Tumor-targeted pH/redox dual-sensitive unimolecular nanoparticles for efficient siRNA delivery

Engineered extracellular vesicles: A new approach for targeted therapy of tumors and overcoming drug resistance

Targeted delivery of anti-tumor drugs and overcoming drug resistance in malignant tumor cells remain significant clinical challenges. However, there are only few effective methods to address these issues. Extracellular vesicles (EVs), actively secreted by cells, play a crucial role in intercellular information transmission and cargo transportation. Recent studies have demonstrated that engineered EVs can serve as drug delivery carriers and showed promising application prospects. Nevertheless, there is an urgent need for further improvements in the isolation and purification of EVs, surface modification techniques, drug assembly processes, and precise recognition of tumor cells for targeted drug delivery purposes. In this review, we summarize the applications of engineered EVs in cancer treatment and overcoming drug resistance, and current challenges associated with engineered EVs are also discussed. This review aims to provide new insights and potential directions for utilizing engineered EVs as targeted delivery systems for anti-tumor drugs and overcoming drug resistance in the near future.

Glycyrrhetinic Acid Receptor-Mediated Zeolitic Imidazolate Framework-8 Loaded Doxorubicin as a Nanotherapeutic System for Liver Cancer Treatment

In this study, we designed and developed a DOX nanodrug delivery system (PEG-GA@ZIF-8@DOX) using ZIF-8 as the carrier and glycyrrhetinic acid (GA) as the targeting ligand. We confirmed that DOX was loaded and PEG-GA was successfully modified on the surface of the nanoparticles. The in vitro release profile of the system was investigated at pH 5.0 and 7.4. The cellular uptake, in vitro cytotoxicity, and lysosomal escape characteristics were examined using HepG2 cells. We established an H22 tumor-bearing mouse model and evaluated the in vivo antitumor activity. The results showed that the system had a uniform nanomorphology. The drug loading capacity was 11.22 ± 0.87%. In acidic conditions (pH 5.0), the final release rate of DOX was 57.73%, while at pH 7.4, it was 25.12%. GA-mediated targeting facilitated the uptake of DOX by the HepG2 cells. PEG-GA@ZIF-8@DOX could escape from the lysosomes and release the drug in the cytoplasm, thus exerting its antitumor effect. When the in vivo efficacy was analyzed, we found that the tumor inhibition rate of PEG-GA@ZIF-8@DOX was 67.64%; it also alleviated the loss of the body weight of the treated mice. This drug delivery system significantly enhanced the antitumor effect of doxorubicin in vitro and in vivo, while mitigating its toxic side effects.

A Comprehensive Review of Small Interfering RNAs (siRNAs): Mechanism, Therapeutic Targets, and Delivery Strategies for Cancer Therapy

Small interfering RNA (siRNA) delivery by nanocarriers has been identified as a promising strategy in the study and treatment of cancer. Short nucleotide sequences are synthesized exogenously to create siRNA, which triggers RNA interference (RNAi) in cells and silences target gene expression in a sequence-specific way. As a nucleic acid-based medicine that has gained popularity recently, siRNA exhibits novel potential for the treatment of cancer. However, there are still many obstacles to overcome before clinical siRNA delivery devices can be developed. In this review, we discuss prospective targets for siRNA drug design, explain siRNA drug properties and benefits, and give an overview of the current clinical siRNA therapeutics for the treatment of cancer. Additionally, we introduce the siRNA chemical modifications and delivery systems that are clinically sophisticated and classify bioresponsive materials for siRNA release in a methodical manner. This review will serve as a reference for researchers in developing more precise and efficient targeted delivery systems, promoting ongoing advances in clinical applications.

Targeting Breast Cancer Signaling via Phytomedicine and Nanomedicine

BACKGROUND

The development of breast cancer (BC) and how it responds to treatment have both been linked to the involvement of inflammation. Chronic inflammation is critical in carcinogenesis, leading to elevated DNA damage, impaired DNA repair machinery, cell growth, apoptosis, angiogenesis, and invasion. Studies have found several targets that selectively modulate inflammation in cancer, limit BC's growth, and boost treatment effectiveness. Drug resistance and the absence of efficient therapeutics for metastatic and triple-negative BC contribute to the poor outlook of BC patients.

SUMMARY

To treat BC, small-molecule inhibitors, phytomedicines, and nanoparticles are conjugated to attenuate BC signaling pathways. Due to their numerous target mechanisms and strong safety records, phytomedicines and nanomedicines have received much attention in studies examining their prospects as anti-BC agents by such unfulfilled demands.

KEY MESSAGES

The processes involved in the affiliation across the progression of tumors and the spread of inflammation are highlighted in this review. Furthermore, we included many drugs now undergoing clinical trials that target cancer-mediated inflammatory pathways, cutting-edge nanotechnology-derived delivery systems, and a variety of phytomedicines that presently address BC.

Facts and prospects of peptide in targeted therapy and immune regulation against triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. Due to the lack of specific therapeutic targets, treatment options are limited, and the recurrence and metastasis rate is high, the overall survival of patients is poor. However, with the discovery of some new targets and the corresponding immune regulation after targeting these targets, TNBC has a new hope in treatment. The peptide has a simple structure, strong binding affinity, and high stability, and has great potential in targeted therapy and immune regulation against TNBC. This review will discuss how single peptides and peptide combinations target triple-negative breast cancer to exert immunomodulatory effects. Among them, single peptides target specific receptors on TNBC cells, act as decoys to target key ligands in the regulatory pathway, and target TME-related cells. The combinations of peptides work in the form of cancer vaccines, engineered exosomes, microRNAs and other immune-related molecular pathways, immune checkpoint inhibitors, chimeric antigen receptor T cells, and drug-peptide conjugates. This article is mainly dedicated to exploring new treatment methods for TNBC to improve the curative effect and prolong the survival time of patients.

Unprotonatable and ROS-Sensitive Nanocarrier for NIR Spatially Activated siRNA Therapy with Synergistic Drug Effect

Although small interfering RNA (siRNA) therapy has achieved great progress, unwanted gene inhibition in normal tissues severely limits its extensive clinical applications due to uncontrolled siRNA biodistribution. Herein, a spatially controlled siRNA activation strategy is developed to achieve tumor-specific siRNA therapy without gene inhibition in the normal tissues. The quaternary ammonium moieties are conjugated to amphiphilic copolymers via reactive oxygen species (ROS)-sensitive thioketal (TK) linkers for co-delivery of siRNA and photosensitizer chlorin e6 (Ce6), showing excellent siRNA complexation capacity and near infrared (NIR)-controlled siRNA release. In the normal tissue, siRNAs are trapped and degraded in the endo-lysosomes due to the unprotonatable property of quaternary ammonium moiety, showing the siRNA activity "off" state. When NIR irradiation is spatially applied to the tumor tissue, the NIR irradiation/Ce6-induced ROS trigger siRNA endo-lysosomal escape and cytosolic release through the photochemical internalization effect and cleavage of TK bonds, respectively, showing the siRNA activity "on" state. The siRNA-mediated glutathione peroxidase 4 gene inhibition enhances ROS accumulation. The synergistic antitumor activity of Ce6 photodynamic therapy and gene inhibition is confirmed in vivo. Spatially controlled tumor-specific siRNA activation and co-delivery with Ce6 using unprotonatable and ROS-sensitive cationic nanocarriers provide a feasible strategy for tumor-specific siRNA therapy with synergistic drug effects.

Challenges for the application of EGFR-targeting peptide GE11 in tumor diagnosis and treatment

Abnormal regulation of cell signaling pathways on cell survival, proliferation and migration contributes to the development of malignant tumors. Among them, epidermal growth factor receptor (EGFR) is one of the most important biomarkers in many types of malignant solid tumors. Its over-expression and mutation status can be served as a biomarker to identify patients who can be benifit from EGFR tyrosine kinase inhibitors and anti-EGFR monocloncal antibody (mAb) therapy. For decades, researches on EGFR targeted ligands were actively carried out to identify potent candidates for cancer therapy. An ideal EGFR ligand can competitively inhibit the binding of endogenous growth factor, such as epidermal growth factor (EGF) and transforming growth factor-α(TGF-α) to EGFR, thus block EGFR signaling pathway and downregulate EGFR expression. Alternatively, conjugation of EGFR ligands on drug delivery systems (DDS) can facilitate targeting delivery of therapeutics or diagnostic agents to EGFR over-expression tumors via EGFR-mediated endocytosis. GE11 peptide is one of the potent EGFR ligand screened from a phage display peptide library. It is a dodecapeptide that can specifically binds to EGFR with high affinity and selectivity. GE11 has been widely used in the diagnosis and targeted delivery of drugs for radiotherapy, genetherapy and chemotherpy against EGFR positive tumors. In this review, the critical factors affecting the in vivo and in vitro targeting performance of GE11 peptide, including ligand-receptor intermolecular force, linker bond properties and physiochemical properties of carrier materials, are detailedly interpreted. This review provides a valuable vision for the rational design and optimization of GE11-based active targeting strategies for cancer treatment, and it will promote the translation studies of GE11 from lab research to clinical application.

Drug Self-delivery Nanorods Enhance Photodynamic Therapy of Triple-Negative Breast Cancer by inhibiting Oxidative Phosphorylation

Photodynamic therapy (PDT) shows very high potential for the clinical treatment of triple-negative breast cancer. However, the efficacy of PDT is significantly weakened by tumor hypoxia, the relatively high intracellular glutathione levels and the active proliferation of cancer cells. To address these issues, we developed a novel drug self-delivery nanorod (defined as AINRs) through the hydrophobic interaction among the mitochondrial complex III inhibitor (atovaquone, ATO), the photosensitizer (indocyanine green, ICG) and the dispersion stabilizer (distearoyl phosphoethanolamine-polyethylene glycol 2000, DSPE-PEG 2000). The AINRs showed a rod-like morphology with a mean diameter of 120.6 ± 5.4 nm, a zeta potential of -26.35 ± 1.63 mV and a significantly high drug loading rate of 93.48%. The results of in vitro cell experiments involving triple-negative breast cancer cell lines (4T1 cells and MDA-MB-231 cells) indicated that the AINRs could effectively block the oxidative phosphorylation of cancer cells through the inhibition of mitochondrial complex III, which results in the reduction of endogenous oxygen consumption and the decrease of the intracellular ATP level. The reduction of ATP content further inhibited the glutathione synthesis and arrested the cell cycle at the S-phase, which results in enhanced in vitro PDT efficacy of ICG. The results of in vivo antitumor activity in 4T1-bearing mice showed that the tumor growth inhibition rate of the AINRs with near-infrared laser irradiation (NIR) was 90%, whereas the tumor growth inhibition rates of the AINRs without NIR, ICG with NIR and doxorubicin (3 mg/kg) were only 31.68%, 61.15% and 24.59%, respectively. In addition, the results of safety studies, including body weights, biochemical indicators and H&E staining images of the main organs demonstrated the security of the AINRs. In summary, this study showed that the oxidative phosphorylation inhibition of triple-negative breast cancer was a safe and effective method to enhance its PDT efficacy.

Activatable “Matryoshka” nanosystem delivery NgBR siRNA and control drug release for stepwise therapy and evaluate drug resistance cancer

Drug resistance is always a challenge in conquering breast cancer clinically. Recognition of drug resistance and enhancing the sensitivity of the tumor to chemotherapy is urgent. Herein, a dual-responsive multi-function “Matryoshka" nanosystem is designed, it activates in the tumor microenvironment, decomposes layer by layer, and release gene and drug in sequence. The cell is re-educated by NgBR siRNA first to regain the chemosensitivity through regulating the Akt pathway and inhibit ERα activation, then the drugs loaded in the core are controlled released to killing cells. Carbonized polymer dots are loaded into the nanosystem as an efficient bioimaging probe, due to the GE11 modification, the nanosystem can be a seeker to recognize and evaluate drug-resistance tumors by photoacoustic imaging. In the tumor-bearing mouse, the novel nanosystem firstly enhances the sensitivity to chemotherapy by knockdown NgBR, inducing a much higher reduction in NgBR up to 52.09%, then effectively inhibiting tumor growth by chemotherapy, tumor growth in nude mouse was inhibited by 70.22%. The nanosystem also can inhibit metastasis, prolong survival time, and evaluate tumor drug resistance by real-time imaging. Overall, based on regulating the key molecules of drug resistance, we created visualization nanotechnology and formatted new comprehensive plans with high bio-safety for tumor diagnosis and treatment, providing a personalized strategy to overcome drug resistance clinically.

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Knockdown NgBR regulate the Akt pathway and inhibit ERα activate, enhance the sensitivity of chemotherapy.

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Knockdown of NgBR inhibits metastasis and prolongs survival.

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Nanosystem can evaluate drug resistance and kill tumors at the same time.

Stimuli-responsive and core cross-linked micelles developed by NiCCo-PISA of helical poly(aryl isocyanide)s

We report the synthesis of redox- and pH-sensitive block copolymer micelles that contain chiral cores composed of helical poly(aryl isocyanide)s. Pentafluorophenyl (PFP) ester-containing micelles synthesised via nickel-catalysed coordination polymerisation-induced self-assembly (NiCCo-PISA) of helical poly(aryl isocyanide) amphiphilic diblock copolymers are modified post-polymerisation with various diamines to introduce cross-links and/or achieve stimulus-sensitive nanostructures. The successful introduction of the diamines is confirmed by Fourier-transform infrared spectroscopy (FT-IR), while the stabilisation effect of the cross-linking is explored by dynamic light scattering (DLS). The retention of the helicity of the core-forming polymer block is verified by circular dichroism (CD) spectroscopy and the stimuli-responsiveness of the nanoparticles towards a reducing agent (l-glutathione, GSH) and pH is evaluated by following the change in the size of the nanoparticles by DLS. These stimuli-responsive nanoparticles could find use in applications such as drug delivery, nanosensors or biological imaging.

Spherical micelles with a helical core synthesised by NiCCo-PISA are functionalised with different cross-linkers to make stimulus-sensitive nanostructures.

Cytosolic protein delivery using pH-responsive, charge-reversible lipid nanoparticles

Although proteins have attractive features as biopharmaceuticals, the difficulty in delivering them into the cell interior limits their applicability. Lipid nanoparticles (LNPs) are a promising class of delivery vehicles. When designing a protein delivery system based on LNPs, the major challenges include: (i) formulation of LNPs with defined particle sizes and dispersity, (ii) efficient encapsulation of cargo proteins into LNPs, and (iii) effective cellular uptake and endosomal release into the cytosol. Dioleoylglycerophosphate-diethylenediamine (DOP-DEDA) is a pH-responsive, charge-reversible lipid. The aim of this study was to evaluate the applicability of DOP-DEDA-based LNPs for intracellular protein delivery. Considering the importance of electrostatic interactions in protein encapsulation into LNPs, a negatively charged green fluorescent protein (GFP) analog was successfully encapsulated into DOP-DEDA-based LNPs to yield diameters and polydispersity index of < 200 nm and < 0.2, respectively. Moreover, ~ 80% of the cargo proteins was encapsulated into the LNPs. Cytosolic distribution of fluorescent signals of the protein was observed for up to ~ 90% cells treated with the LNPs, indicating the facilitated endocytic uptake and endosomal escape of the cargo attained using the LNP system.

Polydopamine nanoparticles with different sizes for NIR-promoted gene delivery and synergistic photothermal therapy

The combination of photothermal therapy and gene therapy has received increasing attention in tumor treatment. However, how to improve synergistic efficacy has become a new challenge. NIR light has a great potential in tumor treatment because of its considerable penetration depth and spatiotemporal controllability. Polydopamine is a popular photothermal conversion agent, which has desirable photothermal conversion ability and good biocompatibility. In this research, polydopamine-polyethyleneimine nanoparticles with diameters of 13 nm (SPPNPs) and 236 nm (LPPNPs) were prepared as gene carriers. The size of polydopamine nanoparticles had great effect on the complexes formation, photothermal conversion ability and gene transfection efficiency. After loading gene, the SPPNPs/gene and LPPNPs/gene complexes were about 60-80 nm and 240 nm respectively, indicating different styles of complexes formation. Both SPPNPs/gene and LPPNPs/gene complexes without NIR irradiation could achieve similar gene transfection efficiency as commercial lipofectamine 2000, while with lower cytotoxicity. Due to better photothermal conversion ability, the transfection level of LPPNPs/pGL-3 complexes increased to 4.5 times after NIR irradiation (2.6 W/cm², 15 min), which ascribed to the quick escape of gene complexes from the endosome. The produced heat under NIR irradiation could also ablate tumor cells. So LPPNPs were chosen to deliver tumor suppressor gene p53 DNA to investigate the synergistic efficacy of gene/photothermal therapy. The tumor in KB tumor-bearing mice was almost eliminated after intratumoral injection, and the tumor inhibition efficacy of gene/photothermal synergistic therapy achieved to 99%. By combining NIR-promoted gene transfection and gene/photothermal synergistic therapy, the LPPNPs hold great promise in practical tumor treatment.

Synchronous conjugation of i-motif DNA and therapeutic siRNA on the vertexes of tetrahedral DNA nanocages for efficient gene silence

The functionality of DNA biomacromolecules has been widely excavated, as therapeutic drugs, carriers, and functionalized modification derivatives. In this study, we developed a series of DNA tetrahedron nanocages (Td), via synchronous conjugating different numbers of i-(X) and therapeutic siRNA on four vertexes of tetrahedral DNA nanocage (aX-Td@bsiRNA, a+b = 4). This i-motif-conjugated Td exhibited good endosomal escape behaviours in A549 tumor cells, and the escape efficiency was affected by the number of i-motif. Furthermore, the downregulating mRNA and protein expression level of epidermal growth factor receptor (EGFR) caused by this siRNA embedded Td were verified in A549 cells. The tumor growth inhibition efficiency of the 2X-Td@2siRNA treated group in tumor-bearing mice was significantly higher than that of non-i-motif-conjugated Td@2siRNA (3.14-fold) and free siRNA (3.63-fold). These results demonstrate a general strategy for endowing DNA nanostructures with endosomal escape behaviours to achieve effective in vivo gene delivery and therapy.

Calcium phosphate-polymeric nanoparticle system for co-delivery of microRNA-21 inhibitor and doxorubicin

Targeted combination therapy has shown promise to achieve maximum therapeutic efficacy by overcoming drug resistance. MicroRNA-21 (miR-21) is frequently overexpressed in various cancer types including breast and non-small cell lung cancer and its functions can be inhibited by miR inhibitor (miR-21i). A combination of miR-21i and a chemo drug, doxorubicin (Dox), can provide synergistic effects. Here, we developed a calcium phosphate (CaP)-coated nanoparticle (NP) formulation to co-deliver miR-21i along with Dox. This NP design can be used to deliver the two agents with different physiochemical properties. The NP formulation was optimized for particle size, polydispersity, Dox loading, and miR-21i loading. The NP formulation was confirmed to downregulate miR-21 levels and upregulate tumor suppressor gene levels. The cytotoxic efficacy of the combined miR-21i and Dox-containing NPs was found to be higher than that of Dox. Therefore, the CaP-coated hybrid lipid-polymeric NPs hold potential for the delivery of miR-21i and Dox.

Novel Approaches of Dysregulating Lysosome Functions in Cancer Cells by Specific Drugs and Its Nanoformulations: A Smart Approach of Modern Therapeutics

The smart strategy of cancer cells to bypass the caspase-dependent apoptotic pathway has led to the discovery of novel anti-cancer approaches including the targeting of lysosomes. Recent discoveries observed that lysosomes perform far beyond just recycling of cellular waste, as these organelles are metabolically very active and mediate several signalling pathways to sense the cellular metabolic status. These organelles also play a significant role in mediating the immune system functions. Thus, direct or indirect lysosome-targeting with different drugs can be considered a novel therapeutic approach in different disease including cancer. Recently, some anticancer lysosomotropic drugs (eg, nortriptyline, siramesine, desipramine) and their nanoformulations have been engineered to specifically accumulate within these organelles. These drugs can enhance lysosome membrane permeabilization (LMP) or disrupt the activity of resident enzymes and protein complexes, like v-ATPase and mTORC1. Other anticancer drugs like doxorubicin, quinacrine, chloroquine and DQ661 have also been used which act through multi-target points. In addition, autophagy inhibitors, ferroptosis inducers and fluorescent probes have also been used as novel theranostic agents. Several lysosome-specific drug nanoformulations like mixed charge and peptide conjugated gold nanoparticles (AuNPs), Au-ZnO hybrid NPs, TPP-PEG-biotin NPs, octadecyl-rhodamine-B and cationic liposomes, etc. have been synthesized by diverse methods. These nanoformulations can target cathepsins, glucose-regulated protein 78, or other lysosome specific proteins in different cancers. The specific targeting of cancer cell lysosomes with drug nanoformulations is quite recent and faces tremendous challenges like toxicity concerns to normal tissues, which may be resolved in future research. The anticancer applications of these nanoformulations have led them up to various stages of clinical trials. Here in this review article, we present the recent updates about the lysosome ultrastructure, its cross-talk with other organelles, and the novel strategies of targeting this organelle in tumor cells as a recent innovative approach of cancer management.

In vivo targeted delivery of nucleic acids and CRISPR genome editors enabled by GSH-responsive silica nanoparticles

The rapid development of gene therapy and genome editing techniques brings up an urgent need to develop safe and efficient nanoplatforms for nucleic acids and CRISPR genome editors. Herein we report a stimulus-responsive silica nanoparticle (SNP) capable of encapsulating biomacromolecules in their active forms with a high loading content and loading efficiency as well as a well-controlled nanoparticle size (~50 nm). A disulfide crosslinker was integrated into the silica network, endowing SNP with glutathione (GSH)-responsive cargo release capability when internalized by target cells. An imidazole-containing component was incorporated into the SNP to enhance the endosomal escape capability. The SNP can deliver various cargos, including nucleic acids (e.g., DNA and mRNA) and CRISPR genome editors (e.g., Cas9/sgRNA ribonucleoprotein (RNP), and RNP with donor DNA) with excellent efficiency and biocompatibility. The SNP surface can be PEGylated and functionalized with different targeting ligands. In vivo studies showed that subretinally injected SNP conjugated with all-trans-retinoic acid (ATRA) and intravenously injected SNP conjugated with GalNAc can effectively deliver mRNA and RNP to murine retinal pigment epithelium (RPE) cells and liver cells, respectively, leading to efficient genome editing. Overall, the SNP is a promising nanoplatform for various applications including gene therapy and genome editing.

2,2-Bis(hydroxymethyl) propionic acid based cyclic carbonate monomers and their (co)polymers as advanced materials for biomedical applications

Designing grafted biodegradable polymers with tailored multi-functional properties is one of the most researched fields with extensive biomedical applications. Among many biodegradable polymers, polycarbonates have gained much attention due to their ease of synthesis, high drug loading, and excellent biocompatibility profiles. Among various monomers, 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) derived cyclic carbonate monomers have been extensively explored in terms of their synthesis as well as their polymerization. Since the late 90s, significant advancements have been made in the design of bis-MPA derived cyclic carbonate monomers as well as in their reaction schemes. Currently, bis-MPA derived polycarbonates have taken a form of an entire platform with a multitude of applications, the latest being in the field of nanotechnology, targeted drug, and nucleic acid delivery. The present review outlines an up to date developments that have taken place in the last two decades in the design, synthesis, and biomedical applications of bis-MPA derived cyclic carbonates and their (co)polymers.

A review of nanoparticle drug delivery systems responsive to endogenous breast cancer microenvironment

Breast cancer, as a malignant disease that seriously threatens women's health, urgently needs to be researched to develop effective and safe therapeutic drugs. Nanoparticle drug delivery systems (NDDS), provide a powerful means for drug targeting to the breast cancer, enhancing the bioavailability and reducing the adverse effects of anticancer drug. However, the breast cancer microenvironment together with heterogeneity of cancer, impedes the tumor targeting effect of NDDS. Breast cancer microenvironment, exerts endogenous stimuli, such as hypoxia, acidosis, and aberrant protease expression, shape a natural shelter for tumor growth, invasion and migration. On the basis of the ubiquitous of endogenous stimuli in the breast cancer microenvironment, researchers exploited them to design the stimuli-responsive NDDS, which response to endogenous stimulus, targeted release drug in breast cancer microenvironment. In this review, we highlighted the effect of the breast cancer microenvironment, summarized innovative NDDS responsive to the internal stimuli in the tumor microenvironment, including the material, the targeting groups, the loading drugs, targeting position and the function of stimuli-responsive nanoparticle drug delivery system. The limitations and potential applications of the stimuli-responsive nanoparticle drug delivery systems for breast cancer treatment were discussed to further the application.

Polypeptide-based drug delivery systems for programmed release

Recent years have seen increasing interests in the use of ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs) to prepare synthetic polypeptides, a class of biocompatible and versatile materials, for various biomedical applications. Because of their rich side-chain functionalities, diverse hydrophilicity/hydrophobicity profiles, and the capability of forming stable secondary structures, polypeptides can assemble into a variety of well-organized nano-structures that have unique advantages in drug delivery and controlled release. Herein, we review the design and use of polypeptide-based drug delivery system derived from NCA chemistry, and discuss the future perspectives of this exciting and important biomaterial area that may potentially change the landscape of next-generation therapeutics and diagnosis. Given the high significance of precise control over release for polypeptide-based systems, we specifically focus on the versatile designs of drug delivery systems capable of programmed release, through the changes in the chemical and physical properties controlled by the built-in molecular structures of polypeptides.

Strategies and challenges to improve the performance of tumor-associated active targeting

Over the past decade, nanoparticle-based drug delivery systems have been extensively explored. However, the average tumour enrichment ratio of passive targeting systems corresponds to only 0.7% due to the nonspecific uptake by normal organs and poor selective retention in tumours. The therapeutic specificity and efficacy of nano-medicine can be enhanced by equipping it with active targeting ligands, although it is not possible to ignore the recognition and clearance of the reticuloendothelial system (RES) caused by targeting ligands. Given the complexity of the systemic circulation environment, it is necessary to carefully consider the hydrophobicity, immunogenicity, and electrical property of targeting ligands. Thus, for an active targeting system, the targeting ligands should be shielded in blood circulation and de-shielded in the tumour region for enhanced tumour accumulation. In this study, strategies for improving the performance of active targeting ligands are introduced. The strategies include irreversible shielding, reversible shielding, and methods of modulating the multivalent interactions between ligands and receptors. Furthermore, challenges and future developments in designing active ligand targeting systems are also discussed.

Polymeric nano-carriers for on-demand delivery of genes via specific responses to stimuli

Polymeric nano-carriers have been developed as a most capable and feasible technology platform for gene therapy. As vehicles, polymeric nano-carriers are obliged to possess high gene loading capability, low immunogenicity, safety, and the ability to transfer various genetic materials into specific sites of target cells to express therapeutic proteins or block a process of gene expression. To this end, various types of polymeric nano-carriers have been prepared to release genes in response to stimuli such as pH, redox, enzymes, light and temperature. These stimulus-responsive nano-carriers exhibit high gene transfection efficiency and low cytotoxicity. In particular, dual- and multi-stimulus-responsive polymeric nano-carriers can respond to a combination of signals. Markedly, these combined responses take place either simultaneously or in a sequential manner. These dual-stimulus-responsive polymeric nano-carriers can control gene delivery with high gene transfection both in vitro and in vivo. In this review paper, we highlight the recent exciting developments in stimulus-responsive polymeric nano-carriers for gene delivery applications.

Hybrid Graphene-Gold Nanoparticle-based Nucleic Acid Conjugates for Cancer-Specific Multimodal Imaging and Combined Therapeutics

Nanoparticle-based nucleic acid conjugates (NP-NACs) hold great promise for theragnostic (diagnostic and therapeutic) applications. However, several limitations have hindered the realization of their full potential in the clinical treatment of cancer and other diseases. In diagnosis, NP-NACs, combined with conventional optical sensing systems, have been applied for cancer detection in vitro, but low signal-to-noise ratios limit their broad in vivo applications. Meanwhile, the efficiency of NP-NAC-mediated cancer therapies has been limited through the adaptation of alternative pro-survival pathways in cancer cells. The recent emergence of personalized and precision medicine has outlined the importance of both accurate diagnosis and efficient therapeutics in a single platform. As such, we report the controlled assembly of hybrid graphene oxide/gold nanoparticle-based cancer-specific NACs (Au@GO NP-NACs) for multimodal imaging and combined therapeutics. Our developed Au@GO NP-NACs shows excellent surface-enhanced Raman scattering (SERS)-mediated live-cell cancer detection and multimodal synergistic cancer therapy through the use of photothermal, genetic, and chemotherapeutic strategies. Synergistic and selective killing of cancer cells were then demonstrated by using in vitro microfluidic models and nine different cancer cell lines by further incorporating near-infrared photothermal hyperthermia, a Topoisomerase II anti-cancer drug, and cancer targeting peptides. Moreover, with distinctive advantages of the Au@GO NP-NACs for cancer theragnostics, we further demonstrated precision cancer treatment through the detection of cancer cells in vivo using SERS followed by efficient ablation of the tumor. Therefore, our Au@GO NP-NACs could pave a new road for the advanced theragnostics of cancer as well as many other diseases.

Silencing of BCSG1 with specific siRNA via nanocarriers for breast cancer treatment

Breast cancer is the most common cancer diagnosed in women worldwide. The current treatments for breast cancer, including surgery, radiotherapy and chemotherapy aim to destroy cancer cells, whereas they also cause damage to normal tissues and cells. Thus, an effective, safe and specific breast cancer treatment is urgently needed. The breast cancer-specific gene 1 (BCSG1) has been shown to be specific for the development of breast cancer and is a target for breast cancer diagnosis and treatment. It is expected to silence the expression of BCSG1 at the gene level for the purpose of treating breast cancer. The effect of RNAi technology on silencing target genes is comparable to gene knockout and has been widely used in animal experiments and plant genetic research. In the field of cancer therapy, numerous investigators have used siRNAs to specifically inhibit target genes, demonstrating that siRNAs can treat cancers at the molecular level. However, the delivery of siRNAs into humans needs to overcome multiple physiological barriers, limiting the clinical applications of siRNAs. This review focuses on the application of BCSG1 gene, siRNAs in cancer treatments, and the nanocarrier delivery system of siRNAs. The potential application and research value of BCSG1-specific siRNA in the treatment of breast cancer are discussed.

Biodegradable dendritic Boltorn™ nanoconstructs: A promising avenue for cancer theranostics

The family of Boltorn™ H40 dendrimers is an imperative subclass of hyperbranched biodegradable polymers (HBPs), which has received mounting attention as a result of its inimitable chemical, physical and biodegradable properties. These properties embrace three-dimensional dendrimeric nanoarchitecture to avert tanglement between polymer branches, adequate spatial cavities for increased encapsulation of guest molecules, good solubility as well as low viscosity to improve processability, and a huge number of surface functional groups for chemical manipulations. Similarly, low toxicity, non-immunogenicity, and natural biodegradation are significant and critical advantages in therapeutic applications as compared to other dendritic polymers. All these characteristics of Boltorn™ H40 are of pronounced importance for planning and developing advanced targeted cargo delivery carriers for cancer therapy. The present review highlights the applications of Boltorn™ H40 HBPs for the transport of chemotherapeutic agents to manage various types of cancers.

Precise design strategies of nanomedicine for improving cancer therapeutic efficacy using subcellular targeting

Therapeutic efficacy against cancer relies heavily on the ability of the therapeutic agents to reach their final targets. The optimal targets of most cancer therapeutic agents are usually biological macromolecules at the subcellular level, which play a key role in carcinogenesis. Therefore, to improve the therapeutic efficiency of drugs, researchers need to focus on delivering not only the therapeutic agents to the target tissues and cells but also the drugs to the relevant subcellular structures. In this review, we discuss the most recent construction strategies and release patterns of various cancer cell subcellular-targeting nanoformulations, aiming at providing guidance in the overall design of precise nanomedicine. Additionally, future challenges and potential perspectives are illustrated in the hope of enhancing anticancer efficacy and accelerating the translational progress of precise nanomedicine.

Robust and smart polypeptide-based nanomedicines for targeted tumor therapy

Nanomedicines based on synthetic polypeptides are among the most versatile and advanced platforms for tumor therapy. Notably, several polypeptide-based nanodrugs are currently under human clinical assessments. The previous (pre)clinical studies clearly show that dynamic stability (i.e. stable in circulation while destabilized in tumor) of nanomedicines plays a vital role in their anti-tumor performance. Various strategies have recently been developed to design dynamically stabilized polypeptide-based nanomedicines by e.g. crosslinking the nanovehicles with acid, reactive oxygen species (ROS), glutathione (GSH), or photo-sensitive linkers, inter-crosslinking between vehicles and drugs, introducing π-π stacking or lipid-lipid interactions in the nanovehicles, chemically conjugating drugs to vehicles, and forming unimolecular micelles. Interestingly, these robust and smart nanodrugs have demonstrated improved tumor targetability, anti-tumor efficacy, as well as safety profiles in different tumor models. In this review, representative strategies to robust and smart polypeptide-based nanomedicines for targeted treatment of varying malignancies are highlighted. The exciting development of dynamic nanomedicines will foresee further increasing clinical translation in the future.

Fluorescence for biological logic gates

Biological logic gates are smart probes able to respond to biological conditions in behaviors similar to computer logic gates, and they pose a promising challenge for modern medicine. Researchers are creating many kinds of smart nanostructures that can respond to various biological parameters such as pH, ion presence, and enzyme activity. Each of these conditions alone might be interesting in a biological sense, but their interactions are what define specific disease conditions. Researchers over the past few decades have developed a plethora of stimuli-responsive nanodevices, from activatable fluorescent probes to DNA origami nanomachines, many explicitly defining logic operations. Whereas many smart configurations have been explored, in this review we focus on logic operations actuated through fluorescent signals. We discuss the applicability of fluorescence as a means of logic gate implementation, and consider the use of both fluorescence intensity as well as fluorescence lifetime.

Stimuli-responsive Drug Delivery Nanocarriers in the Treatment of Breast Cancer

Stimuli-responsive drug-delivery nanocarriers (DDNs) have been increasingly reported in the literature as an alternative for breast cancer therapy. Stimuli-responsive DDNs are developed with materials that present a drastic change in response to intrinsic/chemical stimuli (pH, redox and enzyme) and extrinsic/physical stimuli (ultrasound, Near-infrared (NIR) light, magnetic field and electric current). In addition, they can be developed using different strategies, such as functionalization with signaling molecules, leading to several advantages, such as (a) improved pharmaceutical properties of liposoluble drugs, (b) selectivity with the tumor tissue decreasing systemic toxic effects, (c) controlled release upon different stimuli, which are all fundamental to improving the therapeutic effectiveness of breast cancer treatment. Therefore, this review summarizes the use of stimuli-responsive DDNs in the treatment of breast cancer. We have divided the discussions into intrinsic and extrinsic stimuli and have separately detailed them regarding their definitions and applications. Finally, we aim to address the ability of these stimuli-responsive DDNs to control the drug release in vitro and the influence on breast cancer therapy, evaluated in vivo in breast cancer models.

Hybrid micelles based on Pt (IV) polymeric prodrug and TPGS for the enhanced cytotoxicity in drug-resistant lung cancer cells

Multidrug resistance (MDR) is a primary cause of failure in oncotherapy and interest is growing in the design of multi-stimuli responsive nano-carriers to synergistically deliver chemotherapeutic agents and P-gp inhibitors to reverse MDR. The hybrid micelles based on a Platinum (IV)-coordinate polymeric prodrugs and TPGS were developed to improve chemotherapy and reduce side effects. The pH/redox dual-sensitive polymers were synthesized by condensation polymerization using ortho ester monomer and diamminedichlorodisuccinatoplatinum (DSP). The hybrid micelles possessed uniform size (38 nm) and displayed good stability in various physiological conditions. In contrast, in vitro drug release profiles indicated that these micelles could be completely depolymerized under acidic and reducing environment, thereby more than 80 % cisplatin were released within 12 h at pH 5.0 plus 10 mM DTT. More importantly, a large amount of TPGS released simultaneously could effectively inhibit the function of drug efflux pumps, which significantly enhanced the cytotoxicity of cisplatin against A549/DDP cells. The growth inhibition rate of micelles on A549/DDP multicellular spheroids was 79.5 %, while that of free cisplatin was only 6.8 %. Therefore, these hybrid micelles are promising in overcoming tumor MDR and worth doing further research in vivo and extend to other therapeutic agents.

Silver Nanoparticles Surface-Modified with Carbosilane Dendrons as Carriers of Anticancer siRNA

Gene therapy is a promising approach in cancer treatment; however, current methods have a number of limitations mainly due to the difficulty in delivering therapeutic nucleic acids to their sites of action. The application of non-viral carriers based on nanomaterials aims at protecting genetic material from degradation and enabling its effective intracellular transport. We proposed the use of silver nanoparticles (AgNPs) surface-modified with carbosilane dendrons as carriers of anticancer siRNA (siBcl-xl). Using gel electrophoresis, zeta potential and hydrodynamic diameter measurements, as well as transmission electron microscopy, we characterized AgNP:siRNA complexes and demonstrated the stability of nucleic acid in complexes in the presence of RNase. Hemolytic properties of free silver nanoparticles and complexes, their effect on lymphocyte proliferation and cytotoxic activity on HeLa cells were also examined. Confocal microscopy proved the effective cellular uptake of complexes, indicating the possible use of this type of silver nanoparticles as carriers of genetic material in gene therapy.

Platinum complexes of curcumin delivered by dual-responsive polymeric nanoparticles improve chemotherapeutic efficacy based on the enhanced anti-metastasis activity and reduce side effects

Platinum-based chemotherapy is used for non-small cell lung cancer (NSCLC). However, it has side effects and minimum efficacy against lung cancer metastasis. In this study, platinum-curcumin complexes were loaded into pH and redox dual-responsive nanoparticles (denoted as Pt-CUR@PSPPN) to facilitate intracellular release and synergistic anti-cancer effects. Pt-CUR@PSPPN was prepared by a nano-precipitation method and had a diameter of ∼100 nm. The nanoparticles showed increased anti-cancer effects both in vivo and in vitro. In addition, Pt-CUR@PSPPN blocked PI3K/AKT signal transduction pathway and inhibited MMP2 and VEGFR2, resulting in enhanced anti-metastatic activity. Furthermore, reduced side effects were also observed. In conclusion, Pt-CUR@PSPPN provided a novel and attractive therapeutic strategy for NSCLC.

Photoactivation of sulfonated polyplexes enables localized gene silencing by DsiRNA in breast cancer cells

Translation potential of RNA interference nanotherapeutics remains challenging due to in vivo off-target effects and poor endosomal escape. Here, we developed novel polyplexes for controlled intracellular delivery of dicer substrate siRNA, using a light activation approach. Sulfonated polyethylenimines covalently linked to pyropheophorbide-α for photoactivation and bearing modified amines (sulfo-pyro-PEI) for regulated endosomal escape were investigated. Gene knock-down by the polymer-complexed DsiRNA duplexes (siRNA-NPs) was monitored in breast cancer cells. Surprisingly, sulfo-pyro-PEI/siRNA-NPs failed to downregulate the PLK1 or eGFP proteins. However, photoactivation of these cell associated-polyplexes with a 661-nm laser clearly restored knock-down of both proteins. In contrast, protein down-regulation by non-sulfonated pyro-PEI/siRNA-NPs occurred without any laser treatments, indicating cytoplasmic disposition of DsiRNA followed a common intracellular release mechanism. Therefore, sulfonated pyro-PEI holds potential as a unique trap and release light-controlled delivery platform for on-demand gene silencing bearing minimal off target effects.

CX3CR1-Targeted PLGA Nanoparticles Reduce Microglia Activation and Pain Behavior in Rats with Spinal Nerve Ligation

Activation of CX3CR1 in microglia plays an important role in the development of neuropathic pain. Here, we investigated whether neuropathic pain could be attenuated in spinal nerve ligation (SNL)-induced rats by reducing microglial activation through the use of poly(D,L-lactic-co-glycolic acid) (PLGA)-encapsulated CX3CR1 small-interfering RNA (siRNA) nanoparticles. After confirming the efficacy and specificity of CX3CR1 siRNA, as evidenced by its anti-inflammatory effects in lipopolysaccharide-stimulated BV2 cells in vitro, PLGA-encapsulated CX3CR1 siRNA nanoparticles were synthesized by sonication using the conventional double emulsion (W/O/W) method and administered intrathecally into SNL rats. CX3CR1 siRNA-treated rats exhibited significant reductions in the activation of microglia in the spinal dorsal horn and a downregulation of proinflammatory mediators, as well as a significant attenuation of mechanical allodynia. These data indicate that the PLGA-encapsulated CX3CR1 siRNA nanoparticles effectively reduce neuropathic pain in SNL-induced rats by reducing microglial activity and the expression of proinflammatory mediators. Therefore, we believe that PLGA-encapsulated CX3CR1 siRNA nanoparticles represent a valuable new treatment option for neuropathic pain.

Programmed co-delivery of platinum nanodrugs and gemcitabine by a clustered nanocarrier for precision chemotherapy for NSCLC tumors

A pH/redox dual stimuli-responsive clustered nanoparticles are demonstrated as vehicle for simultaneously delivering ultra-small platinum nanoparticles (USPtNs) and gemcitabine (GEM) to treat non-small-cell lung cancer.

Tumor extracellular pH-sensitive polymeric nanocarrier-grafted platinum(iv) prodrugs for improved intracellular delivery and cytosolic reductive-triggered release

Extracellular pH-sensitive Pt(iv)-based nanodrugs enable preferential toxicity to tumor cells via a selectively endocytosed and triggered drug release strategy.

Multi-functional self-assembled nanoparticles for pVEGF-shRNA loading and anti-tumor targeted therapy

Although RNA interference (RNAi) technology shows great potential in cancer treatment, the tumor target delivery and sufficient cytosolic transport of RNAi agents are still the main obstacles for its clinical applications. Herein, we report a functional supramolecular self-assembled nanoparticle vector for RNAi agent loading and tumor target therapy. Molecular block adamantane-grafted poly(ethylene glycol) (Ad-PEG) was modified with epidermal growth factor receptor (EGFR)-specific binding ligand GE11 or pH-sensitive fusogenic peptide GALA and then used for self-assembly with cyclodextrin-grafted branched polyethylenimine (CD-PEI), adamantane-grafted polyamidoamine dendrimer (Ad-PAMAM), and plasmid DNA containing a small hairpin RNA expression cassette against vascular endothelial growth factor (VEGF) into functional DNA-loaded supramolecular nanoparticles (GE11&GALA-pshVEGF@SNPs) based on molecular recognition and charge interaction. These functional peptides facilitated the target cell binding, internalization, and endosomal escape of GE11&GALA-pshVEGF@SNPs, resulting in increased reporter gene expression and efficient targeted gene silencing. The systemic delivery of the GE11&GALA-pshVEGF@SNPs can efficiently downregulate the intratumoral VEGF protein levels, reduce blood vessel formation, and significantly inhibit A549 xenograft tumor growth. These results reveal the potential of these multifunctional self-assembled nanoparticles as a nucleic acid drug delivery system for the treatment of lung cancer.

pH and reduction dual-responsive micelles based on novel polyurethanes with detachable poly(2-ethyl-2-oxazoline) shell for controlled release of doxorubicin

We describe a biodegradable amphiphilic polyurethane (PU) with disulfide bonds in the main chain [PEtOz-b-PU(SS)-b-PEtOz]. This multi-block PU was synthesized using poly (ε-caprolactone) diol (PCL-SS-PCL) and poly (2-ethyl-2-oxazoline) (PEtOz-OH) as soft segments, and bis (2-isocyanatoethyl) disulfide as the hard segment. Acid-sensitive PEtOz-OH was used as a hydrophilic segment for pH sensitivity. And reduction sensitivity was induced via disulfide bonds incorporated into the hydrophobic poly (ε-caprolactone) segment of the amphiphilic PUs. The system can self-assemble to form micelles responsive to pH and reducing conditions. The properties of the micelle were studied with dynamic light scattering and scanning electron microscopy. Doxorubicin (DOX) was chosen as a model drug. The in vitro release studies showed that PEtOz-b-PU(SS)-b-PEtOz micelle could degrade more rapidly and completely in a reductive and acidic environment [10 mM dl-Dithiothreitol, pH 5.0]. The methyl tetrazolium (MTT) assay and fluorescent microscopy confirmed the cytotoxicity of the DOX-loaded micelles. This work provides a promising dual-responsive drug carrier based on amphiphilic PU to achieve efficient drug delivery.

Overcoming Hurdles in Nanoparticle Clinical Translation: The Influence of Experimental Design and Surface Modification

Nanoparticles are becoming an increasingly popular tool for biomedical imaging and drug delivery. While the prevalence of nanoparticle drug-delivery systems reported in the literature increases yearly, relatively little translation from the bench to the bedside has occurred. It is crucial for the scientific community to recognize this shortcoming and re-evaluate standard practices in the field, to increase clinical translatability. Currently, nanoparticle drug-delivery systems are designed to increase circulation, target disease states, enhance retention in diseased tissues, and provide targeted payload release. To manage these demands, the surface of the particle is often modified with a variety of chemical and biological moieties, including PEG, tumor targeting peptides, and environmentally responsive linkers. Regardless of the surface modifications, the nano-bio interface, which is mediated by opsonization and the protein corona, often remains problematic. While fabrication and assessment techniques for nanoparticles have seen continued advances, a thorough evaluation of the particle's interaction with the immune system has lagged behind, seemingly taking a backseat to particle characterization. This review explores current limitations in the evaluation of surface-modified nanoparticle biocompatibility and in vivo model selection, suggesting a promising standardized pathway to clinical translation.

pH-responsive polydopamine nanoparticles for photothermally promoted gene delivery

Recently, stimuli-responsive gene carriers have been widely studied to overcome the extra- and intracellular barriers in cancer treatment. In this study, we modified polydopamine nanoparticles with low-molecular weight polyethylenimine (PEI_1.8k) and polyethylene glycol-phenylboronic acid (PEG-PBA) to prepare pH-responsive gene carrier PDANP-PEI-rPEG. PBA and polydopamine could form pH-responsive boronate ester bonds. Non-responsive PDANP-PEI-nPEG and non-PEGylated PDANP-PEI were also studied as control. Both PDANP-PEI-rPEG/DNA and PDANP-PEI-nPEG/DNA complexes remained stable in the pH environment of blood circulation or extracellular delivery (pH 7.4) owing to the PEG modification. And after being internalized into endosomes, the boronate ester bonds could be cleaved. The pH responsive ability of PDANP-PEI-rPEG might facilitate complexes dissociation and gene release inside cells. The transfection level of PDANP-PEI-rPEG/DNA complexes was about 100 times higher than that of PDANP-PEI-nPEG/DNA complexes with the same mass ratios. Moreover, after NIR light irradiation at the power density of 2.6 W/cm² for 20 min, the good photothermal conversion ability of PDANP resulted in quick endosomal escape. The transfection level of PDANP-PEI-rPEG/DNA complexes doubled, even higher than that of lipofectamine 2000/DNA complexes. This was also confirmed by Bafilomycin A1 inhibition test and CLSM observation. In response to the acidic pH within cancer cells and the NIR light irradiation, the PDANP-PEI-rPEG carrier could overcome multiple obstacles in gene delivery, which was promising for further application in gene therapy.

Bioreducible and acid-labile polydiethylenetriamines with sequential degradability for efficient transgelin-2 siRNA delivery

The transgelin-2 (TAGLN2) protein plays an important role in multidrug resistance in human breast cancer. siRNA mediated gene silencing of TAGLN2 is a promising strategy for paclitaxel resistance reversal in breast cancer. In this study, a series of bioreducible and acid-labile polydiethylenetriamines (PDs) with different proportions of cross-linkers were synthesized. TAGLN2 siRNA was condensed by PDs to form dual-responsive nanocomplexes, and these nanocomplexes were hypothesized to partially degrade in the acidic environment of endosomes, and then completely degrade in the reducing environment of the cytoplasm to release siRNA. It was found that PDs have good water solubility, acid-base buffering capacity, suitable degradability and high biocompatibility. Moreover, PDCKM can deliver TAGLN2 siRNA into MCF-7/PTX cells and inhibit the expression of TAGLN2 even better than PEI 25k. Besides, paclitaxel showed higher cytotoxicity in cells incubated with PDCKM/TAGLN2 siRNA nanocomplexes. These results suggested that PDs have great potential for safe and efficient siRNA delivery to reverse paclitaxel resistance in breast cancer.

A Multi-crosslinking Nanocapsule-Based Serial-Stimuli-Responsive Leakage-Free Drug-Delivery System In Vitro

As some stimuli utilized in conventional drug delivery systems can also be found in normal cells, it is inevitable that encapsulated drugs escape from carriers into normal cells. Based on mutual interactions among proteins, polyphenol compounds, and metal ions, we developed a serial-stimuli-responsive drug delivery system. With multi-crosslinking structure, nanocapsules can maintain the integrity of the framework, even with a certain amount of stimuli present, and eventually reach tumor cells to initiate apoptosis, and protect normal cells from being damaged. Meanwhile, the fluorescence of DOX will be quenched when encapsulated in nanocapsules. This property means that the DOX that is released from nanocapsules can be monitored in real-time based on the recovery of fluorescence. These versatile nanocapsules exhibit great potentials to treat cancer.