Rational design of polyion complex nanoparticles to overcome cisplatin resistance in cancer therapy

pH-Sensitive Amphiphilic Diblock Polyphosphoesters with Lactate Units: Synthesis and Application as Drug Carriers

pH-sensitive amphiphilic diblock polyphosphoesters containing lactic acid units were synthesized by multistep one-pot polycondensation reactions. They comprise acid-labile P(O)-O-C and C(O)-O-C bonds, the cleavage of which depends on the pH of the medium. The structure of these copolymers was characterized by 1H, 13C {H}, 31P NMR, and size exclusion chromatography (SEC). The newly synthesized polymers self-assembled into the micellar structure in an aqueous solution. The effects of the molecular weight of the copolymer and the length of the hydrophobic chain on micelle formation and stabilityand micelle size were studied via dynamic light scattering (DLS). Drug loading and encapsulation efficiency tests using doxorubicin revealed that hydrophobic drugs can be delivered by copolymers. It was established that the molecular weight of the copolymer, length of the hydrophobic chain and content of lactate units affects the size of the micelles, drug loading, and efficiency of encapsulation. A copolymer with 10.7% lactate content has drug loading (3.2 ± 0.3) and efficiency of encapsulation (57.4 ± 3.2), compared to the same copolymer with 41.8% lactate content (1.63%) and (45.8%), respectively. It was demonstrated that the poly[alkylpoly(ethylene glycol) phosphate-b-alkylpoly(ethylene glycol)lactate phosphate] DOX system has a pH-sensitive response capability in the result in which DOX was selectively accumulated into the tumor, where pH is acidic. The results obtained indicate that amphiphilic diblock polyphosphoesters have potential as drug carriers.

Effective Combination of Targeted Therapies with Sonodynamic Treatment for Use in Exploring Differences in Therapeutic Efficacy across Organelle Targets

Acoustic kinetic therapy systems that target specific organelles can improve the precision of a sonosensitizer, which is a perfect combination of targeted therapy and sonodynamic therapy (SDT) and plays an important role in current acoustic kinetic therapy. In this study, we loaded PpIX, a sonosensitizer, on targeted-functional carbon dots (CDs) via an amide reaction and then generated the mitochondria-targeted system (Mit-CDs-PpIX) and nucleus-targeted system (Nuc-CDs-PpIX), respectively, to deliver the sonosensitizer. Both systems exhibited minimal cytotoxicity in the absence of ultrasound stimulation. The efficacy of the targeted SDT systems was investigated using methylthiazol tetrazolium (MTT) assays, live/dead staining, flow cytometry, etc. Compared with the free PpIX and mitochondria-targeted system, the nucleus-targeted system is more potent in killing effect under ultrasound stimulation and induces apoptosis with higher intensity. To achieve the equal killing effect, the effective concentration of Nuc-CDs-PpIX is just one third of that of Mit-CDs-PpIX.

The diverse effects of cisplatin on tumor microenvironment: Insights and challenges for the delivery of cisplatin by nanoparticles

Cisplatin is a well-known platinum-based chemotherapy medication that is widely utilized for some malignancies. Despite the direct cytotoxic consequences of cisplatin on tumor cells, studies in the recent decade have revealed that cisplatin can also affect different cells and their secretions in the tumor microenvironment (TME). Cisplatin has complex impacts on the TME, which may contribute to its anti-tumor activity or drug resistance mechanisms. These regulatory effects of cisplatin play a paramount function in tumor growth, invasion, and metastasis. This paper aims to review the diverse impacts of cisplatin and nanoparticles loaded with cisplatin on cancer cells and also non-cancerous cells in TME. The impacts of cisplatin on immune cells, tumor stroma, cancer cells, and also hypoxia will be discussed in the current review. Furthermore, we emphasize the challenges and prospects of using cisplatin in combination with other adjuvants and therapeutic modalities that target TME. We also discuss the potential synergistic effects of cisplatin with immune checkpoint inhibitors (ICIs) and other agents with anticancer potentials such as polyphenols and photosensitizers. Furthermore, the potential of nanoparticles for targeting TME and better delivery of cisplatin into tumors will be discussed.

Nanomedicine Combats Drug Resistance in Lung Cancer

Lung cancer is the second most prevalent cancer and the leading cause of cancer-related death worldwide. Surgery, chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy are currently available as treatment methods. However, drug resistance is a significant factor in the failure of lung cancer treatments. Novel therapeutics have been exploited to address complicated resistance mechanisms of lung cancer and the advancement of nanomedicine is extremely promising in terms of overcoming drug resistance. Nanomedicine equipped with multifunctional and tunable physiochemical properties in alignment with tumor genetic profiles can achieve precise, safe, and effective treatment while minimizing or eradicating drug resistance in cancer. Here, this work reviews the discovered resistance mechanisms for lung cancer chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy, and outlines novel strategies for the development of nanomedicine against drug resistance. This work focuses on engineering design, customized delivery, current challenges, and clinical translation of nanomedicine in the application of resistant lung cancer.

Platinum based theranostics nanoplatforms for antitumor applications

Platinum (Pt) based nanoplatforms are biocompatible nanoagents with photothermal antitumor performance, while exhibiting excellent radiotherapy sensitization properties. Pt-nanoplatforms have extensive research prospects in the realm of cancer treatment due to their highly selective and minimally invasive treatment mode with low damage, and integrated diagnosis and treatment with image monitoring and collaborative drug delivery. Platinum based anticancer chemotherapeutic drugs can kill tumor cells by damaging DNA through chemotherapy. Meanwhile, Pt-nanoplatforms also have good electrocatalytic activity, which can mediate novel electrodynamic therapy. Simultaneously, Pt(II) based compounds also have potential as photosensitizers in photodynamic therapy for malignant tumors. Pt-nanoplatforms can also modulate the immunosuppressive environment and synergistically ablate tumor cells in combination with immune checkpoint inhibitors. This article reviews the research progress of platinum based nanoplatforms in new technologies for cancer therapy, starting from widely representative examples of platinum based nanoplatforms in chemotherapy, electrodynamic therapy, photodynamic therapy, photothermal therapy, and immunotherapy. Finally, multimodal imaging techniques of platinum based nanoplatforms for biomedical diagnosis are briefly discussed.

Recent Advances of Platinum-Based Anticancer Complexes in Combinational Multimodal Therapy

Platinum drugs with manifest therapeutic effects are widely used, but their systemic toxicity and the drug resistance acquired by cancer cells limit their clinical applications. Thus, the exploration on appropriate methods and strategies to overcome the limitations of traditional platinum drugs becomes extremely necessary. Combination therapy of platinum drugs can inhibit tumor growth and metastasis in an additive or synergistic manner, and can potentially reduce the systemic toxicity of platinum drugs and overcome platinum-resistance. This review summarizes the various modalities and current progress in platinum-based combination therapy. The synthetic strategies and therapeutic effects of some platinum-based anticancer complexes in the combination of platinum drugs with gene editing, ROS-based therapy, thermal therapy, immunotherapy, biological modelling, photoactivation, supramolecular self-assembly and imaging modality are briefly described. Their potential challenges and prospects are also discussed. It is hoped that this review will inspire researchers to have more ideas for the future development of highly effective platinum-based anti-cancer complexes.

pH and its applications in targeted drug delivery

Physiologic pH is vital for the normal functioning of tissues and varies in different parts of the body. The varying pH of the body has been exploited to design pH-sensitive smart oral, transdermal and vaginal drug delivery systems (DDS). The DDS demonstrated promising results in hard-to-treat diseases such as cancer and Helicobacter pylori infection. In some cases, a change in pH of tissues or body fluids has also been employed as a useful diagnostic biomarker. This paper aims to comprehensively review the development and applications of pH-sensitive DDS as well as recent advances in the field.

A multifunctional theranostics nanosystem featuring self-assembly of alcohol-abuse drug and photosensitizers for synergistic cancer therapy

Conventional treatments for cancer, such as chemotherapy, surgical resection, and radiotherapy, have shown limited therapeutic efficacy, with severe side effects, lack of targeting and drug resistance for monotherapies, which limit their clinical application. Therefore, combinatorial strategies have been widely investigated in the battle against cancer. Herein, we fabricated a dual-targeted nanoscale drug delivery system based on EpCAM aptamer- and lactic acid-modified low-polyamidoamine dendrimers to co-deliver the FDA-approved agent disulfiram and photosensitizer indocyanine green, combining the imaging and therapeutic functions in a single platform. The multifunctional nanoparticles with uniform size had high drug-loading payload, sustained release, as well as excellent photothermal conversion. The integrated nanoplatform showed a superior synergistic effect in vitro and possessed precise spatial delivery to HepG2 cells with the dual-targeting nanocarrier. Intriguingly, a robust anticancer response of chemo-phototherapy was achieved; chemotherapy combined with the efficacy of phototherapy to cause cellular apoptosis of HepG2 cells (>35%) and inhibit the regrowth of damaged cells. Furthermore, the theranostic nanosystem displayed fluorescence imaging in vivo, attributed to its splendid accumulation in the tumor site, and it provided exceptional tumor inhibition rate against liver cancer cells (>76%). Overall, our research presents a promising multifunctional theranostic nanoplatform for the development of synergistic therapeutics for tumors in further applications.

An NIR Discrete Metallacycle Constructed from Perylene Bisimide and Tetraphenylethylene Fluorophores for Imaging-Guided Cancer Radio-Chemotherapy

To promote the clinical theranostic performances of platinum-based anticancer drugs, imaging capability is urgently desired, and their chemotherapeutic efficacy needs to be upgraded. Herein, a theranostic metallacycle (M) is developed for imaging-guided cancer radio-chemotherapy using perylene bisimide fluorophore (PPy) and tetraphenylethylene-based di-Pt(II) organometallic precursor (TPE-Pt) as building blocks. The formation of this discrete supramolecular coordination complex facilitates the encapsulation of M by a glutathione (GSH)-responsive amphiphilic block copolymer to prepare M-loaded nanoparticles (MNPs). TPE-Pt acts as a chemotherapeutic drug and also an excellent radiosensitizer, thus incorporating radiotherapy into the nanomedicine to accelerate the therapeutic efficacy and overcome drug resistance. The NIR-emission of PPy is employed to detect the intracellular delivery and tissue distribution of MNPs in real time. In vitro and in vivo investigations demonstrate the excellent anticancer efficacy combining chemotherapy and radiotherapy; the administration of this nanomedicine effectively inhibits the tumor growth and greatly extends the survival rate of cisplatin-resistant A2780CIS-tumor-bearing mice. Guided by in vivo fluorescence imaging, radio-chemotherapy is precisely carried out, which facilitates boosting of the therapeutic outcomes and minimizing undesired side effects. The success of this theranostic system brings new hope to supramolecular nanomedicines for their potential clinical translations.

Targeting Cancer Chemotherapy Resistance by Precision Medicine-Driven Nanoparticle-Formulated Cisplatin

Therapy resistance is the major cause of cancer death. As patients respond heterogeneously, precision/personalized medicine needs to be considered, including the application of nanoparticles (NPs). The success of therapeutic NPs requires to first identify clinically relevant resistance mechanisms and to define key players, followed by a rational design of biocompatible NPs capable to target resistance. Consequently, we employed a tiered experimental pipeline from in silico to analytical and in vitro to overcome cisplatin resistance. First, we generated cisplatin-resistant cancer cells and used next-generation sequencing together with CRISPR/Cas9 knockout technology to identify the ion channel LRRC8A as a critical component for cisplatin resistance. LRRC8A's cisplatin-specificity was verified by testing free as well as nanoformulated paclitaxel or doxorubicin. The clinical relevance of LRRC8A was demonstrated by its differential expression in a cohort of 500 head and neck cancer patients, correlating with patient survival under cisplatin therapy. To overcome LRRC8A-mediated cisplatin resistance, we constructed cisplatin-loaded, polysarcosine-based core cross-linked polymeric NPs (NP_Cis, Ø ∼ 28 nm) with good colloidal stability, biocompatibility (low immunogenicity, low toxicity, prolonged in vivo circulation, no complement activation, no plasma protein aggregation), and low corona formation properties. 2D/3D-spheroid cell models were employed to demonstrate that, in contrast to standard of care cisplatin, NP_Cis significantly (p < 0.001) eradicated all cisplatin-resistant cells by circumventing the LRRC8A-transport pathway via the endocytic delivery route. We here identified LRRC8A as critical for cisplatin resistance and suggest LRRC8A-guided patient stratification for ongoing or prospective clinical studies assessing therapy resistance to nanoscale platinum drug nanoformulations versus current standard of care formulations.

Linear-Dendritic Polymer-Platinum Complexes Forming Well-Defined Nanocapsules for Acid-Responsive Drug Delivery

Polymeric nanocapsules hold considerable applications in cancer drug delivery, but the synthesis of well-defined nanocapsules with a tunable drug release property remains a significant challenge in fabrication. Herein, we demonstrate a supramolecular complexation strategy to assemble small molecular platinum (Pt) compounds into well-defined nanocapsules with high drug loading, acidity-sensitivity, and tunable Pt releasing profile. The design utilizes poly(ethylene glycol)-dendritic polylysine-G4/amides to complex with Pt compounds, forming stable nanocapsules with diameters approximately ∼20 nm and membrane thickness around several nanometers. The stability, drug content, and release profiles are tunable by tailoring the dendritic structure. The designated polymer-Pt nanocapsules, PEG-G4/MSA-Pt, showed sustained blood retention, preferential tumor accumulation, enhanced cellular uptake, lysosomal drug release, and nuclear delivery capability. PEG-G4/MSA-Pt showed enhanced antitumor efficacy compared to free cisplatin and other nanocapsules, which stopped the progression of both A549 cell xenografts and patient-derived xenografts (PDXs) of hepatocellular carcinoma on a mice tumor model. Thus, we believe this strategy is promising for developing Pt-based nanomedicine for cancer drug delivery.

Preparation and evaluation of reduction-responsive micelles based on disulfide-linked chondroitin sulfate A-tocopherol succinate for controlled antitumour drug release

OBJECTIVES

The study was to construct reduction-responsive chondroitin sulfate A (CSA)-conjugated TOS (CST) micelles with disulfide bond linkage, which was used for controlled doxorubicin (DOX) release and improved drug efficacy in vivo.

METHODS

CST and non-responsive CSA-conjugated TOS (CAT) were synthesized, and the chemical structure was confirmed by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, fluorescence spectrophotometer and dynamic light scattering. Antitumour drug DOX was physically encapsulated into CST and CSA by dialysis method. Cell uptake of DOX-based formulations was investigated by confocal laser scanning microscopy. In vitro cytotoxicity was studied in A549 and AGS cells. Furthermore, antitumour activity was evaluated in A549-bearing mice.

KEY FINDINGS

CST and CAT can form self-assembled micelles, and have low value of critical micelle concentration. Notably, DOX-containing CST (D-CST) micelles demonstrated reduction-triggered drug release in glutathione-containing media. Further, reduction-responsive uptake of D-CST was observed in A549 cells. In addition, D-CST induced stronger cytotoxicity (P < 0.05) than DOX-loaded CAT (D-CAT) against A549 and AGS cells. Moreover, D-CST exhibited significantly stronger antitumour activity in A549-bearing nude mice than doxorubicin hydrochloride and D-CAT.

CONCLUSIONS

The reduction-responsive CST micelles enhanced the DOX effect at tumour site and controlled drug release.

Photoresponsive metallopolymer nanoparticles for cancer theranostics

Over the past decades, transition metal complexes have been successfully used in anticancer phototherapies. They have shown promising properties in many different areas including photo-induced ligand exchange or release, rich excited state behavior, and versatile biochemical properties. When encorporated into polymeric frameworks and become part of nanostructures, photoresponsive metallopolymer nanoparticles (MPNs) show enhanced water solubility, extended blood circulation and increased tumor-specific accumulation, which greatly improves the tumor therapeutic effects compared to low-molecule-weight metal complexes. In this review, we aim to present the recent development of photoresponsive MPNs as therapeutic nanomedicines. This review will summarize four major areas separately, namely platinum-containing polymers, zinc-containing polymers, iridium-containing polymers and ruthenium-containing polymers. Representative MPNs of each type are discussed in terms of their design strategies, fabrication methods, and working mechanisms. Current challenges and future perspectives in this field are also highlighted.

F127/Cisplatin Microemulsions: In Vitro, In Vivo and Computational Studies

The development of effective strategies for local administration of chemotherapeutic drugs, thus minimizing the adverse side effects to patients, is one of the key challenges in biomedicine and cancer research. This work reports the formulation and characterization of PluronicF127 microemulsions to enhance the bioavailability of Cisplatin (Cis). The size of Cis microemulsion was about 12.0 nm, as assessed by dynamic light scattering analysis. In vitro cytotoxic activity of free Cis and F127/Cis microemulsions were studied on malignant (C152 and MCF7) and normal (HUVEC) cells via tetrazolium (MTT) colorimetric assay. Cell morphology was also monitored. In vitro assessments revealed thatF127/Cis microemulsions induced cytotoxicity/morphological changes to a lesser extent than free Cis. Regarding in vivo experiments, F127/Cis microemulsions were injected intraperitoneally at 7 and 14 mg/kg doses into adult male Wistar rats to assess histologic and biochemical changes. In this case, the bulk Cis group caused severe histopathological changes and significant increases in serum liver enzymes and serum kidney function markers. The group treated with the 14 mg/kg dose of F127/Cis microemulsions also showed severe fatty changes and significant increases in serum liver enzymes, blood urea nitrogen, and creatinine levels. The group treated with the low dose of nano-Cis showed a significant increase in serum liver enzymes levels accompanied by mild fatty changes of the liver. Theoretical surveys were performed to get an understanding of the interplay between F127 and Cis. Results reveal that hydrogen bonding (HB) interactions with F127have an influence on the molecular properties of Cis and may playa role in the lower toxicity of F127/Cis in comparison to free Cis.

A carboxymethyl lentinan layer by layer self-assembly system as a promising drug chemotherapeutic platform

Surface functionalization of mesoporous silica nanoparticles (MSNs) has been proposed as an efficient strategy for enhancing the biocompatibility and efficiency of an MSN-based carrier platform. Herein, natural polyelectrolyte multilayers composed of poly-l-ornithine (PLO) and carboxymethyl lentinan (LC) were coated on the surface of MSNs through a layer-by-layer (LbL) self-assembly technique, and were characterized by ζ-potential, FTIR, ¹³C NMR, SEM, TEM, XRD, and TG. The prepared carrier presented alternating positive and negative potentials when coated with the polyelectrolytes, and the surface of MSN-PLO/LC was rougher compared to the naked MSNs. The biocompatibility tests, including cytocompatibility, hemocompatibility, and histocompatibility, showed that MSNs biocompatibility could be improved by modifying LC. A high loading and sustained release drug delivery system was constructed after loading doxorubicin (DOX) into the prepared MSN-PLO/LC, which exhibited significant anti-proliferative efficiency in human cervical cancer cell lines (Hela). Therefore, the PLO/LC LbL NPs (layer-by-layer self-assembled nanoparticles coated with PLO/LC layers) based on MSNs, which is easily prepared by electrostatic interactions, can be considered a promising drug chemotherapeutic platform and delivery technique for future human cervical cancer therapy.

Spatiotemporal Concurrent Liberation of Cytotoxins from Dual-Prodrug Nanomedicine for Synergistic Antitumor Therapy

Nanomedicine developed to date by means of directly encapsulating cytotoxins suffers from crucial drawbacks, including premature release and detoxification prior to arrival at pharmaceutics targets. To these respects, redox-responsive polymeric prodrugs of platinum (Pt) and camptothecin (CPT), selectively and concomitantly activated in the cytoplasm, were elaborated in manufacture of dual prodrug nanomedicine. Herein, multiple CPTs were conjugated to poly(lysine) (PLys) segments of block copolymeric poly(ethylene glycol) (PEG)-PLys through the redox responsive disulfide linkage [PEG-PLys(ss-CPT)] followed by reversible conversion of amino groups from PLys into carboxyl groups based on their reaction with cis-aconitic anhydride [PEG-PLys(ss-CPT&CAA)]. On the other hand, Pt(IV) in conjugation with dendritic polyamindoamine [(G3-PAMAM-Pt(IV)] was synthesized for electrostatic complexation with PEG-PLys(ss-CPT&CAA) into dual prodrug nanomedicine. Subsequent investigations proved that the elaborated nanomedicine could sequentially respond to intracellular chemical potentials to overcome a string of predefined biological barriers and facilitate intracellular trafficking. Notably, PEG-PLys(ss-CPT&CAA) capable of responding to the acidic endosomal microenvironment for transformation into endosome-disruptive PEG-PLys(ss-CPT), as well as release of G3-PAMAM-Pt(IV) from nanomedicine, prompted transclocation of therapeutic payloads from endosomes into cytosols. Moreover, concurrent activation and liberation of cytotoxic CPT and Pt(II) owing to their facile responsiveness to the cytoplasmic reducing microenvironment have demonstrated overwhelming cytotoxic potencies. Eventually, systemic administration of the dual prodrug construct exerted potent tumor suppression efficacy in treatment of intractable solid breast adenocarcinoma, as well as an appreciable safety profile. The present study illustrated the first example of nanomedicine with a dual prodrug motif, precisely and concomitantly activated by the same subcellular stimuli before approaching pharmaceutic action targets, thus shedding important implication in development of advanced nanomedicine to seek maximized pharmaceutic outcomes.

Adjudin-loaded redox-sensitive paclitaxel-prodrug micelles for overcoming multidrug resistance with efficient targeted Colon cancer therapy

Multidrug resistance (MDR) is the primary cause for the failure of chemotherapy in the treatment of colon cancer. Recent research has indicated that the combination of a chemotherapeutic agent and a mitochondrial inhibitor might represent a promising strategy to help overcome MDR. However, for this approach to be clinically effective, it is important that the two drugs can be actively and simultaneously delivered into tumor cells at an optimal ratio and completely released drug within cells. To address these challenges, we designed and prepared a folate receptor-targeted and redox-responsive drug delivery system (FA- ss -P/A) that was able to co-deliver paclitaxel (PTX) and adjudin (ADD) to reverse colon cancer MDR. The PTX prodrug was obtained by conjugating PTX to dextrin via a disulfide-linkage. Then, folic acid (FA) was modified on the PTX prodrug. Finally, ADD, a mitochondrial inhibitor, was encapsulated in the PTX prodrug-formed micelles. A series of in vitro and in vivo experiments subsequently demonstrated that FA- ss -P/A can effectively reverse MDR by increasing cell uptake, inhibiting PTX efflux, and improving drug release.

Advances and perspectives in carrier-free nanodrugs for cancer chemo-monotherapy and combination therapy

Nanocarrier-based drug delivery systems hold impressive promise for biomedical application because of their excellent water dispersibility, prolonged blood circulation time, increased drug accumulation in tumors, and potential in combination therapeutics. However, most nanocarriers suffer from low drug-loading efficiency, poor therapeutic effectiveness, potential systematic toxicity, and unstable metabolism. As an alternative, carrier-free nanodrugs, completely formulated with one or more drugs, have attracted increasing attention in cancer therapy due to their advantage of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug-loading. In recent years, carrier-free nanodrugs have contributed to progress in a variety of therapeutic modalities. In this review, different common strategies for carrier-free nanodrugs preparation are first summarized, mainly including nanoprecipitation, template-assisted nanoprecipitation, thin-film hydration, spray-drying technique, supercritical fluid (SCF) technique, and wet media milling. Then we describe the recently reported carrier-free nanodrugs for cancer chemo-monotherapy or combination therapy. The advantages of anti-cancer drugs combined with other chemotherapeutic, photosensitizers, photothermal, immunotherapeutic or gene drugs have been demonstrated. Finally, a future perspective is introduced to highlight the existing challenges and possible solutions toward clinical application of currently developed carrier-free nanodrugs, which may be instructive to the design of effective carrier-free regimens in the future.

Anticancer Properties of Platinum Nanoparticles and Retinoic Acid: Combination Therapy for the Treatment of Human Neuroblastoma Cancer

Neuroblastoma is the most common extracranial solid tumor in childhood. The different treatments available for neuroblastoma are challenged by high rates of resistance, recurrence, and progression, most notably in advanced cases and highly malignant tumors. Therefore, the development of more targeted therapies, which are biocompatible and without undesired side effects, is highly desirable. The mechanisms of actions of platinum nanoparticles (PtNPs) and retinoic acid (RA) in neuroblastoma have remained unclear. In this study, the anticancer effects of PtNPs and RA on neuroblastoma were assessed. We demonstrated that treatment of SH-SY5Y cells with the combination of PtNPs and RA resulted in improved anticancer effects. The anticancer effects of the two compounds were mediated by cytotoxicity, oxidative stress (OS), mitochondrial dysfunction, endoplasmic reticulum stress (ERS), and apoptosis-associated networks. Cytotoxicity was confirmed by leakage of lactate dehydrogenase (LDH) and intracellular protease, and oxidative stress increased the level of reactive oxygen species (ROS), 4-hydroxynonenal (HNE), malondialdehyde (MDA), and nitric oxide (NO), and protein carbonyl content (PCC). The combination of PtNPs and RA caused mitochondrial dysfunction by decreasing the mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content, number of mitochondria, and expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Endoplasmic reticulum-mediated stress and apoptosis were confirmed by upregulation of protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1), activating transcription factor 6 (ATF6), activating transcription factor 4 (ATF4), p53, Bax, and caspase-3 and down regulation of B-cell lymphoma 2 (BCl-2). PtNPs and RA induced apoptosis, and oxidative DNA damage was evident by the accumulation of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-hydroxyguanosine (8-OHG). Finally, PtNPs and RA increased the differentiation and expression of differentiation markers. Differentiated SH-SY5Y cells pre-treated with PtNPs or RA or the combination of both were more sensitive to the cytotoxic effect of cisplatin than undifferentiated cells. To our knowledge, this is the first study to demonstrate the effect of the combination of PtNPs and RA in neuroblastoma cells. PtNPs may be a potential preconditioning or adjuvant compound in chemotherapeutic treatment. The results of this study provide a rationale for clinical evaluation of the combination of PtNPs and RA for the treatment of children suffering from high-risk neuroblastoma.

Enhanced anticancer effect of doxorubicin by TPGS-coated liposomes with Bcl-2 siRNA-corona for dual suppression of drug resistance

Multiple drug resistance (MDR) is a tough problem in developing hepatocellular carcinoma (HCC) therapy. Here, we developed TPGS-coated cationic liposomes with Bcl-2 siRNA corona to load doxorubicin (Dox) i.e., Bcl-2 siRNA/Dox-TPGS-LPs, to enhance anticancer effect of Dox in HCC-MDR. TPGS i.e., d-α-tocopheryl polyethylene glycol 1000 succinate, inhibited P-glycoprotein (P-gp) efflux pump and Bcl-2 siRNA suppressed anti-apoptotic Bcl-2 protein. The Bcl-2 siRNA loaded in the liposomal corona was observed under transmission electron microscopy. The stability and hemolysis evaluation demonstrated Bcl-2 siRNA/Dox-TPGS-LPs had good biocompatibility and siRNA-corona could protect the liposomal core to avoid the attachment of fetal bovine serum. In drug-resistant cells, TPGS effectively prolonged intracellular Dox retention time and siRNA-corona did improve the internalization of Dox from liposomes. In vitro and in vivo anticancer effect of this dual-functional nanostructure was examined in HCC-MDR Bel7402/5-FU tumor model. MTT assay confirmed the IC50 value of Dox was 20-50 fold higher in Bel7402/5-FU MDR cells than that in sensitive Bel7402 cells. Bcl-2 siRNA corona successfully entered the cytosol of Bel7402/5-FU MDR cells to downregulate Bcl-2 protein levels in vitro and in vivo. Bcl-2 siRNA/Dox-TPGS-LPs showed superior to TPGS- (or siRNA-) linked Dox liposomes in cell apoptosis and cytotoxicity assay in Bel7402/5-FU MDR cells, and 7-fold greater effect than free Dox in tumor growth inhibition of Bel7402/5-FU xenograft nude mice. In conclusion, TPGS-coated cationic liposomes with Bcl-2 siRNA corona had the capacity to inhibit MDR dual-pathways and subsequently improved the anti-tumor activity of the chemotherapeutic agent co-delivered to a level that cannot be achieved by inhibiting a MDR single way.

Dual-Stimuli-Responsive Multifunctional Gd2Hf2O7 Nanoparticles for MRI-Guided Combined Chemo-/Photothermal-/Radiotherapy of Resistant Tumors

The design and synthesis of a novel generation of a nanoscaled platform with imaging-guided therapy remain a real challenge. It can not only improve the imaging sensitivity of tumor tissues for guiding all kinds of treatments but also reduce the harm for healthy tissues. Here, polydopamine (PDA), polyethylene glycol (PEG), and c(RGDyK) peptide (RGD)-modified and cisplatin-loaded Gd₂Hf₂O₇ nanoparticles (Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs) are designed for magnetic resonance imaging (MRI)-guided combined chemo-/photothermal-/radiotherapy of resistant tumors. The as-prepared NPs display high relaxivity (r₁ = 38.28 mM^-1 s^-1) as an MRI contrast agent because of their ultrasmall size and surface modification with polyacrylic acid and PDA. Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs exhibit pH and NIR dual-stimuli responsiveness for cisplatin release. Based on competent NIR absorption and high X-ray attenuation efficiency, Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs show potential photothermal effect by exposing to an 808 nm NIR laser and significantly improve the generation of reactive oxygen species after X-ray radiation. Combined chemo-/photothermal-/radiotherapy can effectively treat the resistant A549R cells, providing the enhanced therapeutic efficiency to cancer tissues and the reduced side effect to healthy tissues. Furthermore, Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs present no obvious toxicity during the treatment, which demonstrates the potential as an efficient MRI-guided combined chemo-/photothermal-/radiotherapy nanoplatform for drug-resistant tumors.

Oxaliplatin-/NLG919 prodrugs-constructed liposomes for effective chemo-immunotherapy of colorectal cancer

High expression of indoleamine 2,3-dioxygenase 1 (IDO1) is a major cause of tumor induced immunosuppression, and appears to be associated with poor prognosis in human colorectal cancer and some others. In this study, we construct a bifunctional liposome by self-assembly of oxaliplatin-prodrug (Oxa(IV)) conjugated phospholipid and alkylated NLG919 (aNLG), an IDO1 inhibitor, together with other commercial lipids. The obtained aNLG/Oxa(IV)-Lip can not only release cytotoxic oxaliplatin inside the reductive cytosol to trigger immunogenic cell death (ICD) of cancer cells, but also efficiently retard the degradation of tryptophan to immunosuppressive kynurenine via the NLG919 mediated inhibition of IDO1. Moreover, in vivo pharmacokinetic studies indicate that such aNLG/Oxa(IV)-Lip has a long blood circulation time, thereby enables highly-efficient passive tumor homing. Upon tumor accumulation, such aNLG/Oxa(IV)-Lip presents superior synergistic antitumor efficacies to both subcutaneous and orthotopic CT26 tumors, ascribing to significantly primed anti-tumor immunity of enhanced intratumoral infiltration of CD8⁺ T cells, scretion of cytotoxic cytokines and downregulation of immunosuppressive regulatory T cells. This work highlights that such bifunctional aNLG/Oxa(IV)-Lip is a potent candidate for future clinical translation owing to its excellent biocompatibility and high therapeutic efficacy.

A Metal-Polyphenol-Coordinated Nanomedicine for Synergistic Cascade Cancer Chemotherapy and Chemodynamic Therapy

The clinical application of chemotherapy is impeded by the unsatisfactory efficacy and severe side effects. Chemodynamic therapy (CDT) has emerged as an efficient strategy for cancer treatment utilizing Fenton chemistry to destroy cancer cells by converting endogenous H2 O2 into highly toxic reactive oxygen species. Apart from the chemotherapeutic effect, cisplatin is able to act as an artificial enzyme to produce H2 O2 for CDT through cascade reactions, thus remarkably improving the anti-tumor outcomes. Herein, an organic theranostic nanomedicine (PTCG NPs) is constructed with high loading capability using epigallocatechin-3-gallate (EGCG), phenolic platinum(IV) prodrug (Pt-OH), and polyphenol modified block copolymer (PEG-b-PPOH) as the building blocks. The high stability of PTCG NPs during circulation stems from their strong metal-polyphenol coordination interactions, and efficient drug release is realized after cellular internalization. The activated cisplatin elevates the intracellular H2 O2 level through cascade reactions. This is further utilized to produce highly toxic reactive oxygen species catalyzed by an iron-based Fenton reaction. In vitro and in vivo investigations demonstrate that the combination of chemotherapy and chemodynamic therapy achieves excellent anticancer efficacy. Meanwhile, systemic toxicity faced by platinum-based drugs is avoided through this nanoformulation. This work provides a promising strategy to develop advanced nanomedicine for cascade cancer therapy.

Intratumoral delivery of CCL25 enhances immunotherapy against triple-negative breast cancer by recruiting CCR9+ T cells

CCR9⁺ T cells have an increased potential to be activated and therefore may mediate strong antitumor responses. Here, we found, however, that CCL25, the only chemokine for CCR9⁺ cells, is not expressed in human or murine triple-negative breast cancers (TNBCs), raising a hypothesis that intratumoral delivery of CCL25 may enhance antitumor immunotherapy in TNBCs. We first determined whether this approach can enhance CD47-targeted immunotherapy using a tumor acidity-responsive nanoparticle delivery system (NP-siCD47/CCL25) to sequentially release CCL25 protein and CD47 small interfering RNA in tumor. NP-siCD47/CCL25 significantly increased infiltration of CCR9⁺CD8⁺ T cells and down-regulated CD47 expression in tumor, resulting in inhibition of tumor growth and metastasis through a T cell-dependent immunity. Furthermore, the antitumor effect of NP-siCD47/CCL25 was synergistically enhanced when used in combination with programmed cell death protein-1/programmed death ligand-1 blockades. This study offers a strategy to enhance immunotherapy by promoting CCR9⁺CD8⁺ T cell tumor infiltration.

Dual pH-Responsive Polymer Nanogels with a Core-Shell Structure for Improved Cell Association

We report the fabrication of polymer nanogels with a pH-responsive core and a pH-sheddable shell and investigate the pH-dependent cell association of the pH-responsive polymer nanogels. The pH-responsive core composed of poly(2-diisopropylaminoethyl methacrylate) (PDPA) with a pK_a ≈ 6.2 was synthesized by using polymerization in emulsion droplets. The pH-sheddable poly(ethylene glycol) (PEG) shell was coated on the amine-modified PDPA nanogels by an acid-degradable amide bond. The PEG shell is cleavable in response to the acidic tumor microenvironment, and subsequently, the surface charge of the nanogels can be reversed, which effectively enhances cellular association of these nanogels. The reported pH-responsive polymer nanogels provide a promising way for the better understanding of bio-nano interactions and potentially enrich the application of therapeutic delivery for cancer therapy.

Intratumoral delivery of M-CSF by calcium crosslinked polymer micelles enhances cancer immunotherapy

Immunotherapy has shown promising results in multiple malignancies. However, there are still significant challenges in cancer immunotherapy including the powerful immunosuppressive tumor microenvironment and adverse off-target side effects. Nanomaterials with defined physico-biochemical properties are versatile drug delivery platforms that may address these key technical challenges faced by cancer immunotherapy. Here, a tumor acidity-responsive biomacromolecule delivery system was designed to intratumorally deliver an immune-activating cytokine, macrophage colony-stimulating factor (M-CSF) and attenuate the acidic microenvironment. This nanoparticle was prepared by introducing CaCO3 as a crosslinker to form an M-CSF-loaded stable micelle (NP/M-CSF/CaCO3). Administration of NP/M-CSF/CaCO3 significantly inhibited tumor growth by enhancing T cell-mediated anti-tumor immune responses and reversing the TAM-mediated immunosuppression. This study provides new avenues for cascade amplification of the antitumor effects by targeting the tumor microenvironment. This approach may also help avoid unwanted complications.

Antifouling and pH-Responsive Poly(Carboxybetaine)-Based Nanoparticles for Tumor Cell Targeting

Nanocarriers with responsibility and surface functionality of targeting molecules have been widely used to improve therapeutic efficiency. Hence, we report the assembly of pH-responsive and targeted polymer nanoparticles (NPs) composed of poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) as the core and poly(carboxybetaine methacrylate) (PCBMA) as the shell, functionalized with cyclic peptides containing Arginine-Glycine-Aspartic acid-D-Phenylalanine-Lysine (RGD). The resulting polymer NPs (PDPA@PCBMA-RGD NPs) can maintain the pH-responsivity of PDPA (pKa ~6.5) and low-fouling property of PCBMA that significantly resist non-specific interactions with RAW 264.7 and HeLa cells. Meanwhile, PDPA@PCBMA-RGD NPs could specifically target αvβ3 integrin-expressed human glioblastoma (U87) cells. The pH-responsiveness and low-fouling properties of PDPA@PCBMA NPs are comparable to PDPA@poly(ethylene glycol) (PDPA@PEG) NPs, which indicates that PCBMA is an alternative to PEG for low-fouling coatings. The advantage of PDPA@PCBMA NPs lies in the presence of carboxyl groups on their surfaces for further modification (e.g., RGD functionalization for cell targeting). The reported polymer NPs represent a new carrier that have the potential for targeted therapeutic delivery.

Nanoscale systems for local drug delivery

Many diseases and conditions affect a relatively localized area of the body. They can be treated either by direct deposition of drug in the target area, or by giving the drug systemically. Here we review nanoparticle-based approaches to achieving both. We highlight advantages and disadvantages that nanoscale solutions have for locally administered therapies, with emphasis on the former. We discuss strategies to enable systemically delivered nanoparticles to deliver their payloads at specific locations in the body, including triggering (local and remote) and targeting.

ROS-Responsive Polymeric Nanocarriers with Photoinduced Exposure of Cell-Penetrating Moieties for Specific Intracellular Drug Delivery

In situ modulation of the surface properties on the micellar drug delivery nanocarriers offers an efficient method to improve the drug delivery efficiency into cells while maintaining stealth and stability during blood circulation. Light has been demonstrated to be a temporally and spatially controllable tool to improve cellular internalization of nanoparticles. Herein, we develop reactive oxygen species (ROS)-responsive mixed polymeric micelles with photoinduced exposure of cell-penetrating moieties via photodynamic ROS production, which can facilitate cellular internalization of paclitaxel (PTX) and chlorin e6 (Ce6)-coloaded micelles for the synergistic effect of photodynamic and chemotherapy. The thioketal-bond-linked block polymers poly(ε-caprolactone)-TL-poly(N,N-dimethylacrylamide) (PCL-TL-PDMA) with a long PDMA block are used to self-assemble into mixed micelles with PCL-b-poly(2-guanidinoethyl methacrylate) (PCL-PGEMA) consisting of a short PGEMA block, which are further used to coencapsulate PTX and Ce6. After intravenous injection, prolonged blood circulation of the micelles guarantees high tumor accumulation. Upon irradiation by 660 nm light, ROS production of the micelles by Ce6 induces cleavage of PDMA to expose PGEMA shells for significantly improved cellular internalization. The combination of photodynamic therapy and chemotherapy inside the tumor cells achieves improved antitumor efficacy. The design of ROS-responsive mixed polymeric nanocarriers represents a novel and efficient approach to realize both long blood circulation and high-efficiency cellular internalization for combined photodynamic and chemotherapy under light irradiation.

pH- and enzyme-triggered drug release as an important process in the design of anti-tumor drug delivery systems

It is necessary to design a reasonable drug delivery system(DDS) for targeted release to overcome the potential toxicity and poor selectivity of anti-tumor drug. How a drug is released from a DDS is a critical issue that determines whether the DDS is designed successfully. We all know that the microenvironment of tumors is quite different from normal tissues, such as its acidic environment, different expression levels of some enzymes, etc. These features are widely used in the design of DDSs and play an important role in the drug release process in vivo. Numerous DDSs have been designed and synthesized. This article attention to how drugs are released from DDSs. We summarizes and classify the characteristic enzymes and chemical bonds used in the drug release process by browsing a large number of papers, and describes how they are applied in DDSs with specific examples. By understanding these acid-sensitive chemical bonds and over-expressed enzymes in tumors, different DDSs can be designed for different drug structures to solve specific problems of anti-tumor drugs.

Surface Coordination of Black Phosphorus with Modified Cisplatin

Black phosphorus (BP) is a two-dimensional (2D) nanomaterial with high charge-carrier mobility, a tunable direct bandgap, and a unique in-plane anisotropic structure; however, the easiness of BP oxidation into P xO y species in ambient conditions largely limits its applications. In this study, modified cisplatin-Pt-NO3 [Pt(NH3)2(NO3)2] is used for surface coordination with BP nanosheets to generate Pt@BP, which maintains the surface morphology and properties of BP nanosheets for more than 24 h in ambient conditions. In addition, Pt@BP interacts with DNA both in vitro and in cell. Pt@BP shows a good cellular uptake rate and significantly increases the drug sensitivity of cisplatin-resistant cancer cell lines (A2780 and HepG2) compared with unmodified cisplatin. Our study is the first attempt to stabilize bare BP with cationic cisplatin species, and the generated Pt@BP could be used for potential synergistic photothermal/chemotherapy of cisplatin-resistant cancer.

Synergistic Effect of Retinoic Acid Polymeric Micelles and Prodrug for the Pharmacodynamic Evaluation of Tumor Suppression

All-trans retinoic acid (ATRA) is an effective agent that induces differentiation, inhibits cell proliferation, and acts as an anticancer agent. ATRA was successfully conjugated with Pluronic F127 via esterification to enhance its anticancer effects. Pluronic-ATRA showed high cytotoxicity and inhibitory concentrations (IC₅₀) 50% lower than those of ATRA in various breast cancer cell lines (4T1:31.16–8.57 μg/mL; EMT6: 50.48–7.08 μg/mL; MDA-MB-231:37.58–8.99 μg/mL; BT474:25.27–9.09 μg/mL). In combination with chemotherapy, Pluronic-ATRA synergistically enhanced the cytotoxic effects of cisplatin (CDDP). Pluronic-ATRA combined with CDDP effectively suppressed breast tumor growth in vivo. The results of this study demonstrate the potential of Pluronic-ATRA as an anticancer agent that can be used in combination therapy against solid tumors.

Pursuing Specific Chemotherapy of Orthotopic Breast Cancer with Lung Metastasis from Docking Nanoparticles Driven by Bioinspired Exosomes

Breast cancer develops from local tissue but is characterized by a distinct metastatic pattern involving regional lymph nodes and distant organs, which is the primary cause of high mortality in breast cancer patients. Herein, optimal docking nanoparticles (NPs) composed of a laurate-functionalized Pt(IV) prodrug (Pt(lau)), human serum albumin (HSA), and lecithin were predicted by computational modeling, prepared by nanoprecipitation, and validated by fluorescence spectroscopy. As macrophages have been reported to be preferentially recruited by breast cancer, Rex, the exosome spontaneously secreted by murine RAW 264.7 cells, was isolated to encapsulate the NPs. This high-performance delivery system, called NPs/Rex, possessed the desired physicochemical properties, enhanced colloidal stability, and redox-triggered release profile. Investigations of cytodynamics proved that NPs/Rex was internalized through multiple pathways, avoided entrapment by bilayers, and successfully platinized nucleic acids after bioreduction in the cytosol. Intracellular activation of Pt(lau) was confirmed by observing the characteristic effects of cisplatin on cell proliferation and the cell cycle following treatment with NPs/Rex. During in vivo application, the bioinspired Rex coating endowed docking NPs with prolonged blood circulation, smart organ tropism, and enhanced biocompatibility, as well as robust platinum (Pt) chemotherapy for breast cancer cells in orthotopic tumors of fat pads and metastatic nodules of lungs. Therefore, this favorable nanoplatform might provide valuable insight into the derivatization and development of Pt anticancer drugs used currently in the clinic.

Peptide-Based Autophagic Gene and Cisplatin Co-delivery Systems Enable Improved Chemotherapy Resistance

Cisplatin-based chemotherapy is a widely used first-line strategy for numerous cancers. However, drug resistances are often inevitable accompanied by the long-term use of cisplatin in vivo, significantly hampering its therapeutic efficacy and clinical outcomes. Among others, autophagy induction is one of the most common causes of tumor resistance to cisplatin. Herein, a self-assembled nanoprodrug platform was developed with the synergistic effect of cisplatin and RNAi to fight against cisplatin-resistant lung cancer. The nanoprodrug platform consists of three molecular modules, including prodrug complex of Pt(IV)-peptide-bis(pyrene), DSPE-PEG, and cRGD-modified DSPE-PEG. The Pt(IV) is immobilized with peptide via amide bonds, allowing the Pt(IV) to be loaded with a loading efficiency of >95% and rapid-release active platinum ions (Pt(II)) in the presence of glutathione (GSH). Meanwhile, the peptide of the prodrug complex could efficiently deliver Beclin1 siRNA ( Beclin1 is an autophagy initiation factor) to the cytoplasm, thereby leading to autophagy inhibition. In addition, incorporation of DSPE-PEG and cRGD-modified DSPE-PEG molecules improves the biocompatibility and cellular uptake of the nanoprodrug platform. In vivo results also indicate that the nanoprodrug platform significantly inhibits the growth of a cisplatin-resistant tumor on xenograft mice models with a remarkable inhibition rate, up to 84% after intravenous injection.

A novel smart PEGylated gelatin nanoparticle for co-delivery of doxorubicin and betanin: A strategy for enhancing the therapeutic efficacy of chemotherapy

Betanin (BET) can reduce the side effects of potent anticancer drugs e.g. doxorubicin (DOX) on the normal tissues in co-administration with them because of the synergistic therapeutic effect and consequently the reduced required amount of anticancer agents. Despite interest in the use of BET, incomplete oral absorption and low stability of BET limit its application. Thus, in this study to overcome the restrictions of BET and providing the synergistic effect of DOX@BET, we designed a new pH-responsive nanocarrier via decoration of gelatin nanoparticles (GNPs) by (methoxy poly (ethylene glycol)-poly ((2-dimethylamino) ethyl methacrylate-co-itaconic acid) (PGNPs). DOX and BET were effectively loaded (the loading capacity of 20.5% and 16.25%, respectively) into the PGNPs and this nanoplatform exhibited the suitable small particle size (162 nm). Additionally, the triggered release ability of drugs was studied through the assessment of simulated physiological and tumor tissue environments and showed the controlled release of DOX and BET with adjusting the pH of environment. Moreover, the synergistic effect of DOX@BET loaded PGNPs decreased the cell viability amount of breast cancer cells (MCF-7) respect to the free form of DOX or BET which indicated that the developed smart nanocarrier will be a hopeful nanocarrier for cancer therapy.

Tumor-Acidity-Cleavable Maleic Acid Amide (TACMAA): A Powerful Tool for Designing Smart Nanoparticles To Overcome Delivery Barriers in Cancer Nanomedicine

Over the past few decades, cancer nanomedicine has been under intensive development for applications in drug delivery, cancer therapy, and molecular imaging. However, there exist a series of complex biological barriers in the path of a nanomedicine from the site of administration to the site of action. These barriers considerably prevent a nanomedicine from reaching its targets in a sufficient concentration and thus severely limit its therapeutic benefits. According to the delivery process, these biological delivery barriers can be briefly summarized in the following order: blood circulation, tumor accumulation, tumor penetration, cellular internalization, and intracellular drug release. The therapeutic effect of a nanomedicine is strongly determined by its ability to overcome these barriers. However, advances in cancer biology have revealed that each barrier has its own distinct microenvironment, which imposes different requirements on the optimal design of nanocarriers, thus further complicating the delivery process. For example, the pH of blood is neutral, while the tumor extracellular environment features an acidic pH (pH_e ≈ 6.5-7.0) and the endosome and lysosome are more acidic (pH 5.5-4.5). The nanoparticles (NPs) should be able to change their properties to adapt to each individual environment for robust and effective delivery. This demand promotes the design and development of smart delivery carriers that can respond to endogenous and exogenous stimuli. It is well-documented that tumors develop acidic extracellular microenvironments with pH ≈ 6.5-7.0 due to their abnormal metabolism in comparison with normal tissues. This provides a unique tool for designing smart NP drug delivery systems. Our studies have revealed that the NPs' physiochemical properties, such as particle size and surface charge, have profound effects on their systemic transport in the body. In different delivery stages, the NPs should possess different sizes or surface charges for optimal performance. We developed a class of stimuli-responsive NPs by incorporating tumor-acidity-cleavable maleic acid amide (TACMAA) as a design feature. TACMAA is produced by the facile reaction of an amino group with 2,3-dimethylmaleic anhydride (DMMA) and its derivatives and can be cleaved under tumor acidity. By virtue of such characteristics, NPs containing TACMAA enable size or surface charge switching at tumor sites so that they can overcome those delivery barriers for improved drug delivery and cancer therapy. In this Account, we systemically review the development and evolution of TACMAA-based delivery systems and elaborate how TACMAA helps the innovation and design of intelligent nanocarriers for overcoming the delivery barriers. In particular, our Account focuses on five parts: TACMAA chemistry, tumor-acidity-triggered charge reversal, tumor-acidity-triggered shell detachment, tumor-acidity-triggered size transition, and tumor-acidity-triggered ligand reactivation. We provide detailed information on how tumor-acidity-triggered property changes correlate with the ability of NPs to overcome delivery barriers.

Engineering Anticancer Amphipathic Peptide-Dendronized Compounds for Highly-Efficient Plasma/Organelle Membrane Perturbation and Multidrug Resistance Reversal

Discovering new strategies for combating drug-resistant tumors becomes a worldwide challenge. Thereinto, stubborn drug-resistant tumor membrane is a leading obstacle on chemotherapy. Herein, we report a novel tumor-activatable amphipathic peptide-dendronized compound, which could form nanoaggregates in aqueous solutions, for perturbing tumor plasma/organelle membrane and reversing multidrug resistance. Distinguished from classical linear amphipathic peptide drugs for membrane disturbance, dendritic lysine-based architecture is designed as a multivalent scaffold to amplify the supramolecular interactions of cationic compound with drug-resistant tumor membrane. Moreover, arginine-rich residues as terminal groups are hopeful to generate multiple hydrogen bonding and electrostatic interactions with tumor membrane. On the other hand, antitumor molecule (doxorubicin) is devised as a hydrophobic moiety to intensify the membrane-inserting ability owing to the prominent interactions with hydrophobic domains of drug-resistant tumor membrane. As expected, these amphipathic peptide-dendronized compounds within the nanoaggregates could severely disturb both the structures and functions of tumor plasma/organelle membrane system, thereby resulting in the rapid leakage of many critical biomolecules, highly efficient apoptotic activation and antiapoptotic inhibition. This strategy on tumor membrane perturbation demonstrates a bran-new antitumor activity with high contributions to cell cycle arrest (at the S phase), strong apoptosis-inducing ability and satisfying cytotoxicity to a variety of drug-resistant tumor cell lines.

Hydrophilic and amphiphilic water-soluble dendrimer prodrugs suitable for parenteral administration of a non-soluble non-nucleoside HIV-1 reverse transcriptase inhibitor thiocarbamate derivative

Drugs delivered by proper carriers enter into the cells much more rapidly and carry out their action much more promptly than in the free forms. A high drug concentration can be sustained for longer periods of time at the target site in the cell. In in vivo conditions, this would translate into a reduction of systemic toxicity, dosage and frequency of dosing. Dendritic polymers significantly affect drug delivery in terms of reaching the target site, modifying the bio-distribution of the drug, and enhancing the efficacy of different drugs including anticancer compounds. 2-({[2-({[(2-tolyl)amino]carbonothioyl}oxy)ethyl]amino}carbo-nyl)benzoic acid 1 is a thiocarbamate derivative belonging to an already reported class of non-nucleoside HIV-1 reverse transcriptase inhibitors. In in vitro assay it showed no cytotoxic effects but was endowed with very low solubility and poor activity against wild-type HIV-1 (EC₅₀ = 27 μM). With the aim at improving its water solubility, 1 has been successfully incorporated inside non-toxic amino acids-modified core-shell hetero dendrimers. IR, NMR, zeta potential, mean size of particles, buffer capacity and in vitro release profile of prepared materials were reported. All dendriplexes were evaluated in cell-based assays to assess their cytotoxic profile. The obtained complexes, which harmonize a peripheral polycationic character and a buffer capacity which presuppose efficient cells penetration and increased residence time with a not PAMAM structured biodegradable scaffold, were well water-soluble and could rationally appear as a promising set of prodrugs for safe in vivo administrations.

The effect of surface poly(ethylene glycol) length on in vivo drug delivery behaviors of polymeric nanoparticles

Engineering nanoparticles of reasonable surface poly(ethylene glycol) (PEG) length is important for designing efficient drug delivery systems. Eliminating the disturbance by other nanoproperties, such as size, PEG density, etc., is crucial for systemically investigating the impact of surface PEG length on the biological behavior of nanoparticles. In the present study, nanoparticles with different surface PEG length but similar other nanoproperties were prepared by using poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) copolymers of different molecular weights and incorporating different contents of PCL₃₅₀₀ homopolymer. The molecular weight of PEG block in PEG-PCL was between 3400 and 8000 Da, the sizes of nanoparticles were around 100 nm, the terminal PEG density was controlled at 0.4 PEG/nm² (or the frontal PEG density was controlled at 0.16 PEG/nm²). Using these nanoproperties well-designed nanoparticles, we demonstrated PEG length-dependent changes in the biological behaviors of nanoparticles and exhibited nonmonotonic improvements as the PEG molecular weight increased from 3400 to 8000 Da. Moreover, under the experimental conditions, we found nanoparticles with a surface PEG length of 13.8 nm (MW = 5000 Da) significantly decreased the absorption with serum protein and interaction with macrophages, which led to prolonged blood circulation time, enhanced tumor accumulation and improved antitumor efficacy. The present study will help to establish a relatively precise relationship between surface PEG length and the in vivo behavior of nanoparticles.

PEI-NIR Heptamethine Cyanine Nanotheranostics for Tumor Targeted Gene Delivery

Polymer-based nanotheranostics are appealing tools for cancer treatment and diagnosis in the fast-growing field of nanomedicine. A straightforward preparation of novel engineered PEI-based nanotheranostics incorporating NIR fluorescence heptamethine cyanine dyes (NIRF-HC) to enable them with tumor targeted gene delivery capabilities is reported. Branched PEI-2 kDa (b2kPEI) is conjugated with IR-780 and IR-783 dyes by both covalent and noncovalent simple preparative methodologies varying their stoichiometry ratio. The as-prepared set of PEI-NIR-HC nanocarriers are assayed in vitro and in vivo to evaluate their gene transfection efficiency, cellular uptake, cytotoxicity, internalization and trafficking mechanisms, subcellular distribution, and tumor specific gene delivery. The results show the validity of the approach particularly for one of the covalent IR783-b2kPEI conjugates that exhibit an enhanced tumor uptake, probably mediated by organic anion transporting peptides, and favorable intracellular transport to the nucleus. The compound behaves as an efficient nanotheranostic transfection agent in NSG mice bearing melanoma G361 xenographs with concomitant imaging signal and gene concentration in the targeted tumor. By this way, advanced nanotheranostics with multifunctional capabilities (gene delivery, tumor-specific targeting, and NIR fluorescence imaging) are generated in which the NIRF-HC dye component accounts for simultaneous targeting and diagnostics, avoiding additional incorporation of additional tumor-specific targeting bioligands.

Ultrafast charge-conversional nanocarrier for tumor-acidity-activated targeted drug elivery

Nanocarriers with tumor-acidity-activated charge-conversional ability are of particular interest for targeted drug delivery in the field of precision nanomedicine. Nevertheless, the key challenge of this strategy is the slowness of reversing the surface charge at the tumor tissue. As a proof-of-concept, we synthesized the amphiphilic triblock polymer poly(ethylene glycol)-block-poly(2-carboxyethylacrylate)-block-poly(2-azepaneethylmethacrylate) (PEG-b-PCEA-b-PAEMA) to prepare the cisplatin-loaded nanocarrier UCC-NP/Pt. The PAEMA block at the physiological pH values was hydrophobic, which formed the core of UCC-NP/Pt. In contrast, at the tumor acidity, the tertiary amine groups of PAEMA block rapidly protonated, resulting in the ultrafast charge conversion of UCC-NP/Pt within 10 s. Such ultrafast charge-conversional effect more efficiently enhanced tumor cell internalization of nanocarriers, thus achieving targeted drug delivery, which in turn exhibited superior anticancer efficacy even in the cisplatin-resistant cells. This approach provides new avenues for tumor-acidity-activated targeted drug delivery.

A Simply Modified Lymphocyte for Systematic Cancer Therapy

Cytotherapy has received considerable attention in the field of cancer therapy, and various chemical or genetic methods have been applied to remold natural cells for improved therapeutic outcome of cytotherapy. A simple method to modify lymphocytes for cancer treatment by using a clinically used molecule, δ-aminolevulinic acid (δ-ALA), is reported here. After incubation with this molecule, tumor-targeted lymphocytes spontaneously synthesize anti-neoplastic drug protoporphyrin X (PpIX), and specifically accumulate in cancer tissue. Under periodic 630 nm laser irradiation, lymphocytes generate vesicle-like apoptotic body (Ab) containing the above-produced PpIX, and the facilitated delivery of PpIX from Ab makes an excellent therapeutic effect for Ras-mutated cancer cells under a second irradiation. Importantly, a microfluidic device is further fabricated to simplify cell sorting and drug synthesis with a one-step operation, which could promote generalization of this strategy. In vitro and in vivo studies confirm the success of such an easy-operated and global-regulated strategy for cancer therapy.

Injectable Bioresponsive Gel Depot for Enhanced Immune Checkpoint Blockade

Although cancer immunotherapy based on immune checkpoint inhibitors holds great promise toward many types of cancers, several challenges still remain, associated with low objective response of patient rate as well as systemic side effects. Here, a combination immunotherapy strategy is developed based on a thermogelling reactive oxygen species (ROS)-responsive polypeptide gel for sustained release of anti-programmed cell death-ligand 1 antibody and dextro-1-methyl tryptophan, inhibitor of indoleamine-2,3-dioxygenase with leveraging the ROS level in the tumor microenvironment. This bioresponsive gel depot can effectively reduce the local ROS level and facilitate release of immunotherapeutics, which leads to enhanced anti-melanoma efficacy in vivo.