Multifunctional Mesoporous Silica Nanoparticles for Cancer‐Targeted and Controlled Drug Delivery

Multifunctional mesoporous silica nanoparticles are developed in order to deliver anticancer drugs to specific cancer cells in a targeted and controlled manner. The nanoparticle surface is functionalized with amino‐β‐cyclodextrin rings bridged by cleavable disulfide bonds, blocking drugs inside the mesopores of the nanoparticles. Poly(ethylene glycol) polymers, functionalized with an adamantane unit at one end and a folate unit at the other end, are immobilized onto the nanoparticle surface through strong β‐cyclodextrin/adamantane complexation. The non‐cytotoxic nanoparticles containing the folate targeting units are efficiently trapped by folate‐receptor‐rich HeLa cancer cells through receptormmediated endocytosis, while folate‐receptor‐poor human embryonic kidney 293 normal cells show much lower endocytosis towards nanoparticles under the same conditions. The nanoparticles endocytosed by the cancer cells can release loaded doxorubicin into the cells triggered by acidic endosomal pH. After the nanoparticles escape from the endosome and enter into the cytoplasm of cancer cells, the high concentration of glutathione in the cytoplasm can lead to the removal of the β‐cyclodextrin capping rings by cleaving the pre‐installed disulfide bonds, further promoting the release of doxorubicin from the drug carriers. The high drug‐delivery efficacy of the multifunctional nanoparticles is attributed to the co‐operative effects of folate‐mediated targeting and stimuli‐triggered drug release. The present delivery system capable of delivering drugs in a targeted and controlled manner provides a novel platform for the next generation of therapeutics.     

Multifunctional Micelles for Cancer Cell Targeting,Distribution Imaging,and Anticancer Drug Delivery

Multifunctional micelles for cancer cell targeting, distribution imaging, and anticancer drug delivery were prepared from an environmentally‐sensitive graft copolymer, poly(N‐isopropyl acrylamide‐co‐methacryl acid)‐g‐poly(D ,L ‐lactide) (P(NIPAAm‐co‐MAAc)‐g‐PLA), a diblock copolymer, methoxy poly(ethylene glycol)‐b‐poly(D ,L ‐lactide) (mPEG‐PLA) and two functionalized diblock copolymers, galactosamine‐PEG‐PLA (Gal‐PEG‐PLA) and fluorescein isothiocyanate‐PEG‐PLA (FITC‐PEG‐PLA). Anticancer drug, free base doxorubicin (Dox) was incorporated into the inner core of multifunctional micelles by dialysis. From the drug release study, a change in pH (from pH 7.4 to 5.0) deformed the structure of the inner core from that of aggregated P(NIPAAm‐co‐MAAc), causing the release of a significant quantity of doxorubicin (Dox) from multifunctional micelles. Multifunctional micelles target specific tumors by an asialoglycoprotein (HepG2 cells)‐Gal (multifunctional micelle) receptor‐mediated tumor targeting mechanism. This mechanism then causes intracellular pH changes which induce Dox release from multifunctional micelles and that micelles have strong effects on the viability of HepG2 cells and are abolished by galactose. Confocal laser scanning microscopy (CLSM) reveals a clear distribution of multifunctional micelles. With careful design and sophisticated manipulation, polymeric micelles can be widely used in cancer diagnosis, cancer targeting, and cancer therapy simultaneously.     

Multifunctional Mesoporous Nanoellipsoids for Biological Bimodal Imaging and Magnetically Targeted Delivery of Anticancer Drugs

A general polyelectrolyte‐mediated self‐assembly technique is adopted to prepare multifunctional mesoporous nanostructures as an effective biological bimodal imaging probe and magnetically targeted anticancer drug (doxorubicin) delivery systems (DDSs). A positively charged polyelectrolyte (PAH) and negatively charged fluorescent quantum dots (QDs) are successfully assembled onto the surface of ellipsoidal Fe₃O₄@SiO₂@mSiO₂ composite nanostructures to combine the merits of tunable fluorescent/magnetic properties, mesoporous nanostructures for drug loading, and the uniform ellipsoidal morphology for enhanced uptake by cancer cells. The resultant nanoellipsoids are homogeneously coated with four layers of PAH/QDs, with an additional PAH layer to make the ellipsoidal surface positively charged. This acts to enhance cellular uptake, which is driven by electrostatic interactions between the positive nanoparticle surface and the negative cell surface. The high biocompatibility of the achieved multifunctional nanoellipsoids is demonstrated by a cell‐cytotoxicity assay, hemolyticity against human red blood cells, and coagulation evaluation of fresh human blood plasma after exposure to the nanoparticles. Moreover, confocal microscopy and bio‐TEM observations show that the cell uptake of nanocarriers is dose‐dependent, and the nanoparticles accumulate mostly in the cytoplasm. The excellent capability of the nanocarriers as contrast agents for MRI is demonstrated by the relatively high r₂ value (143 mM^?1s^?1) and preliminary in vivo characterization. More importantly, the doxorubicin‐loaded DDSs show higher cytotoxicity than the free doxorubicin drug as contributed by the intracellular release pathway of doxorubicin from the DDSs, indicating the potential application of the obtained multifunctional mesoporous nanoellipsoids as highly effective bimodal imaging probes and DDSs for cancer diagnosis and chemotherapy, simultaneously.     

Highly Biocompatible Carbon Nanodots for Simultaneous Bioimaging and Targeted Photodynamic Therapy In Vitro and In Vivo

Photosensitizers (PSs) are light‐sensitive molecules that are highly hydrophobic, which poses a challenge to their use for targeted photodynamic therapy. Hence, considerable efforts have been made to develop carriers for the delivery of PSs. Herein, a novel design is described of highly biocompatible, fluorescent, folic acid (FA)‐functionalized carbon nanodots (CDs) as carriers for the PS zinc phthalocyanine (ZnPc) to achieve simultaneous biological imaging and targeted photodynamic therapy. FA is modified on PEG‐­passivated CDs (CD‐PEG) for targeted delivery to FA‐positive cancer cells, and ZnPc is loaded onto CD‐PEG‐FA via π–π stacking interactions. CD‐PEG‐FA/ZnPc exhibits excellent targeted delivery of the PS, leading to simultaneous imaging and significant targeted photodynamic therapy after irradiation in vitro and in vivo. The present CD‐based targeted delivery of PSs is anticipated to offer a convenient and effective platform for enhanced photodynamic therapy to treat cancers in the near future.     

Near‐Infrared Absorbing Polymeric Nanoparticles as a Versatile Drug Carrier for Cancer Combination Therapy

Poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) nanoparticles, after being coated with polyethylene glycol (PEG), are used as a drug carrier to load various types of aromatic therapeutic molecules, including chemotherapy drugs doxorubicin (DOX) and SN38, as well as a photodynamic agent chlorin e6 (Ce6), through π–π stacking and hydrophobic interaction. Interesting functionalities of PEDOT:PSS‐PEG as an unique versatile drug delivery platform are discovered. Firstly, for water‐insoluble drugs such as SN38, the loading on PEDOT:PSS‐PEG dramatically enhances its water solubility, while maintaining its cytotoxicity to cancer cells. Secondly, the delivery of Ce6 by PEDOT:PSS‐PEG is able to remarkably accelerate the cellular uptake of Ce6 molecules, and thus offers improved photodynamic therapeutic efficacy. Using DOX‐loaded PEDOT:PSS‐PEG as the model system, it is demonstrated that the photothermal effect of PEDOT:PSS‐PEG can be utilized to promote the delivery of this chemotherapeutic agent, achieving a combined photothermal‐ and chemotherapy with an obvious synergistic cancer killing effect. Moreover, it is also shown that multiple types of therapeutic agents could be simultaneously loaded on PEDOT:PSS‐PEG nanoparticles and delivered into cancer cells. This work highlights the great potential of NIR‐absorbing polymeric nanoparticles as multifunctional drug carriers for potential cancer combination therapy with high efficacy.     

Polydopamine as a Biocompatible Multifunctional Nanocarrier for Combined Radioisotope Therapy and Chemotherapy of Cancer

Development of biodegradable nanomaterials for drug delivery and cancer theranostics has attracted great attention in recent years. In this work, polydopamine (PDA), a biocompatible polymer, is developed as a promising carrier for loading of both radionuclides and an anticancer drug to realize nuclear‐imaging‐guided combined radioisotope therapy (RIT) and chemotherapy of cancer in one system. It is found that PDA nanoparticles after modification with poly(ethylene glycol) (PEG) can successfully load several different radionuclides such as ^99mTc and ¹³¹I, as well as an anticancer drug doxorubicin (DOX). While labeling PDA‐PEG with ^99mTc (^99mTc‐PDA‐PEG) enables in vivo single photon emission computed tomography imaging, nanoparticles co‐loaded with ¹³¹I and DOX (¹³¹I‐PDA‐PEG/DOX) can be utilized for combined RIT and chemotherapy, which offers effective cancer treatment efficacy in a remarkably synergistic manner, without rendering significant toxicity to the treated animals. Therefore, this study presents an interesting class of biocompatible nanocarriers, which allow the combination of RIT and chemotherapy, the two extensively applied cancer therapeutic strategies, promising for future clinic translations in cancer treatment.     

Fabricating Aptamer‐Conjugated PEGylated‐MoS2/Cu1.8S Theranostic Nanoplatform for Multiplexed Imaging Diagnosis and Chemo‐Photothermal Therapy of Cancer

Fabricating theranostic nanoparticles combining multimode disease diagnosis and therapeutic has become an emerging approach for personal nanomedicine. However, the diagnostic capability, biocompatibility, and therapeutic efficiency of theranostic nanoplatforms limit their clinic widespread applications. Targeting to the theme of accurate diagnosis and effective therapy of cancer cells, a multifunctional nanoplatform of aptamer and polyethylene glycol (PEG) conjugated MoS₂ nanosheets decorated with Cu_1.8S nanoparticles (ATPMC) is developed. The ATPMC nanoplatform accomplishes photoluminescence imaging, photoacoustic imaging, and photothermal imaging for in vitro and in vivo tumor cells imaging diagnosis. Meanwhile, the ATPMC nanoplatform facilitates selective delivery of gene probe to detect intracellular microRNA aberrantly expressed in cancer cells and anticancer drug doxorubicin (DOX) for chemotherapy. Moreover, the synergistic interaction of MoS₂ and Cu_1.8S renders the ATPMC nanoplatform with superb photothermal conversion efficiency. The ATPMC nanoplatform loaded with DOX displays near‐infrared laser‐induced programmed chemotherapy and advanced photothermal therapy, and the targeted chemo‐photothermal therapy presents excellent antitumor efficiency.     

Integrated Multifunctional Nanosystems for Medical Diagnosis and Treatment

This article provides an overview on the development of integrated multifunctional nanosystems for medical diagnosis and treatment. In particular, a novel system is developed specifically for achieving simultaneous diagnosis and treatment of cancer. Critical issues are addressed on the architecture and assembly of nanocomponents based on medical requirements: targeted in vivo imaging, controlled drug release, localized hyperthermia, and toxicity. Nanotube‐based carriers are summarized with surface functionalized properties. Other types of nanocarriers are also included such as super paramagnetic composite nanospheres and biodegradable hydroxylapatite nanoparticles. In addition, polymeric‐based nanosystems are introduced with several novel features: they can be bio‐dissolved due to environmental pH and temperature fluctuations. The nanocarriers are surface tailored with key functionalities: surface antibodies for cell targeting, anti‐cancer drug loading, and magnetic nanoparticles for both hyperthermia and MRI. Future requirements, aims, and trends in the development of multifunctional nanosystems, particularly with intelligent functionalities for fundamental studies, are also provided.     

Gold Nanoshell Nanomicelles for Potential Magnetic Resonance Imaging,Light‐Triggered Drug Release,and Photothermal Therapy

A novel multifunctional drug‐delivery platform is developed based on cholesteryl succinyl silane (CSS) nanomicelles loaded with doxorubicin, Fe₃O₄ magnetic nanoparticles, and gold nanoshells (CDF‐Au‐shell nanomicelles) to combine magnetic resonance (MR) imaging, magnetic‐targeted drug delivery, light‐triggered drug release, and photothermal therapy. The nanomicelles show improved drug‐encapsulation efficiency and loading level, and a good response to magnetic fields, even after the formation of the gold nanoshell. An enhancement for T₂‐weighted MR imaging is observed for the CDF‐Au‐shell nanomicelles. These nanomicelles display surface plasmon absorbance in the near‐infrared (NIR) region, thus exhibiting an NIR (808 nm)‐induced temperature elevation and an NIR light‐triggered and stepwise release behavior of doxorubicin due to the unique characteristics of the CSS nanomicelles. Photothermal cytotoxicity in vitro confirms that the CDF‐Au‐shell nanomicelles cause cell death through photothermal effects only under NIR laser irradiation. Cancer cells incubated with CDF‐Au‐shell nanomicelles show a significant decrease in cell viability only in the presence of both NIR irradiation and a magnetic field, which is attributed to the synergetic effects of the magnetic‐field‐guided drug delivery and the photothermal therapy. Therefore, such multicomponent nanomicelles can be developed as a smart and promising nanosystem that integrates multiple capabilities for effective cancer diagnosis and therapy.     

A Bio‐Inspired Rod‐Shaped Nanoplatform for Strongly Infecting Tumor Cells and Enhancing the Delivery Efficiency of Anticancer Drugs

The rapid clearance of circulating nanocarriers in blood during systemic drug delivery remains a challenging hurdle in cancer chemotherapy. Here, inspired by the unique features of bacterial pathogens, an original biodegradable polymer micellar system with a rod‐like shape similar to the morphology of bacterial pathogens is developed. These novel nanocarriers have excellent features such as a great capacity of overcoming the rapid clearance of reticuloendothelial system (RES) with long blood circulation, high cellular internalization, and enhanced therapeutic efficacy against cancers. In vivo pharmacokinetic studies in mice reveal that the rod‐like micelles of ≈40 nm in diameter and 600 nm in length possess a minimal uptake by the RES and excellent blood circulation half‐lives (t_1/2β = 24.23 ± 2.87 h) for carrying doxorubicin in contrast to spheres (t_1/2β = 8.39 ± 0.53 h). The antitumor activity of the rod‐shaped micelles in Balb/c mice bearing H22 tumor xenograft models reveals that they are promptly internalized by tumor cells, resulting in their superior potency and efficacy against artificial solid tumors. These findings suggest that the bio‐inspired nanocarriers as an emerging drug delivery platform may have considerable benefits for enhancing the delivery efficiency of anticancer drugs and in turn enhancing cancer therapy in future clinical applications.     

Multiple Layer‐by‐Layer Lipid‐Polymer Hybrid Nanoparticles for Improved FOLFIRINOX Chemotherapy in Pancreatic Tumor Models

The FOLFIRINOX regimen, a combination of three chemotherapy agents (5‐fluorouracil, irinotecan, oxaliplatin) and folinic acid (a vitamin B derivatives reducing the side effect of 5‐fluorouracil), has proved to be effective in the treatment of pancreatic cancer, and is more efficacious than the long‐term reference standard, gemcitabine. However, the FOLFIRINOX is associated with high‐grade toxicity, which markedly limits its clinical application. Encapsulation of drugs in nanocarriers that selectively target cancer cells promises to be an effective method for co‐delivery of drug combinations and to mitigate the side effects of conventional chemotherapy. Here we reported the development of multiple layer‐by‐layer lipid‐polymer hybrid nanoparticles with targeting capability that show excellent biocompatibility and synergistically combine the favorable properties of liposomes and polymer nanoparticles. Relative to nanoparticles consisting of polymer alone, these novel nanocarriers have a long half‐life in vivo and a higher stability in serum. The nanocarriers were loaded with the three active antitumor constituents of FOLFIRINOX regimen. Little drugs were released from the nanoparticles in phosphate buffered saline (PBS) solution, but the cargoes were quickly released after the nanoparticles were taken up by tumor cells. These innovative drug‐loaded nanoparticles achieved higher antitumor efficacy and showed minimal side effects compared with the FOLFIRINOX regimen alone. Our study suggested that the multiple layer‐by‐layer hybrid nanoparticles have great potential for improving the chemotherapeutic efficacy for the patients with pancreatic cancer. This platform also provides new opportunities for tailored design of nanoparticles that may offer therapeutics benefits for a range of other tumors.     

Light‐Responsive,Singlet‐Oxygen‐Triggered On‐Demand Drug Release from Photosensitizer‐Doped Mesoporous Silica Nanorods for Cancer Combination Therapy

Smart drug delivery systems with on‐demand drug release capability are rather attractive to realize highly specific cancer treatment. Herein, a novel light‐responsive drug delivery platform based on photosensitizer chlorin e6 (Ce6) doped mesoporous silica nanorods (CMSNRs) is developed for on‐demand light‐triggered drug release. In this design, CMSNRs are coated with bovine serum albumin (BSA) via a singlet oxygen (SO)‐sensitive bis‐(alkylthio)alkene (BATA) linker, and then modified with polyethylene glycol (PEG). The obtained CMSNR‐BATA‐BSA‐PEG, namely CMSNR‐B‐PEG, could act as a drug delivery carrier to load with either small drug molecules such as doxorubicin (DOX), or larger macromolecules such as cis‐Pt (IV) pre‐drug conjugated third generation dendrimer (G3‐Pt), both of which are sealed inside the mesoporous structure of nanorods by BSA coating. Upon 660 nm light irradiation with a rather low power density, CMSNRs with intrinsic Ce6 doping would generate SO to cleave BATA linker, inducing detachment of BSA‐PEG from the nanorod surface and thus triggering release of loaded DOX or G3‐Pt. As evidenced by both in vitro and in vivo experiments, such CMSNR‐B‐PEG with either DOX or G3‐Pt loading offers remarkable synergistic therapeutic effects in cancer treatment, owing to the on‐demand release of therapeutics specifically in the tumor under light irradiation.     

Gadolinium‐Doped Iron Oxide Nanoprobe as Multifunctional Bioimaging Agent and Drug Delivery System

In this study, a high‐performance T₁–T₂ dual‐model contrast agent by gadolinium‐doped iron oxide nanoparticle (GION) is developed. Following its development, the application of this agent in vivo by combining doxorubicin (DOX) and folic acid (FA) (FA–GION–DOX) for targeted drug delivery to monitor cancer treatment is explored. GION showed transverse and longitudinal relaxivities up to 182.7 × 10^?3 and 7.87 × 10^?3m ^?1 s^?1, respectively, upon Gd/Fe ratio in GION at 1/4. DOX released from FA–GION–DOX is pH dependent and only kills cancer cell after FA receptor‐mediated internalization into the acidic environment of endosomes and lysosomes. Systemic delivery of FA–GION–DOX significantly inhibits the growth of tumors and shows good magnetic resonance enhancement in a human cervical cancer xenograft model. Thus, FA–GION–DOX has a potential application for the targeted and magnetic resonance imaging guided therapy of cervical cancer.     

MAPK‐Targeted Drug Delivered by a pH‐Sensitive MSNP Nanocarrier Synergizes with PD‐1 Blockade in Melanoma without T‐Cell Suppression

The combination of BRAF/MEK‐targeted therapy with immune checkpoint blockade is regarded as a promising regimen for patients with metastatic melanoma due to their complementary advantages. However, MEK‐inhibitor‐induced T‐cell toxicity impedes effective cooperation. In this experiment, a pH‐responsive on‐demand controlled release mesoporous silica nanoparticles (MSNPs) system is designed. Fluorescein‐isothiocyanate‐loaded MSNP can be specifically delivered into tumor cells rather than T‐cells. MEK‐inhibitor‐loaded MSNP avoids proliferative and functional inhibitions of T‐cells, while preserving growth suppression of tumor cells in vitro. In an in vivo model, MSNP encapsulation reverses the MEK‐inhibitor‐induced suppression of activated CD8⁺ T‐cells, and enhances the secretion of INF‐γ and IL‐2. The combination of BRAF inhibitor plus MSNP‐loaded MEK inhibitor and anti‐PD‐1 antibody synergistically inhibits tumor growth via promoting robust immune‐related antitumor response. This work provides a novel and generalized framework for combining T‐cell‐impaired targeted therapy and immune checkpoint blockade by using a nanoparticle‐based delivery system.     

Multifunctional Up‐Converting Nanocomposites with Smart Polymer Brushes Gated Mesopores for Cell Imaging and Thermo/pH Dual‐Responsive Drug Controlled Release

Multifunctional nanocarriers based on the up‐conversion luminescent nanoparticles of NaYF₄:Yb³⁺/Er³⁺ core (UCNPs) and thermo/pH‐coupling sensitive polymer poly[(N‐isopropylacrylamide)‐co‐(methacrylic acid)] (P(NIPAm‐co‐MAA)) gated mesoporous silica shell are reported for cancer theranostics, including fluorescence imaging, and for controlled drug release for therapy. The as‐synthesized hybrid nanospheres UCNPs@mSiO₂‐P(NIPAm‐co‐MAA) show bright green up‐conversion fluorescence under 980 nm laser excitation and the thermo/pH‐sensitive polymer is active as a “valve” to moderate the diffusion of the embedded drugs in‐and‐out of the pore channels of the silica container. The anticancer drug doxorubicin hydrochloride (DOX) can be absorbed into UCNPs@mSiO₂‐P(NIPAm‐co‐MAA) nanospheres and the composite drug delivery system (DDS) shows a low level of leakage at low temperature/high pH values but significantly enhanced release at higher temperature/lower pH values, exhibiting an apparent thermo/pH controlled “on‐off” drug release pattern. The as‐prepared UCNPs@mSiO₂‐P(NIPAm‐co‐MAA) hybrid nanospheres can be used as bioimaging agents and biomonitors to track the extent of drug release. The reported multifunctional nanocarriers represent a novel and versatile class of platform for simultaneous imaging and stimuli‐responsive controlled drug delivery.     

Self‐Assembled Nanoparticles with Dual Effects of Passive Tumor Targeting and Cancer‐Selective Anticancer Effects

Nanoparticular drug delivery systems may help to overcome the limitations of conventional chemotherapy. They have been reported to improve the specificity of distribution, the bioavailability, and the solubility of drugs, as well as the duration of drug efficacy, and helping to overcome multidrug resistance. Although various polymeric nanoparticles have been developed for delivery of anticancer agents, most nanoparticles still focus on solubilizing drugs, improving targeting ability, and reducing side effects. In particular, targeting to the tumor is typically improved through passive or active targeting. Despite great achievements in both strategies, yet to be resolved are issues of toxicity in normal cells and enhancement of tumor‐specificity. A new approach combining the dual strategies of passive tumor targeting and cancer‐selective efficacy is proposed. Recombinant human gelatin conjugated with lipoic acid (rHG‐LA) developed in this study forms nanoparticles spontaneously in aqueous solution and encapsulates alpha‐tocopheryl succinate (α‐TOS), a well‐known cancer‐selective apoptosis‐inducing agent, within a hydrophobic core during the self‐assembly. This study describes the promising applicability of α‐TOS‐loaded rHG‐LA nanoparticles with passive targeting ability and cancer‐specificity.     

Use of Ferritin Capped Mesoporous Silica Nanoparticles for Redox and pH Triggered Drug Release In Vitro and In Vivo

Mesoporous silica nanoparticles (MSNs) functionalized with redox‐sensitive or pH‐sensitive nanovalves for doxorubicin delivery and release by using recombinant human H chain ferritin (HFn) as a cap have been designed and fabricated. In both cases, transmission electron microscope observatory, dynamic light scattering change, Fourier transform infrared spectra examination, thermogravimetric analysis show that HFn can be chemically bonded to MSNs while retaining its ability to target transferrin receptor 1 (TfR1). Cargo loading and release studies demonstrate that HFn is an efficient capping agent, blocking the pores of MSN preventing cargo molecules from diffusing out, and is responsive to redox stimuli or pH changes. More importantly, HFn can not only cap the MSNs, but also enables targeted cargo delivery to malignant cells by binding to the TfR1 that has been overexpressed in various tumors, which can be reflected by the cell viability and fluorescence microscope analysis results comparing with cyclodextrin as the capping agent and TfR1 blocking assay. The in vivo study reveals the excellent efficacy of doxorubicin loaded and HFn capped MSNs on suppression of tumor growth. The new developed drug delivery system features mutually benefit and mutually support, providing strategy for achieving specific‐site therapeutics delivery systems.     

Charge‐Reversal Drug Conjugate for Targeted Cancer Cell Nuclear Drug Delivery

DNA‐toxin anticancer drugs target nuclear DNA or its associated enzymes to elicit their pharmaceutical effects, but cancer cells have not only membrane‐associated but also many intracellular drug‐resistance mechanisms that limit their nuclear localization. Thus, delivering such drugs directly to the nucleus would bypass the drug‐resistance barriers. The cationic polymer poly(L ‐lysine) (PLL) is capable of nuclear localization and may be used as a drug carrier for nuclear drug delivery, but its cationic charges make it toxic and cause problems in in‐vivo applications. Herein, PLL is used to demonstrate a pH‐triggered charge‐reversal carrier to solve this problem. PLL's primary amines are amidized as acid‐labile β‐carboxylic amides (PLL/amide). The negatively charged PLL/amide has a very low toxicity and low interaction with cells and, therefore, may be used in vivo. But once in cancer cells' acidic lysosomes, the acid‐labile amides hydrolyze into primary amines. The regenerated PLL escapes from the lysosomes and traverses into the nucleus. A cancer‐cell targeted nuclear‐localization polymer–drug conjugate has, thereby, been developed by introducing folic‐acid targeting groups and an anticancer drug camptothecin (CPT) to PLL/amide (FA‐PLL/amide‐CPT). The conjugate efficiently enters folate‐receptor overexpressing cancer cells and traverses to their nuclei. The CPT conjugated to the carrier by intracellular cleavable disulfide bonds shows much improved cytotoxicity.     

Noncovalent Polymer‐Gatekeeper in Mesoporous Silica Nanoparticles as a Targeted Drug Delivery Platform

Selective targeting of tumor cells and release of drug molecules inside the tumor microenvironment can reduce the adverse side effects of traditional chemotherapeutics because of the lower dosages required. This can be achieved by using stimuli‐responsive targeted drug delivery systems. In the present work, a robust and simple one‐pot route is developed to synthesize polymer‐gatekeeper mesoporous silica nanoparticles by noncovalent capping of the pores of drug‐loaded nanocontainers with disulfide cross‐linkable polymers. The method offers very high loading efficiency because chemical modification of the mesoporous nanoparticles is not required; thus, the large empty pore volume of pristine mesoporous silica nanoparticles is entirely available to encapsulate drug molecules. Furthermore, the polymer shell can be easily decorated with a targeting ligand for selective delivery to specific cancer cells by subsequent addition of the thiol‐containing ligand molecule. The drug molecules loaded in the nanocontainers can be released by the degradation of the polymer shell in the intracellular reducing microenvironment, which consequentially induces cell death.     

Triphenylphosphonium‐Conjugated Poly(ε‐caprolactone)‐Based Self‐Assembled Nanostructures as Nanosized Drugs and Drug Delivery Carriers for Mitochondria‐Targeting Synergistic Anticancer Drug Delivery

For mitochondria‐targeting delivery, a coupling reaction between poly(ε‐caprolactone) diol (PCL diol) and 4‐carboxybutyltriphenylphosphonium (4‐carboxybutyl TPP) results in the synthesis of amphiphilic TPP‐PCL‐TPP (TPCL) polymers with a bola‐like structure. In aqueous environments, the TPCL polymer self‐assembled via cosolvent dispersion and film hydration, resulting in the formation of cationic nanoparticles (NPs) less than 50 nm in size with zeta‐potentials of approximately 40 mV. Interestingly, different preparation methods for TPCL NPs result in various morphologies such as nanovesicles, nanofibers, and nanosheets. In vitro cytotoxicity results with TPCL NPs indicate IC₅₀ values of approximately 10–60 μg mL^?1, suggesting their potential as anticancer nanodrugs. TPCL NPs can be loaded both with hydrophobic doxorubicin (Dox) and its hydrophilic salt form (Dox·HCl), and their drug loading contents are approximately 2–10 wt% depending on the loading method and the hydrophilicity/hydrophobicity of the drugs. Although Dox·HCl exhibits more cellular and nuclear uptake, resulting in greater antitumor effects than Dox, most drug‐loaded TPCL NPs exhibit higher mitochondrial uptake and approximately 2–7‐fold higher mitochondria‐to‐nucleus preference than free drugs, resulting in superior (approximately 7.5–18‐fold) tumor‐killing activity for most drug‐loaded TPCL NPs compared with free drugs. In conclusion, TPCL‐based nanoparticles have potential both as antitumor nanodrugs themselves and as nanocarriers for chemical therapeutics.