Folate-conjugated and pH-responsive polymeric micelles for target-cell-specific anticancer drug delivery

Folic acid grafted mixed polymeric micelles as a targeted delivery strategy for tamoxifen citrate in treatment of breast cancer

The objective of this study was to develop folic acid (FA) grafted mixed polymeric micelles loaded with Tamoxifen citrate (TMXC) to enhance its antitumor activity in breast tissues. The conjugated folic acid Pluronic 123 (FA-P123) was prepared using carbonyl diimidazole cross-linker chemistry and confirmed using FTIR and 1HNMR. TMXC-loaded P123/P84 (unconjugated) and TMXC-loaded FA-P123/P84 (conjugated) micelles were examined for encapsulation efficiency, particle size, surface charge, in vitro drug release, cytotoxic effect, and cellular uptake by a breast cancer cell line. The conjugated TMXC-loaded micelle exhibited a nanoparticle size of 35.01 ± 1.20 nm, a surface charge of-20.50 ± 0.95 mV, entrapped 87.83 ± 5.10% and released 67.58 ± 2.47% of TMXC after 36 h. The conjugated micelles exhibited a significantly higher cellular uptake of TMXC by the MCF-7 cell line and improved in vitro cytotoxicity by 2.48 folds compared to the TMXC-loaded unconjugated micelles. The results of in vivo studies indicated that TMXC-loaded FA-P123/P84 has a potential antitumor activity, as revealed by a significant reduction of tumor volume in tumor-bearing mice compared to TMXC-loaded unconjugated micelles. In conclusion, the obtained results suggested that conjugated FA-P123/P84 micelles could be an encouraging carrier for the treatment of breast cancer with TMXC.

Modulation of macrophage polarity with carboxymethyl chitin gated hollow mesoporous silica nanoparticles for elevating anti-tumor chemotherapy

The weak immunity of tumors after chemotherapy could cause tumor metastasis and progression. Therefore, to overcome the dilemma of obvious immune deficiency caused by chemotherapy, a nanosystem (N-IL-12/DOX/α-TOS) consisted of thioketal (TK) bonds linked-hollow mesoporous silica nanoparticles (HMSNs) coated with carboxymethyl chitin (CMCH) by electrostatic interaction, and surface-functionalized glucose-regulated protein 78 binding peptide was prepared for loading doxorubicin (DOX), IL-12 and α-tocopheryl succinate (α-TOS). N-IL-12/DOX/α-TOS displayed a mean size of 275 nm after encapsulated DOX, IL-12 and α-TOS with loading contents of 2.04 × 10-4, 4.01 × 10-2 and 7.12 × 10-2, respectively. The drug-free nanoparticles (NPs) showed good biocompatibility to both 4 T1 cells and RAW264.7 macrophages. N-IL-12/DOX/α-TOS could achieve localized release of IL-12, DOX and α-TOS by pH and H2O2 trigger in the tumor microenvironment (TME). Moreover, the combined therapy by N-IL-12/DOX/α-TOS remarkably elevated the anti-tumor therapeutic efficacy, enhanced immune responses via promoting tumor-associated macrophage (TAM) polarization into tumoricidal M1 phenotypes, and decreased lung metastasis with reduced side effects. N-IL-12/DOX/α-TOS exhibited as a promising strategy for combining chemotherapy and local macrophage modulation-immunotherapy for anti-tumor therapy.

CD44-Targeted Photoactivatable Polymeric Nanosystem with On-Demand Drug Release as a "Photoactivatable Bomb" for Combined Photodynamic Therapy-Chemotherapy of Cancer

Nowadays, the combined use of chemotherapy and photodynamic therapy (PDT) remains the most popular strategy for cancer treatment with high theraprutic efficacy. However, targeted therapy with the on-demand release of drugs is what most clinical treatments lack, leading to heavy side effects. Herein, a new CD44-targeted and red-light-activatable nanosystem, Ru-HA@DOX nanoparticles (NPs), was developed by conjugating hydrophilic biodegradable hyaluronic acid (HA) and hydrophobic photoresponsive ruthenium (Ru) complexes, which could encapsulate the chemotherapeutic drug doxrubicin (DOX). Ru-HA@DOX NPs can selectively accumulate at the tumor through the enhanced permeability and retention (EPR) effect and CD44-mediated endocytosis, thus avoiding off-target toxicity during circulation. After 660 nm of irradiation at the tumor site, Ru-HA@DOX NPs, as a "photoactivatable bomb", was split via the photocleavable Ru-N coordination bond to fast release DOX and produce singlet oxygen (¹O₂) for PDT. In general, Ru-HA@DOX NPs retained its integrity before irradiation and possessed minimal cytotoxicity, while under red-light irradiation, Ru-HA@DOX NPs showed significant cytotoxicity due to the release of DOX and production of ¹O₂ at the tumor. Chemotherapy-PDT of Ru-HA@DOX NPs resulted in a significant inhibition of tumor growth in A549-tumor-bearing mice and reduced the cardiotoxicity of DOX. Therefore, this study offers a novel CD44-targeted drug-delivery system with on-demand drug release for synergistic chemotherapy-PDT.

Doxorubicin-loaded micelles in tumor cell-specific chemotherapy

Nanomedicine is a field that combines biology and engineering to improve disease treatment, particularly in cancer therapy. One of the promising techniques utilized in this area is the use of micelles, which are nanoscale delivery systems that are known for their simple preparation, high biocompatibility, small particle size, and the ability to be functionalized. A commonly employed chemotherapy drug, Doxorubicin (DOX), is an effective inhibitor of topoisomerase II that prevents DNA replication in cancer cells. However, its efficacy is frequently limited by resistance resulting from various factors, including increased activity of drug efflux transporters, heightened oncogenic factors, and lack of targeted delivery. This review aims to highlight the potential of micelles as new nanocarriers for delivering DOX and to examine the challenges involved with employing chemotherapy to treat cancer. Micelles that respond to changes in pH, redox, and light are known as stimuli-responsive micelles, which can improve the targeted delivery of DOX and its cytotoxicity by facilitating its uptake in tumor cells. Additionally, micelles can be utilized to administer a combination of DOX and other drugs and genes to overcome drug resistance mechanisms and improve tumor suppression. Furthermore, micelles can be used in phototherapy, both photodynamic and photothermal, to promote cell death and increase DOX sensitivity in human cancers. Finally, the alteration of micelle surfaces with ligands can further enhance their targeted delivery for cancer suppression.

Poly(l-Ornithine)-Based Polymeric Micelles as pH-Responsive Macromolecular Anticancer Agents

Anticancer peptides and polymers represent an emerging field of tumor treatment and can physically interact with tumor cells to address the problem of multidrug resistance. In the present study, poly(l-ornithine)-b-poly(l-phenylalanine) (PLO-b-PLF) block copolypeptides were prepared and evaluated as macromolecular anticancer agents. Amphiphilic PLO-b-PLF self-assembles into nanosized polymeric micelles in aqueous solution. Cationic PLO-b-PLF micelles interact steadily with the negatively charged surfaces of cancer cells via electrostatic interactions and kill the cancer cells via membrane lysis. To alleviate the cytotoxicity of PLO-b-PLF, 1,2-dicarboxylic-cyclohexene anhydride (DCA) was anchored to the side chains of PLO via an acid-labile β-amide bond to fabricate PLO(DCA)-b-PLF. Anionic PLO(DCA)-b-PLF showed negligible hemolysis and cytotoxicity under neutral physiological conditions but recovered cytotoxicity (anticancer activity) upon charge reversal in the weakly acidic microenvironment of the tumor. PLO-based polypeptides might have potential applications in the emerging field of drug-free tumor treatment.

Zein-based nano-delivery systems for encapsulation and protection of hydrophobic bioactives: A review

Zein is a kind of excellent carrier materials to construct nano-sized delivery systems for hydrophobic bioactives, owing to its unique interfacial behavior, such as self-assembly and packing into nanoparticles. In this article, the chemical basis and preparation methods of zein nanoparticles are firstly reviewed, including chemical crosslinking, emulsification/solvent evaporation, antisolvent, pH-driven method, etc., as well as the pros and cons of different preparation methods. Various strategies to improve their physicochemical properties are then summarized. Lastly, the encapsulation and protection effects of zein-based nano-sized delivery systems (e.g., nanoparticles, nanofibers, nanomicelles and nanogels) are discussed, using curcumin as a model bioactive ingredient. This review will provide guidance for the in-depth development of hydrophobic bioactives formulations and improve the application value of zein in the food industry.

Development of Highly Sensitive Molecular Blocks at Cancer Microenvironment for Rapid Cancer Cell Death

Improving the efficiency and selectivity of drug delivery systems (DDS) is still a major challenge in cancer therapy. Recently, the low transport efficiency of anticancer drugs using a nanocarrier due to the elimination of the carriers from the blood circulation and the blocking by tumor stromal tissues surrounding cancer cells has been reported. Furthermore, multiple steps are required for their intracellular delivery. We recently reported a cancer microenvironment-targeting therapy termed molecular block (MB) which induced cancer cell death by a pH-driven self-aggregation and cell membrane disruption at tumor microenvironment. The MB were designed to disperse as nanoscale assemblies in the bloodstream for efficient circulation and penetration through the stromal tissues. When the MBs reach the tumor site, they self-assembled in microscale aggregates on the cancer cell surfaces in response to the cancer microenvironment and induced cancer cell death. However, in vivo study in mice showed that the MB could not efficiently accumulate at the tumor site because slight hydrophobic aggregations in the bloodstream might potentially be the reason for the off-target accumulation. In this study, we optimize the hydrophilic-hydrophobic balance of MB for avoiding the off-target accumulation and for gaining higher sensitivity to the cancer microenvironment at weak acid condition. Copper-free click reaction with propiolic acid was used to reduce the hydrophobicity of the main chain and obtain higher responsive MB at cancer microenvironment for rapid cell killing. The optimized MB can be considered as a promising approach for an improved cancer cell targeting.

Inhaled mRNA Nanoformulation with Biogenic Ribosomal Protein Reverses Established Pulmonary Fibrosis in a Bleomycin-Induced Murine Model

Idiopathic pulmonary fibrosis (IPF), a lethal respiratory disease with few treatment options, occurs due to repetitive microinjuries to alveolar epithelial cells (AECs) and progresses with an overwhelming deposition of extracellular matrix (ECM), ultimately resulting in fibrotic scars and destroyed the alveolar architecture. Here, an inhaled ribosomal protein-based mRNA nanoformulation is reported for clearing the intrapulmonary ECM and re-epithelializing the disrupted alveolar epithelium, thereby reversing established fibrotic foci in IPF. The nanoformulation is sequentially assembled by a ribosomal protein-condensed mRNA core, a bifunctional peptide-modified corona and keratinocyte growth factor (KGF) with a PEGylated shielding shell. When inhaled via a nebulizer, the nanoformulations carried by microdrops are deposited in the alveoli, and penetrate into fibrotic foci, where the outer KGFs are detached after matrix metalloproteinase 2 (MMP2) triggering. The RGD motif-grafted cores then expose and specifically target the integrin-elevated cells for the intracellular delivery of mRNA. Notably, repeated inhalation of the nanoformulations accelerates the clearance of locoregional collagen by boosting the intralesional expression of MMP13 and alveolar re-epithelialization mediated by KGFs, which synergistically ameliorates the lung function of a bleomycin-induced murine model. Therefore, this work provides an alternative mRNA-inhalation delivery strategy, which shows great potential for the treatment of IPF.

Stromal Barrier-Dismantled Nanodrill-Like and Cancer Cell-Targeted pH-Responsive Polymeric Micelles for Further Enhancing the Anticancer Efficacy of Doxorubicin

Cancer-associated fibroblasts (CAFs) were believed to establish a tight physical barrier and a dense scaffold for tumor cells to make them maintain immunosuppression and drug resistance, strongly hindering nanoparticles to penetrate into the core of tumor tissues and limiting the performance of tumor cell-targeted nanoparticles. Here, we fabricated the substrate Z-Gly-Pro of fibroblast activation protein α (FAPα) and folic acid-codecorated pH-responsive polymeric micelles (dual ligand-modified PEOz-PLA polymeric micelles, DL-PP-PMs) that possessed nanodrill and tumor cell-targeted functions based on Z-Gly-pro-conjugated poly(2-ethyl-2-oxazoline)-poly(D,l-lactide) (ZGP-PEOz-PLA), folic acid (FA)-conjugated PEOz-PLA (FA-PEOz-PLA), and PEOz-PLA for cancer therapy. The micelles with about 40 nm particle size and a narrow distribution exhibited favorable pH-activated endo/lysosome escape induced by their pH responsibility. In addition, the enhancement of in vitro cellular uptake and cytotoxicity to folate receptors or FAPα-positive cells for doxorubicin (DOX)/DL-PP-PMs compared with DOX/PP-PMs evidenced the dual target ability of DOX/DL-PP-PMs, which was further supported by in vivo biodistribution results. As expected, in the human oral epidermal carcinoma (KB) cells xenograft nude mice model, the remarkable enhancement of antitumor efficacy for DOX/DL-PP-PMs with low toxicity was observed compared with DOX/FA-PP-PMs and DOX/ZGP-PP-PMs. The possible mechanism was elucidated to be the dismantling of the stromal barrier by nanodrill-like DOX/DL-PP-PMs via the deletion of CAFs evidenced by the downregulation of α-SMA and inhibition of their functions proved by the decrease in the microvascular density labeled with CD31 and the reduction in the extracellular matrix detected by the collagen content, thereby promoting tumor penetration and enhancing their uptake by tumor cells. The present research offered an alternative approach integrating anticancer and antifibrosis effects in one delivery system to enhance the delivery efficiency and therapeutic efficacy of anticancer drugs.

Application or function of citric acid in drug delivery platforms

Nontoxic materials with natural origin are promising materials in the designing and preparation of the new drug delivery systems (DDSs). Today's, citric acid (CA) has attracted a great deal of attention because of its special features; green nature, biocompatibility, low price, biodegradability, and commercially available property. So, CA has been employed in the preparation of the various platforms to induce a suitable property on their structure. Recently, several research groups investigated the CA-based platforms in different forms like tablets, dendrimers, hyperbranched polymers, (co)polymer, hydrogels, and nanoparticles as efficient DDSs. By considering an increasing amount of published articles in this field, for the first time, in this review, an overview of the published works regarding CA applications in the design of various DDSs is presented with a detailed and insightful discussion.

Micelles Based on Lysine, Histidine, or Arginine: Designing Structures for Enhanced Drug Delivery

Natural amino acids and their derivatives are excellent building blocks of polymers for various biomedical applications owing to the non-toxicity, biocompatibility, and ease of multifunctionalization. In the present review, we summarized the common approaches to designing and constructing functional polymeric micelles based on basic amino acids including lysine, histidine, and arginine and highlighted their applications as drug carriers for cancer therapy. Different polypeptide architectures including linear polypeptides and dendrimers were developed for efficient drug loading and delivery. Besides, polylysine- and polyhistidine-based micelles could enable pH-responsive drug release, and polyarginine can realize enhanced membrane penetration and gas therapy by generating metabolites of nitric oxide (NO). It is worth mentioning that according to the structural or functional characteristics of basic amino acids and their derivatives, key points for designing functional micelles with excellent drug delivery efficiency are importantly elaborated in order to pave the way for exploring micelles based on basic amino acids.

pH/ROS dual-sensitive and chondroitin sulfate wrapped poly (β-amino ester)-SA-PAPE copolymer nanoparticles for macrophage-targeted oral therapy for ulcerative colitis

An oral nanoparticle (NPs) encapsulated in chitosan/alginate hydrogel (CA-Gel) with dual-sensitive in pH and reactive oxygen species (ROS) was developed to load curcumin (CUR) based on the intracellular-specific characteristics of macrophages. Chondroitin sulfate (CS) wrapped PBAE-SA-PAPE with intracellular pH/ROS dual-sensitive characteristics and CUR via a simple nanoprecipitation method to form NPs (CS-CUR-NPs), and mixed CA-Gel to acquire the final preparation (CS-CUR-NPs-Gel). CS-CUR-NPs displayed an ideal average particle size (179.19±5.61nm) and high encapsulating efficiency (94.74±1.15%). CS showed a good targeting ability on macrophages and the CA-Gel contribution in protecting NPs from being destroyed in the upper gastrointestinal tract. As expected, CS-CUR-NPs-Gel could significantly alleviate inflammation in DSS-induced UC mice via TLR4-MAPK/NF-κB pathway. This study is the first to attempt to design a novel pH/ROS dual-stimulated release strategy in helping intracellular CUR delivery and anticipated for efficient anti-UC therapy.

An iron oxide nanoparticle-based transdermal nanoplatform for dual-modal imaging-guided chemo-photothermal therapy of superficial tumors

Transdermal delivery is an attractive strategy for treating superficial tumors. However, the applications of existing transdermal systems have been limited by low transdermal efficiency and poor therapeutic outcomes. Here, we develop a transdermal nanoplatform (+)T-SiDs, based on superparamagnetic iron oxide core, surface-modified with cationic lipids, transdermal enhanced peptide TD, and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR), and loaded with doxorubicin. The (+)T-SiDs compositions enable MR/NIR dual-modal imaging guided synergistic chemo-photothermal therapy to superficial tumors treatment via transdermal delivery. The (+)T-SiDs exhibit good stability, efficient cellular uptake, pH/photothermal responsive drug release, and high photothermal conversion efficiency (47.45%). Importantly, the transdermal delivery of (+)T-SiDs is significantly enhanced by TD functionalization. In vivo MR/NIR imaging shows that the (+)T-SiDs exhibit high transdermal efficiency and specificity in localization to the tumor site. Moreover, in comparison with individual chemo- or photothermal therapies, the combination of chemo-photothermal therapy exhibits more efficient tumor inhibition effects. This work presents a new transdermal treatment nanoplatform for dual-modal imaging-guided chemo-photothermal therapy of superficial tumors, with efficient tumor eradication and low systemic toxicity thus offering strong potential for clinical adoption. STATEMENT OF SIGNIFICANCE: Transdermal delivery is an attractive strategy for treating superficial tumors. However, a highly efficient transdermal nanoplatform remains to be developed. Herein, we designed a multifunctional transdermal nanoplatform for dual-modal imaging-guided chemo-photothermal therapy of superficial tumors, comprised of a super-paramagnetic iron oxide (SPIO) nanoparticle, which can act as an MRI contrast agent and photothermal agent; a transdermal enhanced peptide (TD) and cationic lipids, which can accelerate skin penetration; and a NIR dye (DiR) and doxorubicin (DOX), which can achieve a synergistic enhanced chemo-photothermal therapy with NIR imaging ability. The transdermal nanoplatform achieved efficient tumor eradication and low systemic toxicity, thus offering strong potential for clinical adoption.

A general prodrug nanohydrogel platform for reduction-triggered drug activation and treatment of taxane-resistant malignancies

Chemotherapy has been widely used for treating the vast majority of cancer patients. Unfortunately, only a fraction of patients can respond to chemotherapies, but these patients still experience severe side effects. In this context, a wide range of nanotherapeutic platforms have been developed with the aim of improving treatment outcomes while reducing drug toxicities. Nanohydrogels are highly appealing "smart" biocompatible and biodegradable vehicles for either local or systemic delivery of bioactive compounds. Here, we developed prodrug hydrogelators that can undergo one-step distillation-precipitation polymerization to form systemically injectable nanohydrogels. The optimized nanohydrogels were capable of rapidly releasing active agents (e.g., the cytotoxic agent cabazitaxel or the PI3K molecular inhibitor PI103) in response to the reducing tumor microenvironment, while drug release was very slow in the absence of the reductive reagent glutathione. Cabazitaxel-loaded nanogels showed preferential tumor accumulation, and administration of nanogels produced durable tumor regression in a docetaxel-resistant cervical tumor xenograft-bearing mouse model. More significantly, nanogel-based therapy was proven to demonstrate a higher safety profile than solution-based free cabazitaxel. Collectively, this study provides an alternative formulation that meets the essential requirements of high stability in the blood, spontaneous drug release at diseased sites, favorable safety in vivo, and translational capacity for further investigations. STATEMENT OF SIGNIFICANCE: Chemotherapy remains a considerable challenge and only a fraction of patients can respond to chemotherapies. Here we report an intratumoral reducing agent-activatable, tumor-targeting prodrug nanogel platform for therapeutic delivery. To this end, two anticancer agents (e.g., cytotoxic cabazitaxel or PI3K molecular inhibitor PI103) are tested. Prodrug nanogels are stable in the blood but performed reduction-triggered release of chemically unmodified drug molecules in cancerous tissues. Cabazitaxel-loaded nanogels exhibit satisfactory anticancer performance in a preclinical docetaxel-resistant tumor model. This is a practical and expedient approach that combines the prodrug strategy and nanogel scaffold to re-engineer a hydrophobic and toxic anticancer drug. The approach also is broadly applicable for the formulation of other agents to improve the therapeutic index.

Poly(α-l-lysine)-based nanomaterials for versatile biomedical applications: Current advances and perspectives

Poly(α-l-lysine) (PLL) is a class of water-soluble, cationic biopolymer composed of α-l-lysine structural units. The previous decade witnessed tremendous progress in the synthesis and biomedical applications of PLL and its composites. PLL-based polymers and copolymers, till date, have been extensively explored in the contexts such as antibacterial agents, gene/drug/protein delivery systems, bio-sensing, bio-imaging, and tissue engineering. This review aims to summarize the recent advances in PLL-based nanomaterials in these biomedical fields over the last decade. The review first describes the synthesis of PLL and its derivatives, followed by the main text of their recent biomedical applications and translational studies. Finally, the challenges and perspectives of PLL-based nanomaterials in biomedical fields are addressed.

Recent progress on charge-reversal polymeric nanocarriers for cancer treatments

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

A novel GSH-triggered polymeric nanomicelles for reversing MDR and enhancing antitumor efficiency of hydroxycamptothecin

Tumor multidrug resistance (MDR) is one of the main reasons for the failure of clinical chemotherapy. Here, a bio-responsive anti-drug-resistant polymer micelle that can respond to the reductive GSH in the tumor microenvironment (TME) for delivery of HCPT was designed. A new type of polymer with anti-drug resistance and anti-tumor effect was synthesized and used to encapsulated HCPT to form reduction-sensitive micelles (PDSAH) by a thin-film dispersion method. It is demonstrated that the micelle formulation improves the anti-tumor activity and biosafety of HCPT, and also plays a significant role in reversing the drug resistance, which contributes to inhibiting the tumor growth and prolonging the survival time of H22 tumor-bearing mice. The results indicate that this nanoplatform can serve as a flexible and powerful system for delivery of other drugs that are tolerated by tumors or bacteria.

Nanocarrier-delivered small interfering RNA for chemoresistant ovarian cancer therapy

Ovarian cancer is the fifth leading cause of cancer-related death in women in the United States. Because success in early screening is limited, and most patients with advanced disease develop resistance to multiple treatment modalities, the overall prognosis of ovarian cancer is poor. Despite the revolutionary role of surgery and chemotherapy in curing ovarian cancer, recurrence remains a major challenge in treatment. Thus, improving our understanding of the pathogenesis of ovarian cancer is essential for developing more effective treatments. In this review, we analyze the underlying molecular mechanisms leading to chemotherapy resistance. We discuss the clinical benefits and potential challenges of using nanocarrier-delivered small interfering RNA to treat chemotherapy-resistant ovarian cancer. We aim to elicit collaborative studies on nanocarrier-delivered small interfering RNA to improve the long-term survival rate and quality of life of patients with ovarian cancer. This article is categorized under: RNA Methods > RNA Nanotechnology Regulatory RNAs/RNAi/Riboswitches > RNAi: Mechanisms of Action.

Dual-responsive click-crosslinked micelles designed for enhanced chemotherapy for solid tumors

The design of multiple stimuli-responsive, stable polymeric drug carriers is key for efficient drug release against solid tumors. Herein, core-crosslinked micelles were readily prepared from a pair of redox/pH-sensitive clickable copolymers. The two copolymers comprised the same poly(ethylene glycol) (PEG)-poly(ε-benzyloxycarbonyl-l-lysine) (PZLL) block but with either disulfide-linked azadibenzocyclooctyne (DBCO) or azide (AZ) group-tagged branched polyethylenimine (BPEI, 1.8 kDa). The data showed that an equivalent of the two copolymers could self-assemble into nanosized micelles with the crosslinked core via the DBCO-AZ click chemistry. The click-crosslinked micelles showed excellent size stability under multiple dilutions but destabilization in an acidic or reductive environment. Besides, they could load doxorubicin (DOX), an anticancer drug, and mediate slow drug release in a neutral environment but sufficient drug unloading under acidic plus reductive conditions. In vitro, DOX-loaded crosslinked micelles led to higher DOX accumulation in the cellular nucleus in comparison with non-crosslinked micelles from the PEG-PZLL-BPEI copolymer (PP), thus causing more marked cytotoxicity in SKOV-3 cells. In vivo, DOX-loaded crosslinked micelles caused significant growth inhibition of SKOV-3 tumors xenografted in BALB/c nude mice, and showed superior anticancer efficacy to non-crosslinked PP micelles. Chemotherapy with core-crosslinked micelles had no adverse side effects on the health (serum levels and body weight) of the mice. This study highlights the design of clickable block copolymers to easily construct core-crosslinked and multiple stimuli-responsive micelles for enhanced anticancer therapy.

Dual-modal imaging-guided theranostic nanocarriers based on 2-methoxyestradiol and indocyanine green

Drug toxicity and insufficient drug dosing place a limit on the effect of chemotherapy. Optimal efficacy is achieved by exposing tumor cells to the maximum tolerated dose of a chemotherapeutic drug. In this study, we developed a strategy (graphic summary) for enhancing the therapeutic and diagnostic capabilities of known chemotherapeutics. We used a dual-mode near-infrared (NIR) fluorescence/photoacoustic imaging technology to achieve actively guided tumor targeting of the photothermal therapeutic agent indocyanine green (ICG) and the chemotherapeutic drug 2-methoxyestradiol (2-ME), which were loaded into thermosensitive liposomes (TSLs) with surface-grafted tumor-targeting peptide cRGDyk (cRGDyk-2-ME@ICG-TSLs). In vitro studies demonstrated that cRGDyk-2-ME@ICG-TSLs effectively induced drug accumulation and cytotoxicity in NIR laser-irradiated B16-F10 melanoma cells using dual targeting based on the cRGDyk peptide and temperature sensitivity. An in vivo study showed that 24 h after intravenously injecting cRGDyk-2-ME@ICG-TSLs into melanoma tumor-bearing mice, the dual-mode NIR fluorescence/photoacoustic imaging could accurately identify tumors and normal tissues. In addition, the combination of cRGDyk-2-ME@ICG-TSLs and NIR radiation suppressed tumor growth in tumor-bearing nude mice and was associated with a low risk of side effects on normal organs. Our results indicate that TSLs are a suitable drug delivery system for diagnostic and chemotherapeutic agents guided by dual-mode imaging.

Facile Fabrication of Nanoparticles with Dual-Targeting Ligands for Precise Hepatocellular Carcinoma Therapy In Vitro and In Vivo

Efficient hepatocellular carcinoma (HCC) therapy remains a significant challenge due to the unsatisfactory targeting efficiency of nanoparticles (NPs) with either a passive targeting or a single active targeting property. Although a dual-targeting mechanism-based strategy can promote the partial targeting efficiency, most of the reported NPs with dual-targeting properties generally suffer from sophisticated chemical design, multistep synthesis, and purification procedures, leading to batch-to-batch variation and difficulties in scalable production. To develop a facile yet efficient strategy toward dual-targeting ligand-functionalized NPs for precise HCC therapy and potential clinical translation, folic acid (FA) was readily introduced as a hydrophobic and targeting component to a hydrophilic macromolecular prodrug, galactosylated chitosan-5-fluorouracil acetic acid (GC-FU), to afford FA-GC-FU formulation that can self-assemble into NPs driven by the solubility variation of FA and GC-FU without the necessity of previously used physical cross-linking. The resulting nanoparticles of FA-GC-FU can target the overexpressed asialoglycoprotein receptors (ASGPRs) and folate receptors (FRs) on the surface of HCC cells, respectively, via the FA and lactobionic acid (LA) residues exposed on the surface of the NPs, leading to the maximized targeting efficiency of HCC and minimized nonspecific uptake by normal hepatocytes in vitro and in vivo. Therefore, this study not only developed a simple yet efficient strategy toward a facile fabrication of NPs with dual-targeting ligands but also presented a precise therapeutic platform for HCC with great potential for clinical translation.

Rational design and latest advances of codelivery systems for cancer therapy

Current treatments have limited effectiveness in treating tumors. The combination of multiple drugs or treatment strategies is widely studied to improve therapeutic effect and reduce adverse effects of cancer therapy. The codelivery system is the key to realize combined therapies. It is necessary to design and construct different codelivery systems in accordance with the variable structures and properties of cargoes and vectors. This review presented the typical design considerations about codelivery vectors for cancer therapy and described the current state of codelivery systems from two aspects: different types of vectors and collaborative treatment strategies. The commonly used loading methods of cargoes into the vectors, including physical and chemical processes, are discussed in detail. Finally, we outline the challenges and perspectives about the improvement of codelivery systems.

Nano Encapsulated Curcumin: And Its Potential for Biomedical Applications

Curcumin, a yellow-colored polyphenol extracted from the rhizome of turmeric root, is commonly used as a spice and nutritional supplement. It exhibits many pharmacological activities such as anti-inflammatory, anti-bacterial, anti-cancer, anti-Alzheimer, and anti-fungal. However, the therapeutic application of curcumin is limited by its extremely low solubility in aqueous buffer, instability in body fluids, and rapid metabolism. Nano delivery system has shown excellent potential to improve the solubility, biocompatibility and therapeutic effect of curcumin. In this review, we focus on the recent development of nano encapsulated curcumin and its potential for biomedical applications.

Redox dual-stimuli responsive drug delivery systems for improving tumor-targeting ability and reducing adverse side effects

Cancer is a big challenge that has plagued the human beings for ages and one of the most effective treatments is chemotherapy. However, the low tumor-targeting ability limits the wide clinical application of chemotherapy. The microenvironment plays a critical role in many aspects of tumor genesis. It generates the tumor vasculature and it is highly implicated in the progression to metastasis. To maintain a suitable environment for tumor progression, there are special microenvironment in tumor cell, such as low pH, high level of glutathione (GSH) and reactive oxygen species (ROS), and more special enzymes, which is different to normal cell. Microenvironment-targeted therapy strategy could create new opportunities for therapeutic targeting. Compared to other targeting strategies, microenvironment-targeted therapy strategy will control the drug release into tumor cells more accurately. Redox responsive drug delivery systems (DDSs) are developed based on the high level of GSH in tumor cells. However, there are also GSH in normal cell though its level is lower. In order to control the release of drugs more accurately and reduce side effects, other drug release stimuli have been introduced to redox responsive DDSs. Under the synergistic reaction of two stimuli, redox dual-stimuli responsive DDSs will control the release of drugs more accurately and quickly and even increase the accumulation. This review summarizes strategies of redox dual-stimuli responsive DDSs such as pH, light, enzyme, ROS, and magnetic guide to delivery chemotherapeutic agents more accurately, aiming at providing new ideas for further promoting the drug release, enhancing tumor-targeting and improving anticancer effects. To better illustrate the redox dual-stimuli responsive DDS, preparations of carriers are also briefly described in the review.

Reduction-sensitive poly(ethylene glycol)-polypeptide conjugate micelles for highly efficient intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

The non-specific biodistribution of traditional chemotherapeutic drugs against tumors is the key factor that causes systemic toxicity and hinders their clinical application. In this study, a reduction-sensitive polymer conjugate micelle was manufactured to achieve tumor-specific targeting, reduce toxic side-effects and improve anti-tumor activity of a natural anti-cancer drug, hydroxycamptothecin (HCPT). Therefore, HCPT was conjugated with methoxy-poly(ethylene glycol)-poly(β-benzyl-L-aspartate) (mPEG-PBLA) by a disulfide bond or succinate bond for the first time to obtain the mPEG-PBLA-SS-HCPT (PPSH) and mPEG-PBLA-CC-HCPT (PPCH) that would form micelles after high-speed agitation and dialysis. The PPSH micelles showed an average particle size of 126.3 nm, a low polydispersity index of 0.209, and a negative surface charge of -21.1 mV zeta potential. Transmission electron microscopy showed the PPSH micelles to have spherical morphology. PPSH had a low critical micelle concentration of 1.29 μg ml^-1 with high dilution stability, storage stability and reproducibility. Moreover, the particle size of the PPSH micelles had no significant change after incubation with rat plasma for 72 h, probably resulting in high long circulation in the blood. The PPSH micelles showed significant reduction sensitivity to glutathione. Their sizes increased by 403.2 nm after 24 h post-incubation, and 87.6% drug release was achieved 48 h post-incubation with 40 mM glutathione solutions. The PPSH micelles showed stronger inhibition of HepG2 cells in vitro and growth of H-22 tumor in vivo than the PPCH and HCPT solutions after intravenous injection. The accumulation of PPSH micelles in the tumor tissue contributed to the high anti-tumor effect with little side-effect on the normal tissues. The reduction-sensitive PPSH micelles were a promising carrier of HCPT and other poorly soluble anti-cancer drugs.

Nanomagnetic liposome-encapsulated parthenolide and indocyanine green for targeting and chemo-photothermal antitumor therapy

Aim: To synthesize a drug-delivery system with chemo-photothermal function and magnetic targeting, to validate its antitumor effect. Materials & methods: Parthenolide (PTL), employing chemotherapy and indocyanine green (ICG) providing phototherapy, were encased separately in the lipid and aqueous phases of liposomes (Lips). The Fe₃O₄ nanoparticles (MNPs), endowing magnetic targeting, were modified on the surface of Lips. The antitumor effects were investigated in vitro and in vivo. Results: ICG-PTL-Lips@MNPs showed outstanding synergistic antitumor efficacy in vitro and in vivo. Especially, after 14-day treatment, the tumor volumes decreased significantly and the biotoxicity was very low. Conclusion: The designed ICG-PTL-Lips@MNPs possess synergistic effects of chemotherapy, photothermal and targeting therapy, which are expected to provide an alternative way to further improve antitumor efficacy.

Stimuli-responsive Drug Delivery Systems as an Emerging Platform for Treatment of Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a systemic autoimmune disease accompanied by chronic inflammation. Due to the long-term infiltration in inflammatory sites, joints get steadily deteriorated, eventually resulting in functional incapacitation and disability. Despite the considerable effect, RA sufferers treated with current drug therapeutic efficacy are exposed to severe side effects. Application of Drug Delivery Systems (DDS) has improved these situations while the problem of limited drug exposure remains untackled. Stimuli-responsive DDS that are responsive to a variety of endogenous and exogenous stimuli, such as pH, redox status, and temperature, have emerged as a promising therapeutic strategy to optimize the drug release. Herein, we discussed the therapeutic regimes and serious side effects of current RA therapy, as well as focused on some of the potential stimuliresponsive DDS utilized in RA therapy. Besides, the prospective room in designing DDS for RA treatment has also been discussed.

Preparation, In Vivo and In Vitro Release of Polyethylene Glycol Monomethyl Ether-Polymandelic Acid Microspheres Loaded Panax Notoginseng Saponins

In order to enrich the types of Panax notoginseng saponins (PNS) sustained-release preparations and provide a new research idea for the research and development of traditional Chinese medicine sustained-release formulations, a series of Panax notoginseng saponins microspheres was prepared by a double emulsion method using a series of degradable amphiphilic macromolecule materials polyethylene glycol monomethyl ether-polymandelic acid (mPEG-PMA) as carrier. The structure and molecular weight of the series of mPEG-PMA were determined by nuclear magnetic resonance spectroscopy (1 HNMR) and gel chromatography (GPC). The results of the appearance, particle size, drug loading and encapsulation efficiency of the drug-loaded microspheres show that the mPEG10000-PMA (1:9) material is more suitable as a carrier for loading the total saponins of Panax notoginseng. The particle size was 2.51 ± 0.21 μm, the drug loading and encapsulation efficiency were 8.54 ± 0.16% and 47.25 ± 1.64%, respectively. The drug-loaded microspheres were used for in vitro release and degradation experiments to investigate the degradation and sustained release behaviour of the drug-loaded microspheres. The biocompatibility of the microspheres was studied by haemolytic, anticoagulant and cytotoxicity experiments. The pharmacological activity of the microspheres was studied by anti-inflammatory and anti-tumour experiments. The results showed that the drug-loaded microspheres could be released stably for about 12 days and degraded within 60 days. At the same time, the microspheres had good biocompatibility, anti-inflammatory and anti-tumour activities.

A polymeric micelle with an endosomal pH-sensitivity for intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

Amphiphilic poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) and poly(ethylene glycol)-poly(benzyl-l-aspartate) (PPA) block copolymers were synthesized as pH-responsive and pH-nonresponsive copolymers, respectively. Polymer micelles were fabricated by the film dispersion method, and hydroxycamptothecin (HCPT) was physically encapsulated into the micelles. The average diameter of the HCPT-loaded PIPA micelles (PIPAH micelles) was approximately 230 nm, which was slightly smaller than that of the HCPT-loaded PPA micelles (PPAH micelles, approximately 260 nm). The drug-loading content and encapsulation efficiency of the PIPAH micelles (3.33% and 68.89%, respectively) were slightly higher than those of the PPAH micelles (2.90% and 59.68%, respectively). The PIPAH micelles exhibited better colloid stability, storage stability, and plasma stability than the PPAH micelles. Drug release from the PIPAH micelles with imino groups was pH dependent, and more than 75% or 65% of the loaded HCPT was released within 24 h in weakly acidic media (pH 5.0 or 6.0, respectively). An in vitro cell assay demonstrated that the pH-sensitive micelles exhibited potent suppression of cancer cell proliferation and little cytotoxicity on normal cells. Additionally, these micelles could be efficiently internalized by the tumor cells through macropinocytosis- and caveolin-mediated endocytotic pathways. HCPT-loaded micelles had longer circulation time than the HCPT solution in a pharmacokinetic study. In vivo antitumor experiments indicate that the PIPAH micelles had better antitumor efficacy than the pH-insensitive PPAH micelles and the HCPT solution. Therefore, the pH-responsive PIPAH micelles have great potential for high-efficiency delivery of HCPT. STATEMENT OF SIGNIFICANCE: In this study, a new type of pH-responsive amphiphilic copolymer, poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) block copolymer, was synthesized. This copolymer had then self-assembled to form nanomicelles for tumor intracellular delivery of hydroxycamptothecin (HCPT) for the first time. In in vitro test, the PIPAH micelles exhibited adequate stability and pH-dependent drug release. To one's excitement, the PIPAH micelles exhibited better antitumor efficacy and biosafety than the pH-insensitive micelles (PPAH) and the HCPT solution in in vitro and in vivo antitumor experiments. Therefore, the pH-responsive micelles in this study have significant potential to be used for high-performance delivery of HCPT and potentially for the targeted delivery of other cancer therapeutic agents. The polymer designed in this study can be used as a carrier of poorly soluble drugs or other active ingredients.

Tumor-targeting micelles based on folic acid and α-tocopherol succinate conjugated hyaluronic acid for paclitaxel delivery

Tumor-targeting micelles for the delivery of paclitaxel (PTX) were developed based on folic acid and α-tocopherol succinate conjugated hyaluronic acid (FA-HA-TOS). The conjugate FA-HA-TOS was synthesized by an esterification reaction and was characterized by proton nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FT-IR) analysis. The conjugate self-assembles into nanosized micelles in aqueous medium with a critical micellar concentration (CMC) of 1.12 × 10^-2 mg/mL. The FA-HA-TOS micelles demonstrated high drug loading and entrapment efficiency for PTX, with respective values of 21.37% and 90.48%. The physicochemical properties of the micelles were measured by DLS, TEM and XRD. Moreover, in vitro and in vivo evaluations were performed to demonstrate the superior antitumor activity of the PTX-loaded micelles. It was suggested that the FA-HA-TOS micelle system represents a promising nanocarrier for targeted delivery of PTX.

Logical design and application of prodrug platforms

This review summarizes the current state of prodrugs and elaborates the logical design and future development of the prodrug platform.

Construction of a biodegradable, versatile nanocarrier for optional combination cancer therapy

A novel biodegradable versatile nanocarrier (FA-CM) was fabricated based on the self-assembly of delaminated CoAl-layered double hydroxides (LDHs) and manganese dioxide (MnO₂) for optional combination cancer therapy. Biodegradation, versatility, targeting, bioimaging, in vitro cytotoxicity and in vivo antitumor efficacy were evaluated. The results showed that FA-CM could not only be effectively degraded into Co²⁺, Al³⁺ and Mn²⁺ to overcome the long-term toxic side effects, but also successfully load any positive-charged, negative-charged, hydrophilic, and hydrophobic drug, meeting the critical requirement of versatile nanocarrier. Meanwhile, the presence of FA led to the higher uptake efficiency, cytotoxicity, and excellent fluorescence imaging of FA-CM toward cancerous cells. In particular, FA-CM exhibited glutathione and pH dual-response drug release, avoiding any premature leakage and side effects. The applicability of the FA-CM was determined by co-loading hydrophilic (doxorubicin (DOX)) and hydrophobic drug (paclitaxel (PTX)) for synergistic combination chemotherapy. In vitro cytotoxicity evaluation and a xenograft tumor model of hepatoma showed that this combination exhibited more efficient anticancer effects compared with either free drug alone or the corresponding cocktail solutions. Especially, the ratios of DOX and PTX loaded on FA-CM could be tuned as needed. A powerful approach is provided for the design and preparation of a biodegradable versatile nanocarrier with targeted ability and excellent biocompatibility, which can be potentially applied in clinical practice and medical imaging. STATEMENT OF SIGNIFICANCE: Drug delivery nanocarriers that can transport an effective dosage of drug molecules to targeted cells and tissues have been extensively designed to overcome the adverse side effects and low effectiveness of conventional chemotherapy. However, lack of biodegradability and versatility existing in majority of nanocarriers limit their further clinical applications. Thus, constructing a novel biodegradable versatile nanocarrier that can carry various types of drugs, is in urgent need and more suitable for commercial production and clinical use. In this study, we developed a novel biodegradable versatile nanocarrier (FA-CM) based on the self-assembly of delaminated CoAl-layered double hydroxides (LDHs) and manganese dioxide (MnO₂) for optional combination cancer therapy. This work provides a new strategy for constructing versatile biodegradable platform for targeted drug delivery, which would have broad applications in cancer theranostics.

Sialic Acid-Functionalized pH-Triggered Micelles for Enhanced Tumor Tissue Accumulation and Active Cellular Internalization of Orthotopic Hepatocarcinoma

Both targeted and stimuli-sensitive drug-delivery systems (DDSs) have been developed to augment antitumor effects. However, lack of knowledge regarding tumor tissue targeting and different effects of the stimuli-sensitive DDSs in orthotropic and ectopic tumors have impeded further advances in their clinical applications. Herein, we first reported a pH-triggered micelle with sialic acid (SA)-driven targeting ability (SA-poly(ethylene glycol)-hydrazone linker-doxorubicin (DOX), SPD). The SPD micelles encapsulated with DOX (SPDD) showed sustained drug release over 48 h in response to the pH gradient in vivo, slow under physical conditions and accelerated in the acid tumor microenvironment. In addition, the SPD micelles showed 2.3-fold higher accumulation in tumors after 48 h compared to the micelles lacking the SA moiety. The overexpression of E-selectin on the inflammatory vascular endothelial cells surrounding the tumors increased the accumulation of SPD micelles in tumor tissues, whereas that on the tumor cells increased the internalization of micelles. Consequently, SPDD micelles exerted remarkable antitumor effects in both orthotopic and ectopic models. Application of SPDD micelles in the in situ model reduced the tumor volume (77.57 mm³ vs 62.13 mm³) and metastasis after treatment for 25 days. These results suggest that SA-driven targeted DDS with a pH-responsive switch has the potential to treat hepatocarcinoma effectively both ectopically and orthotopically.

Dual-targeting liposomes for enhanced anticancer effect in somatostatin receptor II-positive tumor model

Aim: We developed octreotide-modified magnetic liposomes (OMlips) as dual-targeting drug carriers to enhance the drug accumulation in tumor site. Materials & methods: Octreotide acts as a modified ligand for receptor-mediated targeting and the coated Fe3O4 nanoparticles offer the magnetic targeting property. SSTR2 overexpressed A549 cells and S180 cells were chosen to explore the targeting ability and antitumor effect of the oleanolic acid (OA)-loaded OMlips in vitro and in vivo. Results: The OMlips platform significantly improves the targeting, penetrating and accumulation of OA at the SSTR2 overexpressed cells and SSTR2-positive tumor-bearing mice. Conclusion: The OA-loaded OMlips have better antitumor effect and lower systemic toxicity. Such a receptor-mediated and magnetically-orienting dual-targeting drug nanocarriers may have great potentials in clinical practice.

Au-CGKRK Nanoconjugates for Combating Cancer through T-Cell-Driven Therapeutic RNA Interference

Numerous prior studies on fighting cancer have been based on using inhibitors of JAK-STAT pathway (signal transducer and activator of transcription 3 (STAT3) inhibitor in particular), a signaling pathway responsible for progression of many types of cancer cells. However, recent studies have shown that STAT3 activation leads to upregulation of program death receptor-ligand 1 (PD-L1, an immune checkpoint protein that plays a major role behind evasion of immune systems by growing tumors) expression levels in tumor cells, leading to enhanced immune suppression. This is why global efforts are being witnessed in combating cancer through use of immune checkpoint inhibitors. Herein, we report on the design, synthesis, physicochemical characterizations, and bioactivity evaluation of novel tumor- and tumor-vasculature-targeting noncytotoxic Au-CGKRK nanoconjugates (17-80 nm) for combating tumor. Using a syngeneic mouse tumor model, we show that intraperitoneal (i.p.) administration of the Au-CGKRK nanoparticles (NPs) complexed with both PD-L1siRNA (the immune checkpoint inhibitor) and STAT3siRNA (the JAK-STAT pathway inhibitor) results in significant (>70%) enhancement in overall survivability (OS) in melanoma-bearing mice (n = 5) when compared to the OS in the untreated mice group. The expression levels of CD8 and CD4 proteins in the tumor lysates of differently treated mice groups (by Western blotting) are consistent with the observed OS enhancement being a T-cell-driven process. Biodistribution study using near-infrared dye-loaded Au-CGKRK nanoconjugates revealed selective accumulation of the dye in mouse tumor. Notably, the overall survival benefits were significantly less (∼35%) when melanoma-bearing mice were treated (i.p.) with Au-CGKRK NPs complexed with only PD-L1siRNA or with STAT3siRNA alone. The presently described Au-CGKRK nanoconjugates are expected to find future use in therapeutic RNA-interference-based cancer immunotherapy.

Reduction-sensitive CD44 receptor-targeted hyaluronic acid derivative micelles for doxorubicin delivery

Introduction

A reduction-sensitive CD44-positive tumor-targetable drug delivery system for doxorubicin (DOX) delivery was developed based on hyaluronic acid (HA)-grafted polymers.

Materials and methods

HA was conjugated with folic acid (FA) via a reduction-sensitive disulfide linkage to form an amphiphilic polymer (HA-ss-FA). The chemical structure of HA-ss-FA was analyzed by ultraviolet spectroscopy, Fourier transform infrared spectroscopy, and ¹H nuclear magnetic resonance (NMR) spectroscopy. The molecular weight of HA-ss-FA was determined by high-performance gel permeation chromatography. Blank HA-ss-FA micelles and DOX-loaded micelles were prepared and characterized. The reduction responsibility, cellular uptake, and in vivo biodistribution of HA-ss-FA micelles were investigated.

Results

DOX-loaded micelles were of high encapsulation efficiency (88.09%), high drug-loading content (22.70%), appropriate mean diameter (100-120 nm), narrow size distribution, and negative zeta potential (-6.7 to -31.5 mV). The DOX release from the micelles was significantly enhanced in reduction environment compared to normal environment. The result of in vitro cytotoxicity assay indicated that the blank micelles were of low toxicity and good biocompatibility and the cell viabilities were >100% with the concentration of HA-ss-FA from 18.75 to 600.00 μg/mL. Cellular uptake and in vivo biodistribution studies showed that DOX-loaded micelles were tumor-targetable and could significantly enhance cellular uptake by CD44 receptor-mediated endocytosis, and the cellular uptake of DOX in CD44-positve A549 cells was 1.6-fold more than that in CD44-negative L02 cells. In vivo biodistribution of HA-ss-FA micelles showed that micelles were of good in vivo tumor targetability and the fluorescence of indocyanine green (ICG)-loaded micelles was 4- to 6.6-fold stronger than free ICG within 6 h in HCCLM3 tumor-bearing nude mice.

Conclusion

HA-ss-FA is a promising nanocarrier with excellent biocompatibility, tumor targetability, and controlled drug release capability for delivery of chemotherapy drugs in cancer therapy.

Combinatorial approaches in post-polymerization modification for rational development of therapeutic delivery systems

The combinatorial polymer library approach has been proven to be effective for the optimization of therapeutic delivery systems. The library of polymers with chemical diversity has been synthesized by (i) polymerization of functionalized monomers or (ii) post-polymerization modification of reactive polymers. Most scientists have followed the first approach so far, and the second method has emerged as a versatile approach for combinatorial biomaterials discovery. This review focuses on the second approach, especially discussing the post-modifications that employ reactive polymers as templates for combinatorial synthesis of a library of functional polymers with distinct structural diversity or a combination of different functionalities. In this way, the functional polymers have a consistent chain length and distribution, which allows for systematic optimization of therapeutic delivery polymers for the efficient delivery of genes, small-molecule drugs, and protein therapeutics. In this review, the modification of representative reactive polymers for the delivery of different therapeutic payloads are summarized. The recent advances in rational design and optimization of therapeutic delivery systems based on reactive polymers are highlighted. This review ends with a summary of the current achievements and the prospect on future directions in applying the approach of post-polymerization modification of polymers to accelerate the development of therapeutic delivery systems.

STATEMENT OF SIGNIFICANCE

A strategy to rationally design and systematically optimize polymers for the efficient delivery of specific therapeutics is highly needed. The combinatorial polymer library approach could be an effective way to this end. The post-polymerization modification of reactive polymer precursors is applicable for the combinatorial synthesis of a library of functional polymers with distinct structural diversity across a consistent degree of polymerization. This allows for parallel comparison and systematic evaluation/optimization of functional polymers for efficient therapeutic delivery. This review summarizes the key elements of this combinatorial polymer synthesis approach realized by post-polymerization modification of reactive polymer precursors towards the development and identification of optimal polymers for the efficient delivery of therapeutic agents.

Fullerenol-Based Intracellular Delivery of Methotrexate: A Water-Soluble Nanoconjugate for Enhanced Cytotoxicity and Improved Pharmacokinetics

Derivatization of fullerenes to polyhydroxylated fullerenes, i.e., fullerenols (FLU), dramatically decreases their toxicity and has been reported to enhance the solubility as well as cellular permeability. In this paper, we report synthesis of FLU as nanocarrier and subsequent chemical conjugation of Methotrexate (MTX) to FLU with a serum-stable and intracellularly hydrolysable ester bond between FLU and MTX. The conjugate was characterized for physiochemical attributes, micromeritics, drug-loading, and drug-release and evaluated for cancer cell-toxicity, cellular-uptake, hemocompatibility, protein binding, and pharmacokinetics. The developed hemocompatible FL-MTX offered lower protein binding vis-à-vis naïve drug and substantially higher drug loading. The conjugate offered pH-dependent release of 38.20 ± 1.19% at systemic pH and 85.67 ± 3.39% at the cancer cell pH. FLU-MTX-treated cells showed significant reduction in IC₅₀ value vis-à-vis the cells treated with pure MTX. Analogously, the results from confocal scanning laser microscopy also confirmed the easy access of the dye-tagged FLU-MTX conjugate to the cell interiors. In pharmacokinetics, the AUC of MTX was enhanced by approx. 6.15 times and plasma half-life was enhanced by 2.45 times, after parenteral administration of single equivalent dose in rodents. FLU-MTX offered enhanced availability of drug to the biological system, meanwhile improved the cancer-cell cytotoxicity, sustained the effective plasma drug concentrations, and offered substantial compatibility to erythrocytes.