A convergent synthetic platform for single-nanoparticle combination cancer therapy: ratiometric loading and controlled release of cisplatin, doxorubicin, and camptothecin

Advanced LC-analysis of human plasma for metallodrug metabolites

Understanding the fate of metallodrugs in the bloodstream is critical to assess if the parent drug has a reasonable probability to reach the intended target tissue and to predict toxic side-effects. To gain insight into these processes, we have added pharmacologically relevant doses of metallodrugs to blood plasma and applied an LC-method to directly analyze the latter for metallodrug metabolites. Using human or rabbit plasma, this LC-method was employed to gain insight into the metabolism of clinically used as well as emerging anticancer metallodrugs and to unravel the mechanisms by which small molecular weight compounds that - when co-administered with a metallodrug - decrease the toxic side-effects of the metallodrug by modulating its metabolism. The results suggest that the developed LC-method is useful to probe the fate of biologically active novel metal-complexes in plasma to help select those which may be advanced to animal/clinical studies to ultimately develop safer metallodrugs.

Chimeric Nanoparticle: A Platform for Simultaneous Targeting of Phosphatidylinositol-3-Kinase Signaling and Damaging DNA in Cancer Cells

Phosphatidylinositol-3-kinase (PI3K) signaling has been hijacked in different types of cancers. Hence, PI3K inhibitors have emerged as novel targeted therapeutics in cancer treatment as mono and combination therapy along with other DNA damaging drugs. However, targeting PI3K signaling with small molecules leads to the emergence of drug resistance and severe side effects to the cancer patients. To address these, we have developed a biocompatible, biodegradable cholesterol-based chimeric nanoparticle (CNP), which can simultaneously load PI103, doxorubicin, and cisplatin in a controlled ratiometric manner. Size, shape, and morphology of these CNPs were characterized by dynamic light scattering (DLS), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Increased amounts of PI103, doxorubicin, and cisplatin were released from CNPs through controlled and continuous manner over 120 h at pH = 5.5 compared to neutral pH. The CNPs showed much enhanced in vitro cytotoxicity in HeLa, HL60, MCF7, and MDA-MB-231 cancer cells compared to a free drug cocktail at 24 and 48 h by inducing apoptosis. Confocal laser scanning microscopy (CLSM) imaging revealed that indeed these CNPs were internalized into subcellular lysosomes through endocytosis in a time dependent mode over 6 h and retained inside for 48 h in HeLa, MDA-MB-231, and MCF7 cells. These CNPs showed their efficacy by damaging DNA and inhibiting Akt as a downstream modulator of PI3K signaling in HeLa cervical cancer cells. These CNPs have the potential to open up new directions in next-generation nanomedicine by simultaneous targeting of multiple oncogenic signaling pathways and inducing DNA damage for augmented therapeutic outcome by reducing toxic side effects and overcoming drug resistance.

Recent Advances in Platinum (IV) Complex-Based Delivery Systems to Improve Platinum (II) Anticancer Therapy

Cisplatin and its platinum (Pt) (II) derivatives play a key role in the fight against various human cancers such as testicular, ovarian, head and neck, lung tumors. However, their application in clinic is limited due to dose- dependent toxicities and acquired drug resistances, which have prompted extensive research effort toward the development of more effective Pt (II) delivery strategies. The synthesis of Pt (IV) complex is one such an area of intense research fields, which involves their in vivo conversion into active Pt (II) molecules under the reducing intracellular environment, and has demonstrated encouraging preclinical and clinical outcomes. Compared with Pt (II) complexes, Pt (IV) complexes not only exhibit an increased stability and reduced side effects, but also facilitate the intravenous-to-oral switch in cancer chemotherapy. The overview briefly analyzes statuses of Pt (II) complex that are in clinical use, and then focuses on the development of Pt (IV) complexes. Finally, recent advances in Pt (IV) complexes in combination with nanocarriers are highlighted, addressing the shortcomings of Pt (IV) complexes, such as their instability in blood and irreversibly binding to plasma proteins and nonspecific distribution, and taking advantage of passive and active targeting effect to improve Pt (II) anticancer therapy.

Photoresponsive nanoparticles for drug delivery

Externally triggerable drug delivery systems provide a strategy for the delivery of therapeutic agents preferentially to a target site, presenting the ability to enhance therapeutic efficacy while reducing side effects. Light is a versatile and easily tuned external stimulus that can provide spatiotemporal control. Here we will review the use of nanoparticles in which light triggers drug release or induces particle binding to tissues (phototargeting).

Structure, function, self-assembly, and applications of bottlebrush copolymers

Bottlebrush polymers are a type of branched or graft polymer with polymeric side-chains attached to a linear backbone, and the unusual architectures of bottlebrushes provide a number of unique and potentially useful properties. These include a high entanglement molecular weight, enabling rapid self-assembly of bottlebrush block copolymers into large domain structures, the self-assembly of bottlebrush block copolymer micelles in a selective solvent even at very low dilutions, and the functionalization of bottlebrush side-chains for recognition, imaging, or drug delivery in aqueous environments. This review article focuses on recent developments in the field of bottlebrush polymers with an emphasis on applications of bottlebrush copolymers. Bottlebrush copolymers contain two (or more) different types of polymeric side-chains. Recent work has explored the diverse properties and functions of bottlebrush polymers and copolymers in solutions, films, and melts, and applications explored include photonic materials, bottlebrush films for lithographic patterning, drug delivery, and tumor detection and imaging. We provide a brief introduction to bottlebrush synthesis and physical properties and then discuss work related to: (i) bottlebrush self-assembly in melts and bulk thin films, (ii) bottlebrushes for photonics and lithography, (iii) bottlebrushes for small molecule encapsulation and delivery in solution, and (iv) bottlebrush micelles and assemblies in solution. We briefly discuss three potential areas for future research, including developing a more quantitative model of bottlebrush self-assembly in the bulk, studying the properties of bottlebrushes at interfaces, and investigating the solution assembly of bottlebrush copolymers.

Dual Role for 1,2,4,5-Tetrazines in Polymer Networks: Combining Diels-Alder Reactions and Metal Coordination To Generate Functional Supramolecular Gels

The inverse-electron demand Diels-Alder cycloaddition of tetrazines and olefins has emerged as a powerful coupling reaction for the formation of polymer gels with diverse applications. Tetrazines are also excellent ligands for metal atoms. For example, 3,6-bis(2-pyridyl)-1,2,4,5-tetrazines (bptz) have been used to generate discrete supramolecular M_xbptz_y metal clusters and extended 2D grid structures. We reasoned that both the Diels-Alder and the metal-coordination modes of reactivity of bptz derivatives could be leveraged in the context of hydrogel design to yield novel hybrid materials. Here we report on the formation of supramolecular hydrogels via substoichiometric Diels-Alder functionalization of bptz ligands bound to the ends of poly(ethylene glycol) (PEG) chains followed by metal-coordination-induced gelation in the presence of Ni²⁺ and Fe²⁺ salts. Our results show that simple bptz-based polymers are versatile precursors to a diverse range of novel functional materials.

Dual drug conjugated nanoparticle for simultaneous targeting of mitochondria and nucleus in cancer cells

Effective targeting of mitochondria has emerged as an alternative strategy in cancer chemotherapy. However, considering mitochondria's crucial role in cellular energetics, metabolism and signaling, targeting mitochondria with small molecules would lead to severe side effects in cancer patients. Moreover, mitochondrial functions are highly dependent on other cellular organelles like nucleus. Hence, simultaneous targeting of mitochondria and nucleus could lead to more effective anticancer strategy. To achieve this goal, we have developed sub 200 nm particles from dual drug conjugates derived from direct tethering of mitochondria damaging drug (α- tocopheryl succinate) and nucleus damaging drugs (cisplatin, doxorubicin and paclitaxel). These dual drug conjugated nanoparticles were internalized into the acidic lysosomal compartments of the HeLa cervical cancer cells through endocytosis and induced apoptosis through cell cycle arrest. These nanoparticles damaged mitochondrial morphology and triggered the release of cytochrome c. Furthermore, these nanoparticles target nucleus to induce DNA damage, fragment the nuclear morphology and damage the cytoskeletal protein tubulin. Therefore, these dual drug conjugated nanoparticles can be successfully used as a platform technology for simultaneous targeting of multiple subcellular organelles in cancer cells to improve the therapeutic efficacy of the free drugs.

Glutathione- and pH-responsive nonporous silica prodrug nanoparticles for controlled release and cancer therapy

A myriad of drug delivery systems such as liposomes, micelles, polymers and inorganic nanoparticles (NPs) have been developed for cancer therapy. Very few of them, however, have the ability to integrate multiple functionalities such as specific delivery, high circulation stability, controllable release and good biocompatibility and biodegradability in a single system to improve the therapeutic efficacy. Herein, we report two types of stimuli-responsive nonporous silica prodrug NPs towards this goal for controlled release of anticancer drugs and efficient combinatorial cancer therapy. As a proof of concept, anticancer drugs camptothecin (CPT) and doxorubicin (DOX) were covalently encapsulated into silica matrices through glutathione (GSH)-responsive disulfide and pH-responsive hydrazone bonds, respectively, resulting in NPs with sizes tunable in the range of 50-200 nm. Both silica prodrug NPs showed stimuli-responsive controlled release upon exposure to a GSH-rich or acidic environment, resulting in improved anticancer efficacy. Notably, two prodrug NPs simultaneously taken up by HeLa cells showed a remarkable combinatorial efficacy compared to free drug pairs. These results suggest that the stimuli-responsive silica prodrug NPs are promising anticancer drug carriers for efficient cancer therapy.

Size and rigidity of cylindrical polymer brushes dictate long circulating properties in vivo

Studies of spherical nanoengineered drug delivery systems have suggested that particle size and mechanical properties are key determinants of in vivo behavior; however, for more complex structures, detailed analysis of correlations between in vitro characterization and in vivo disposition is lacking. Anisotropic materials in particular bear unknowns in terms of size tolerances for in vivo clearance and the impact of shape and rigidity. Herein, we employed cylindrical polymer brushes (CPBs) to answer questions related to the impact of size, length and rigidity on the in vivo behavior of PEGylated anisotropic structures, in particular their pharmacokinetics and biodistribution. The modular grafting assembly of CPBs allowed for the systematic tailoring of parameters such as aspect ratio or rigidity while keeping the overall chemical composition the same. CPBs with altered length were produced from polyinitiator backbones with different degrees of polymerization. The side chain grafts consisted of a random copolymer of poly[(ethylene glycol) methyl ether methacrylate] (PEGMA) and poly(glycidyl methacrylate) (PGMA), and rendered the CPBs water-soluble. The epoxy groups of PGMA were subsequently reacted with propargylamine to introduce alkyne groups, which in turn were used to attach radiolabels via copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC). Radiolabeling allowed the pharmacokinetics of intravenously injected CPBs to be followed as well as their deposition into major organs post dosing to rats. To alter the rigidity of the CPBs, core-shell-structured CPBs with polycaprolactone (PCL) as a water-insoluble and crystalline core and PEGMA-co-PGMA as the hydrophilic shell were synthesized. This modular buildup of CPBs allowed their shape and rigidity to be altered, which in turn could be used to influence the in vivo circulation behavior of these anisotropic polymer particles. Increasing the aspect ratio or altering the rigidity of the CPBs led to reduced exposure, higher clearance rates, and increased mononuclear phagocytic system (MPS) organ deposition.

"Triple-punch" strategy for triple negative breast cancer therapy with minimized drug dosage and improved antitumor efficacy

Effective therapeutics against triple negative breast cancer (TNBC), which has no standard-of-care therapy, needs to be developed urgently. Here we demonstrated a strategy of integrating indocyanine green (ICG), paclitaxel (PTX), and survivin siRNA into one thermosensitive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate)-co-2-(dimethylamino)ethyl methacrylate-b-poly(D,L-lactide-co-glycolide) (P (MEO2MA-co-OEGMA-co-DMAEMA)-b-PLGA) nanoparticle (NP-IPS) for triple-punch strategy against TNBC. The NP-IPS significantly enhanced the stability of ICG. Controlled release of the PTX in tumor regions was triggered by the hyperthermia produced by laser irradiated ICG. The NP-IPS exhibited remarkable antitumor efficacy (almost complete ablation of the tumor xenografts) due to the combinational effects of chemotherapy, photothermal therapy, and gene therapy with low drug dose (ICG, 0.32 μmol/kg; PTX, 0.54 μmol/kg; siRNA, 1.5 mg/kg) and minimal side effects. Taken together, our current study demonstrates a nanoplatform for triple-therapy, which reveals a promising strategy for TNBC treatment.

Intelligent Nanoparticles for Advanced Drug Delivery in Cancer Treatment

Treatment of cancer using nanoparticle-based approaches relies on the rational design of carriers with respect to size, charge, and surface properties. Polymer-based nanomaterials, inorganic materials such as gold, iron oxide, and silica as well as carbon based materials such as carbon nanotubes and graphene are being explored extensively for cancer therapy. The challenges associated with the delivery of these nanoparticles depend greatly on the type of cancer and stage of development. This review highlights design considerations to develop nanoparticle-based approaches for overcoming physiological hurdles in cancer treatment, as well as emerging research in engineering advanced delivery systems for the treatment of primary, metastatic, and multidrug resistant cancers. A growing understanding of cancer biology will continue to foster development of intelligent nanoparticle-based therapeutics that take into account diverse physiological contexts of changing disease states to improve treatment outcomes.

Ring-opening polymerization of prodrugs: a versatile approach to prepare well-defined drug-loaded nanoparticles

The synthesis of polymer-drug conjugates from prodrug monomers consisting of a cyclic polymerizable group that is appended to a drug through a cleavable linker is achieved by organocatalyzed ring-opening polymerization. The monomers polymerize into well-defined polymer prodrugs that are designed to self-assemble into nanoparticles and release the drug in response to a physiologically relevant stimulus. This method is compatible with structurally diverse drugs and allows different drugs to be copolymerized with quantitative conversion of the monomers. The drug loading can be controlled by adjusting the monomer(s)/initiator feed ratio and drug release can be encoded into the polymer by the choice of linker. Initiating these monomers from a poly(ethylene glycol) macroinitiator results in amphiphilic diblock copolymers that spontaneously self-assemble into micelles with a long plasma circulation, which is useful for systemic therapy.

Multi-drug delivery nanocarriers for combination therapy

The main focus of this review is to discuss recent advances in nanoparticle-based multi-drug delivery platforms towards combination therapy.

Recent advances towards the fabrication and biomedical applications of responsive polymeric assemblies and nanoparticle hybrid superstructures

We highlight recent developments, microstructural control, and biomedical applications of stimuli-responsive polymeric assemblies and responsive hybrid superstructures.

Self-delivery nanoparticles from an amphiphilic covalent drug couple of irinotecan and bendamustine for cancer combination chemotherapy

We demonstrate an approach to prepare an anticancer drug self-delivery system from an amphiphilic covalent drug couple (Ir–Bd) for cancer combination chemotherapy.

Degradable cross-linked polymer vesicles for the efficient delivery of platinum drugs

Nontoxic and acid-degradable polymer vesicles were synthesized as drug carriers. In vitro dose–response cytotoxicity studies suggested that the drug-loaded polymer vesicles were more efficient in delivering cis-platin into cancer cells compared to the internalization of the free drug.

Well-defined diblock brush polymer–drug conjugates for sustained delivery of paclitaxel

The synthesis, characterization and property studies of paclitaxel (PTXL)-containing brush polymer–drug conjugates (BPDCs) are presented and the influence of grafting structures of BPDCs on their assembly behaviour, drug release profile and therapeutic effects is discussed in this article.

A degradable brush polymer–drug conjugate for pH-responsive release of doxorubicin

We report the synthesis, characterization andin vitroassessment of a degradable brush polymer–drug conjugate which can enable acid-triggered release of doxorubicin (DOX).

Computational tool for risk assessment of nanomaterials: novel QSTR-perturbation model for simultaneous prediction of ecotoxicity and cytotoxicity of uncoated and coated nanoparticles under multiple experimental conditions

Nanomaterials have revolutionized modern science and technology due to their multiple applications in engineering, physics, chemistry, and biomedicine. Nevertheless, the use and manipulation of nanoparticles (NPs) can bring serious damages to living organisms and their ecosystems. For this reason, ecotoxicity and cytotoxicity assays are of special interest in order to determine the potential harmful effects of NPs. Processes based on ecotoxicity and cytotoxicity tests can significantly consume time and financial resources. In this sense, alternative approaches such as quantitative structure-activity/toxicity relationships (QSAR/QSTR) modeling have provided important insights for the better understanding of the biological behavior of NPs that may be responsible for causing toxicity. Until now, QSAR/QSTR models have predicted ecotoxicity or cytotoxicity separately against only one organism (bioindicator species or cell line) and have not reported information regarding the quantitative influence of characteristics other than composition or size. In this work, we developed a unified QSTR-perturbation model to simultaneously probe ecotoxicity and cytotoxicity of NPs under different experimental conditions, including diverse measures of toxicities, multiple biological targets, compositions, sizes and conditions to measure those sizes, shapes, times during which the biological targets were exposed to NPs, and coating agents. The model was created from 36488 cases (NP-NP pairs) and exhibited accuracies higher than 98% in both training and prediction sets. The model was used to predict toxicities of several NPs that were not included in the original data set. The results of the predictions suggest that the present QSTR-perturbation model can be employed as a highly promising tool for the fast and efficient assessment of ecotoxicity and cytotoxicity of NPs.

Advances in combination therapies based on nanoparticles for efficacious cancer treatment: an analytical report

The main objective of nanomedicine research is the development of nanoparticles as drug delivery systems or drugs per se to tackle diseases as cancer, which are a leading cause of death with developed nations. Targeted treatments against solid tumors generally lead to dramatic regressions, but, unfortunately, the responses are often short-lived due to resistant cancer cells. In addition, one of the major challenges of combination drug therapy (called "cocktail") is the crucial optimization of different drug parameters. This issue can be solved using combination nanotherapy. Nanoparticles developed in oncology based on combination nanotherapy are either (a) those designed to combat multidrug resistance or (b) those used to circumvent resistance to clinical cancer drugs. This review provides an overview of the different nanoparticles currently used in clinical treatments in oncology. We analyze in detail the development of combinatorial nanoparticles including dendrimers for dual drug delivery via two strategic approaches: (a) use of chemotherapeutics and chemosensitizers to combat multidrug resistance and (b) use of multiple cytotoxic drugs. Finally, in this review, we discuss the challenges, clinical outlook, and perspectives of the nanoparticle-based combination therapy in cancer.

Redox-responsive branched-bottlebrush polymers for in vivo MRI and fluorescence imaging

Stimuli-responsive multimodality imaging agents have broad potential in medical diagnostics. Herein, we report the development of a new class of branched-bottlebrush polymer dual-modality organic radical contrast agents--ORCAFluors--for combined magnetic resonance and near-infrared fluorescence imaging in vivo. These nitroxide radical-based nanostructures have longitudinal and transverse relaxation times that are on par with commonly used heavy-metal-based magnetic resonance imaging (MRI) contrast agents. Furthermore, these materials display a unique compensatory redox response: fluorescence is partially quenched by surrounding nitroxides in the native state; exposure to ascorbate or ascorbate/glutathione leads to nitroxide reduction and a concomitant 2- to 3.5-fold increase in fluorescence emission. This behaviour enables correlation of MRI contrast, fluorescence intensity and spin concentration with tissues known to possess high concentrations of ascorbate in mice. Our in vitro and in vivo results, along with our modular synthetic approach, make ORCAFluors a promising new platform for multimodality molecular imaging.

Synthesis of Acid-Labile PEG and PEG-Doxorubicin-Conjugate Nanoparticles via Brush-First ROMP

A panel of acid-labile bis-norbornene cross-linkers was synthesized and evaluated for the formation of acid-degradable brush-arm star polymers (BASPs) via the brush-first ring-opening metathesis polymerization (ROMP) method. An acetal-based cross-linker was identified that, when employed in conjunction with a poly(ethylene glycol) (PEG) macromonomer, provided highly controlled BASP formation reactions. A combination of this new cross-linker with a novel doxorubicin (DOX)-branch-PEG macromonomer provided BASPs that simultaneously degrade and release cytotoxic DOX in vitro.