Using an RNAi Signature Assay To Guide the Design of Three-Drug-Conjugated Nanoparticles with Validated Mechanisms, In Vivo Efficacy, and Low Toxicity

Modifying the Backbone Chemistry of PEG-Based Bottlebrush Block Copolymers for the Formation of Long-Circulating Nanoparticles

Nanoparticle physicochemical properties have received great attention in optimizing the performance of nanoparticles for biomedical applications. For example, surface functionalization with small molecules or linear hydrophilic polymers is commonly used to tune the interaction of nanoparticles with proteins and cells. However, it is challenging to control the location of functional groups within the shell for conventional nanoparticles. Nanoparticle surfaces composed of shape-persistent bottlebrush polymers allow hierarchical control over the nanoparticle shell but the effect of the bottlebrush backbone on biological interactions is still unknown. The synthesis is reported of novel heterobifunctional poly(ethylene glycol) (PEG)-norbornene macromonomers modified with various small molecules to form bottlebrush polymers with different backbone chemistries. It is demonstrated that micellar nanoparticles composed of poly(lactic acid) (PLA)-PEG bottlebrush block copolymer (BBCP) with neutral and cationic backbone modifications exhibit significantly reduced cellular uptake compared to conventional unmodified BBCPs. Furthermore, the nanoparticles display long blood circulation half-lives of ≈22 hours and enhanced tumor accumulation in mice. Overall, this work sheds light on the importance of the bottlebrush polymer backbone and provides a strategy to improve the performance of nanoparticles in biomedical applications.

Nanomedomics

Nanomaterials have attractive physicochemical properties. A variety of nanomaterials such as inorganic, lipid, polymers, and protein nanoparticles have been widely developed for nanomedicine via chemical conjugation or physical encapsulation of bioactive molecules. Superior to traditional drugs, nanomedicines offer high biocompatibility, good water solubility, long blood circulation times, and tumor-targeting properties. Capitalizing on this, several nanoformulations have already been clinically approved and many others are currently being studied in clinical trials. Despite their undoubtful success, the molecular mechanism of action of the vast majority of nanomedicines remains poorly understood. To tackle this limitation, herein, this review critically discusses the strategy of applying multiomics analysis to study the mechanism of action of nanomedicines, named nanomedomics, including advantages, applications, and future directions. A comprehensive understanding of the molecular mechanism could provide valuable insight and therefore foster the development and clinical translation of nanomedicines.

On the mechanism of action of arsenoplatins: arsenoplatin-1 binding to a B-DNA dodecamer

The reaction of Pt-based anticancer agents with arsenic trioxide affords robust complexes known as arsenoplatins. The prototype of this family of anticancer compounds is arsenoplatin-1 (AP-1) that contains an As(OH)2 fragment linked to a Pt(II) moiety derived from cisplatin. Crystallographic and spectrometric studies of AP-1 binding to a B-DNA double helix dodecamer are presented here, in comparison with cisplatin and transplatin. Results reveal that AP-1, cisplatin and transplatin react differently with the DNA model system. Notably, in the AP-1/DNA systems, the Pt-As bond can break down with time and As-containing fragments can be released. These results have implications for the understanding of the mechanism of action of arsenoplatins.

Enzyme-Responsive Nanoparticles for Dexamethasone Targeted Delivery to Treat Inflammation in Diabetes

Diabetes is a global epidemic accompanied by impaired wound healing and increased risk of persistent infections and resistance to standard treatments. Therefore, there is an immense need to develop novel methods to specifically target therapeutics to affected tissues and improve treatment efficacy. This study aims to use enzyme-responsive nanoparticles for the targeted delivery of an anti-inflammatory drug, dexamethasone, to treat inflammation in diabetes. These nanoparticles are assembled from fluorescently-labeled, dexamethasone-loaded peptide-polymer amphiphiles. The nanoparticles are injected in vivo, adjacent to labeled collagen membranes sub-periosteally implanted on the calvaria of diabetic rats. Following their implantation, collagen membrane resorption is linked to inflammation, especially in hyperglycemic individuals. The nanoparticles show strong and prolonged accumulation in inflamed tissue after undergoing a morphological switch into microscale aggregates. Significantly higher remaining collagen membrane area and less inflammatory cell infiltration are observed in responsive nanoparticles-treated rats, compared to control groups injected with free dexamethasone and non-responsive nanoparticles. These factors indicate improved therapeutic efficacy in inflammation reduction. These results demonstrate the potential use of enzyme-responsive nanoparticles as targeted delivery vehicles for the treatment of diabetic and other inflammatory wounds.

Hydrogen Peroxide-Triggered Disassembly of Boronic Ester-Cross-Linked Brush-Arm Star Polymers

The concentrations of reactive oxygen species (ROS), e.g., H2O2, are often elevated in diseased tissue microenvironments. Therefore, the selective detection of ROS could enable new diagnostic methods or tools for chemical biology. Here, we report the synthesis of boronic ester-bis-norbornene core-cross-linked brush-arm star polymers (BASPs) with polyethylene glycol (PEG) or PEG-branch-spirocyclohexyl nitroxide (chex) shells. Size exclusion chromatography (SEC) and dynamic light scattering (DLS) showed that these BASPs have narrowly dispersed molar masses and average hydrodynamic diameters of 23 ± 2 nm, respectively. Moreover, due to their core-shell structures, these BASPs disassemble into bottlebrush fragments with improved selectivity for H2O2 over ROS such as peroxynitrite (ONOO-) and hypochlorite (-OCl). Finally, H2O2 induced disassembly of chex-containing BASPs induces a change in transverse magnetic relaxivity that can be detected via magnetic resonance imaging (MRI). Chex-BASPs may represent a valuable new diagnostic tool for H2O2 sensing.

Cisplatin-Conjugated Polyurethane Capsule for Dual Drug Delivery to a Cancer Cell

This paper describes the synthesis of a polymer-prodrug conjugate, its aqueous self-assembly, noncovalent encapsulation of a second drug, and stimuli-responsive intracellular dual drug delivery. Condensation polymerization between a functionalized diol and a commercially available diisocyanate in the presence of poly(ethylene glycol) hydroxide (PEG-OH) as the chain stopper produces an ABA-type amphiphilic block copolymer (PU-1) in one pot, with the middle hydrophobic block being a polyurethane containing a pendant tert-butyloxycarbonyl (Boc)-protected amine in every repeating unit. Deprotection of the Boc group, followed by covalent attachment of the Pt(IV) prodrug using the pendant amine groups, produces the polymer-prodrug conjugate PU-Pt-1, which aggregates to nanocapsule-like structures in water with a hydrophilic interior. In the presence of sodium ascorbate, the Pt(IV) prodrug can be detached from the polymer backbone, producing the active Pt(II) drug. Cell culture studies show appreciable cell viability by the parent polymer. However, the polymer-prodrug conjugate nanocapsules exhibit cellular uptake and intracellular release of the active drug under a reducing environment. The capsule-like aggregates of the polymer-prodrug conjugate were used for noncovalent encapsulation of a second drug, doxorubicin (Dox), and Dox-loaded PU-Pt-1 aggregate showed a significantly superior cell killing efficiency compared to either of the individual drugs, highlighting the promising application of such a dual-drug-delivery approach.

An orthogonally activatable CRISPR-Cas13d nanoprodrug to reverse chemoresistance for enhanced chemo-photodynamic therapy

A logic-gated CRISPR-Cas13d-based nanoprodrug was rationally designed for orthogonal photomodulation of gene editing and prodrug release for enhanced chemo-photodynamic therapy.

Star-Shaped ROMP Polymers Coated with Oligothiophenes That Exhibit Unique Emission

A series of oligo(thiophene)-modified "soluble" star-shaped ring-opening metathesis polymerization (ROMP) polymers were prepared by sequential living ROMP of norbornene and a cross-linking agent using a molybdenum-alkylidene catalyst, followed by Wittig-type coupling for termination with oligo(thiophene) carboxaldehydes. The resultant star-shaped ROMP polymers displayed unique emission properties affected by the core size and arm repeat units as well as the kind of oligothiophene coated. The effects of the thiophene groups on photophysical properties of star-shaped/linear polymers were studied via time-resolved fluorescence spectroscopy. Fluorescence lifetimes were determined in THF as 400, 640, 730, and 820 ps for Star 3TPh, Linear 3TPh, Star 4T, and Linear 4T, respectively. A significant enhancement of the nonradiative rate constants k _nr in the star-shaped polymers results in relatively lower fluorescence quantum yields and shorter fluorescence lifetimes compared to the corresponding linear polymers.

Bottlebrush polymers with flexible enantiomeric side chains display differential biological properties

Chirality and molecular conformation are central components of life: biological systems rely on stereospecific interactions between discrete (macro)molecular conformers, and the impacts of stereochemistry and rigidity on the properties of small molecules and biomacromolecules have been intensively studied. Nevertheless, how these features affect the properties of synthetic macromolecules has received comparably little attention. Here we leverage iterative exponential growth and ring-opening metathesis polymerization to produce water-soluble, chiral bottlebrush polymers (CBPs) from two enantiomeric pairs of macromonomers of differing rigidity. Remarkably, CBPs with conformationally flexible, mirror image side chains show several-fold differences in cytotoxicity, cell uptake, blood pharmacokinetics and liver clearance; CBPs with comparably rigid, mirror image side chains show no differences. These observations are rationalized with a simple model that correlates greater conformational freedom with enhanced chiral recognition. Altogether, this work provides routes to the synthesis of chiral nanostructured polymers and suggests key roles for stereochemistry and conformational rigidity in the design of future biomaterials.

Assembly of catechol-modified polymer brushes for drug delivery

The anticancer drug of Bortezomib conjugated onto catechol-modified bottlebrush block copolymers can be intracellularly released owing to the pH-responsive behavior, resulting in considerable cell death and tumor growth inhibition.

Near-Infrared Fluorescent Micelles from Poly(norbornene) Brush Triblock Copolymers for Nanotheranostics

This contribution describes the design and synthesis of multifunctional micelles based on amphiphilic brush block copolymers (BBCPs) for imaging and selective drug delivery of natural anticancer compounds. Well-defined BBCPs were synthesized via one-pot multi-step sequential grafting-through ring-opening metathesis polymerization (ROMP) of norbornene-based macroinitiators. The norbornenes employed contain a poly(ethylene glycol) methyl ether chain, an alkyl bromide chain, and/or a near-infrared (NIR) fluorescent cyanine dye. After block copolymerization, post-polymerization transformations using bromide-azide substitution, followed by the strain-promoted azide-alkyne cycloaddition (SPAAC) allowed for the functionalization of the BBCPs with the piplartine (PPT) moiety, a natural product with well-documented cytotoxicity against cancer cell lines, via an ester linker between the drug and the polymer side chain. The amphiphilic BBCPs self-assembled in aqueous media into nano-sized spherical micelles with neutral surface charges, as confirmed by dynamic light scattering analysis and transmission electron microscopy. During self-assembly, paclitaxel (PTX) could be effectively encapsulated into the hydrophobic core to form stable PTX-loaded micelles with high loading capacities and encapsulation efficiencies. The NIR fluorescent dye-containing micelles exhibited remarkable photophysical properties, excellent colloidal stability under physiological conditions, and a pH-induced disassembly under slightly acidic conditions, allowing for the release of the drug in a controlled manner. The in vitro studies demonstrated that the micelles without the drug (blank micelles) are biocompatible at concentrations of up to 1 mg mL^-1 and present a high cellular internalization capacity toward MCF-7 cancer cells. The drug-functionalized micelles showed in vitro cytotoxicity comparable to free PPT and PTX against MCF-7 and PC3 cancer cells, confirming efficient drug release into the tumor environment upon cellular internalization. Furthermore, the drug-functionalized micelles exhibited higher selectivity than the pristine drugs and preferential cellular uptake in human cancer cell lines (MCF-7 and PC3) when compared to the normal breast cell line (MCF10A). This study provides an efficient strategy for the development of versatile polymeric nanosystems for drug delivery and image-guided diagnostics. Notably, the easy functionalization of BBCP side chains via SPAAC opens up the possibility for the preparation of a library of multifunctional systems containing other drugs or functionalities, such as target groups for recognition.

Use of pH-Active Catechol-Bearing Polymeric Nanogels with Glutathione-Responsive Dissociation to Codeliver Bortezomib and Doxorubicin for the Synergistic Therapy of Cancer

Synergistic therapy holds promising potential in cancer treatment. Here, the inclusion of catechol moieties, a disulfide cross-linked structure, and pendent carboxyl into the network of polymeric nanogels with glutathione (GSH)-responsive dissociation and pH-sensitive release is first disclosed for the codelivery of doxorubicin (DOX) and bortezomib (BTZ) in synergistic cancer therapy. The pendent carboxyl groups and catechol moieties are exploited to absorb DOX through electrostatic interaction and conjugate BTZ through boronate ester, respectively. Both electrostatic interactions and boronate ester are stable at neutral or alkaline pH, while they are instable in an acidic environment to further recover the activities of BTZ and DOX. The polymeric nanogels possess a superior stability to prevent the premature leakage of drugs in a physiological environment, while their structure is destroyed in response to a typical endogenous stimulus (GSH) to unload drugs. The dissociation of the drug-loaded nanogels accelerates the intracellular release of DOX and BTZ and further enhances the therapeutic efficacy. In vitro and in vivo investigations revealed that the dual-drug loaded polymeric nanogels exhibited a strong ability to suppress tumor growth. This study thus proposes a new perspective on the production of multifunctional polymeric nanogels through the introduction of different functional monomers.

Dual drug-paired polyprodrug nanotheranostics reverse multidrug resistant cancers via mild photothermal-cocktail chemotherapy

Combating multidrug resistance (MDR) of tumors is still challenging for clinical chemotherapy, cocktail chemotherapy (CCT), and currently widely-studied nanodrug-based treatments. Inspired by different MDR-overcoming and antitumor mechanisms of CCT and photothermal therapy (PT), a dual drug-paired polyprodrug nanoparticle (PDCN25-CDDP) was constructed to achieve the combination therapy PT-CCT for reversing MDR and combating multidrug resistant cancers. The PT-CCT treatment can greatly downregulate the P-gp expression level and achieve utmost MDR-reversal and antitumor efficacy by both a cocktail effect of CCT and a synergistic effect of CCT with PT; meanwhile, PT can inhibit the expression of heat shock protein 90 and enhance the thermosensitivity of cancer cells. Upon NIR irradiation, PDCN25-CDDPin vivo produced a selective tumor accumulation effect and relatively deep tumor penetration, as evidenced by fluorescent and photoacoustic imaging and CLSM. The mild PT-CCT treatment completely eradicated MCF-7/ADR and OVCAR-3/DDP tumors without skin damage or tumor recurrence for 30 days, exhibiting synergistic MDR-reversal and superior antitumor efficacy in vivo. Importantly, this work provides an innovative strategy for reversing MDR and combating DOX-resistant breast and CDDP-resistant ovarian cancers.

Pro-organic radical contrast agents ("pro-ORCAs") for real-time MRI of pro-drug activation in biological systems

Nitroxide-based organic-radical contrast agents (ORCAs) are promising as safe, next-generation magnetic resonance imaging (MRI) tools. Nevertheless, stimuli-responsive ORCAs that enable MRI monitoring of prodrug activation have not been reported; such systems could open new avenues for prodrug validation and image-guided drug delivery. Here, we introduce a novel "pro-ORCA" concept that addresses this challenge. By covalent conjugation of nitroxides and drug molecules (doxorubicin, DOX) to the same brush-arm star polymer (BASP) through chemically identical cleavable linkers, we demonstrate that pro-ORCA and prodrug activation, i.e., ORCA and DOX release, leads to significant changes in MRI contrast that correlate with cytotoxicity. This approach is shown to be general for a range of commonly used linker cleavage mechanisms (e.g., photolysis and hydrolysis) and release rates. Pro-ORCAs could find applications as research tools or clinically viable "reporter theranostics" for in vitro and in vivo MRI-correlated prodrug activation.

A hollow-structured nanohybrid: Intelligent and visible drug delivery and photothermal therapy for cancer

It is of great valuable in drug delivery to fabricate multifunctional nanovehicle for cancer therapy. Herein, hollow-structured hCu_2-xS@Au nanoshell/satellite composite with doxorubicin-carrying was designed and synthesized for intelligent and visible drug delivery and satisfactory photothermal therapy. By modification of disulfide linkage bridged Au nanoshell and multi-carboxylic graphene quantum dots (MC-GODs) on the surface of hCu_2-xS@Au nanoparticles, both the high concentration of glutathione and low pH in cancer cell/tissue can induce responsive drug release. The satisfactory photothermal conversion efficiency (32%) of hCu_2-xS@Au@MC-GODs under 808 nm near-infrared (NIR) laser irradiation ascribed to the reduced bandgap and more circuit paths for electron transitions for hCuS modified with Au nanoparticles depend on density functional theory, which antitumor therapy efficacy was greatly enhanced by combining chemo- and photothermal therapy. Moreover, the fluorescence of MC-GODs was quenched/"turn off" as linking to the surface of hCu_2-xS@Au, and also restored/"turn on" as the MC-GODs detaching from the surface of hCu_2-xS@Au. The fluorescent switch of MC-GODs can serve as both a controllable drug release "guard" and "eyes" for visualized monitoring. The multi-modality therapy with controllable drug delivery, visual monitoring and high photothermal conversion efficiency may be anticipated by this versatile strategy.

Arm-degradable star polymers with crosslinked ladder-motif cores as a route to soluble microporous nanoparticles

Star polymers were synthesized via cores crosslinking of (macro)molecular ladder motifs and converted to microporous polymer particles after arm degradation.

Diblock brush-arm star copolymers via a core-first/graft-from approach using γ-cyclodextrin and ROMP: a modular platform for drug delivery

Water-soluble diblock brush-arm star copolymers using γ-CD-based core-first ring-opening metathesis polymerization, allowing for anticancer drug delivery via host–guest interaction.

Length effects of cylindrical polymer brushes on their in vitro and in vivo properties

Understanding the relationship between the morphology and biological performance of nanomaterials is very important for their biomedical applications. However, most of the published research focused on spherical systems. The biological properties of the anisotropic nanomaterials have not been studied enough. In this study, we synthesized three sets of cylindrical polymer brushes (CPBs) with different lengths (∼34, 60 and 119 nm) by taking advantage of controlled radical polymerization and Cu(i)-catalyzed alkyne-azide click chemistry. These CPBs had one-dimensional wormlike morphology, the same chemical structure and diameter, desirable water solubility, abundant amino groups and narrowly distributed lengths. These characteristics encouraged us to study length effects on their in vitro and in vivo properties. We demonstrated that longer CPBs had higher cellular uptake, lower tissue permeability, shorter blood circulation time, lower tumor accumulation and rapider body clearance than their shorter counterparts. This work might provide important guidance for the design of biomedical nanomaterials.

Arsenoplatin-1 Is a Dual Pharmacophore Anticancer Agent

Arsenoplatins are adducts of two chemically important anticancer drugs, cisplatin and arsenic trioxide, that have a Pt(II) bond to an As(III) hydroxide center. Screens of the NCI-60 human tumor cell lines reveal that arsenoplatin-1 (AP-1), [Pt(μ-NHC(CH3)O)2ClAs(OH)2], the first representative of this novel class of anticancer agents, displays a superior activity profile relative to the parent drugs As2O3 or cisplatin in a majority of cancer cell lines tested. These activity profiles are important because the success of arsenic trioxide in blood cancers (such as APL) has not been seen in solid tumors due to the rapid clearance of arsenous acid from the body. To understand the biological chemistry of these compounds, we evaluated interactions of AP-1 with the two important classes of biomolecules-proteins and DNA. The first structural studies of AP-1 bound to model proteins reveal that platinum(II) binds the Nε of His in a manner that preserves the Pt-As bond. We find that AP-1 readily enters cells and binds to DNA with an intact Pt-As bond (Pt:As ratio of 1). At longer incubation times, however, the Pt:As ratio in DNA samples increases, suggesting that the Pt-As bond breaks and releases the As(OH)2 moiety. We conclude that arsenoplatin-1 has the potential to deliver both Pt and As species to a variety of hematological and solid cancers.

Design and synthesis of a dual imageable theranostic platinum prodrug for efficient cancer therapy

Platinum-based chemotherapeutic agents are considered first-line treatments for various cancers but their application is limited by the lack of site specificity and severe side effects.

Synthesis of Soluble Star-Shaped Polymers via In and Out Approach by Ring-Opening Metathesis Polymerization (ROMP) of Norbornene: Factors Affecting the Synthesis

The methods for one-pot synthesis of ‘soluble’ star-shaped polymers by sequential living ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and cross-linking (CL) reagent using Mo(CHCMe2Ph)(N-2,6-iPr2C6H3)(OtBu)2 have been explored. The method (called the “in and out” or core-first approach) basically consists of (i) the living ROMP of NBE (formation of arm), (ii) reaction with CL (formation of core), (iii) additional living ROMP of NBE (propagating arms from the core, formation of star), (iv) end-modification via Wittig-type cleavage of metal–carbon double bonds containing polymer chain with aldehyde. Two different approaches in the core formation step (reaction with CL mixed with/without NBE) for synthesis of the high molecular weight star-shaped ROMP polymers with more branching, unimodal molecular weight distributions have been explored in detail. The method (reacting CL with NBE in the core formation step) under highly diluted conditions afforded the high molecular weight polymers with unimodal molecular weight distributions.

Brush-First and ROMP-Out with Functional (Macro)monomers: Method Development, Structural Investigations, and Applications of an Expanded Brush-Arm Star Polymer Platform

The efficient synthesis of complex functional polymeric nanomaterials is often challenging. Ru-initiated ring-opening metathesis polymerization (ROMP) of multivalent macromonomers followed by cross-linking to form brush-arm star (BASP) polymers enables access to well-defined nano-structures with diverse functionality. This "brush-first" method leaves active Ru in the BASP microgel core, which could potentially be used in a subsequent "ROMP-out" (RO) step to introduce further modifications to the BASP structure via the addition of (macro)monomers. Here, we study this RO approach in depth. The efficiency of RO is assessed for a variety of BASP compositions using a combination of inductively coupled plasma mass spectrometry and gel permeation chromatography. To demonstrate the modularity of the RO process, arylboronic acid-functionalized BASPs were prepared; uptake of these RO-BASPs into hypersialylated cancer cells was enhanced relative to non-functionalized BASPs as determined by flow cytometry and fluorescence microscopy. In addition, the self-assembly of miktoarm BASPs prepared via brush-first and RO with different macromonomers is demonstrated. The combination of brush-first ROMP with RO provides a simple, modular strategy for access to a wide array of functional nanomaterials.

Triply Loaded Nitroxide Brush-Arm Star Polymers Enable Metal-Free Millimetric Tumor Detection by Magnetic Resonance Imaging

Nitroxides occupy a privileged position among plausible metal-free magnetic resonance imaging (MRI) contrast agents (CAs) due to their inherently low-toxicity profiles; nevertheless, their translational development has been hindered by a lack of appropriate contrast sensitivity. Nanostructured materials with high nitroxide densities, where each individual nitroxide within a macromolecular construct contributes to the image contrast, could address this limitation, but the synthesis of such materials remains challenging. Here, we report a modular and scalable synthetic approach to nitroxide-based brush-arm star polymer (BASP) organic radical CAs (ORCAs) with high nitroxide loadings. The optimized ∼30 nm diameter "BASP-ORCA3" displays outstanding T2 sensitivity with a very high molecular transverse relaxivity ( r2 > 1000 mM-1 s-1). BASP-ORCA3 further exhibits excellent stability in vivo, no acute toxicity, and highly desirable pharmacokinetic and biodistribution profiles for longitudinal detection of tumors by MRI. When injected intravenously into mice bearing subcutaneous plasmacytomas, BASP-ORCA3 affords distinct in vivo visualization of tumors on translationally relevant time scales. Leveraging its high sensitivity, BASP-ORCA3 enables efficient mapping of tumor necrosis, which is an important biomarker to predict therapeutic outcomes. Moreover, BASP-ORCA3 allows for detection of millimetric tumor implants in a disseminated murine model of advanced-stage human ovarian cancer that possess genetic, histological, and vascular characteristics that are similar to those seen in patients. This work establishes BASP-ORCA3 as a promising metal-free spin contrast agent for MRI.

Reduction of liver fibrosis by rationally designed macromolecular telmisartan prodrugs

At present there are no drugs for the treatment of chronic liver fibrosis that have been approved by the Food and Drug administration of the United States. Telmisartan, a small-molecule antihypertensive drug, displays antifibrotic activity, but its clinical use is limited because it causes systemic hypotension. Here, we report the scalable and convergent synthesis of macromolecular telmisartan prodrugs optimized for preferential release in diseased liver tissue. We optimized the release of active telmisartan in fibrotic liver to be depot-like (that is, a constant therapeutic concentration) through the molecular design of telmisartan brush-arm star polymers, and show that these lead to improved efficacy and to the avoidance of dose-limiting hypotension in both metabolically and chemically induced mouse models of hepatic fibrosis, as determined by histopathology, enzyme levels in the liver, intact-tissue protein markers, hepatocyte necrosis protection, and gene-expression analyses. In rats and dogs, the prodrugs are retained long-term in liver tissue and have a well-tolerated safety profile. Our findings support the further development of telmisartan prodrugs that enable infrequent dosing in the treatment of liver fibrosis.

Translation of combination nanodrugs into nanomedicines: lessons learned and future outlook

The concept of nanomedicine is not new. For instance, some nanocrystals and colloidal drug molecules are marketed that improve pharmacokinetic characteristics of single-agent therapeutics. For the past two decades, the number of research publications on single-agent nanoformulations has grown exponentially. However, formulations advancing to pre-clinical and clinical evaluations that lead to therapeutic products has been limited. Chronic diseases such as cancer and HIV/AIDS require drug combinations, not single agents, for durable therapeutic responses. Therefore, development and clinical translation of drug combination nanoformulations could play a significant role in improving human health. Successful translation of promising concepts into pre-clinical and clinical studies requires early considerations of the physical compatibility, pharmacological synergy, as well as pharmaceutical characteristics (e.g. stability, scalability and pharmacokinetics). With this approach and robust manufacturing processes in place, some drug-combination nanoparticles have progressed to non-human primate and human studies. In this article, we discuss the rationale and role of drug-combination nanoparticles, the pre-clinical and clinical research progress made to date and the key challenges for successful clinical translation. Finally, we offer insight to accelerate clinical translation through leveraging robust nanoplatform technologies to enable implementation of personalised and precision medicine.

Scalable Synthesis of Multivalent Macromonomers for ROMP

The polymerization of functional monomers provides direct access to functional polymers without need for postpolymerization modification; however, monomer synthesis can become a bottleneck of this approach. New methods that enable rapid installation of functionality into monomers for living polymerization are valuable. Here, we report the three-step convergent synthesis (two-step longest linear sequence) of a divalent exo-norbornene imide capable of efficient coupling with various nucleophiles and azides to produce diversely functionalized branched macromonomers optimized for ring-opening metathesis polymerization (ROMP). In addition, we describe an efficient iterative procedure for the synthesis of tri-and tetra-valent branched macromonomers. We demonstrate the use of these branched macromonomers for the synthesis of Janus bottlebrush block copolymers as well as for the generation of bottlebrush polymers with up to three conjugated small molecules per repeat unit. This work significantly expands the scalability and diversity of nanostructured macromolecules accessible via ROMP.

Unsymmetrical difunctionalization of cyclooctadiene under continuous flow conditions: expanding the scope of ring opening metathesis polymerization

Functionalized cyclooctenes (FCOEs) are important monomers in ring-opening metathesis polymerization (ROMP). Herein, a new library of disubstituted FCOEs bearing adjacent heteroatoms were synthesized and applied in ROMP. To address the issues associated with the handling of the reactive thienyl chloride intermediate, a two-step continuous flow method has been developed to prepare 5-thio-6-chlorocyclooctene compounds from abundant cyclooctadiene starting materials. These newly synthesized FCOE monomers were subsequently polymerized through ROMP, giving rise to a range of functionalized polymers with high molecular weights. Furthermore, we demonstrated that the thermal properties of these polymers could be fine-tuned by changing the functional groups in the FCOE monomers. We expect that this functionalization-polymerization strategy will enable the preparation of a range of polymeric materials with complex structures.

One-pot synthesis of end-functionalised soluble star-shaped polymers by living ring-opening metathesis polymerisation using a molybdenum-alkylidene catalyst

Precise synthesis of soluble star-shaped polymers has been achieved by adopting living ring-opening metathesis polymerisation (ROMP) using a molybdenum-alkylidene catalyst with sequential addition of norbornene and cross-linking agent; the method provides efficient one-pot synthesis of high molecular weight end-functionalised star-shaped polymers (M_n = >1.37 × 10⁵) with more arms (branching) with rather low PDI values (M_w/M_n = 1.17–1.37) under the optimised conditions.

Precise synthesis of star-shaped polymers has been achieved by living ROMP using a molybdenum catalyst with sequential addition of norbornene and cross-linker.

Nanoparticle conjugates of a highly potent toxin enhance safety and circumvent platinum resistance in ovarian cancer

Advanced-stage epithelial ovarian cancers are amongst the most difficult to treat tumors and have proven to be refractory to most cytotoxic, molecularly targeted, or immunotherapeutic approaches. Here, we report that nanoparticle-drug conjugates (NDCs) of monomethyl auristatin E (MMAE) significantly increase loading on a per-vehicle basis as compared to antibody-drug conjugates (ADCs). Their intraperitoneal administration enabled triggered release of the active MMAE toxin to inhibit tumor growth and to extend animal survival to >90 days in a cell-line xenograft model of disseminated ovarian cancer. In a patient-derived xenograft model of advanced-stage and platinum-resistant ovarian cancer, an MMAE-based NDC doubled the duration of tumor growth inhibition as compared to cisplatin. NDCs of highly potent toxins thus introduce a translatable platform that may be exploited to maximize the safety and efficacy of cytotoxic chemotherapies, combining the best features of ADCs with those of nanoparticle-based therapeutics.

Improving the safety and efficacy of chemotherapeutics will help to enhance their effects. Here, the authors show that intraperitoneal delivery of nanoparticle conjugates of a potent toxin prolongs tumor inhibition and survival as compared to cisplatin in advanced-stage and platinum-resistant ovarian cancer mouse models.

Biopolymer-Drug Conjugate Nanotheranostics for Multimodal Imaging-Guided Synergistic Cancer Photothermal-Chemotherapy

Some of the biomedical polymer-drug conjugates are being translated into clinical trials; however, they intrinsically lack photothermal and multi-imaging capabilities, hindering them from imaging-guided precision cancer therapy and complete tumor regression. We introduce a new concept of all-in-one biopolymer-drug conjugate nanotheranostics and prepare a kind of intracellular pH-sensitive polydopamine-doxorubicin (DOX) conjugate nanoparticles (PDCNs) under mild conditions. Significantly, this strategy integrates polymeric prodrug-induced chemotherapy (CT), near-infrared (NIR) light-mediated photothermal therapy (PT), and triple modalities including DOX self-fluorescence, photothermal, and photoacoustic (PA) imaging into one conjugate nanoparticle. The PDCNs present excellent photothermal property, dual stimuli-triggered drug release behavior, and about 12.4-fold blood circulation time compared to free DOX. Small animal fluorescent imaging technique confirms that PDCNs have preferential tumor accumulation effect in vivo, giving a 12.8-fold DOX higher than the control at 12 h postinjection. Upon NIR laser irradiation (5 min, 808 nm, and 2 W·cm^-2), the PDCN-mediated photothermal effect can quickly elevate the tumor over 50 °C, exhibiting good photothermal and PA imaging functions, of which the PA amplitude is 3.6-fold greater than the control. In vitro and in vivo assays persuasively verify that intravenous photothermal-CT of PDCNs produces synergistic antitumor activity compared to single PT or CT, achieving complete tumor ablation during the evaluation period.

Mikto-Brush-Arm Star Polymers via Cross-Linking of Dissimilar Bottlebrushes: Synthesis and Solution Morphologies

A convergent brush-first ring-opening metathesis polymerization (ROMP) approach for the synthesis of mikto-brush-arm star polymers (MBASPs) via cross-linking of dissimilar bottlebrush polymers is reported. Living bottlebrush polymers prepared via ROMP of norbornene-terminated poly(ethylene glycol) (PEG) or polystyrene (PS) macromonomers (MMs) were mixed together in a desired ratio and exposed to a bis-norbornene cross-linker to yield MBASPs with narrow size distributions. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that the solution morphologies of MBASPs depended on the feed ratio of the PEG and PS bottlebrush polymers at the cross-linking stage. This work provides a robust and modular strategy for the synthesis of a new type of miktoarm star polymer wherein the star arms are bottlebrush polymers.

Nitroxide-Based Macromolecular Contrast Agents with Unprecedented Transverse Relaxivity and Stability for Magnetic Resonance Imaging of Tumors

Metal-free magnetic resonance imaging (MRI) agents could overcome the established toxicity associated with metal-based agents in some patient populations and enable new modes of functional MRI in vivo. Herein, we report nitroxide-functionalized brush-arm star polymer organic radical contrast agents (BASP-ORCAs) that overcome the low contrast and poor in vivo stability associated with nitroxide-based MRI contrast agents. As a consequence of their unique nanoarchitectures, BASP-ORCAs possess per-nitroxide transverse relaxivities up to ∼44-fold greater than common nitroxides, exceptional stability in highly reducing environments, and low toxicity. These features combine to provide for accumulation of a sufficient concentration of BASP-ORCA in murine subcutaneous tumors up to 20 h following systemic administration such that MRI contrast on par with metal-based agents is observed. BASP-ORCAs are, to our knowledge, the first nitroxide MRI contrast agents capable of tumor imaging over long time periods using clinical high-field 1H MRI techniques.

Cisplatin Cross-Linked Multifunctional Nanodrugplexes for Combination Therapy

Combination therapy efficiently tackles cancer by hitting multiple action mechanisms. However, drugs administered, simultaneously or sequentially, may not reach the targeted sites with the desired dose and ratio. The outcomes of combination therapy could be improved with a polymeric nanoparticle, which can simultaneously transport an optimal combination of drugs. We have demonstrated a simple one-pot strategy to formulate nanomedicines based on platinum coordination and the noncovalent interactions of the drugs. A naturally occurring polymer, hyaluronan (HA), was chosen as the building scaffold to form a nanodrugplex with cisplatin and aromatic-cationic drugs. The platinum coordination between cisplatin and HA induces the formation of a nanocomplex. The aromatic-cationic drugs are tightly packed by an electrostatic interaction and π-π stacking. The nanodrugplex bears excellent flexibility in drug combination and size control. It is stable in storage and has favorable release kinetics and targeting capabilities toward CD44, a receptor for HA that is highly expressed on many types of cancer cells.

A subset of platinum-containing chemotherapeutic agents kills cells by inducing ribosome biogenesis stress

Cisplatin and its platinum analogs, carboplatin and oxaliplatin, are some of the most widely used cancer chemotherapeutics. Although cisplatin and carboplatin are used primarily in germ cell, breast and lung malignancies, oxaliplatin is instead used almost exclusively to treat colorectal and other gastrointestinal cancers. Here we utilize a unique, multi-platform genetic approach to study the mechanism of action of these clinically established platinum anti-cancer agents, as well as more recently developed cisplatin analogs. We show that oxaliplatin, unlike cisplatin and carboplatin, does not kill cells through the DNA-damage response. Rather, oxaliplatin kills cells by inducing ribosome biogenesis stress. This difference in drug mechanism explains the distinct clinical implementation of oxaliplatin relative to cisplatin, and it might enable mechanistically informed selection of distinct platinum drugs for distinct malignancies. These data highlight the functional diversity of core components of front-line cancer therapy and the potential benefits of applying a mechanism-based rationale to the use of our current arsenal of anti-cancer drugs.

Luminescent Difluoroboron β-Diketonate PLA-PEG Nanoparticle

Luminescent difluoroboron β-diketonate poly(lactic acid) (BF₂bdkPLA) materials serve as biological imaging agents. In this study, dye structures were modified to achieve emission colors that span the visible region with potential for multiplexing applications. Four dyes with varying π-conjugation (phenyl, naphthyl) and donor groups (-OMe, -NMe₂) were coupled to PLLA-PEG block copolymers (∼11 kDa) by a postpolymerization Mitsunobu reaction. The resulting dye-polymer conjugates were fabricated as nanoparticles (∼55 nm diameter) to produce nanomaterials with a range of emission colors (420-640 nm). For increased stability, dye-PLLA-PEG conjugates were also blended with dye-free PDLA-PEG to form stereocomplex nanoparticles of smaller size (∼45 nm diameter). The decreased dye loading in the stereoblocks blue-shifted the emission, generating a broader range of fluorescence colors (410-620 nm). Tumor accumulation was confirmed in a murine model through biodistribution studies with a red emitting dimethyl amino-substituted dye-polymer analogue. The synthesis, optical properties, oxygen-sensing capabilities, and stability of these block copolymer nanoparticles are presented.