Programmed Nanococktail Based on pH-Responsive Function Switch for Self-Synergistic Tumor-Targeting Therapy

Stimuli-Responsive Prodrug Chemistries for Cancer Therapy

Prodrugs are pharmacologically inactive, chemically modified derivatives of active drugs, which, following in vivo administration, are converted to the parent drugs through chemical or enzymatic cleavage. The prodrug approach holds tremendous potential to create the enhanced version of an existing pharmacological agent and leverage those improvements to augment the drug molecules' bioavailability, targeting ability, therapeutic efficacy, safety, and marketability. Especially in cancer therapy, prodrug application has received substantial attention. A prodrug can effectively broaden the therapeutic window of its parent drug by enhancing its release at targeted tumor sites while reducing its access to healthy cells. The spatiotemporally controlled release can be achieved by manipulating the chemical, physical, or biological stimuli present at the targeted tumor site. The critical strategy comprises drug-carrier linkages that respond to physiological or biochemical stimuli in the tumor milieu to yield the active drug form. This review will focus on the recent advancements in the development of various fluorophore-drug conjugates that are widely used for real-time monitoring of drug delivery. The use of different stimuli-cleavable linkers and the mechanisms of linker cleavage will be discussed. Finally, the review will conclude with a critical discussion of the prospects and challenges that might impede the future development of such prodrugs.

Nanoliposome based biosensors for probing mycotoxins and their applications for food: A review

Mycotoxins are the most common feed and food contaminants affecting animals and humans, respectively; continuous exposure causes tremendous health problems such as kidney disorders, infertility, immune suppression, liver inflammation, and cancer. Consequently, their control and quantification in food materials is crucial. Biosensors are potential tools for the rapid detection and quantification of mycotoxins with high sensitivity and selectivity. Nanoliposomes (NLs) are vesicular carriers formed by self-assembling phospholipids that surround the aqueous cores. Utilizing their biocompatibility, biodegradability, and high carrying capacity, researchers have employed NLs in biosensors for monitoring various targets in biological and food samples. The NLs are used for surface modification, signal marker delivery, and detection of toxins, bacteria, pesticides, and diseases. Here, we review marker-entrapped NLs used in the development of NL-based biosensors for mycotoxins. These biosensors are sensitive, selective, portable, and cost-effective analytical tools, and the resulting signal can be produced and/or amplified with or without destroying the NLs. In addition, this review emphasizes the benefits of the immunoliposome method in comparison with traditional detection approaches. We expect this review to serve as a valuable reference for researchers in this rapidly growing field. The insights provided may facilitate the rational design of next-generation NL-based biosensors.

Tumor Microenvironment-Based Stimuli-Responsive Nanoparticles for Controlled Release of Drugs in Cancer Therapy

With the development of nanomedicine technology, stimuli-responsive nanocarriers play an increasingly important role in antitumor therapy. Compared with the normal physiological environment, the tumor microenvironment (TME) possesses several unique properties, including acidity, high glutathione (GSH) concentration, hypoxia, over-expressed enzymes and excessive reactive oxygen species (ROS), which are closely related to the occurrence and development of tumors. However, on the other hand, these properties could also be harnessed for smart drug delivery systems to release drugs specifically in tumor tissues. Stimuli-responsive nanoparticles (srNPs) can maintain stability at physiological conditions, while they could be triggered rapidly to release drugs by specific stimuli to prolong blood circulation and enhance cancer cellular uptake, thus achieving excellent therapeutic performance and improved biosafety. This review focuses on the design of srNPs based on several stimuli in the TME for the delivery of antitumor drugs. In addition, the challenges and prospects for the development of srNPs are discussed, which can possibly inspire researchers to develop srNPs for clinical applications in the future.

Opportunities and Challenges of Switchable Materials for Pharmaceutical Use

Switchable polymeric materials, which can respond to triggering signals through changes in their properties, have become a major research focus for parenteral controlled delivery systems. They may enable externally induced drug release or delivery that is adaptive to in vivo stimuli. Despite the promise of new functionalities using switchable materials, several of these concepts may need to face challenges associated with clinical use. Accordingly, this review provides an overview of various types of switchable polymers responsive to different types of stimuli and addresses opportunities and challenges that may arise from their application in biomedicine.

Emerging Strategies in Stimuli-Responsive Prodrug Nanosystems for Cancer Therapy

Prodrugs are chemically modified drug molecules that are inactive before administration. After administration, they are converted in situ to parent drugs and induce the mechanism of action. The development of prodrugs has upgraded conventional drug treatments in terms of bioavailability, targeting, and reduced side effects. Especially in cancer therapy, the application of prodrugs has achieved substantial therapeutic effects. From serendipitous discovery in the early stage to functional design with pertinence nowadays, the importance of prodrugs in drug design is self-evident. At present, studying stimuli-responsive activation mechanisms, regulating the stimuli intensity in vivo, and designing nanoscale prodrug formulations are the major strategies to promote the development of prodrugs. In this review, we provide an outlook of recent cutting-edge studies on stimuli-responsive prodrug nanosystems from these three aspects. We also discuss prospects and challenges in the future development of such prodrugs.

Progress of Research in In Situ Smart Hydrogels for Local Antitumor Therapy: A Review

Cancer seriously threatens human health. Surgery, radiotherapy and chemotherapy are the three pillars of traditional cancer treatment, with targeted therapy and immunotherapy emerging over recent decades. Standard drug regimens are mostly executed via intravenous injection (IV), especially for chemotherapy agents. However, these treatments pose severe risks, including off-target toxic side effects, low drug accumulation and penetration at the tumor site, repeated administration, etc., leading to inadequate treatment and failure to meet patients’ needs. Arising from these challenges, a local regional anticancer strategy has been proposed to enhance therapeutic efficacy and concomitantly reduce systemic toxicity. With the advances in biomaterials and our understanding of the tumor microenvironment, in situ stimulus-responsive hydrogels, also called smart hydrogels, have been extensively investigated for local anticancer therapy due to their injectability, compatibility and responsiveness to various stimuli (pH, enzyme, heat, light, magnetic fields, electric fields etc.). Herein, we focus on the latest progress regarding various stimuli that cause phase transition and drug release from smart hydrogels in local regional anticancer therapy. Additionally, the challenges and future trends of the reviewed in situ smart hydrogels for local drug delivery are summarized and proposed.

Targeted Cancer Therapy via pH-Functionalized Nanoparticles: A Scoping Review of Methods and Outcomes

(1) Background: In recent years, several studies have described various and heterogenous methods to sensitize nanoparticles (NPs) to pH changes; therefore, in this current scoping review, we aimed to map current protocols for pH functionalization of NPs and analyze the outcomes of drug-loaded pH-functionalized NPs (pH-NPs) when delivered in vivo in tumoral tissue. (2) Methods: A systematic search of the PubMed database was performed for all published studies relating to in vivo models of anti-tumor drug delivery via pH-responsive NPs. Data on the type of NPs, the pH sensitization method, the in vivo model, the tumor cell line, the type and name of drug for targeted therapy, the type of in vivo imaging, and the method of delivery and outcomes were extracted in a separate database. (3) Results: One hundred and twenty eligible manuscripts were included. Interestingly, 45.8% of studies (n = 55) used polymers to construct nanoparticles, while others used other types, i.e., mesoporous silica (n = 15), metal (n = 8), lipids (n = 12), etc. The mean acidic pH value used in the current literature is 5.7. When exposed to in vitro acidic environment, without exception, pH-NPs released drugs inversely proportional to the pH value. pH-NPs showed an increase in tumor regression compared to controls, suggesting better targeted drug release. (4) Conclusions: pH-NPs were shown to improve drug delivery and enhance antitumoral effects in various experimental malignant cell lines.

Bioresponsive nanomedicines based on dynamic covalent bonds

Trends in the development of modern medicine necessitate the efficient delivery of therapeutics to achieve the desired treatment outcomes through precise spatiotemporal accumulation of therapeutics at the disease site. Bioresponsive nanomedicine is a promising platform for this purpose. Dynamic covalent bonds (DCBs) have attracted much attention in studies of the fabrication of bioresponsive nanomedicines with an abundance of combinations of therapeutic modules and carrier function units. DCB-based nanomedicines could be designed to maintain biological friendly synthesis and site-specific release for optimal therapeutic effects, allowing the complex to retain an integrated structure before accumulating at the disease site, but disassembling into individual active components without compromising function in the targeted organs or tissues. In this review, we focus on responsive nanomedicines containing dynamic chemical bonds that can be cleaved by various specific stimuli, enabling achievement of targeted drug release for optimal therapy in various diseases.

Self-recognizing and stimulus-responsive carrier-free metal-coordinated nanotheranostics for magnetic resonance/photoacoustic/fluorescence imaging-guided synergistic photo-chemotherapy

Carrier-free nanotheranostics directly assembled by using clinically used photosensitizers and chemotherapeutic drugs are a promising alternative to tumor theranostics. However, the weak interaction-driven assembly still suffers from low structural stability against disintegration, lack of targeting specificity, and poor stimulus-responsive property. Moreover, almost all exogenous ligands possess no therapeutic effect. Enlightened by the concept of metal-organic frameworks, we developed a novel self-recognizing metal-coordinated nanotheranostic agent by the coordination-driven co-assembly of photosensitizer indocyanine green (ICG) and chemo-drug methotrexate (MTX, also served as a specific "targeting ligand" towards folate receptors), in which ferric (FeIII) ions acted as a bridge to tightly associate ICG with MTX. Such carrier-free metal-coordinated nanotheranostics with high dual-drug payload (∼94 wt%) not only possessed excellent structural and physiological stability, but also exhibited prolonged blood circulation. In addition, the nanotheranostics could achieve the targeted on-demand drug release by both stimuli of internal lysosomal acidity and external near-infrared laser. More importantly, the nanotheranostics could self-recognize the cancer cells and selectively target the tumors, and therefore they decreased toxicity to normal tissues and organs. Consequently, the nanotheranostics showed strongly synergistic potency for tumor photo-chemotherapy under the precise guidance of magnetic resonance/photoacoustic/fluorescence imaging, thereby achieving highly effective tumor curing efficiency. Considering that ICG and bi-functional MTX are approved by the Food and Drug Administration, and FeIII ions have high biosafety, the self-recognizing and stimulus-responsive carrier-free metal-coordinated nanotheranostics may hold potential applications in tumor theranostics.

Stimulus-cleavable chemistry in the field of controlled drug delivery

Stimulus-cleavable nanoscale drug delivery systems are receiving significant attention owing to their capability of achieving exquisite control over drug release via the exposure to specific stimuli. Central to the construction of such systems is the integration of cleavable linkers showing susceptibility to one stimulus or several stimuli with drugs, prodrugs or fluorogenic probes on the one hand, and nanocarriers on the other hand. This review summarises recent advances in stimulus-cleavable linkers from various research areas and the corresponding mechanisms of linker cleavage and biological applications. The feasibility of extending their applications to the majority of nanoscale drug carriers including nanomaterials, polymers and antibodies are further highlighted and discussed. This review also provides general design guidelines to incorporate stimulus-cleavable linkers into nanocarrier-based drug delivery systems, which will hopefully spark new ideas and applications.

Liposome surface modification by phospholipid chemical reactions

Liposomal systems are well known for playing an important role as drug carriers, presenting several therapeutic applications in different sectors, such as in drug delivery, diagnosis, and in many other academic areas. A novel class of this nanoparticle is the actively target liposome, which is constructed with the surface modified with appropriated molecules (or ligands) to actively bind a target molecule of certain cells, system, or tissue. There are many ways to functionalize these nanostructures, from non-covalent adsorption to covalent bond formation. In this review, we focus on the strategies of modifying liposomes by glycerophospholipid covalent chemical reaction. The approach used in this text summarizes the main reactions and strategies used in phospholipid modification that can be carried out by chemists and researchers from other areas. The knowledge of these methodologies is of great importance for planning new studies using this material and also for manipulating its properties.

Effects of buoyant and Saffman lift force on magnetic drug targeting in microvessel in the presence of inertia

The conventional techniques in treating cancerous cells in a human body are conducted either by surgery or oral medication or injecting anticancer drugs, which may have several side effects on healthy cells. Compared to these techniques, site-specific delivery of drugs can be one of the pillars of cancer treatment. It could allow for better treatment efficiency and lesser adverse effects. A promising drug delivery approach is magnetic drug targeting, which can be realized if a drug delivery vehicle possesses an intense magnetic moment. Here, we discuss different types of magnetic nanomaterials, which can be used as magnetic drug delivery vehicles, approaches to magnetically targeted delivery, and promising strategies for the enhancement of the imaging-guided delivery and the therapeutic action. The present study aims to discuss all significant factors that influence the process of magnetic drug targeting through microvessels, such as fluidic force, magnetic force, particle-particle interaction, inertia force, Saffman lift force, and permeability of the microvessel. We consider the nature of blood flow as non-Newtonian in single-phase and two-phase models so that a realistic rheological model for an effective magnetic drug targeting can be established through proper comparison. Here we present a comprehensive mathematical model on magnetic drug targeting that could help the medical experts and biomedical engineers in applying the methodology of magnetic drug targeting effectively to cure cancerous disease.

"Watson-Crick G[triple bond, length as m-dash]C"-inspired supramolecular nanodrug of methotrexate and 5-fluorouracil for tumor microenvironment-activatable self-recognizing synergistic chemotherapy

Carrier-free nanodrugs, generated via the straightforward small-molecule self-assembly of anticancer drugs, provide a promising route for cancer chemotherapy. However, their low structural stability, lack of targeting specificity, and poor stimulus responsiveness are still limiting their therapeutic effect. Inspired by Watson-Crick G[triple bond, length as m-dash]C base pairing, the FDA-approved chemo-drug methotrexate (MTX, which can bind with folate receptors) and 5-fluorouracil (5-FU, a DNA/RNA synthetase inhibitor) were adopted for direct assembly into self-recognizing MTX-5-FU nanoparticles via "Watson-Crick-like base pairing"-driven precise supramolecular assembly. Sequentially, our synthesized weak acidity-responsive polyethylene glycol (PEG) was inserted onto the nanoparticle surface to temporarily shield the self-targeting function of MTX and prolong the blood circulation time. Once PEG-MTX-5-FU nanoparticles reached the weakly acidic tumor microenvironment, the PEG corona could be cleaved from their surface and then MTX could be re-exposed to recover its self-recognition ability and significantly elevate tumor cell uptake; furthermore, the de-PEGylated MTX-5-FU nanoparticles could respond to the stronger acidity of lysosome, triggering core disassembly and thus the burst release of both MTX and 5-FU. Further in vitro and in vivo studies consistently confirmed that the nanodrugs exhibited preferable accumulation at the tumor sites with highly synergistic chemotherapeutic effects. The supramolecular recognition-inspired, cascade-triggered self-targeting and controlled release of nanodrugs could be a promising strategy to improve synergistic chemotherapy.

Tumor Microenvironment-Activated and Viral-Mimicking Nanodrugs Driven by Molecular Precise Recognition for dNTP Inhibition-Induced Synergistic Cancer Therapy

The medical application of nanotechnology is promising for cancer chemotherapy. However, most of the small-molecule drug assemblies still have such disadvantages as serious drug leakage and nonideal synergistic mechanisms, resulting in undesired therapeutic effect. Both nucleoside analogue-based clofarabine (CA) and methotrexate (MTX) were used as the first-line anticancer medication. However, a single-agent chemotherapy still faced many challenges including low bioavailability and toxic side effects to normal tissues due to nonspecific biodistribution of drugs. Herein, we designed and fabricated novel viral-mimicking and carry-free nanodrugs (CA-MTX NPs) via molecular recognition-driven precise self-assembly between CA and MTX. After introduction of mild acid-responsive PEG-lipid on the surface of CA-MTX NPs, the synthetic nanodrugs with a diameter of ∼150 nm exhibited tumor microenvironment-activated characteristics and self-targeting property. The results suggested that our nanodrugs could achieve superior tumor accumulation and synergistically promote the tumor suppression by collaboratively inhibiting dNTP pools. We foresaw that the well-designed smart nanodrugs delivery system would open a new avenue in synergistic cancer therapeutics.

Light-Activatable Prodrug and AIEgen Copolymer Nanoparticle for Dual-Drug Monitoring and Combination Therapy

Polyprodrug nanoparticles have been employed recently for safer and more effective cancer treatment. However, it remains a challenge to elucidate how and when the polyprodrug nanoparticles are dissociated and activated to release active drugs in cancer cells. Herein, a visible light-activatable Pt(IV) prodrug and an aggregation-induced emission luminogen (AIEgen) were copolymerized and embedded in the main chain of PtAIECP, and the chemotherapeutic doxorubicin (DOX) was subsequently encapsulated in the nanoparticles self-assembled by PtAIECP (PtAIECP@DOX NP). PtAIECP@DOX NP enabled the monitoring of both the light-activation of Pt(IV) prodrug to active Pt(II) and release of encapsulated DOX intracellularly through the fluorescence "turn-on" in the course of visible-light-induced polymer-main-chain cleavage and self-assembled structure dissociation in vitro and ex vivo. The synergistic anticancer efficacy of the activated Pt(II) drug and DOX in PtAIECP@DOX NP was also investigated in vitro and in vivo. The implementation of polyprodrug and AIE combination strategy empowered dual drug release and monitoring, which could be further used to guide the temporal and spatial control of light irradiation to maximize therapeutic efficiency, and will inspire other combinational bioimaging and therapy strategies.

pH-Responsive Polymer Nanoparticles for Drug Delivery

Stimuli-responsive nanoparticles have the potential to improve the delivery of therapeutics to a specific cell or region within the body. There are many stimuli that have shown potential for specific release of cargo, including variation of pH, redox potential, or the presence of enzymes. pH variation has generated significant interest for the synthesis of stimuli-responsive nanoparticles because nanoparticles are internalized into cells via vesicles that are acidified. Additionally, the tumor microenvironment is known to have a lower pH than the surrounding tissue. In this review, different strategies to design pH-responsive nanoparticles are discussed, focusing on the use of charge-shifting polymers, acid labile linkages, and crosslinking.

Transformative hyaluronic acid-based active targeting supramolecular nanoplatform improves long circulation and enhances cellular uptake in cancer therapy

Hyaluronic acid (HA) is a natural ligand of tumor-targeted drug delivery systems (DDS) due to the relevant CD44 receptor overexpressed on tumor cell membranes. However, other HA receptors (HARE and LYVE-1) are also overexpressing in the reticuloendothelial system (RES). Therefore, polyethylene glycol (PEG) modification of HA-based DDS is necessary to reduce RES capture. Unfortunately, pegylation remarkably inhibits tumor cellular uptake and endosomal escapement, significantly compromising the in vivo antitumor efficacy. Herein, we developed a Dox-loaded HA-based transformable supramolecular nanoplatform (Dox/HCVBP) to overcome this dilemma. Dox/HCVBP contains a tumor extracellular acidity-sensitive detachable PEG shell achieved by a benzoic imine linkage. The in vitro and in vivo investigations further demonstrated that Dox/HCVBP could be in a "stealth" state at blood stream for a long circulation time due to the buried HA ligands and the minimized nonspecific interaction by PEG shell. However, it could transform into a "recognition" state under the tumor acidic microenvironment for efficient tumor cellular uptake due to the direct exposure of active targeting ligand HA following PEG shell detachment. Such a transformative concept provides a promising strategy to resolve the dilemma of natural ligand-based DDS with conflicting two processes of tumor cellular uptake and in vivo nonspecific biodistribution.

Magnetic Drug Delivery: Where the Field Is Going

Targeted delivery of anticancer drugs is considered to be one of the pillars of cancer treatment as it could allow for a better treatment efficiency and less adverse effects. A promising drug delivery approach is magnetic drug targeting which can be realized if a drug delivery vehicle possesses a strong magnetic moment. Here, we discuss different types of magnetic nanomaterials which can be used as magnetic drug delivery vehicles, approaches to magnetic targeted delivery as well as promising strategies for the enhancement of the imaging-guided delivery and the therapeutic action.

Recent Advances in Targeted Tumor Chemotherapy Based on Smart Nanomedicines

Efficacy and safety of chemotherapeutic drugs constitute two major criteria in tumor chemotherapy. Nanomedicines with tumor-targeted properties hold great promise for improving the efficacy and safety. To design targeted nanomedicines, the pathological characteristics of tumors are extensively and deeply excavated. Here, the rationale, principles, and advantages of exploiting these pathological characteristics to develop targeted nanoplatforms for tumor chemotherapy are discussed. Homotypic targeting with the ability of self-recognition to source tumors is reviewed individually. In the meanwhile, the limitations and perspective of these targeted nanomedicines are also discussed.

Development of dual-drug-loaded stealth nanocarriers for targeted and synergistic anti-lung cancer efficacy

Combination chemotherapy is widely exploited for suppressing drug resistance and achieving synergistic anticancer efficacy in the clinic. In this paper, the nanostructured targeting methotrexate (MTX) plus pemetrexed (PMX) chitosan nanoparticles (CNPs) were developed by modifying methoxy polye (thylene glycol) (mPEG), in which PEGylation CNPs was used as stealth nanocarriers (PCNPs) and MTX was employed as a targeting ligand and chemotherapeutic agent as well. Studies were undertaken on human lung adenocarcinoma epithelial (A549) and Lewis lung carcinoma (LLC) cell lines, revealing the anti-tumor efficacy of nanoparticle drug delivery system. The co-delivery nanoparticles (MTX-PMX-PCNPs) had well-dispersed with sustained release behavior. Cell counting kit-8 (CCK8) has been used to measure A549 cell viability and the research showed that MTX-PMX-PCNPs were much more effective than free drugs when it came to the inhibition of growth and proliferation. Cell cycle assay by flow cytometry manifested that the MTX-PMX-PCNPs exhibited stronger intracellular taken up ability than free drugs at the same concentration. In vivo anticancer effect results indicated that MTX-PMX-PCNPs exhibited a significantly prolong blood circulation, more tumoral location accumulation, and resulted in a robust synergistic anticancer efficacy in lung cancer in mice. The results clearly demonstrated that such unique synergistic anticancer efficacy of co-delivery of MTX and PMX via stealth nanocarriers, providing a prospective strategy for lung cancer treatment.

Integration of phospholipid-hyaluronic acid-methotrexate nanocarrier assembly and amphiphilic drug-drug conjugate for synergistic targeted delivery and combinational tumor therapy

Combinational cancer therapy has been considered as a promising strategy to achieve synergetic therapeutic effects and suppression of multidrug resistance. Herein, we adopted a combination of methotrexate (MTX), an antimetabolite acting on cytoplasm, and 10-hydroxycamptothecin (HCPT), an alkaloid acting on nuclei, to treat cancer. Given the different solubilities, membrane permeabilities, and anticancer mechanisms of both drugs, we developed a dual-targeting delivery system based on 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-hyaluronic acid (a principal ligand of CD44 receptors)-MTX (a selective ligand of folate receptors) nanoparticles, which was exploited to carry HCPT-MTX conjugate for synergistically boosting dual-drug co-delivery. The HCPT-MTX conjugate was synthesized by a blood-stable yet intracellularly hydrolysable ester bond. The core-shell-corona DSPE-HA-MTX nanoparticles encapsulating HCPT-MTX (HCPT-MTX@DHM) exhibited high drug entrapment efficiency (∼91.8%) and pH/esterase-controlled release behavior. Cellular uptake studies confirmed significant increase in the efficiency of selective internalization of HCPT-MTX@DHM via CD44/folate receptors compared with those of DSPE-HA nanoparticles encapsulating HCPT-MTX (HCPT-MTX@DH), both drugs, or each individual drug. Furthermore, in vivo near-infrared fluorescence and photoacoustic dual-modal imaging indicated that DiR-doped HCPT-MTX@DHM nanoparticles efficiently accumulated at the tumor sites through passive-plus-active targeting. Finally, the synergistic active targeting and synchronous dual-drug release at a synergistic drug-to-drug ratio resulted in highly synergetic tumor cell-killing and tumor growth inhibition in MCF-7 tumor-bearing mice. Therefore, HCPT-MTX@DHM nanoparticles can be an efficient and smart platform for tumor-targeting therapy.

Dual pH-Responsive Shell-Cleavable Polycarbonate Micellar Nanoparticles for in Vivo Anticancer Drug Delivery

To exploit tumor and intracellular microenvironments, pH-responsive diblock copolymers of poly(ethylene glycol) and catechol-functionalized polycarbonate with acid-labile acetal bond as the linker are synthesized to prepare micellar nanoparticles that shed the shell at acidic tumor tissues and inside cancer cells, hence accelerating drug release at the target. The pH-dependent cleavage of the shell is demonstrated at pH 5.0 and 6.5 using ¹H NMR. Bortezomib (BTZ, an anticancer drug containing a phenylboronic acid group) is conjugated to the polymers through formation of pH-responsive boronate ester bond between boronic acid and catechol in the polymers. Dual pH-responsive bortezomib-polymer conjugates (BTZ-PC) self-assemble into micellar nanoparticles of small size (<110 nm) with narrow size distribution and high drug loading capacity. Acidic pH accelerates BTZ release from BTZ-PC micelles and enhances intracelluar uptake of the micelles, hence increasing in vitro cytotoxicity against human breast cancer cells. More importantly, the BTZ-PC micelles achieve a stronger antitumor effect in a human breast cancer BT-474 xenograft mouse model than free BTZ and mitigate in vivo hepatotoxicity of BTZ. These dual pH-responsive shell-cleavable nanoparticles are a potentially promising carrier for BTZ delivery.

Tetrac-decorated chitosan-coated PLGA nanoparticles as a new platform for targeted delivery of SN38

New integrin-targeted nanoparticles made of chitosan-stabilized PLGA matrix was developed to specifically target colon adenocarcinoma. To this aim, SN38-encapsulated chitosan-coated PLGA NPs were conjugated with tetrac for integrin receptor-guided delivery. To provide a sustained release pattern for SN38, it was loaded into nanoparticles using single emulsion method. The size of NPs were 174.23 ± 6.12 nm with drug encapsulation efficiency and loading content of 73.16 ± 11.15 and 4.45 ± 0.31, respectively. The in vitro results confirmed that the designed nanoplatform showed specific cellular uptake and cytotoxicity in integrin overexpressing cancer cells and provided a sustained release profile for SN38. Additionally, an increased therapeutic potency of targeted formulation over both non-targeted and free drug was shown in vivo.

Design of pH-sensitive methotrexate prodrug-targeted curcumin nanoparticles for efficient dual-drug delivery and combination cancer therapy

Aim

We designed acid-labile methotrexate (MTX) targeting prodrug self-assembling nanoparticles loaded with curcumin (CUR) drug for simultaneous delivery of multi-chemotherapeutic drugs and combination cancer therapy.

Methods

A dual-acting MTX, acting as both an anticancer drug and as a tumor-targeting ligand, was coupled to 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[aldehyde(polyethylene glycol)-2000] via Schiff's base reaction. The synthesized prodrug conjugate (DSPE-PEG-Imine-MTX) could be self-assembled into micellar nanoparticles (MTX-Imine-M) in aqueous solution, which encapsulated CUR into their core by hydrophobic interactions (MTX-Imine-M-CUR).

Results

The prepared MTX-Imine-M-CUR nanoparticles were composed of an inner hydrophobic DSPE/CUR core and an outside hydrophilic bishydroxyl poly (ethyleneglycol) (PEG) shell with a self-targeting MTX prodrug corona. The imine linker between 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[aldehyde(polyethyleneglycol)-2000] and MTX, as a dynamic covalent bond, was strong enough to remain intact in physiological pH, even though it is rapidly cleaved in acidic pH. The MTX-Imine-M-CUR could codeliver MTX and CUR selectively and efficiently into the cancer cells via folate receptor-mediated endocytosis followed by the rapid intracellular release of CUR and the active form of MTX via the acidity of endosomes/lysosomes. Moreover, the MTX-Imine-M-CUR resulted in significantly higher in vitro and in vivo anticancer activity than pH-insensitive DSPE-PEGAmide-MTX assembling nanoparticles loaded with CUR (MTX-Amide-M-CUR), MTX unconjugated DSPE-PEG assembling micellar nanoparticles loaded with CUR (M-CUR), combination of both free drugs, and individual free drugs.

Conclusion

The smart system provided a simple, yet feasible, drug delivery strategy for targeted combination chemotherapy.