH-responsive oxygen self-sufficient smart nanoplatform for enhanced tumor chemotherapy and photodynamic therapy

Premature drug release in chemotherapy and hypoxic conditions in photodynamic therapy (PDT) are perplexing problems in tumor treatment. Thus, it is of great significance to develop the novel therapeutic system with controllable drug release and effective oxygen generation. Herein, a pH-responsive oxygen self-sufficient smart nanoplatform (named DHCCC), integrating hollow mesoporous silica nanoparticles (HMSNs), chitosan (CS), doxorubicin hydrochloride (DOX), chlorin e6 (Ce6) and catalase (CAT), is fabricated to enhance the tumor therapeutic efficacy efficiently through avoiding premature drug release and mitigating hypoxia of tumor microenvironment (TME). The drug DOX can be efficiently loaded into the HMSNs with large cavity and be controllable released because of the pH responsiveness of CS to the weak acidic TME, thereby elevating the chemotherapy efficacy. Meanwhile, CAT can catalyze the decomposition of endogenous hydrogen peroxide in situ generating oxygen to alleviate the hypoxia and enhance the PDT efficiency considerably. In vitro and in vivo results demonstrate that the combined chemo-photodynamic therapy based on the DHCCC nanoplatform exerts more effective antitumor efficacy than chemotherapy or PDT alone. The current study provides a promising inspiration to construct the pH-responsive oxygen self-sufficient smart nanomedicine with potentials to prevent premature drug leakage and overcome hypoxia for efficient tumor therapy.

A chitosan-camouflaged nanomedicine triggered by hierarchically stimuli to release drug for multimodal imaging-guided chemotherapy of breast cancer

Breast cancer remains one of the most intractable diseases, especially the malignant form of metastasis, with which the cancer cells are hard to track and eliminate. Herein, the common known carbohydrate polymer chitosan (CS) was innovatively used as a shelter for the potent tumor-killing agent. The designed nanoparticles (NPs) not only enhance the solubility of hydrophobic paclitaxel (PTX), but also provide a "hide" effect for cytotoxic PTX in physiological condition. Moreover, coupled with the photothermal (PTT) properties of MoS2, results in a potent chemo/PTT platform. The MoS2@PTX-CS-K237 NPs have a uniform size (135 ± 17 nm), potent photothermal properties (η = 31.5 %), and environment-responsive (low pH, hypoxia) and near infrared (NIR) laser irradiation-triggered PTX release. Through a series of in vitro and in vivo experiments, the MoS2@PTX-CS-K237 showed high affinity and specificity for breast cancer cells, impressive tumor killing capacity, as well as the effective inhibitory effect of metastasis. Benefit from the unique optical properties of MoS2, this multifunctional nanomedicine also exhibited favorable thermal/PA/CT multimodality imaging effect on tumor-bearing mice. The system developed in this work represents the advanced design concept of hierarchical stimulus responsive drug release, and merits further investigation as a potential nanotheranostic platform for clinical translation.

Nanoparticles with transformable physicochemical properties for overcoming biological barriers

In recent years, tremendous progress has been made in the development of nanomedicines for advanced therapeutics, yet their unsatisfactory targeting ability hinders the further application of nanomedicines. Nanomaterials undergo a series of processes, from intravenous injection to precise delivery at target sites. Each process faces different or even contradictory requirements for nanoparticles to pass through biological barriers. To overcome biological barriers, researchers have been developing nanomedicines with transformable physicochemical properties in recent years. Physicochemical transformability enables nanomedicines to responsively switch their physicochemical properties, including size, shape, surface charge, etc., thus enabling them to cross a series of biological barriers and achieve maximum delivery efficiency. In this review, we summarize recent developments in nanomedicines with transformable physicochemical properties. First, the biological dilemmas faced by nanomedicines are analyzed. Furthermore, the design and synthesis of nanomaterials with transformable physicochemical properties in terms of size, charge, and shape are summarized. Other switchable physicochemical parameters such as mobility, roughness and mechanical properties, which have been sought after most recently, are also discussed. Finally, the prospects and challenges for nanomedicines with transformable physicochemical properties are highlighted.

A multi-bioresponsive self-assembled nano drug delivery system based on hyaluronic acid and geraniol against liver cancer

Herein, a multi-bioresponsive self-assembled nano-drug delivery system (HSSG) was constructed by conjugating the anticancer drug Geraniol (GER) to hyaluronic acid (HA) via a disulfide bond. The HSSG NPs displayed a uniform spherical shape with an average diameter of ∼110 nm, maintained high stability, and realized controlled drug release in the tumor microenvironment (pH/glutathione/hyaluronidase). Results of fluorescence microscopy and flow cytometry verified that HSSG NPs were selectively uptaken by human hepatocellular carcinoma cell lines HepG2 and Huh7 via CD44 receptor-mediated internalization. Studies on H22 tumor-bearing mice demonstrate that HSSG NPs could effectively accumulate at the tumor site for a long period. In vitro and in vivo studies show that HSSG NPs significantly promoted the death of cancer cells while reducing the toxicity as compared to GER. Therefore, the HSSG NPs have great potential in the treatment of tumors.

Stimuli-responsive nanocarrier delivery systems for Pt-based antitumor complexes: a review

Platinum-based anticancer drugs play a crucial role in the clinical treatment of various cancers. However, the application of platinum-based drugs is heavily restricted by their severe toxicity and drug resistance/cross resistance. Various drug delivery systems have been developed to overcome these limitations of platinum-based chemotherapy. Stimuli-responsive nanocarrier drug delivery systems as one of the most promising strategies attract more attention. And huge progress in stimuli-responsive nanocarrier delivery systems of platinum-based drugs has been made. In these systems, a variety of triggers including endogenous and extracorporeal stimuli have been employed. Endogenous stimuli mainly include pH-, thermo-, enzyme- and redox-responsive nanocarriers. Extracorporeal stimuli include light-, magnetic field- and ultrasound responsive nanocarriers. In this review, we present the recent advances in stimuli-responsive drug delivery systems with different nanocarriers for improving the efficacy and reducing the side effects of platinum-based anticancer drugs.

Design of Disintegrable Nanoassemblies to Release Multiple Small-Sized Nanoparticles

The therapeutic and diagnostic effects of nanoparticles depend on the efficiency of their delivery to targeted tissues, such as tumors. The size of nanoparticles, among other characteristics, plays a crucial role in determining their tissue penetration and retention. Small nanoparticles may penetrate deeper into tumor parenchyma but are poorly retained, whereas large ones are distributed around tumor blood vessels. Thus, compared to smaller individual nanoparticles, assemblies of such nanoparticles due to their larger size are favorable for prolonged blood circulation and enhanced tumor accumulation. Upon reaching the targeted tissues, nanoassemblies may dissociate at the target region and release the smaller nanoparticles, which is beneficial for their distribution at the target site and ultimate clearance. The recent emerging strategy that combines small nanoparticles into larger, biodegradable nanoassemblies has been demonstrated by several groups. This review summarizes a variety of chemical and structural designs for constructing stimuli-responsive disintegrable nanoassemblies as well as their different disassembly routes. These nanoassemblies have been applied as demonstrators in the fields of cancer therapy, antibacterial infection, ischemic stroke recovery, bioimaging, and diagnostics. Finally, we summarize stimuli-responsive mechanisms and their corresponding nanomedicine designing strategies, and discuss potential challenges and barriers towards clinical translation.

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

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

Boosting cisplatin chemotherapy by nanomotor-enhanced tumor penetration and DNA adducts formation

Despite many nano-based strategies devoted to delivering cisplatin for tumor therapy, its clinical benefits are compromised by poor tissue penetration and limited DNA adducts formation of the drug. Herein, a cisplatin loading nanomotor based janus structured Ag-polymer is developed for cisplatin delivery of deeper tissue and increased DNA adducts formation. The nanomotor displayed a self‐propelled tumor penetration fueled by hydrogen peroxide (H₂O₂) in tumor tissues, which is catalytically decomposed into a large amount of oxygen bubbles by Ag nanoparticles (NPs). Notably, cisplatin could elevate the intracellular H₂O₂ level through cascade reactions, further promote the degradation of Ag NPs accompanied with the Ag⁺ release, which could downregulate intracellular Cl⁻ through the formation of AgCl precipitate, thereby enhancing cisplatin dechlorination and Pt–DNA formation. Moreover, polymer can also inhibit the activity of ALKBH2 (a Fe²⁺-dependent DNA repair enzyme) by chelating intracellular Fe²⁺ to increase the proportion of irreparable Pt–DNA cross-links. It is found that deep tissue penetration, as well as the increased formation and maintenance of Pt–DNA adducts induced by the nanomotor afford 80% of tumor growth inhibition with negligible toxicity. This work provides an important perspective of resolving chemotherapeutic barriers for boosting cisplatin therapy.

Nano-drug delivery system with enhanced tumour penetration and layered anti-tumour efficacy

The low delivery efficiency of nano-drugs and limited tumour penetration are still huge challenges in treating solid tumours. Herein, we developed a pH-responsive nano-drug delivery system, CALS/PDMA@DOX, with a size conversion-layered delivery function. The system is composed of a pH-responsive cationic liposome loaded with DOX (CALS) and a polyamidoamine dendrimer loaded with DOX (PAMAM@DOX) modified with 2,3-dimethylmaleic anhydride (PDMA@DOX) using electrostatic adsorption. In the tumour microenvironment, the positively-charged large-size CALS and the positively-charged small-size PAMAM@DOX were dissociated to exert anti-tumour effects. CALS preferentially targeted tumour angiogenesis endothelial cells. Because of its small size and positive charge, PAMAM@DOX showed excellent tumour penetration. Significant tumour suppression by the system in vivo was confirmed in a 4T1 tumour xenograft mouse model. This pH-triggered size-switching layered delivery nanosystem is a safe and effective cancer treatment delivery platform that improves drug permeability and therapeutic efficacy.

Polysaccharide/mesoporous silica nanoparticle-based drug delivery systems: A review

Mesoporous silica nanoparticles (MSNs) have been well-researched in the design and fabrication of advanced drug delivery systems (DDSs) due to their advantages such as good biocompatibility, large specific surface area and pore volume for drug loading, easily surface modification, adjusted size and good thermal/chemical stability. For MSN-based DDSs, gate materials are also necessary. And natural polysaccharides, one kind of the most abundant natural resource, have been widely applied as the "gatekeepers" in MSN-based DDSs. Polysaccharides are cheap and rich in sources with good biocompatibility, and some of them have important biological functions. In this review article, polysaccharides including chitosan, hyaluronic acid, sodium alginate and dextran, et al. are briefly introduced. And the preparation processes and properties such as controlled drug release, cancer targeting and disease diagnosis of functional polysaccharide/MSN-based DDSs are discussed.

Constructing nanocomplexes by multicomponent self-assembly for curing orthotopic glioblastoma with synergistic chemo-photothermal therapy

The blood-brain barrier (BBB) is one of the major limitations of glioblastoma therapy in the clinic. Nanodrugs have shown great potential for glioblastoma therapy. Herein, we purposefully developed a multicomponent self-assembly nanocomplex with very high drug loading content for curing orthotopic glioblastoma with synergistic chemo-photothermal therapy. The nanocomplex consisted of self-assembled pH-responsive nanodrugs derived from amino acid-conjugated camptothecin (CPT) and canine dyes (IR783) coated with peptide Angiopep-2-conjugated copolymer of Ang-PEG-g-PLL. Specifically, the carrier-free nanocomplex exhibited a high drug loading content (up to 62%), good biocompatibility, and effective glioma accumulation ability. Moreover, the nanocomplex displayed good stability and pH-responsive behavior ex vivo. Both in vitro and in vivo results revealed that the nanocomplex could effectively cross the BBB and target glioma cells. Furthermore, the combination of chemotherapy and photothermal therapy of the nanocomplex achieved a better therapeutic effect, longer survival time, and minimized toxic side effects in orthotopic glioblastoma tumor-bearing nude mice. Overall, we modified the chemotherapeutic drug CPT so that it could self-assemble with other molecules into nanoparticles, which providing an alternative for the preparation of the carrier-free nanodrugs. The results highlighted the potential of self-assembly nanodrugs as a novel platform for effective glioblastoma therapy.

Recent progress on charge-reversal polymeric nanocarriers for cancer treatments

Nanocarriers (NCs) for delivery anticancer therapeutics have been under development for decades. Although great progress has been achieved, the clinic translation is still in the infancy. The key challenge lies in the biological barriers which lie between the NCs and the target spots, including blood circulation, tumor penetration, cellular uptake, endo-/lysosomal escape, intracellular therapeutics release and organelle targeting. Each barrier has its own distinctive microenvironment and requires different surface charge. To address this challenge, charge-reversal polymeric NCs have been a hot topic, which are capable of overcoming each delivery barrier, by reversing their charges in response to certain biological stimuli in the tumor microenvironment. In this review, the triggering mechanisms of charge reversal, including pH, enzyme and redox approaches are summarized. Then the corresponding design principles of charge-reversal NCs for each delivery barrier are discussed. More importantly, the limitations and future prospects of charge-reversal NCs in clinical applications are proposed.

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.

Advances in Multiple Stimuli-Responsive Drug-Delivery Systems for Cancer Therapy

Nanomedicines afford unique advantages in therapeutic intervention against tumors. However, conventional nanomedicines have failed to achieve the desired effect against cancers because of the presence of complicated physiological fluids and the tumor microenvironment. Stimuli-responsive drug-delivery systems have emerged as potential tools for advanced treatment of cancers. Versatile nano-carriers co-triggered by multiple stimuli in different levels of organisms (eg, extracorporeal, tumor tissue, cell, subcellular organelles) have aroused widespread interest because they can overcome sequential physiological and pathological barriers to deliver diverse therapeutic “payloads” to the desired targets. Furthermore, multiple stimuli-responsive drug-delivery systems (MSR-DDSs) offer a good platform for co-delivery of agents and reversing multidrug resistance. This review affords a comprehensive overview on the “landscape” of MSR-DDSs against tumors, highlights the design strategies of MSR-DDSs in recent years, discusses the putative advantage of oncotherapy or the obstacles that so far have hindered the clinical translation of MSR-DDSs.

Targeted polymeric nanoparticles for drug delivery to hypoxic, triple-negative breast tumors

High recurrence and metastasis to vital organs are the major characteristics of triple-negative breast cancer (TNBC). Low vascular oxygen tension promotes resistance to chemo- and radiation therapy. Neuropilin-1 (NRP-1) receptor is highly expressed on TNBC cells. The tumor-penetrating iRGD peptide interacts with the NRP-1 receptor, triggers endocytosis and transcytosis, and facilitates penetration. Herein, we synthesized a hypoxia-responsive diblock PLA-diazobenzene-PEG copolymer and prepared self-assembled hypoxia-responsive polymersomes (Ps) in an aqueous buffer. The iRGD peptide was incorporated into the polymersome structure to make hypoxia-responsive iRGD-conjugated polymersomes (iPs). Doxorubicin (DOX) was encapsulated in the polymersomes to prepare both targeted and non-targeted hypoxia-responsive polymersomes (DOX-iPs and DOX-Ps, respectively). The polymeric nanoparticles released less than 30% of their encapsulated DOX within 12 hours under normoxic conditions (21% oxygen), whereas under hypoxia (2% Oxygen), doxorubicin release remarkably increased to over 95%. The targeted polymersomes significantly decreased TNBC cells' viability in monolayer and spheroid cultures under hypoxia compared to normoxia. Animal studies displayed that targeted polymersomes significantly diminished tumor growth in xenograft nude mice. Overall, the targeted polymersomes exhibited potent anti-tumor activity in monolayer, spheroid, and animal models of TNBC. With further developments, the targeted nanocarriers discussed here might have the translational potential as drug carriers for the treatment of TNBC.

Enhancement of tumour penetration by nanomedicines through strategies based on transport processes and barriers

Nanomedicines for antitumour therapy have been widely studied in recent decades, but only a few have been used in clinical applications. One of the most important reasons is the poor tumour permeability of the nanomedicines. In this three-part review, intravascular, transvascular and extravascular transport were introduced one by one according to their roles in the overall process of nanomedicine transport into tumours. Transportation obstacles, such as elevated interstitial fluid pressure (IFP), abnormal blood vessels, dense tumour extracellular matrix (ECM) and binding site barriers (BSB), were each discussed in the context of the respective transport processes. Furthermore, homologous resolution strategies were summarized on the basis of each transportation obstacle, such as the normalization of blood vessels, regulation of the tumour microenvironment (TME) and application of transformable nanoparticles. At the end of this review, we propose holistic, concrete, and innovative views for better tumour penetration of nanomedicines.

Small Morph Nanoparticles for Deep Tumor Penetration via Caveolae-Mediated Transcytosis

The tumor penetration of nanomedicines constitutes a great challenge in the treatment of solid tumors, leading to the highly compromised therapeutic efficacy of nanomedicines. Here, we developed small morph nanoparticles (PDMA) by modifying polyamidoamine (PAMAM) dendrimers with dimethylmaleic anhydride (DMA). PDMA achieved deep tumor penetration via an active, energy-dependent, caveolae-mediated transcytosis, which circumvented the obstacles in the process of deep penetration. PDMA remained negatively charged under normal physiological conditions and underwent rapid charge reversal from negative to positive under acidic conditions in the tumor microenvironment (pH < 6.5), which enhanced their uptake by tumor cells and their deep penetration into tumor tissues in vitro and in vivo. The deep tumor penetration of PDMA was achieved mainly by caveolae-mediated transcytosis, which could be attributed to the small sizes (5-10 nm) and positive charge of the morphed PDMA. In vivo studies demonstrated that PDMA exhibited increased tumor accumulation and doxorubicin-loaded PDMA (PDMA/DOX) showed better antitumor efficacy. Overall, the small morph PDMA for enhanced deep tumor penetration via caveolae-mediated transcytosis could provide new inspiration for the design of anticancer drug delivery systems.

Cell Type-Dependent Specificity and Anti-Inflammatory Effects of Charge-Reversible MSNs-COS-CMC for Targeted Drug Delivery in Cervical Carcinoma

The surface charge of nanocarriers inevitably affects drug delivery efficiency; however, the cancer cell specificity, anti-inflammatory effects, and charge-reversal points remain to be further addressed in biomedical applications. The aim of this study was to comprehensively assess the cancer cell specificity of DOX-loaded mesoporous silica-chitosan oligosaccharide-carboxymethyl chitosan nanoparticles (DOX@MSNs-COS-CMC) in MCF-7 and HeLa cells, inhibit the production of inflammatory cytokines, and improve the drug accumulation in the tumor site. Intracellular results reveal that the retention time prolonged to 48 h in both HeLa and MCF-7 cells at pH 7.4. However, DOX@MSNs-COS-CMC exhibited a cell type-dependent cytotoxicity and enhanced intracellular uptake in HeLa cells at pH 6.5, due to the clathrin-mediated endocytosis and macropinocytosis in HeLa cells in comparison with the vesicular transport in MCF-7 cells. Moreover, Pearson's correlation coefficient value significantly decreased to 0.25 after 8 h, prompting endosomal escape and drug delivery into the HeLa nucleus. After the treatment of MSNs-COS-CMC at 200 μg/mL, the inflammatory cytokines IL-6 and TNF-α level decreased by 70% and 80%, respectively. Tumor inhibition of DOX@MSNs-COS-CMC was 0.4 times higher than free DOX, alleviating cardiotoxicity and inflammation in the HeLa xenograft tumor model. Charge-reversible DOX@MSNs-COS-CMC could be a possible candidate for clinical therapy of cervical carcinoma.

Core-Shell Imidazoline-Functionalized Mesoporous Silica Superparamagnetic Hybrid Nanoparticles as a Potential Theranostic Agent for Controlled Delivery of Platinum(II) Compound

Introduction

As widely used chemotherapeutic agents, platinum compounds have several therapeutic challenges, such as drug resistance and adverse effects. Theranostic systems, macromolecular or colloidal therapeutics with companion diagnostics, not only address controlled drug delivery but also enable real-time monitoring of tumor sites.

Methods

Synthesis of magnetic mesoporous silica nanoparticles (MMSNs) was performed for dual magnetic resonance imaging and drug delivery. MMSN surfaces were modified by imidazoline groups (MMSN-Imi) for cisplatin (Cis-Pt) conjugation via free N-termini to achieve well-controlled drug-release kinetics. Cis-Pt adsorption isotherms and drug-release profile at pH 5 and 7.4 were investigated using inductively coupled plasma atomic emission spectroscopy.

Results

MMSN-Imi showed a specific surface area of 517.6 m² g⁻¹, mean pore diameter of 3.26 nm, and saturated magnetization of 53.63 emu/g. A relatively high r₂/r₁ relaxivity value was obtained for MMSN-Imi. The nanoparticles provided high Cis-Pt loading with acceptable loading capacity (~30% w:w). Sustained release of Cis-Pt under acidic conditions led to specific inhibitory effects on the growth of human epithelial ovarian carcinoma cells, determined using MTT assays. Dual acridine orange–propidium iodide staining was investigated, confirming induction of apoptosis and necrotic cell death.

Conclusion

MMSN-Imi exhibited potential for applications in cancer chemotherapy and combined imaging.

Potential drug delivery nanosystems for improving tumor penetration

Nanosystems, as one of the most important drug delivery systems, play a crucial rule in tumor therapy. However, the deep tumor penetration is retarded by the tumor physiological factors and nanomedicine properties. In this review, we firstly elaborate the factors which impact tumor penetration, including the tumor physiological factors and nanomedicine properties. Then, the latest and potential drug delivery nanosystems for improving tumor penetration are summarized and analyzed in detail. Moreover, recent combination therapies for improving penetration are described to enhance penetration. Finally, we summarize the typical clinical therapies of potential drug delivery nanosystems.

Construction of redox-responsive tumor targeted cisplatin nano-delivery system for effective cancer chemotherapy

Cisplatin is one of the most widely used platinum-based anticancer chemotherapeutic drugs. However, its low solubility, serious side effects and the development of cisplatin resistance limit its further use in the clinic. Controlling the delivery and release of cisplatin at the targeted site efficiently is a meaningful way to overcome these undesirable side effects of cisplatin. Herein, a tumor targeted and stimuli responsive nano-delivery system for cisplatin was constructed using branched polyethyleneimine (BPEI) as the backbone, disulfide bond as the redox-responsive covalent linker and hyaluronic acid (HA) as targeting recognition unit which can bind selectively to the receptor of CD44, which is highly expressed on the A549 tumor cells. The cisplatin-polyethyleneimine conjugate BPEI-SS-Pt was prepared and the drug loading of cisplatin was up to 32.66 ± 0.06%. After optimized the coating weight ratio of HA and BPEI-SS-Pt, the nanoparticle delivery system HA-(BPEI-SS-Pt)-1/4 outperformed with smaller particle size of 159.0 ± 21.0 nm, narrow polydispersity index (PDI) of 0.069 ± 0.022 and higher cisplatin loading of 29.23 ± 0.18%, showing specific tumor-targeting ability and redox-responsive drug release manner. Moreover, for the treatment of cancer in vivo, it achieved more effective antitumor performance along with minor side effects and systemic toxicity compared with cisplatin which is of great significance for the chemotherapeutic drug in the clinic.

Restoration and Enhancement of Immunogenic Cell Death of Cisplatin by Coadministration with Digoxin and Conjugation to HPMA Copolymer

Complete tumor eradication is the ultimate goal of cancer therapy. However, the majority of anticancer drugs cause nonimmunogenic cell death and only exert on-site anticancer activities. The intrinsic genomic instability of cancer allows for the persistence and later expansion of treatment-resistant clones after surviving a sort of Darwinian selection of chemotherapy. Additional incorporation of immunotherapy, which is robust and individualized could be game-changing. Herein, we report a combination strategy that delivers nonimmunogenic cell death inducer Cisplatin to treat primary tumors and converts the tumor cells into vaccines that spurs a long-lasting immune response against residual tumors to prevent tumor recurrence and metastasis. Cisplatin(IV) prodrug was linked to the N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer (P-Cis) and coadministered with digoxin (Dig), which eventually launched two attacks to cancer cells. First, P-Cis exhibited superior tumor retention and cytotoxicity over free Cisplatin (to inhibit the primary tumor growth). Then, Dig reversed the inability of Cisplatin to trigger calreticulin exposure, and HPMA copolymer-amplified Cisplatin-induced ATP release. These complementary mechanisms induced potent immunogenic cell death that promotes dendritic cell maturation and activates CD8⁺ T cell responses. In established tumor models, P-Cis + Dig combination completely eradicate tumors with no residual cancer cells remaining. Cancer cells succumbing to P-Cis + Dig could protect syngeneic mice against the subsequent challenge with living cells of the same type and stimulated robust abscopal and antimetastatic effects. Such a strategy might be promising to restore the immunogenicity of nonimmunogenic drugs and generate vaccine-like functions for improved immunochemotherapy.

New Advances in In Vivo Applications of Gated Mesoporous Silica as Drug Delivery Nanocarriers

One appealing concept in the field of hybrid materials is related to the design of gated materials. These materials are prepared in such a way that the release of chemical or biochemical species from voids of porous supports to a solution is triggered upon the application of external stimuli. Such gated materials are mainly composed of two subunits: i) a porous inorganic scaffold in which a cargo is stored, and ii) certain molecular or supramolecular entities, grafted onto the external surface, that can control mass transport from the interior of the pores. On the basis of this concept, a large number of examples are developed in the past ten years. A comprehensive overview of gated materials used in drug delivery applications in in vivo models from 2016 to date is thus given here.

A Sequential Target-Responsive Nanocarrier with Enhanced Tumor Penetration and Neighboring Effect In Vivo

Nanodrug-based cancer therapy is impeded by poor penetration into deep tumor tissues mainly due to the overexpression of hyaluronic acid (HA) in the tumor extracellular matrix (ECM). Although modification of nanoparticles (NPs) with hyaluronidase (HAase) is a potent strategy, it remains challenging to get a uniform distribution of drug at the tumor site because of the internalization of NPs by the cells in the tumor and HA regeneration. Herein, an intelligent nanocarrier, which can release HAase in response to the acidic tumor microenvironment (pH 6.5) and perform a strong neighboring effect with size reduction to overcome the above two problems and accomplish drug deep tumor penetration in vivo, is reported. In this design, HAase is encapsulated on the surfaces of doxorubicin (DOX) preloaded ZnO-DOX NPs using a charge convertible polymer PEG-PAH-DMMA (ZDHD). The polymer can release HAase to degrade HA in the tumor ECM (pH 6.5). ZnO-DOX NPs can release DOX in lysosomes (pH 4.5) to induce cell apoptosis, and exert a neighboring effect with size reduction to infect neighboring cells. The hierarchical targeted release of HAase and drugs is demonstrated to enhance tumor penetration and decrease side effects in vivo. This work shows promise for further application of ZDHD NPs in cancer therapy.

A chitosan-based cascade-responsive drug delivery system for triple-negative breast cancer therapy

BACKGROUND

It is extremely difficult to develop targeted treatments for triple-negative breast (TNB) cancer, because these cells do not express any of the key biomarkers usually exploited for this goal.

RESULTS

In this work, we develop a solution in the form of a cascade responsive nanoplatform based on thermo-sensitive poly(N-vinylcaprolactam) (PNVCL)-chitosan (CS) nanoparticles (NPs). These are further modified with the cell penetrating peptide (CPP) and loaded with the chemotherapeutic drug doxorubicin (DOX). The base copolymer was optimized to undergo a phase change at the elevated temperatures of the tumor microenvironment. The acid-responsive properties of CS provide a second trigger for drug release, and the inclusion of CPP should ensure the formulations accumulate in cancerous tissue. The resultant CPP-CS-co-PNVCL NPs could self-assemble in aqueous media into spherical NPs of size < 200 nm and with low polydispersity. They are able to accommodate a high DOX loading (14.8% w/w). The NPs are found to be selectively taken up by cancerous cells both in vitro and in vivo, and result in less off-target cytotoxicity than treatment with DOX alone. In vivo experiments employing a TNB xenograft mouse model demonstrated a significant reduction in tumor volume and prolonging of life span, with no obvious systemic toxicity.

CONCLUSIONS

The system developed in this work has the potential to provide new therapies for hard-to-treat cancers.

Cascade-amplification of therapeutic efficacy: An emerging opportunity in cancer treatment

Increasing research evidence reveals that cancer is complex disease involving many biological factors, processes and systems, which may severely limit the actual efficacy of conventional monotonic anticancer approaches. To overcome these obstacles in cancer treatment, a new strategy has been proposed by combining multiple synergistic therapeutic modalities accessing different but inherently related targets and acting sequentially. A major benefit of this strategy is that the multi-target mechanism could result in a cascade-amplification effect leading to enhanced anticancer activity. In this review, we provide a critical discussion on the application of cascade-amplification strategy in the treatment of various cancer indications, focusing on the rational combination of therapeutic agents and their mechanisms of action. A concise yet comprehensive analysis on the potential therapeutic benefit of this strategy was also included. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Particle toxicology and health - where are we?

BACKGROUND

Particles and fibres affect human health as a function of their properties such as chemical composition, size and shape but also depending on complex interactions in an organism that occur at various levels between particle uptake and target organ responses. While particulate pollution is one of the leading contributors to the global burden of disease, particles are also increasingly used for medical purposes. Over the past decades we have gained considerable experience in how particle properties and particle-bio interactions are linked to human health. This insight is useful for improved risk management in the case of unwanted health effects but also for developing novel medical therapies. The concepts that help us better understand particles' and fibres' risks include the fate of particles in the body; exposure, dosimetry and dose-metrics and the 5 Bs: bioavailability, biopersistence, bioprocessing, biomodification and bioclearance of (nano)particles. This includes the role of the biomolecule corona, immunity and systemic responses, non-specific effects in the lungs and other body parts, particle effects and the developing body, and the link from the natural environment to human health. The importance of these different concepts for the human health risk depends not only on the properties of the particles and fibres, but is also strongly influenced by production, use and disposal scenarios.

CONCLUSIONS

Lessons learned from the past can prove helpful for the future of the field, notably for understanding novel particles and fibres and for defining appropriate risk management and governance approaches.