Well-defined, reversible disulfide cross-linked micelles for on-demand paclitaxel delivery

Novel self-assembled micelles of dual-modified dextrin with pH responsiveness via grafted octenyl succinic anhydride and cysteamine for curcumin delivery

In this study, a novel dextrin-based micelle (OSAD-SH), dual-modified with octenyl succinic anhydride (OSA) and cysteamine, was developed to address the acid instability issues of micelle modified only by OSA and designed for curcumin delivery. Three amphiphilic OSAD-SH polymers with different free sulfhydryl content were first synthesized. The study demonstrated that OSAD-SH micelles exhibited strong self-assembly properties, appearing as spheres with diameters ranging from 92.41 to 194.20 nm. Blank micelles showed good dilution resistance, as well as stability against acid, thermal, and ionic strength. The curcumin encapsulated by the micelles was in an amorphous state. In vitro release experiment demonstrated that curcumin released from OSAD-SH micelles exhibited pH responsiveness. The Ritger-Peppas model effectively predicted the release behavior of curcumin, which followed a super case-II transport. The OSAD-SH micelle will be a promising nanocarrier for improving the physicochemical properties of curcumin in food fields.

Biogenic crocetin-crosslinked chitosan nanoparticles with high stability and drug loading for efficient radioprotection

The risk of radiation exposure increases with the development of nuclear energy and technology, and radiation protection receives more and more attention from public health and safety. However, the numerous adverse effects and low drug utilization limit the practical applications of radioprotective agents. In this study, we developed a biogenic crocetin-crosslinked chitosan nanoparticle with high stability and drug loading for efficient radioprotection. In detail, the nanoparticles were prepared using the natural antioxidant crocetin as a cross-linking reagent in amidation reactions of chitosan and mPEG-COOH. The nanoparticles exhibit a quick scavenging ability for common reactive oxygen species and reactive nitrogen in vitro. Meanwhile, cellular experiments demonstrate the good biocompatibility of the nanoparticles and the alleviation of radiation damage by scavenging reactive oxygen species, reducing apoptosis, and inhibiting DNA damage, etc. Importantly, the nanoparticles are effective in mitigating oxidative damage in major organs and maintaining peripheral blood cell content. In addition, they perform better radioprotective properties than free drug due to the significant extension of the blood half-life of crocetin in vivo from 10 min to 5 h. This work proposes a drug-crosslinking strategy for the design of a highly efficient radioprotective agent, which exhibits a promising prospect in the fields of nuclear emergency and public health.

Impact of the Core Chemistry of Self-Assembled Spherical Nucleic Acids on their In Vitro Fate

Nucleic acid therapeutics (NATs), such as mRNA, small interfering RNA or antisense oligonucleotides are extremely efficient tools to modulate gene expression and tackle otherwise undruggable diseases. Spherical nucleic acids (SNAs) can efficiently deliver small NATs to cells while protecting their payload from nucleases, and have improved biodistribution and muted immune activation. Self-assembled SNAs have emerged as nanostructures made from a single DNA-polymer conjugate with similar favorable properties as well as small molecule encapsulation. However, because they maintain their structure by non-covalent interactions, they might suffer from disassembly in biologically relevant conditions, especially with regard to their interaction with serum proteins. Here, we report a systematic study of the factors that govern the fate of self-assembled SNAs. Varying the core chemistry and using stimuli-responsive disulfide crosslinking, we show that extracellular stability upon binding with serum proteins is important for recognition by membrane receptors, triggering cellular uptake. At the same time, intracellular dissociation is required for efficient therapeutic release. Disulfide-crosslinked SNAs combine these two properties and result in efficient and non-toxic unaided gene silencing therapeutics. We anticipate these investigations will help the translation of promising self-assembled structures towards in vivo gene silencing applications.

Aptamer-based self-assembled nanomicelle enables efficient and targeted drug delivery

Nucleic acid aptamer-based nanomicelles have great potential for nanomedicine and nanotechnology applications. However, amphiphilic aptamer micelles are known to be inherently unstable upon interaction with cell membranes in the physiological environment, thus potentially compromising their specific targeting against cancer cells. This flaw is addressed in the present work which reports a superstable micellar nanodelivery system as an amphiphilic copolymer self-assembled micelle composed of nucleic acid aptamer and polyvalent hydrophobic poly(maleic anhydride-alt-1-octadecene) (C18PMH). Using Ce6 as a drug model, these C18-aptamer micelles exhibit efficient tumor-targeting and -binding ability, facilitating the entry of Ce6 into targeted cells for photodynamic therapy. In addition, they can be loaded with other hydrophobic drugs and still demonstrate favorable therapeutic effects. As such, these C18-aptamer micelles can serve as a universal platform for loading multiple drugs, providing a safer and more effective solution for treating cancer.

Tuning the Cross-Linking Density and Cross-Linker in Core Cross-Linked Polymeric Micelles and Its Effects on the Particle Stability in Human Blood Plasma and Mice

Core cross-linked polymeric micelles (CCPMs) are designed to improve the therapeutic profile of hydrophobic drugs, reduce or completely avoid protein corona formation, and offer prolonged circulation times, a prerequisite for passive or active targeting. In this study, we tuned the CCPM stability by using bifunctional or trifunctional cross-linkers and varying the cross-linkable polymer block length. For CCPMs, amphiphilic thiol-reactive polypept(o)ides of polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine) [pSar-b-pCys(SO2Et)] were employed. While the pCys(SO2Et) chain lengths varied from Xn = 17 to 30, bivalent (derivatives of dihydrolipoic acid) and trivalent (sarcosine/cysteine pentapeptide) cross-linkers have been applied. Asymmetrical flow field-flow fraction (AF4) displayed the absence of aggregates in human plasma, yet for non-cross-linked PM and CCPMs cross-linked with dihydrolipoic acid at [pCys(SO2Et)]17, increasing the cross-linking density or the pCys(SO2Et) chain lengths led to stable CCPMs. Interestingly, circulation time and biodistribution in mice of non-cross-linked and bivalently cross-linked CCPMs are comparable, while the trivalent peptide cross-linkers enhance the circulation half-life from 11 to 19 h.

Tumor acidity-induced surface charge modulation in covalent nanonetworks for activated cellular uptake: targeted delivery of anticancer drugs and selective cancer cell death

A β-thioester and tertiary amine based covalently cross-linked nanoassembly coined as a nanonetwork (NN) endowed with dual pH responsive features (tumor acidity induced surface charge modulation and endosomal pH triggered controlled degradation) has been designed and synthesized for stable sequestration and sustained release of drug molecules in response to endosomal pH. An amphiphile integrated with tertiary amine and acrylate (ATA) functionalities was synthesized to fabricate the nanonetwork. This amphiphile showed entropically driven self-assembly and micellar nanostructures (nanoassemblies), which can sequester hydrophobic drug molecules at neutral pH. To further stabilize the nanoassemblies and the sequestered drug molecules even below its critical aggregation concentration (CAC), the micellar core was cross-linked via the thiol-acrylate Michael addition click reaction to generate multiple copies of acid labile β-thioester functionalities in the core, which undergo slow hydrolysis at endosomal pH (∼5.0), thus enabling sustained release of the anti-cancer drug doxorubicin at endosomal pH. The nanonetworks showed a significant decrease in drug leakage compared to the nanoassemblies (NAs), which was also justified by a low leakage coefficient calculated from the fluorescence resonance energy transfer experiment. The NN also exhibited dilution insensitivity and high serum stability, whereas the NA disassembled upon dilution and during serum treatment. The biological evaluation revealed tumor extracellular matrix pH (∼6.4-6.8) induced surface charge modulation and cancer cell (HeLa) selective activated cellular uptake of the doxorubicin loaded nanonetwork (NN-DOX). In contrast, the benign nature of NN-DOX towards normal cells (H9c2) suggests excellent cell specificity. Thus, we believe that the ease of synthesis, nanonetwork fabrication reproducibility, robust stability, smart nature of tumor microenvironment sensitive surface charge modulation, boosted tumoral-cell uptake, and triggered drug release will make this system a potential nanomedicine for chemotherapeutic treatments.

Enzyme and pH dual responsive linear-dendritic block copolymer micelles based on a phenylalanyl-lysine motif and peripherally ketal-functionalized dendron as potential drug carriers

Stimuli-responsive linear-dendritic block copolymers (LDBCs) have attracted significant research attention as novel drug carriers. We report here three generations of new enzyme and pH dual responsive linear-dendritic block copolymers (LDBCs) with a phenylalanyl-lysine (Phe-Lys) dipeptide linking hydrophilic linear poly(N-vinylpyrrolidone) (PNVP) and a hydrophobic peripherally ketal-functionalized dendron derived from 2,2'-bis(hydroxymethyl)propionic acid (bis-MPA). The LDBCs are synthesized via a combination of interchange of xanthates/reversible addition-fragmentation chain transfer (MADIX/RAFT) polymerization of N-vinylpyrrolidone (NVP) and "chain-first" strategy. Their structures are confirmed by ¹H NMR spectra. The gel permeation chromatograph (GPC) analysis revealed that the LDBCs have a narrow molecular weight distribution (PDI ≤ 1.25). The amphiphilic LDBCs can self-assemble into spherical nanomicelles in aqueous solution. The presence of enzyme or/and the change of pH cause disassembly of micelles to release encapsulated cargos. The release rates of the guest molecules are faster in buffer solution at pH 5.0 than those upon the addition of the activating enzyme and can be fine-tuned by changing the generation of bis-MPA dendrons. The combination of enzyme and pH dual stimuli results in significantly accelerated and more complete release of the loaded hydrophobic guests. The cell viability assay confirmed the favorable biocompatibility until the LDBC micelle concentration reached 800 μg mL^-1. These results indicate that the LDBCs can be considered as a good candidate for targeting drug delivery.

Polymeric core-crosslinked particles prepared via a nanoemulsion-mediated process: from particle design and structural characterization to in vivo behavior in chemotherapy

Various polymeric nanoparticles have been used as drug carriers in drug delivery systems (DDSs). Most of them were constructed from dynamic self-assembly systems formed via hydrophobic interactions and from structures that are unstable in an in vivo environment owing to their relatively weak formation forces. As a solution to this issue, physically stabilized core-crosslinked particles (CP) with chemically crosslinked cores have received attention as alternatives to the dynamic nanoparticles. This focused review summarizes recent advances in the construction, structural characterization, and in vivo behavior of polymeric CPs. First, we introduce a nanoemulsion-mediated method to create polyethylene glycol (PEG)-bearing CPs and their structural characterization. The relationship between the PEG chain conformations in the particle shell and the in vivo fate of the CPs is also discussed. After that, the development and advantages of zwitterionic amino acid-based polymer (ZAP)-bearing CPs are presented to address the poor penetration and the internalization of PEG-based CPs into tumor tissues and cells, respectively. Finally, we conclude and discuss prospects for application of polymeric CPs in the DDS field.

Redox-Responsive Comparison of Diselenide and Disulfide Core-Cross-Linked Micelles for Drug Delivery Application

In this study, diselenide (Se–Se) and disulfide (S–S) redox-responsive core-cross-linked (CCL) micelles were synthesized using poly(ethylene oxide)2k-b-poly(furfuryl methacrylate)1.5k (PEO2k-b-PFMA1.5k), and their redox sensitivity was compared. A single electron transfer-living radical polymerization technique was used to prepare PEO2k-b-PFMA1.5k from FMA monomers and PEO2k-Br initiators. An anti-cancer drug, doxorubicin (DOX), was incorporated into PFMA hydrophobic parts of the polymeric micelles, which were then cross-linked with maleimide cross-linkers, 1,6-bis(maleimide) hexane, dithiobis(maleimido) ethane and diselenobis(maleimido) ethane via Diels–Alder reaction. Under physiological conditions, the structural stability of both S–S and Se–Se CCL micelles was maintained; however, treatments with 10 mM GSH induced redox-responsive de-cross-linking of S–S and Se–Se bonds. In contrast, the S–S bond was intact in the presence of 100 mM H2O2, while the Se–Se bond underwent de-crosslinking upon the treatment. DLS studies revealed that the size and PDI of (PEO2k-b-PFMA1.5k-Se)2 micelles varied more significantly in response to changes in the redox environment than (PEO2k-b-PFMA1.5k-S)2 micelles. In vitro release studies showed that the developed micelles had a lower drug release rate at pH 7.4, whereas a higher release was observed at pH 5.0 (tumor environment). The micelles were non-toxic against HEK-293 normal cells, which revealed that they could be safe for use. Nevertheless, DOX-loaded S–S/Se–Se CCL micelles exhibited potent cytotoxicity against BT-20 cancer cells. Based on these results, the (PEO2k-b-PFMA1.5k-Se)2 micelles can be more sensitive drug carriers than (PEO2k-b-PFMA1.5k-S)2 micelles.

Bioderived Lipoic Acid-Based Dynamic Covalent Nanonetworks of Poly(disulfide)s: Enhanced Encapsulation Stability and Cancer Cell-Selective Delivery of Drugs

Dynamic covalent poly(disulfide)-based cross-linked nanoaggregates, termed nanonetworks (NNs), endowed with pH- and redox-responsive degradation features have been fabricated for stable noncovalent encapsulation and triggered cargo release in a controlled fashion. A bioderived lipoic acid-based Gemini surfactant-like amphiphilic molecule was synthesized for the preparation of nanoaggregates. It self-assembles by a entropy-driven self-assembly process in aqueous milieu. To further stabilize the self-assembled nanostructure, the core was cross-linked by ring-opening disulfide exchange polymerization (RODEP) of 1,2-dithiolane rings situated inside the core of the nanoaggregates. The cross-linked nanoaggregates, i.e., nanonetwork, are found to be stable in the presence of blood serum, and also, they maintain the self-assembled structure even below the critical aggregation concentration (CAC) as probed by dynamic light scattering (DLS) experiments. The nanonetwork showed almost 50% reduction in guest leakage compared to that of the nanoaggregates as shown by the release profile in the absence of stimuli, suggesting high encapsulation stability as evidenced by the fluorescence resonance energy transfer (FRET) experiment. The decross-linking of the nanonetwork occurs in response to redox and pH stimuli due to disulfide reduction and β-thioester hydrolysis, respectively, thus empowering disassembly-mediated controlled cargo release up to ∼87% for 55 h of incubation. The biological evaluation of the doxorubicin (DOX)-loaded nanonetwork revealed environment-specific surface charge modulation-mediated cancer cell-selective cellular uptake and cytotoxicity. The benign nature of the nanonetwork toward normal cells makes the system very promising in targeted drug delivery applications. Thus, the ease of synthesis, nanonetwork fabrication reproducibility, robust stability, triggered drug release in a controlled fashion, and cell-selective cytotoxicity behavior, we believe, will make the system a potential candidate in the development of robust materials for chemotherapeutic applications.

Redox-Responsive Core-Cross-Linked Micelles of Miktoarm Poly(ethylene oxide)-b-poly(furfuryl methacrylate) for Anticancer Drug Delivery

The physiological instability of nanocarriers, premature drug leakage during blood circulation, and associated severe side effects cause compromised therapeutic efficacy, which have significantly hampered the progress of nanomedicines. The cross-linking of nanocarriers while keeping the effectiveness of their degradation at the targeted site to release the drug has emerged as a potent strategy to overcome these flaws. Herein, we have designed novel (poly(ethylene oxide))₂-b-poly(furfuryl methacrylate) ((PEO_2K)₂-b-PFMA_nk) miktoarm amphiphilic block copolymers by coupling alkyne-functionalized PEO (PEO_2K-C≡H) and diazide-functionalized poly(furfuryl methacrylate) ((N₃)₂-PFMA_nk) via click chemistry. (PEO_2K)₂-b-PFMA_nk self-assembled to form nanosized micelles (mikUCL) with hydrodynamic radii in the range of 25∼33 nm. The hydrophobic core of mikUCL was cross-linked by a disulfide-containing cross-linker using the Diels-Alder reaction to avoid unwanted leakage and burst release of a payload. As expected, the resulting core-cross-linked (PEO_2K)₂-b-PFMA_nk micelles (mikCCL) exhibited superior stability under a normal physiological environment and were de-cross-linked to rapidly release doxorubicin (DOX) upon exposure to a reduction environment. The micelles were compatible with HEK-293 normal cells, while DOX-loaded micelles (mikUCL/DOX and mikCCL/DOX) induced high antitumor activity in HeLa and HT-29 cells. mikCCL/DOX preferentially accumulated at the tumor site and was more efficacious than free DOX and mikUCL/DOX for tumor inhibition in HT-29 tumor-bearing nude mice.

Stimuli-responsive crosslinked nanomedicine for cancer treatment

Nanomedicines are attractive paradigms to deliver drugs, contrast agents, immunomodulators, and gene editors for cancer therapy and diagnosis. However, the currently developed nanomedicine suffers from poor serum stability, premature drug release, and lack of responsiveness. Crosslinking strategy can be utilized to overcome these shortcomings by employing stimuli-responsive chemical bonds to tightly hold the nanostructure and releasing the payloads spatiotemporally in a highly controlled manner. In this Review, we summarize the recently ingenious design of the stimuli-responsive crosslinked nanomedicines (SCN) in the field of cancer treatment and their advances in circumventing the drawbacks of the conventional drug delivery system. We classify the SCNs into three categories based on the crosslinking strategies, including built-in, on-surface, and inter-particle crosslinking nanomedicines. Thanks to the stimuli-responsive crosslinkages, SCNs are capable of keeping robust stability during systemic circulation. They also respond to the particular tumoral conditions to experience a series of dynamic changes, such as the changes in size, surface charge, targeting moieties, integrity, and imaging signals. These characteristics allow them to efficiently overcome different biological barriers and substantially improve the drug delivery efficiency, tumor-targeting ability, and imaging sensitivities. With the examples discussed, we envision that our perspectives can inspire more attempts to engineer intelligent nanomedicine to achieve effective cancer therapy and diagnosis.

Transformable nanoparticles to bypass biological barriers in cancer treatment

Nanomedicine based drug delivery platforms provide an interesting avenue to explore for the future of cancer treatment. Here we discuss the barriers for drug delivery in cancer therapeutics and how nanomaterials have been designed to bypass these blockades through stimuli responsive transformation in the most recent update. Nanomaterials that address the challenges of each step provide a promising solution for new cancer therapeutics.

Nanoradiosensitizer with good tissue penetration and enhances oral cancer radiotherapeutic effect

Low dose non-toxic disulfide cross-linked micelle (DCM) encapsulated paclitaxel (PTX) was found to be highly efficacious as a radiosensitizer against oral cancer preclinical model. Intensity-modulated radiation therapy was locally administered for three consecutive days 24 h after intravascular injection of DCM-[PTX] at 5 mg/kg PTX. DCM-[PTX] NPs combined with conventional radiotherapy (2 Gy) resulted in a 1.7-fold improvement in therapeutic efficacy compared to conventional PTX plus radiotherapy. Interestingly, we found that radiotherapy can decrease tight junctions and increase the accumulation of DCM-[PTX] in tumor sites. Stereotactic body radiotherapy (SBRT) given at 6 Gy was used to further investigate the synergistic anti-tumor effect. Tumor tissues were collected to analyze the relationship between the time interval after SBRT and the biodistribution of the nanomaterials. Compared to combination DCM-[PTX] with conventional radiation dose, combination DCM-PTX with SBRT was found to be more efficacious in inhibiting tumor growth.

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

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

Hybrid Arborescent Polypeptide-Based Unimolecular Micelles: Synthesis, Characterization, and Drug Encapsulation

This paper reports novel hybrid arborescent polypeptides based on poly(γ-benzyl l-glutamate)-co-poly(γ-tert-butyl l-glutamate)-g-polysarcosine [P(BG-co-Glu(OtBu))-g-PSar]. The synthesis is launched by ring-opening polymerization (ROP) of N-carboxyanhydride of γ-benzyl l-glutamate (BG-NCA) and γ-tert-butyl l-glutamate (Glu(OtBu)-NCA) to synthesize a random copolymer P(BG-co-Glu(OtBu)) serving as a precursor for the arborescent system, followed by deprotection of the tert-butyl (tBu) groups to afford free COOH moieties serving as coupling sites. Two copolymerization reactions were carried out to afford the side chains. One type of side chain was a random copolymer P(BG-co-Glu(OtBu)), while the other type was a triblock copolymer PGlu(OtBu)-b-PBG-b-PGlu(OtBu). The peptide coupling reactions were conducted between the COOH moieties on the precursor and the terminus amine on the chain end of the P(BG-co-Glu(OtBu)) random copolymer or the PGlu(OtBu)-b-PBG-b-PGlu(OtBu) triblock copolymer to obtain G0 polymers. Afterward, hydrolyzing the tBu moieties of the G0 substrates yielded randomly functionalized G0 and end-functionalized G0. Randomly functionalized G0 was used as a substrate for the next generation G1 (randomly functionalized and end-functionalized G1 after deprotection) or coated with polysarcosine (PSar) to gain G0-g-PSar. The G0 substrate prepared with the triblock copolymer PGlu(OtBu)-b-PBG-b-PGlu(OtBu) was only grafted with PSar after deprotection, resulting in G0-eg-PSar. Depending on the functionality mode of the G1 substrate, the PSar coating yielded two different graft polymers, G1-g-PSar and G1-eg-PSar, for randomly functionalized and end-functionalized G1, respectively. The PSar hydrophilic shell was decorated with the sequence of (arginine, glycine, and aspartic acid) tripeptides (RGD) as a targeting ligand to improve the potentiality of the arborescent unimolecular micelles as drug carriers. Preparative size exclusion chromatography (SEC) was used to fractionate these complex macromolecular architectures. Nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR), Raman spectroscopy, and SEC were used for molecular characterization of all intermediate and final products and dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) for micellar characterization. A comparison between randomly grafted (g) and end-grafted (eg) unimolecular micelles demonstrates that the former has an undefined core-shell structure, unlike its end-grafted analog. In addition, this study has proved that decoration of the shell with RGD contributed to avoiding micelle aggregation but limited chemotherapy agent encapsulation. However, more than their naked analog, the sustained release was noticeable in decorated micelles. Doxorubicin was utilized as a chemotherapy model, and loading was achieved successfully by physical entrapment.

Redox-Responsive Crosslinked Mixed Micelles for Controllable Release of Caffeic Acid Phenethyl Ester

We report the elaboration of redox-responsive functional micellar nanocarriers designed for triggered release of caffeic acid phenethyl ester (CAPE) in cancer therapy. Three-layered micelles, comprising a poly(ε-caprolactone) (PCL) core, a middle poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) layer and a PEO outer corona, were prepared by co-assembly of PEO₁₁₃-b-PCL₃₅-b-PEO₁₁₃ and PAA₁₃-b-PCL₃₅-b-PAA₁₃ amphiphilic triblock copolymers in aqueous media. The preformed micelles were loaded with CAPE via hydrophobic interactions between the drug molecules and PCL core, and subsequently crosslinked by reaction of carboxyl groups from PAA and a disulfide crosslinking agent. The reaction of crosslinking took place in the middle layer of the nanocarriers without changing the encapsulation efficiency (EE~90%) of the system. The crosslinked polymeric micelles (CPMs) exhibited superior structural stability and did not release CAPE in phosphate buffer (pH 7.4). However, in weak acidic media and in the presence of 10 mM reducing agent (dithiothreitol, DTT), the payload was released at a high rate from CPMs due to the breakup of disulfide linkages. The physicochemical properties of the nanocarriers were investigated by dynamic and electrophoretic light scattering (DLS and ELS) and atomic force microscopy (AFM). The rapid release of CAPE under intracellular-like conditions and the lack of premature drug release in media resembling the blood stream (neutral pH) make the developed CPMs a promising candidate for controllable drug release in the microenvironment of tumors.

Single and Multiple Stimuli-Responsive Polymer Particles for Controlled Drug Delivery

Polymers that can change their properties in response to an external or internal stimulus have become an interesting platform for drug delivery systems. Polymeric nanoparticles can be used to decrease the toxicity of drugs, improve the circulation of hydrophobic drugs, and increase a drug’s efficacy. Furthermore, polymers that are sensitive to specific stimuli can be used to achieve controlled release of drugs into specific areas of the body. This review discusses the different stimuli that can be used for controlled drug delivery based on internal and external stimuli. Internal stimuli have been defined as events that evoke changes in different characteristics, inside the body, such as changes in pH, redox potential, and temperature. External stimuli have been defined as the use of an external source such as light and ultrasound to implement such changes. Special attention has been paid to the particular chemical structures that need to be incorporated into polymers to achieve the desired stimuli response. A current trend in this field is the incorporation of several stimuli in a single polymer to achieve higher specificity. Therefore, to access the most recent advances in stimuli-responsive polymers, the focus of this review is to combine several stimuli. The combination of different stimuli is discussed along with the chemical structures that can produce it.

The Cationic Amphiphilic Drug Hexamethylene Amiloride Eradicates Bulk Breast Cancer Cells and Therapy-Resistant Subpopulations with Similar Efficiencies

The resistance of cancer cell subpopulations, including cancer stem cell (CSC) populations, to apoptosis-inducing chemotherapeutic agents is a key barrier to improved outcomes for cancer patients. The cationic amphiphilic drug hexamethylene amiloride (HMA) has been previously demonstrated to efficiently kill bulk breast cancer cells independent of tumor subtype or species but acts poorly toward non-transformed cells derived from multiple tissues. Here, we demonstrate that HMA is similarly cytotoxic toward breast CSC-related subpopulations that are resistant to conventional chemotherapeutic agents, but poorly cytotoxic toward normal mammary stem cells. HMA inhibits the sphere-forming capacity of FACS-sorted human and mouse mammary CSC-related cells in vitro, specifically kills tumor but not normal mammary organoids ex vivo, and inhibits metastatic outgrowth in vivo, consistent with CSC suppression. Moreover, HMA inhibits viability and sphere formation by lung, colon, pancreatic, brain, liver, prostate, and bladder tumor cell lines, suggesting that its effects may be applicable to multiple malignancies. Our observations expose a key vulnerability intrinsic to cancer stem cells and point to novel strategies for the exploitation of cationic amphiphilic drugs in cancer treatment.

Engineered Aptamer-Organic Amphiphile Self-Assemblies for Biomedical Applications: Progress and Challenges

Currently, nucleic acid aptamers are exploited as robust targeting ligands in the biomedical field, due to their specific molecular recognition, little immunogenicity, low cost, ect. Thanks to the facile chemical modification and high hydrophilicity, aptamers can be site-specifically linked with hydrophobic moieties to prepare aptamer-organic amphiphiles (AOAs), which spontaneously assemble into aptamer-organic amphiphile self-assemblies (AOASs). These polyvalent self-assemblies feature with enhanced target-binding ability, increased resistance to nuclease, and efficient cargo-loading, making them powerful platforms for bioapplications, including targeted drug delivery, cell-based cancer therapy, biosensing, and bioimaging. Besides, the morphology of AOASs can be elaborately manipulated for smarter biomedical functions, by regulating the hydrophilicity/hydrophobicity ratio of AOAs. Benefiting from the boom in DNA synthesis technology and nanotechnology, various types of AOASs, including aptamer-polymer amphiphile self-assemblies, aptamer-lipid amphiphile self-assemblies, aptamer-cell self-assemblies, ect, have been constructed with great biomedical potential. Particularly, stimuli-responsive AOASs with transformable structure can realize site-specific drug release, enhanced tumor penetration, and specific target molecule detection. Herein, the general synthesis methods of oligonucleotide-organic amphiphiles are firstly summarized. Then recent progress in different types of AOASs for bioapplications and strategies for morphology control are systematically reviewed. The present challenges and future perspectives of this field are also discussed.

Orthogonal characterization and pharmacokinetic studies of polylactide-polyethyleneglycol polymeric nanoparticles with different physicochemical properties

To optimize prolonged and sustained delivery of polylactide-block-polyethyleneglycol polymeric nanoparticles (PLA-PEG NPs), in terms of the PLA isomer and molecular weight, we performed orthogonal physicochemical characterization and evaluated the pharmacokinetics of tamoxifen (TAM)-loaded PLA-PEG NPs. DL-lactide- (DL-PEG NP), L-lactide- (L-PEG NPs), and stereocomplex-based (SC-PEG NPs) PLA-PEGs, with two different PLA to PEG ratios (12k-5k and 5k-5k Da) were synthesized, and NPs were prepared by anti-solvent precipitation. Size exclusion chromatography, multi-angle light scattering, dynamic light scattering, and ¹H nuclear magnetic resonance studies revealed that SC-PEG NPs (12k-5k) had a compact structure and the highest PEG density, followed by L-PEG NPs (12k-5k), DL-PEG NPs (12k-5k), and all PLA-PEG NPs (5k-5k). Additionally, solid-phase extraction indicated that SC-PEG NPs (12k-5k) had the highest drug loading content and the lowest surface TAM adsorption, of the PLA-PEGs evaluated. These results were explained by the crystallinity of the PLA core, which was analyzed by X-ray diffraction. In the pharmacokinetic studies, ¹⁴C-TAM-loaded ¹¹¹In-SC-PEG NPs (12k-5k) exhibited the highest area under the plasma concentration-time curve, followed by L-PEG NPs (12k-5k) and DL-PEG NPs (12k-5k), after intravenous injection in mice. These results indicate that SC-PEG NPs (12k-5k) are promising drug carriers for the sustained and prolonged delivery of TAM.

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.

Concentration-Independent Multivalent Targeting of Cancer Cells by Genetically Encoded Core-Crosslinked Elastin/Resilin-like Polypeptide Micelles

Valency is a fundamental principle to control macromolecular interactions and is used to target specific cell types by multivalent ligand-receptor interactions using self-assembled nanoparticle carriers. At the concentrations encountered in solid tumors upon systemic administration, these nanoparticles are, however, likely to show critical micelle concentration (CMC)-dependent disassembly and thus loss of function. To overcome this limitation, core-crosslinkable micelles of genetically encoded resilin-/elastin-like diblock polypeptides were recombinantly synthesized. The amphiphilic constructs were covalently photo-crosslinked through the genetically encoded unnatural amino acid para-azidophenylalanine in their hydrophobic block and they carried different anticancer ligands on their hydrophilic block: the wild-type tenth human fibronectin type III domain, a GRGDSPAS peptide-both targeting α_vβ₃ integrin-and an engineered variant of the third fibronectin type III domain of tenascin C that is a death receptor 5 agonist. Although uncrosslinked micelles lost most of their targeting ability below their CMC, the crosslinked analogues remained active at concentrations up to 1000-fold lower than the CMC, with binding affinities that are comparable to antibodies.

Glutathione Reductase-Sensitive Polymeric Micelles for Controlled Drug Delivery on Arthritic Diseases

Inflammation plays an essential role in arthritis development and progression. Despite the advances in the pharmaceutical field, current treatments still present low efficacy and severe side effects. Considering the high activity of the glutathione reductase (GR) enzyme in inflamed joints, a distinctive drug delivery system sensitive to the GR enzyme was designed for efficient drug delivery on arthritic diseases. A linear amphiphilic polymer composed of methoxypolyethylene glycol amine-glutathione-palmitic acid (mPEG-GSH_n-PA) was synthesized and the intermolecular oxidation of the thiol groups from GSHs retain the drug inside the resulting micelles. Stable polymeric micelles of 100 nm of size presented a loading capacity of dexamethasone (Dex) up to 65%. Although in physiological conditions the Dex release presented slow and sustained kinetics, in the presence of the GR enzyme, there was a burst release (stimuli-responsive properties). Biological assays demonstrated their cytocompatibility in contact with human articular chondrocytes, macrophages, and endothelial cells as well as their hemocompatibility. Importantly, in an in vitro model of inflammation, the polymeric micelles promoted a controlled drug release in the presence of GR, exhibiting a higher efficacy than the free Dex while reducing the negative effects of the drug into normal cells. In conclusion, this formulation is a promising approach to treat arthritic diseases and other inflammatory conditions.

Synergistic effect of the anti-PD-1 antibody with blood stable and reduction sensitive curcumin micelles on colon cancer

Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is a potent anticancer drug with versatile biological activities, while the clinical translation of curcumin is severely limited due to its hydrophobicity, rapid elimination, and metabolism in the blood circulation. Herein, we aim to unravel the potential of curcumin as a synergistic agent with immunotherapy in the treatment of cancers. In an effort to minimize premature release and improve the systemic bioavailability, a superior blood stable and reduction sensitive curcumin micellar formulation, of which the release can be triggered by cancer cells, is rationally designed. We have synthesized a telodendrimer (mPEG-PLA-(LA)₄) capable of forming reversible disulfide crosslinked micelles (DCMs). The curcumin loaded DCMs (Cur/DCMs) are spherical with a uniform size of 24.6 nm. The in vitro release profile demonstrates that curcumin releases significantly slower from DCMs than that from non-crosslinked micelles (NCMs), while the release can be accelerated with the increasing concentration of reducing agent glutathione (GSH). Intravenous administration of Cur/DCMs stably retains curcumin in the bloodstream and efficiently improves the systemic bioavailability. Furthermore, Cur/DCMs exhibit synergistic anticancer efficacy when combined with the anti-PD-1 antibody in an MC-38 colon cancer xenograft model. Our results potentiate the integration of blood stable curcumin nanoformulation and immunotherapy for cancer treatment.

Reduction-Responsive Anticancer Nanodrug Using a Full Poly(ethylene glycol) Carrier

Poly(ethylene glycol) (PEG) is applied extensively in biomedical fields because of its nontoxic, nonimmunogenic, and protein resistance properties. However, the strong hydrophilicity of PEG prevents it from self-assembling into an amphiphilic micelle in water, making it a challenge to fabricate a full-PEG carrier to deliver hydrophobic anticancer drugs. Herein, a paclitaxel (PTX)-loaded nanodrug was readily prepared through self-assembly of PTX and an amphiphilic PEG derivative, which was synthesized via melt polycondensation of two PEG diols (i.e., PEG₂₀₀ and PEG_10k) and mercaptosuccinic acid. The full PEG component endows the nanocarrier with good biocompatibility. Furthermore, because of the core cross-linked structure via the oxidation of mercapto groups, the nanodrug can be selectively disassociated under an intratumor reductive microenvironment through the reduction of disulfide bonds to release the loaded PTX and kill the cancer cells while maintaining high stability under the extratumor physiological condition. Additionally, it was confirmed that the nanodrug not only prolongs the biocirculation time of PTX but also possesses excellent in vivo antitumor efficacy while avoiding side effects of free PTX, for example, liver damage, which is promising for delivering clinical hydrophobic drugs to treat a variety of malignant tumors.

Nanoplatforms for Targeted Stimuli-Responsive Drug Delivery: A Review of Platform Materials and Stimuli-Responsive Release and Targeting Mechanisms

To achieve the promise of stimuli-responsive drug delivery systems for the treatment of cancer, they should (1) avoid premature clearance; (2) accumulate in tumors and undergo endocytosis by cancer cells; and (3) exhibit appropriate stimuli-responsive release of the payload. It is challenging to address all of these requirements simultaneously. However, the numerous proof-of-concept studies addressing one or more of these requirements reported every year have dramatically expanded the toolbox available for the design of drug delivery systems. This review highlights recent advances in the targeting and stimuli-responsiveness of drug delivery systems. It begins with a discussion of nanocarrier types and an overview of the factors influencing nanocarrier biodistribution. On-demand release strategies and their application to each type of nanocarrier are reviewed, including both endogenous and exogenous stimuli. Recent developments in stimuli-responsive targeting strategies are also discussed. The remaining challenges and prospective solutions in the field are discussed throughout the review, which is intended to assist researchers in overcoming interdisciplinary knowledge barriers and increase the speed of development. This review presents a nanocarrier-based drug delivery systems toolbox that enables the application of techniques across platforms and inspires researchers with interdisciplinary information to boost the development of multifunctional therapeutic nanoplatforms for cancer therapy.

Supramolecular Functionalizable Linear-Dendritic Block Copolymers for the Preparation of Nanocarriers by Microfluidics

Hybrid linear-dendritic block copolymers (LDBCs) having dendrons with a precise number of peripheral groups that are able to supramolecular bind functional moieties are challenging materials as versatile polymeric platforms for the preparation of functional polymeric nanocarriers. PEG2k-b-dxDAP LDBCs that are based on polyethylene glycol (PEG) as hydrophilic blocks and dendrons derived from bis-MPA having 2,6-diacylaminopyridine (DAP) units have been efficiently synthesized by the click coupling of preformed blocks, as was demonstrated by spectroscopic techniques and mass spectrometry. Self-assembly ability was first checked by nanoprecipitation. A reproducible and fast synthesis of aggregates was accomplished by microfluidics optimizing the total flow rate and phase ratio to achieve spherical micelles and/or vesicles depending on dendron generation and experimental parameters. The morphology and size of the self-assemblies were studied by TEM, Cryogenic Transmission Electron Microscopy (cryo-TEM), and Dynamic Light Scattering (DLS). The cytotoxicity of aggregates synthesized by microfluidics and the influence on apoptosis and cell cycle evaluation was studied on four cell lines. The self-assemblies are not cytotoxic at doses below 0.4 mg mL-1. Supramolecular functionalization using thymine derivatives was explored for reversibly cross-linking the hydrophobic blocks. The results open new possibilities for their use as drug nanocarriers with a dynamic cross-linking to improve nanocarrier stability but without hindering disassembly to release molecular cargoes.

LHRH-Targeted Redox-Responsive Crosslinked Micelles Impart Selective Drug Delivery and Effective Chemotherapy in Triple-Negative Breast Cancer

Systemic chemotherapy is efficacious against triple-negative breast cancer (TNBC), but it is often associated with serious side effects. Here, a luteinizing hormone-releasing hormone (LHRH) receptor-targeted and tumor microenvironment-responsive nanoparticle system to selectively deliver chemotherapeutic drugs to TNBC cells, is reported. This delivery system (termed "LHRH-DCMs") contains poly(ethylene glycol) and dendritic cholic acid as a micellar carrier, reversible intra-micellar disulfide bond as a redox-responsive crosslink, and synthetic high-affinity (D-Lys)-LHRH peptide as a targeting moiety. LHRH-DCMs exhibit high drug loading efficiency, optimal particle size, good colloidal stability, and glutathione-responsive drug release. As expected, LHRH-DCMs are more efficiently internalized into human TNBC cells through receptor-mediated endocytosis, resulting in stronger cytotoxicity against these cancer cells than the non-targeted counterpart when encapsulated with paclitaxel (PTX). Furthermore, near-infrared fluorescence and magnetic resonance imaging demonstrate that LHRH-DCMs facilitate the tumor distribution and penetration of payloads in three different animal models of breast cancer, including cell line-derived xenograft (CDX), patient-derived xenograft (PDX), and transgenic mammary carcinoma. Finally, in vivo therapeutic studies show that PTX-LHRH-DCMs outperform both the corresponding nontargeted PTX-DCMs and the current clinical formulation (Taxol) in an orthotopic TNBC model. These results provide new insights into approaches for precise drug delivery of TNBC.

Iron-crosslinked Rososome with robust stability and high drug loading for synergistic cancer therapy

Development of liposomal nanomedicine with robust stability, high drug loading and synergistic efficacy is a promising strategy for effective cancer therapy. Here, we present an iron-crosslinked rosmarinic liposome (Rososome) which can load high contents of drugs (including 25.8% rosmarinic acid and 9.04% doxorubicin), keep stable in a high concentration of anionic detergent and exhibit synergistic anti-cancer efficacy. The Rososomes were constructed by rosmarinic acid-lipid conjugates which not only work synergistically with doxorubicin by producing reactive oxygen species but also provide catechol moieties for the iron cross-linkages. The cross-linkages can lock the payloads tightly, endowing the crosslinked Rososome with better stability and pharmacokinetics than its non-crosslinked counterpart. On the syngeneic mouse model of breast cancer, the iron-crosslinked Rososomes exhibit better anticancer efficacy than free rosmarinic acid, doxorubicin, non-crosslinked Rososome and commercial liposomal formulation of doxorubicin (DOXIL). This study introduces a novel strategy for the development of liposomes with robust stability, high drug loading and synergistic anti-cancer efficacy.

Robust and smart polypeptide-based nanomedicines for targeted tumor therapy

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

Novel nanococktail of a dual PI3K/mTOR inhibitor and cabazitaxel for castration-resistant prostate cancer

Prognosis of castration-resistant prostate cancer (CRPC) carries is poor, and no effective therapeutic regimen is yet known. The phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway played a predominant role and may be a promising molecular target for CRPC. However, the toxicity of the dual PI3K inhibitors in clinical trials limits their clinical efficacy for CRPC. To solve this problem, we employed a highly integrated precision nanomedicine strategy to molecularly and physically target CRPC through synergistic effects, enhanced targeted drug delivery efficiency, and reduced unwanted side-effects. Gedatolisib (Ge), a potent inhibitor of PI3K/mTOR, was formulated into our disulfied-crosslinked micelle plateform (NanoGe), which exhibits excellent water solubility, small size (23.25±2 nm), excellent stability with redox stimulus-responsive disintegration, and preferential uptake at tumor sites. NanoGe improved the anti-neoplastic effect of free Ge by 53 times in PC-3M cells and 13 times in C4-2B cells though its enhanced uptake via caveolae- and clathrin-mediated endocytic pathways and the subsequent inhibition of the PI3K/mTOR pathway, resulting in Bax/Bcl-2 dependent apoptosis. In an animal xenograft model, NanoGe showed superior efficacy than free Ge, and synergized with nanoformulated cabazitaxel (NanoCa) as a nanococktail format to achieve a cure rate of 83%. Taken together, our results demonstrate the potency of NanoGe in combination with NanoCa is potent against prostate cancer.

Telodendrimers: Promising Architectural Polymers for Drug Delivery

Architectural complexity has played a key role in enhancing the efficacy of nanocarriers for a variety of applications, including those in the biomedical field. With the continued evolution in designing macromolecules-based nanoparticles for drug delivery, the combination approach of using important features of linear polymers with dendrimers has offered an advantageous and viable platform. Such nanostructures, which are commonly referred to as telodendrimers, are hybrids of linear polymers covalently linked with different dendrimer generations and backbones. There is considerable variety in selection from widely studied linear polymers and dendrimers, which can help tune the overall composition of the resulting hybrid structures. This review highlights the advances in articulating syntheses of these macromolecules, and the contributions these are making in facilitating therapeutic administration. Limited progress has been made in the design and synthesis of these hybrid macromolecules, and it is through an understanding of their physicochemical properties and aqueous self-assembly that one can expect to fully exploit their potential in drug delivery.

Intrinsic stimuli-responsive nanocarriers for smart drug delivery of antibacterial agents-An in-depth review of the last two decades

Antibiotic resistance due to suboptimal targeting and inconsistent antibiotic release at bacterial infection sites has driven the formulation of stimuli-responsive nanocarriers for antibacterial therapy. Unlike conventional nanocarriers, stimuli-responsive nanocarriers have the ability to specifically enhance targeting and drug release profiles. There has been a significant escalation in the design and development of novel nanomaterials worldwide; in particular, intrinsic stimuli-responsive antibiotic nanocarriers, due to their enhanced activity, improved targeted delivery, and superior potential for bacterial penetration and eradication. Herein, we provide an extensive and critical review of pH-, enzyme-, redox-, and ionic microenvironment-responsive nanocarriers that have been reported in literature to date, with an emphasis on the mechanisms of drug release, the nanomaterials used, the nanosystems constructed and the antibacterial efficacy of the nanocarriers. The review also highlights further avenues of research for optimizing their potential and commercialization. This review confirms the potential of intrinsic stimuli-responsive nanocarriers for enhanced drug delivery and antibacterial killing. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Two-way magnetic resonance tuning and enhanced subtraction imaging for non-invasive and quantitative biological imaging

Distance-dependent magnetic resonance tuning (MRET) technology enables the sensing and quantitative imaging of biological targets in vivo, with the advantage of deep tissue penetration and fewer interactions with the surroundings as compared with those of fluorescence-based Förster resonance energy transfer. However, applications of MRET technology in vivo are currently limited by the moderate contrast enhancement and stability of T₁-based MRET probes. Here we report a new two-way magnetic resonance tuning (TMRET) nanoprobe with dually activatable T₁ and T₂ magnetic resonance signals that is coupled with dual-contrast enhanced subtraction imaging. This integrated platform achieves a substantially improved contrast enhancement with minimal background signal and can be used to quantitatively image molecular targets in tumours and to sensitively detect very small intracranial brain tumours in patient-derived xenograft models. The high tumour-to-normal tissue ratio offered by TMRET in combination with dual-contrast enhanced subtraction imaging provides new opportunities for molecular diagnostics and image-guided biomedical applications.

A pH and reduction dual-sensitive polymeric nanomicelle for tumor microenvironment triggered cellular uptake and controlled intracellular drug release

Minimal drug leakage during blood circulation and intracellular drug delivery in tumor sites are of great significance in chemotherapeutics. Herein we propose an interlayer crosslinked polymeric micelle with tumor acidity and reduction dual sensitivity for highly efficient drug delivery to cancer cells. A novel copolymer mPEG-C[double bond, length as m-dash]N-PAsp(MEA)-CA was synthesized and self-assembled into a dual-sensitive interlayer-crosslinked micelle (ICM). The micelle was composed of a tumor acidity sheddable PEG outer layer, a reduction-sensitive disulfide-crosslinked interlayer (PAsp(MEA)) and a hydrophobic core of cholic acid (CA) for doxorubicin (DOX) delivery. The nano-sized ICM was stable and showed little drug leakage in a neutral physiological environment. In tumor microenvironments (TMEs) with mild acidity, the PEG outer layer was readily detached due to the hydrolysis of the Schiff base linker, and the surface of the ICM was switched to positively charged to enhance the cellular uptake. Furthermore, inside tumor cells DOX was rapidly released due to the reduction of disulfide bonds by glutathione (GSH). The DOX-loaded ICM exhibited an effective anticancer effect against C6 glioma and reduced side effects both in vitro and in vivo. The study reveals that this pH and reduction dual-sensitive micelle may have great potential to mediate effective anticancer therapy.

Furry nanoparticles: synthesis and characterization of nanoemulsion-mediated core crosslinked nanoparticles and their robust stability in vivo

Core crosslinked nanoparticles were prepared via nanoemulsion stabilized by a poly(ethylene glycol)-bearing surfactant, which show high structural stability in vivo.

Recent advances on small-molecule nanomedicines for cancer treatment

Nanomedicines have made important contributions in the development of cancer therapies due to their tumor selectivity, multifunctionality, and synergistic effect between the payloads. In addition to the required pharmaceutical ingredients, nanomedicines are generally composed of nonpharmaceutical excipients. These excipients generally form a large proportion of the nanomedicine, and they may have potential toxicity and greatly increase the cost for drug development. Small molecule nanomedicines (SMNs) minimize or abandon the excipients and are directly assembled from pharmaceutical ingredients, which can largely improve the drug delivery efficiency and biosafety while also relieving the financial burden of drug development. In this review, we summarize recently developed SMNs that are composed of a single drug, physical mixtures of multiple drugs, drug-drug covalent conjugates, dyes with drugs, photosensitizers with drugs, photosensitizers with peptides, and drugs with peptides. This review focuses on the SMN's applications in cancer treatments, their limitations, and the future development outlook of SMNs. We hope that our insights on SMNs may be helpful to the future of drug development and make nanomedicine more powerful in the battle with cancer. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

The preparation of pH and GSH dual responsive thiolated heparin/DOX complex and its application as drug carrier

The complicated preparation procedure and carrier's suspicious biocompatibility are two major limitations for traditional drug carrier. In this manuscript, a novel polyion complex (PIC) was prepared by simply mixing two biocompatible components, thiolated heparin and doxorubicin (DOX), and subsequently crosslinking under atmosphere, so that it can overcome the above limitations. The PIC's particle size kept stable for one week storage in PBS, and the particles wouldn't decomposed by the dilution, indicating excellent storage and anti-dilution stability resulting from the crosslinking. The PIC can release the larger amount of DOX in acidic environment than psychological environment, and largest amount in acidic and glutathione (GSH) environment, showing the pH and GSH dual sensitive drug release behavior. Furthermore, the PIC exhibited obvious tumor inhibition effect in vivo as well as long circulation ability and low heart toxicity by anti-tumor tests on tumor-bearing mice. Consequently, as-prepared PIC shows promising potential in drug carrier application.

Progress in research on paclitaxel and tumor immunotherapy

Paclitaxel is a well-known anticancer agent with a unique mechanism of action. It is considered to be one of the most successful natural anticancer drugs available. This study summarizes the recent advances in our understanding of the sources, the anticancer mechanism, and the biosynthetic pathway of paclitaxel. With the advancement of biotechnology, improvements in endophytic fungal strains, and the use of recombination techniques and microbial fermentation engineering, the yield of extracted paclitaxel has increased significantly. Recently, paclitaxel has been found to play a large role in tumor immunity, and it has a great potential for use in many cancer treatments.

Porphyrin-Based Nanomedicines for Cancer Treatment

As unique molecules with both therapeutic and diagnostic properties, porphyrin derivatives have been extensively employed for cancer treatment. Porphyrins not only show powerful phototherapeutic effects (photodynamic and photothermal therapies), but also exhibit excellent imaging capacities, such as near-infrared fluorescent imaging (NIRFI), magnetic resonance imaging (MRI), photoacoustic imaging (PAI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). In order to take advantage of their robust phototherapeutic effects and excellent imaging capacities, porphyrins can be used to create nanomedicines with effective therapeutic and precise diagnostic properties for cancer treatment. In this Review, we summarize porphyrin-based nanomedicines which have been developed recently, including porphyrin-based liposomes, micelles, polymeric nanoparticles, peptide nanoparticles, and small-molecule nanoassemblies, and their applications on cancer therapy and diagnosis. The outlook and limitation of porphyrin-based nanomedicines are also reviewed.

Daunorubicin-containing CLL1-targeting nanomicelles have anti-leukemia stem cell activity in acute myeloid leukemia

Patients with acute myeloid leukemia have a very poor prognosis related to a high rate of relapse and drug-related toxicity. The ability of leukemia stem cells (LSCs) to survive chemotherapy is primarily responsible for relapse, and eliminating LSCs is ultimately essential for cure. We developed novel disulfide-crosslinked CLL1-targeting micelles (DC-CTM), which can deliver high concentrations of daunorubicin (DNR) into both bulk leukemia cells and LSCs. Compared to free DNR, DC-CTM-DNR had a longer half-life, increased DNR area under the curve concentration by 11-fold, and exhibited a superior toxicity profile. In patient-derived AML xenograft models, DC-CTM-DNR treatment led to significant decreases in AML engraftment and impairment of secondary transplantation compared to control groups. Collectively, we demonstrate superior anti-LSC/AML efficacy, and preferable pharmacokinetic and toxicity profiles of DC-CTM-DNR compared to free DNR. DC-CTM-DNR has the potential to significantly improve treatment outcomes and reduce therapy-related morbidity and mortality for patients with AML.