Click Chemistry for Biofunctional Polymers: From Observing to Steering Cell Behavior

Click chemistry has become one of the most powerful construction tools in the field of organic chemistry, materials science, and polymer science, as it offers hassle-free platforms for the high-yielding synthesis of novel materials and easy functionalization strategies. The absence of harsh reaction conditions or complicated workup procedures allowed the rapid development of novel biofunctional polymeric materials, such as biopolymers, tailor-made polymer surfaces, stimulus-responsive polymers, etc. In this review, we discuss various types of click reactions─including azide-alkyne cycloadditions, nucleophilic and radical thiol click reactions, a range of cycloadditions (Diels-Alder, tetrazole, nitrile oxide, etc.), sulfur fluoride exchange (SuFEx) click reaction, and oxime-hydrazone click reactions─and their use for the formation and study of biofunctional polymers. Following that, we discuss state-of-the-art biological applications of "click"-biofunctionalized polymers, including both passive applications (e.g., biosensing and bioimaging) and "active" ones that aim to direct changes in biosystems, e.g., for drug delivery, antiviral action, and tissue engineering. In conclusion, we have outlined future directions and existing challenges of click-based polymers for medicinal chemistry and clinical applications.

Reversing Anticancer Drug Resistance by Synergistic Combination of Chemotherapeutics and Membranolytic Antitumor β-Peptide Polymer

Multidrug resistance is the main obstacle to cancer chemotherapy. Overexpression of drug efflux pumps causes excessive drug efflux from cancer cells, ultimately leading to drug resistance. Hereby, we raise an effective strategy to overcome multidrug resistance using a synergistic combination of membranolytic antitumor β-peptide polymer and chemotherapy drugs. This membrane-active β-peptide polymer promotes the transmembrane transport of chemotherapeutic drugs by increasing membrane permeability and enhances the activity of chemotherapy drugs against multidrug-resistant cancer cells. As a proof-of-concept demonstration, the synergistic combination of β-peptide polymer and doxorubicin (DOX) is substantially more effective than DOX alone against drug-resistant cancer both in vitro and in vivo. Notably, the synergistic combination maintains a potent anticancer activity after continuous use. Collectively, this combination therapy using membrane lytic β-peptide polymer appears to be an effective strategy to reverse anticancer drug resistance.

Microenvironmentally Responsive Chemotherapeutic Prodrugs and CHEK2 Inhibitors Self-Assembled Micelles: Protecting Fertility and Enhancing Chemotherapy

Chemotherapy is a widely used and effective adjuvant treatment for cancer, and it has unavoidable damage to female fertility, with statistics showing 38% of women who have received chemotherapy are infertile. How to reduce fertility toxicity while enhancing the oncologic chemotherapy is a clinical challenge. Herein, co-delivery micelles (BML@PMP) are developed, which are composed of a reduction-sensitive paclitaxel prodrug (PMP) for chemotherapy and a CHEK2 inhibitor (BML277) for both fertility protection and chemotherapy enhancement. BML@PMP achieves fertility protection through three actions: (1) Due to the enhanced permeability and retention (EPR) effect, BML@PMP is more enriched in the tumor, while very little in the ovary (about 1/10th of the tumor). (2) Glutathione (GSH) triggers the release of PTX, and with low levels of GSH in the ovary, the amount of PTX released in the ovary is correspondingly reduced. (3) BML277 inhibits oocyte apoptosis by inhibiting the CHEK2-TAp63α pathway. Because of the different downstream targets of CHEK2 in tumor cells and oocytes, BML277 also enhances chemotherapeutic efficacy by reducing DNA damage repair which is activated through the CHEK2 pathway. This bidirectional effect of CHEK2 inhibitor-based co-delivery system represents a promising strategy for improving oncology treatment indices and preventing chemotherapy-associated fertility damage.

Characterization and Preliminary In Vitro Antioxidant Activity of a New Multidrug Formulation Based on the Co-Encapsulation of Rutin and the α-Acylamino-β-Lactone NAAA Inhibitor URB894 within PLGA Nanoparticles

A biodegradable and biocompatible polymeric matrix made up of poly(d,l-lactide-co-glycolide) (PLGA) was used for the simultaneous delivery of rutin and the (S)-N-(2-oxo-3-oxetanyl)biphenyl-4-carboxamide derivative (URB894). The goal was to exploit the well-known radical scavenging properties of rutin and the antioxidant features recently reported for the molecules belonging to the class of N-acylethanolamine-hydrolyzing acid amidase (NAAA) inhibitors, such as URB894. The use of the compounds, both as single agents or in association promoted the development of negatively-charged nanosystems characterized by a narrow size distribution and an average diameter of ~200 nm when 0.2-0.6 mg/mL of rutin or URB894 were used. The obtained multidrug carriers evidenced an entrapment efficiency of ~50% and 40% when 0.4 and 0.6 mg/mL of rutin and URB894 were associated during the sample preparation, respectively. The multidrug formulation evidenced an improved in vitro dose-dependent protective effect against H₂O₂-related oxidative stress with respect to that of the nanosystems containing the active compounds as a single agent, confirming the rationale of using the co-encapsulation approach to obtain a novel antioxidant nanomedicine.

Acid-Responsive Micelles Releasing Cinnamaldehyde Enhance RSL3-Induced Ferroptosis in Tumor Cells

Ferroptosis is a novel type of regulated cell death characterized by the accumulation of lipid peroxides to lethal levels. Most tumor cells are extremely vulnerable to ferroptosis due to the high levels of reactive oxygen species (ROS) produced by their active metabolism. Therefore, tumor cells rely on glutathione (GSH) to reduce lipid peroxides catalyzed by glutathione peroxidase 4 (GPX4), and this pathway is also an important target for a variety of drugs that promote tumor cell ferroptosis. Herein, RSL3@PCA was designed to simultaneously deplete intracellular GSH and inhibit the activity of GPX4, thereby significantly promoting tumor cell ferroptosis. RSL3@PCA was successfully prepared by encapsulating a selective inhibitor of GPX4 into acid-responsive nanoparticle PCA. After being taken up by tumor cells, the acid-responsive nanoparticle gradually degraded to release cinnamaldehyde (CA) and the encapsulated RSL3. CA and RSL3 block the reduction of lipid peroxides in cells, thereby inducing ferroptosis. By a cytotoxicity assay and 4T1 cell xenotransplantation model, we confirmed that RSL3@PCA has excellent inhibition of tumor growth without significant toxicity to normal cells and tissues and still has a good therapeutic effect on tumor cells that are resistant to conventional chemotherapy drugs. This work provides new drug combinations for promoting ferroptosis in tumor cells without severe side effects in normal organs.

A Co-delivery System Based on a Dimeric Prodrug and Star-Shaped Polymeric Prodrug Micelles for Drug Delivery

Chemotherapy is one of the commonly used therapies for the treatment of malignant tumors. Insufficient drug-loading capacity is the major challenge for polymeric micelle-based drug delivery systems of chemotherapy. Here, the redox-responsive star-shaped polymeric prodrug (PSSP) and the dimeric prodrug of paclitaxel (PTX) were prepared. Then the dimeric prodrug of PTX (diPTX, diP) was loaded into the core of the star-shaped polymeric prodrug micelles of PSSP by hydrophobic interaction forming the redox-responsive prodrug micelles of diPTX@PSSP for intracellular drug release in tumor cells. The hydrodynamic diameter of diPTX@PSSP nanoparticles was 114.3 nm ± 2.1 (PDI = 0.219 ± 0.016), and the micelles had long-term colloidal stability and the drug-loading content (DLC) of diPTX and PTX is 16.7 and 46.9%, respectively. The prepared micelles could broke under the reductive microenvironment within tumor cells, as a result, the dimeric prodrug of diP and polymeric prodrug micelles of PSSP were rapidly disassembled, leading to the rapid release of intracellular drugs. In vitro release studies showed that under the condition of reduced glutathione (GSH) (10 mM), the release of PTX was significantly accelerated with approximately 86.6% released within 21 h, and the released PTX in cytoplasm could promote the disintegration of microtubules and induce cell apoptosis. These results indicated that the new type of this reduction-sensitive nanodrug delivery system based on dimeric prodrug@polymeric prodrug micelles would be a promising technology in chemotherapy.

Functionalized Particles Designed for Targeted Delivery

Pure bioactive compounds alone can only be exceptionally administered in medical treatment. Usually, drugs are produced as various forms of active compounds and auxiliary substances, combinations assuring the desired healing functions. One of the important drug forms is represented by a combination of active substances and particle-shaped polymer in the nano- or micrometer size range. The review describes recent progress in this field balanced with basic information. After a brief introduction, the paper presents a concise overview of polymers used as components of nano- and microparticle drug carriers. Thereafter, progress in direct synthesis of polymer particles with functional groups is discussed. A section is devoted to formation of particles by self-assembly of homo- and copolymer-bearing functional groups. Special attention is focused on modification of the primary functional groups introduced during particle preparation, including introduction of ligands promoting anchorage of particles onto the chosen living cell types by interactions with specific receptors present in cell membranes. Particular attention is focused on progress in methods suitable for preparation of particles loaded with bioactive substances. The review ends with a brief discussion of the still not answered questions and unsolved problems.

Self-Guiding Polymeric Prodrug Micelles with Two Aggregation-Induced Emission Photosensitizers for Enhanced Chemo-Photodynamic Therapy

Nowadays, aggregation-induced emission luminogens (AIEgens) with reactive oxygen species (ROS) generating ability have been used as photosensitizers for imaging guided photodynamic therapy (PDT). To achieve enhanced antitumor outcomes, combining AIEgens-based PDT with chemotherapy is an efficient strategy. However, the therapeutic efficiency is hampered by the limited cellular uptake efficiency and the appropriate light irradiation occasion. In this paper, a self-guiding polymeric micelle (TB@PMPT) composed of two AIE photosensitizers and a reduction-sensitive paclitaxel prodrug (PTX-SS-N₃) was established for enhanced chemo-photodynamic therapy by a dual-stage light irradiation strategy. When the micelles were accumulated in tumor tissues, the first light irradiation (L₁, 6 min) was utilized to facilitate cellular uptake by "photochemical internalization" (PCI). Then, the intracellular glutathione (GSH) would induce the PTX release, micelles disassembly and the aggregation state change of AIEgens. The fluorescence signal change of two AIEgens-based ratiometric fluorescent probe could not only precisely guide the second light irradiation (L₂, 18 min) for sufficient ROS production, but also monitor the nonfluorescent drug PTX release in turn. Both in vivo and in vitro studies demonstrated that the dual-stage light irradiation strategy employed for TB@PMPT micelles exhibited a superior therapeutic effect over only 24 min continuous light irradiation.

Bioinspired design of amphiphilic particles with tailored compartments for dual-drug controlled release

Inspired by the phenomenon of water droplets hanging over rose petals, we propose a green interfacial self-assembly strategy to construct amphiphilic particles with controllable compartments for dual-drug encapsulation and controlled release. The method involves fabrication of "sticky" superhydrophobic materials, assembling superhydrophilic hydrogel beads with "sticky" superhydrophobic material into an amphiphilic particle, and amphiphilicity induced self-organization of several small amphiphilic particles into a large-sized amphiphilic multicompartmental particle. With the employment of this approach, amphiphilic particles with tailored sizes, controllable morphology, and tunable numbers of compartments are successfully constructed. The formation process and the underlying principle are further clarified. We finally investigate the potential application of the amphiphilic multicompartmental particles to load both hydrophilic and hydrophobic species in separated domains and release them in a controllable manner without interference. This novel approach may offer a new route to generate amphiphilic materials for the purpose of multidrug combination therapy, multiple-cell encapsulation, and so on.

An AIE-driven fluorescent polysaccharide polymersome as an enzyme-responsive FRET nanoprobe to study the real-time delivery aspects in live cells

An enzyme-responsive FRET nanoprobe was designed and developed based on AIE-driven fluorescent polysaccharide polymersomes to study the real-time delivery aspects in the intracellular compartments in live cancer cells.

Stimuli-Responsive Aliphatic Polycarbonate Nanocarriers for Tumor-Targeted Drug Delivery

Nanoparticles based on amphiphilic copolymers with tunable physicochemical properties can be used to encapsulate delicate pharmaceutics while at the same time improving their solubility, stability, pharmacokinetic properties, reducing immune surveillance, or achieving tumor-targeting ability. Those nanocarriers based on biodegradable aliphatic polycarbonates are a particularly promising platform for drug delivery due to flexibility in the design and synthesis of appropriate monomers and copolymers. Current studies in this field focus on the design and the synthesis of new effective carriers of hydrophobic drugs and their release in a controlled manner by exogenous or endogenous factors in tumor-specific regions. Reactive groups present in aliphatic carbonate copolymers, undergo a reaction under the action of a stimulus: e.g., acidic hydrolysis, oxidation, reduction, etc. leading to changes in the morphology of nanoparticles. This allows the release of the drug in a highly controlled manner and induces a desired therapeutic outcome without damaging healthy tissues. The presented review summarizes the current advances in chemistry and methods for designing stimuli-responsive nanocarriers based on aliphatic polycarbonates for controlled drug delivery.

Nanostructured Biosilica of Diatoms: From Water World to Biomedical Applications

Diatoms—unicellular photosynthetic algae—are promising natural sources of nanostructured silica. These microorganisms produce in their membrane approximately a highly ordered porous cell wall called a frustule as protection from environmental stress. Diatom frustules consist of hydrated silica that show peculiar properties including biocompatibility, tailorable surface chemistry, chemical inertness, and thermal stability. Frustules harvested from aquatic ecosystems or diatomaceous fossil sediments represent an excellent cost-effective source of biosilica for a broad range of biomedical applications. The porous ultrastructure of the frustules displays a large surface area available for coating with various biomolecules through different functionalization methods. In this review article, we highlight the main features of diatom biosilica and present some of the most advantageous properties that support the employment of frustules in the field of drug delivery, biosensing, and regenerative medicine. In particular, it is offered an insight into the most common functionalization strategies through which diatom physicochemical properties can be modified and tailored according to the described field of application.

Biodegradable pH-responsive micelles loaded with 8-hydroxyquinoline glycoconjugates for Warburg effect based tumor targeting

Biodegradable triblock copolymer poly(ethylene glycol)-b-polycarbonate-b-oligo([R]-3-hydroxybutyrate) was prepared via metal-free ring-opening polymerization of ketal protected six-membered cyclic carbonate followed by esterification with bacterial oligo([R]-3-hydroxybutyrate) (oPHB). Amphiphilic triblock copolymer self-organizes into micelles with a diameter of ~25 nm. Acid-triggered hydrolysis of ketal groups to two hydroxyl groups causes an increase in hydrophilicity of the hydrophobic micelle core, resulting in the micelles swell and drug release. oPHB was added as core-forming block to increase the stability of prepared micelles in all pH (7.4, 6.4, 5.5) studied. Doxorubicin and 8-hydroxyquinoline glucose- and galactose conjugates were loaded in the micelles. In vitro drug release profiles in PBS buffers with different pH showed that a small amount of loaded drug was released in PBS at pH 7.4, while the drug was released much faster at pH 5.5. MTT assay showed that the blank micelles were non-toxic to different cell lines, while glycoconjugates-loaded micelles, showed significantly increased ability to inhibit the proliferation of MCF-7 and HCT-116 cells compared to free glycoconjugates. The glycoconjugation of anti-cancer drugs and pH-responsive nanocarriers have separately shown great potential to increase the tumor-targeted drug delivery efficiency. The combination of drug glycoconjugation and the use of pH-responsive nanocarrier opens up new possibilities to develop novel strategies for efficient tumor therapy.

Redox-Responsive Heparin-Chlorambucil Conjugate Polymeric Prodrug for Improved Anti-Tumor Activity

Polymeric prodrug-based delivery systems have been extensively studied to find a better solution for the limitations of a single drug and to improve the therapeutic and pharmacodynamics properties of chemotherapeutic agents, which can lead to efficient therapy. In this study, redox-responsive disulfide bond-containing amphiphilic heparin-chlorambucil conjugated polymeric prodrugs were designed and synthesized to enhance anti-tumor activities of chlorambucil. The conjugated prodrug could be self-assembled to form spherical vesicles with 61.33% chlorambucil grafting efficiency. The cell viability test results showed that the prodrug was biocompatible with normal cells (HaCaT) and that it selectively killed tumor cells (HeLa cells). The uptake of prodrugs by HeLa cells increased with time. Therefore, the designed prodrugs can be a better alternative as delivery vehicles for the chlorambucil controlled release in cancer cells.

Diatoms embedded, self-assembled carriers for dual delivery of chemotherapeutics in cancer cell lines

The concept of dual drug delivery to treat relapsing tumors is a well-studied approach to improve the antitumor efficacies and to reduce the side effects of single drug chemotherapeutic treatments. One of the major issues with dual drug delivery to treat drug resistant tumors is the concentration and ratio dependent antagonistic behavior of two drugs, which may reverse the anticancer efficacies of individual chemotherapeutics and stimulate the growth of tumor cells. In this paper, we address this issue by developing diatomaceous earth embedded core shell materials, which are capable of encapsulating two chemotherapeutic drugs at constant molar ratios, in different compartments of a single drug delivery carrier. The encapsulation of each drug in different compartments of delivery carrier (core of diatoms versus shell of cyclodextrin) then controls the release rate of both drugs in situ, and maintains the optimal molar ratios required for their synergistic outcomes in vitro.

Doxorubicin and adjudin co-loaded pH-sensitive nanoparticles for the treatment of drug-resistant cancer

Multi-drug resistance (MDR) of tumor is a major cause of chemotherapy failure. In this study, a pH-sensitive graft copolymer, poly(β-amino ester)-g-β-cyclodextrin (PBAE-g-β-CD), was synthesized via Michael addition polymerization and was employed to co-deliver doxorubicin (DOX), a chemotherapy agent, and adjudin (ADD), a mitochondrial inhibitor, in the form of dual-drug co-loaded nanoparticles (NPs). Specifically, DOX was conjugated to 1-adamantaneacetic acid (Aa) to generate a prodrug that was subsequently encapsulated in the cavity of cyclodextrin via host-guest interactions. In addition, ADD was encapsulated by poly(β-aminoester) (PBAE). The introduction of the Aa-d-α-tocopheryl polyethylene glycolsuccinate (TPGS) conjugate enhanced the biocompatibility and serum stability of the resulting NPs. The NPs can realize precise ratiometric control of drugs being loaded, increase cellular uptake of the drugs, induce mitochondrial dysfunction and augment tumor treatment efficiency by inducing apoptosis. Western blot and polymerase chain reaction analyses showed that inhibition of P-glycoprotein and X-linked inhibitor of apoptosis protein expression may underlie inhibition of tumor resistance mediated by NPs. The MCF-7/ADR xenograft tumor model also revealed that in comparison with DOX, the NPs exhibited satisfactory performance in promoting apoptosis of tumor cells and achieved high therapeutic outcomes for MDR tumors. STATEMENT OF SIGNIFICANCE: Combination chemotherapy is an effective way to overcome MDR of tumor. However, one of the major obstacles for successful combination chemotherapy is the co-loading, co-delivery and controlled release of two different drugs, whose chemo-physical properties may be totally different. In this study, a pH-sensitive NP system was designed to realize the co-loading and precise ratiometric control of DOX and ADD, as well as the programmed drug release. That is, ADD release was triggered by low pH in endo/lysosome after endocytosis and then DOX was hydrolyzed to achieve a sustained release in tumor cells. Therefore, the NPs exhibited an effectively growth inhibition against MDR cells both in vitro and in vivo via the synergistic effect of ADD and DOX, which provided a promising strategy for treatment of MDR cancer.

Recent Developments in the Area of Click-Crosslinked Nanocarriers for Drug Delivery

Click-crosslinking has been widely used for the fabrication of nanocarriers in recent years. Crosslinking can enhance the stability of nanocarriers that have served as an emerging platform for drug delivery to achieve cancer diagnosis and therapy. In crosslinking methods, click reactions have attracted increasing attention owing to their high reaction specificity and physiologically stable products. These reports on click-crosslinked nanocarriers are divided into four sections (nanogels, nanoparticles, micelles, and capsules) according to the types of nanocarriers. Click-crosslinked nanocarriers enhance the solubility of hydrophobic drugs and improve the efficacy of drug delivery owing to their good stability. Stimuli-responsive and targeted strategies can be introduced into click-crosslinked nanocarriers to enhance drug accumulation in tumors.

One-shot synthesis and solution properties of ROS/pH responsive methoxy poly(ethylene glycol)-b-polycarbonate

A one-shot method was employed to synthesize ROS/pH responsive methoxy poly(ethylene glycol)-b-polycarbonate (mPEG-b-poly(MN-co-MSe)) with the selenide and tertiary amine groups situated on the backbone.

Dual-drug delivery based charge-conversional polymeric micelles for enhanced cellular uptake and combination therapy

We herein report on the synthesis and characterization of a dual-drug conjugated prodrug, and the self-assembled micelles showed a charge-conversion behavior and synergistic effectin vitro.

GSH/pH dual-responsive biodegradable camptothecin polymeric prodrugs combined with doxorubicin for synergistic anticancer efficiency

GSH and pH dual-responsive camptothecin polymeric prodrugs combined doxorubicin for synergistic drug delivery to highly improved selectivity and synergy benefiting from good long-term stability, better internalization and sensitive dual-responsibility.

Recent advances in stimuli-responsive polymeric micelles via click chemistry

Stimuli-responsive polymeric micelles via click chemistry are divided into six major sections (temperature, light, ultrasound, pH, enzymes, and redox).

A high therapeutic efficacy of polymeric prodrug nano-assembly for a combination of photodynamic therapy and chemotherapy

Combination of photodynamic therapy and chemotherapy has been emerging as a new strategy for cancer treatment. Conventional photosensitizer tends to aggregate in aqueous media, which causes fluorescence quenching, reduces reactive oxygen species (ROS) production, and limits its clinical application to photodynamic therapy. Traditional nanoparticle drug delivery system for chemotherapy also has its disadvantages, such as low drug loading content, drug leakage, and off-target toxicity for normal tissues. Here, we developed a reduction-sensitive co-delivery micelles TB@PMP for combinational therapy, which composed of entrapping a red aggregation-induced emission fluorogen (AIEgen) for photodynamic therapy and PMP that contains a reduction-sensitive paclitaxel polymeric prodrug for chemotherapy. AIEgen photosensitizer illustrates a much improved photostability and ROS production efficiency in aggregate state and PMP loads a high dose of paclitaxel and carries a smart stimuli-triggered drug release property. This co-delivery system provides a better option that replaces AIEgen photosensitizer for cancer diagnosis and therapy.

Xiaoqing Yi et al. report a co-drug delivery micelle system that demonstrates a high therapeutic efficacy for cancer. This system shows a much improved drug load, photostability, and production of reactive oxygen species, compared to traditional photosensitizer-loaded nanoparticles.

Fabrication of dual stimuli-responsive multicompartmental drug carriers for tumor-selective drug release

There has been increasing attention to the development of multi-stimuli-responsive drug carriers for precisely controlled drug release at target disease areas. In this study, pH- and redox-responsive hybrid drug carriers were fabricated by using both ketal-based acid-cleavable precursors and disulfide-based reducible precursors via stop-flow lithography. pH- and redox-sensitive drug release of the dual stimuli-responsive hybrid particles was confirmed, demonstrating their feasibility for selective and efficient drug release into tumor tissues in acidic and highly reductive environments. It was also found that the drug release rate of the particles was fine-tuned by modulating monomer compositions in the precursor. Importantly, the dual stimuli-responsive hybrid particles exhibited synergistic, controlled drug release in complex stimuli (both pH and redox stimuli) environments. To achieve tumor-selective combination chemotherapy, multicompartmental drug carriers consist of an acid-degradable compartment and a reducible compartment, which can separately encapsulate individual model drugs in each of the compartments. The multicompartmental particles exhibited independent drug release upon exposure to the corresponding stimulus. The dual stimuli-responsive, multicompartmental particles are effective drug carriers for tumor-selective release of a drug cocktail, leading to synergistic combination chemotherapy.

Controllable synthesis of a novel magnetic core-shell nanoparticle for dual-modal imaging and pH-responsive drug delivery

In this study, novel magnetic core-shell nanoparticles Fe₃O₄@La-BTC/GO have been synthesized by the layer-by-layer self-assembly (LBL) method and further modified by attachment of amino-modified PEG chains. The nanoparticles were thoroughly characterized by x-ray diffraction, FTIR, scanning electron microscopy and transmission electron microscopy. The core-shell structure was shown to be controlled by the LBL method. The drug loading of doxorubicin (DOX) within the Fe₃O₄@La-BTC/GO-PEG nanoparticles with different numbers of deposited layers was investigated. It was found that DOX loading increased with increasing number of metal organic framework coating layers, indicating that the drug loading can be controlled through the controllable LBL method. Cytotoxicity assays indicated that the Fe₃O₄@La-BTC/GO-PEG nanoparticles were biocompatible. The DOX was released rapidly at pH 3.8 and pH 5.8, but at pH 7.4 the rate and extent of release was greatly attenuated. The nanoparticles therefore demonstrate an excellent pH-triggered drug release. In addition, the particles could be tracked by magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI). A clear dose-dependent contrast enhancement in T ₂-weighted MR images and fluorescence images indicate the potential of these nanoparticles as dual-mode MRI/FOI contrast agents.

Novel Biodegradable Polymer with Redox-Triggered Backbone Cleavage Through Sequential 1,6-Elimination and 1,5-Cyclization Reactions

In the past decade, the self-immolative biodegradable polymer arose as a novel paradigm for its efficient degradation mechanism and vast potential for advanced biomedical applications. This study reports successful synthesis of a novel biodegradable polymer capable of self-immolative backbone cleavage. The monomer is designed by covalent conjugations of both pendant redox-trigger (p-nitrobenzyl alcohol) and self-immolative linker (p-hydroxybenzyl alcohol) to the cyclization spacer (n-2-(hydroxyethyl)ethylene diamine), which serves as the structural backbone. The polymerization of the monomer with hexamethylene diisocyanate yields a linear redox-sensitive polymer that can systemically degrade via sequential 1,6-elimination and 1,5-cyclization reactions within an effective timeframe. Ultimately, the polymer's potential for biomedical application is simulated through in vitro redox-triggered release of paclitaxel from polymeric nanoparticles.

Precise ratiometric loading of PTX and DOX based on redox-sensitive mixed micelles for cancer therapy

PTX and DOX have different anticancer mechanisms. The combination of the two anticancer drugs could synergically enhance their anticancer effect, but simultaneously accompanied by severe side effects. In the present study, we constructed a mixed micelle system based on redox-sensitive mPEG-SS-PTX and mPEG-SS-DOX conjugate. The drug delivery system has a fixed and high drug loading content of 24.2% (PTX∼14.8% and DOX∼9.4%) with a precise ratio of PTX and DOX to realize the synchronized and controlled release. The mixed micelle has an average size of 93.3nm with a narrow distribution, suitable for passive targeting to tumor tissues by the EPR effect. In vitro release profile and in vitro anticancer results show the mixed micelles have obvious redox-sensitive release properties in reducing environment and have a significant cytotoxicity to A549 and B16 cells. Importantly, in vivo study shows the mixed micelles have no obvious side effect on mice compared to free PTX/DOX samples during the treatment. Therefore, the constructed redox-sensitive mixed micelle is a promising drug delivery system for cancer therapy.

Recent development of functional aliphatic polycarbonates for the construction of amphiphilic polymers

Functional aliphatic polycarbonates in the construction of amphiphilic polymers are summarized in seven categories (hydrophobic, hydrophilic, or/and functional unit).

Drug delivery via anion exchange of salicylate decorating poly(meth)acrylates based on a pharmaceutical ionic liquid

Poly[trimethylammonium (meth)acrylate]s decorated by salicylate anions were investigated as drug carriers. Efficient exchange of drug was provided by phosphate anions contained in the medium within 4 h.