Hydrophobic Cysteine Poly(disulfide)-based Redox-Hypersensitive Nanoparticle Platform for Cancer Theranostics

Polymer-drug and polymer-protein conjugated nanocarriers: Design, drug delivery, imaging, therapy, and clinical applications

Polymer-drug conjugates and polymer-protein conjugates have been pivotal in the realm of drug delivery systems for over half a century. These polymeric drugs are characterized by the conjugation of therapeutic molecules or functional moieties to polymers, enabling a range of benefits including extended circulation times, targeted delivery, controlled release, and decreased immunogenicity. This review delves into recent advancements and challenges in the clinical translations and preclinical studies of polymer-drug conjugates and polymer-protein conjugates. The design principles and functionalization strategies crucial for the development of these polymeric drugs were explored followed by the review of structural properties and characteristics of various polymer carriers. This review also identifies significant obstacles in the clinical translation of polymer-drug conjugates and provides insights into the directions for their future development. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Optimized DOX Drug Deliveries via Chitosan-Mediated Nanoparticles and Stimuli Responses in Cancer Chemotherapy: A Review

Chitosan nanoparticles (NPs) serve as useful multidrug delivery carriers in cancer chemotherapy. Chitosan has considerable potential in drug delivery systems (DDSs) for targeting tumor cells. Doxorubicin (DOX) has limited application due to its resistance and lack of specificity. Chitosan NPs have been used for DOX delivery because of their biocompatibility, biodegradability, drug encapsulation efficiency, and target specificity. In this review, various types of chitosan derivatives are discussed in DDSs to enhance the effectiveness of cancer treatments. Modified chitosan-DOX NP drug deliveries with other compounds also increase the penetration and efficiency of DOX against tumor cells. We also highlight the endogenous stimuli (pH, redox, enzyme) and exogenous stimuli (light, magnetic, ultrasound), and their positive effect on DOX drug delivery via chitosan NPs. Our study sheds light on the importance of chitosan NPs for DOX drug delivery in cancer treatment and may inspire the development of more effective approaches for cancer chemotherapy.

Smart Nanomaterials in Cancer Theranostics: Challenges and Opportunities

Cancer is ranked as the second leading cause of death globally. Traditional cancer therapies including chemotherapy are flawed, with off-target and on-target toxicities on the normal cells, requiring newer strategies to improve cell selective targeting. The application of nanomaterial has been extensively studied and explored as chemical biology tools in cancer theranostics. It shows greater applications toward stability, biocompatibility, and increased cell permeability, resulting in precise targeting, and mitigating the shortcomings of traditional cancer therapies. The nanoplatform offers an exciting opportunity to gain targeting strategies and multifunctionality. The advent of nanotechnology, in particular the development of smart nanomaterials, has transformed cancer diagnosis and treatment. The large surface area of nanoparticles is enough to encapsulate many molecules and the ability to functionalize with various biosubstrates such as DNA, RNA, aptamers, and antibodies, which helps in theranostic action. Comparatively, biologically derived nanomaterials perceive advantages over the nanomaterials produced by conventional methods in terms of economy, ease of production, and reduced toxicity. The present review summarizes various techniques in cancer theranostics and emphasizes the applications of smart nanomaterials (such as organic nanoparticles (NPs), inorganic NPs, and carbon-based NPs). We also critically discussed the advantages and challenges impeding their translation in cancer treatment and diagnostic applications. This review concludes that the use of smart nanomaterials could significantly improve cancer theranostics and will facilitate new dimensions for tumor detection and therapy.

Influence of the Topology of Poly(L-Cysteine) on the Self-Assembly, Encapsulation and Release Profile of Doxorubicin on Dual-Responsive Hybrid Polypeptides

Τhe synthesis of a series of novel hybrid block copolypeptides based on poly(ethylene oxide) (PEO), poly(l-histidine) (PHis) and poly(l-cysteine) (PCys) is presented. The synthesis of the terpolymers was achieved through a ring-opening polymerization (ROP) of the corresponding protected N-carboxy anhydrides of Nim-Trityl-l-histidine and S-tert-butyl-l-cysteine, using an end-amine-functionalized poly(ethylene oxide) (mPEO-NH2) as macroinitiator, followed by the deprotection of the polypeptidic blocks. The topology of PCys was either the middle block, the end block or was randomly distributed along the PHis chain. These amphiphilic hybrid copolypeptides assemble in aqueous media to form micellar structures, comprised of an outer hydrophilic corona of PEO chains, and a pH- and redox-responsive hydrophobic layer based on PHis and PCys. Due to the presence of the thiol groups of PCys, a crosslinking process was achieved further stabilizing the nanoparticles (NPs) formed. Dynamic light scattering (DLS), static light scattering (SLS) and transmission electron microscopy (TEM) were utilized to obtain the structure of the NPs. Moreover, the pH and redox responsiveness in the presence of the reductive tripeptide of glutathione (GSH) was investigated at the empty as well as the loaded NPs. The ability of the synthesized polymers to mimic natural proteins was examined by Circular Dichroism (CD), while the study of zeta potential revealed the "stealth" properties of NPs. The anticancer drug doxorubicin (DOX) was efficiently encapsulated in the hydrophobic core of the nanostructures and released under pH and redox conditions that simulate the healthy and cancer tissue environment. It was found that the topology of PCys significantly altered the structure as well as the release profile of the NPs. Finally, in vitro cytotoxicity assay of the DOX-loaded NPs against three different breast cancer cell lines showed that the nanocarriers exhibited similar or slightly better activity as compared to the free drug, rendering these novel NPs very promising materials for drug delivery applications.

Biodegradable disulfide crosslinked chitosan/stearic acid nanoparticles for dual drug delivery for colorectal cancer

Herein, redox responsive chitosan/stearic acid nanoparticles (CSSA NPs) (≈200 nm) are developed for dual drug delivery. These degradable nanoparticles are prepared based on disulfide (SS) crosslinking chemistry avoiding the use of any external crosslinking agent. CSSA NPs are further loaded with both DOX (hydrophilic) and curcumin (hydrophobic) drugs with ≈86 % and ≈82 % encapsulation efficiency respectively. This approach of combining anticancer therapeutics having different mode of anticancer action allows to develop systems for cancer therapy with enhanced efficacy. In vitro drug release experiments clearly exhibit the low leakage of drug under physiological conditions while ≈98 % DOX and ≈96 % curcumin is released after 136 h under GSH reducing conditions. The cytotoxicity experiments against HCT116 cells demonstrate higher cytotoxicity of dual drug loaded CSSA NPs. In vivo biodistribution experiments with c57bl/6j mice confirms the retention of CSSA NPs in the colon area up to 24 h exhibiting their potential for colorectal cancer therapy.

Targeted Delivery of Chemo-Sonodynamic Therapy via Brain Targeting, Glutathione-Consumable Polymeric Nanoparticles for Effective Brain Cancer Treatment

Glioblastoma (GBM) is the most aggressive tumor of the central nervous system and remains universally lethal due to lack of effective treatment options and their inefficient delivery to the brain. Here the development of multifunctional polymeric nanoparticles (NPs) for effective treatment of GBM is reported. The NPs are synthesized using a novel glutathione (GSH)-reactive poly (2,2″-thiodiethylene 3,3″-dithiodipropionate) (PTD) polymer and engineered for brain penetration through neutrophil elastase-triggered shrinkability, iRGD-mediated targeted delivery, and lexiscan-induced autocatalysis. It is found that the resulting lexiscan-loaded, iRGD-conjugated, shrinkable PTD NPs, or LiPTD NPs, efficiently penetrate brain tumors with high specificity after intravenous administration. Furthermore, it is demonstrated that LiPTD NPs are capable of efficient encapsulation and delivery of chemotherapy doxorubicin and sonosensitizer chlorin e6 to achieve combined chemotherapy and sonodynamic therapy (SDT). It is demonstrated that the capability of GSH depletion of LiPTD NPs further augments the tumor cell killing effect triggered by SDT. As a result, treatment with LiPTD NPs effectively inhibits tumor growth and prolongs the survival of tumor-bearing mice. This study may suggest a potential new approach for effective GBM treatment.

Intrinsically fluorescent polyureas toward conformation-assisted metamorphosis, discoloration and intracellular drug delivery

Peptidomimetic polymers have attracted increasing interest because of the advantages of facile synthesis, high molecular tunability, resistance to degradation, and low immunogenicity. However, the presence of non-native linkages compromises their ability to form higher ordered structures and protein-inspired functions. Here we report a class of amino acid-constructed polyureas with molecular weight- and solvent-dependent helical and sheet-like conformations as well as green fluorescent protein-mimic autofluorescence with aggregation-induced emission characteristics. The copolymers self-assemble into vesicles and nanotubes and exhibit H-bonding-mediated metamorphosis and discoloration behaviors. We show that these polymeric vehicles with ultrahigh stability, superfast responsivity and conformation-assisted cell internalization efficiency could act as an “on-off” switchable nanocarrier for specific intracellular drug delivery and effective cancer theranosis in vitro and in vivo. This work provides insights into the folding and hierarchical assembly of biomacromolecules, and a new generation of bioresponsive polymers and nonconventional luminescent aliphatic materials for diverse applications.

Biomimetic materials are of interest but can often suffer from limitations caused by the non-native linkages used. Here, the authors report on the creation of amino acid constructed polyureas which can self-assemble into vesicles and nanotubes with aggregation induced fluorescence and the potential for drug delivery applications.

Responsive polyprodrug for anticancer nanocarriers

Nanocarriers responsive to glutathione (GSH), a molecule overexpressed in cancer cells, are extensively investigated for the delivery of Pt-based chemotherapeutics for cancer treatment.

In vivo metabolizable branched poly(ester amide) based on inositol and amino acids as a drug nanocarrier for cancer therapy

Amino acid-based poly(ester amide) (PEA) has been utilized for various biomedical applications due to its tunable mechanical properties, good biocompatibility, and biodegradability. However, bioactive components have rarely been incorporated into the PEA structure, and there has been no systematic investigation of amino acid-based PEAs with branched structures. Herein, an in vivo metabolizable branched poly(ester amide) (BPEA) was synthesized from inositol (a natural growth factor) and amino acids for drug delivery in cancer therapy. The bioactive components, inositol, arginine, and phenylalanine, could improve the biocompatibility of the BPEA nanocarrier, and convert into other valuable biomolecules (phosphatidylinositol for cell signaling, functional protein, or other amino acids including ornithine, citrulline, and tyrosine) after accomplishing drug delivery and biodegradation. Paclitaxel (PTX) was encapsulated into BPEA nanocarriers to formulate drug-loaded BPEA nanoparticles (BPEA@PTX NPs). In vitro results indicated that BPEA@PTX NPs had a sub 100 nm size and could effectively inhibit the growth and migration of cancer cells. In vivo experiments further demonstrated significant suppression of tumor size compared with that with free PTX. Both in vitro and in vivo results confirmed the superior biosafety of BPEA, indicating that BPEA exhibits excellent biocompatibility and considerable potential as a drug carrier.

Polymeric nanoparticles for RNA delivery

As exemplified by recent clinical approval of RNA drugs including the latest COVID-19 mRNA vaccines, RNA therapy has demonstrated great promise as an emerging medicine. Central to the success of RNA therapy is the delivery of RNA molecules into the right cells at the right location. While the clinical success of nanotechnology in RNA therapy has been limited to lipid-based nanoparticles currently, polymers, due to their tunability and robustness, have also evolved as a class of promising material for the delivery of various therapeutics including RNAs. This article overviews different types of polymers used in RNA delivery and the methods for the formulation of polymeric nanoparticles and highlights recent progress of polymeric nanoparticle-based RNA therapy.

Cellular- and Subcellular-Targeted Delivery Using a Simple All-in-One Polymeric Nanoassembly

Nanocarrier-mediated drug delivery is a promising strategy to maximize the power of chemotherapy and minimize side effects. However, current approaches show insufficient drug-loading capacity and inefficient drug release, and require complex modification processes. Attempts to enhance one of these features often compromise other merits. We describe here a block copolymer assembly system that combines desirable characteristics. The design of self-immolative and crosslinkable hydrophobic moieties offer stable and high encapsulation. Redox-triggerable polymer self-immolation promotes drug release by switching the hydrophobic core into completely hydrophilic chains. The reactive amine handles, presented on their surface, allow "plug to direct" modification with targeting ligands. Functionalized nanoassemblies have been programmed to target specific subcellular compartments. The simplicity, versatility, and efficacy of the system open up possibilities for an all-in-one delivery system.

Diselenide-crosslinked zwitterionic nanogels with dual redox-labile properties for controlled drug release

We developed a diselenide-crosslinked zwitterionic nanogel based on poly(2-methacryloyloxyethyl phosphorylcholine), which has sensitive dual redox-degradability and high colloidal stability.

Porphyrin Nanocage-Embedded Single-Molecular Nanoparticles for Cancer Nanotheranostics

Single molecular nanoparticles (SMNPs) integrating imaging and therapeutic capabilities exhibit unparalleled advantages in cancer theranostics, ranging from excellent biocompatibility, high stability, prolonged blood lifetime to abundant tumor accumulation. Herein, we synthesize a sophisticated porphyrin nanocage that is further functionalized with twelve polyethylene glycol arms to prepare SMNPs (porSMNPs). The porphyrin nanocage embedded in porSMNPs can be utilized as a theranostic platform. PET imaging allows dynamic observation of the bio-distribution of porSMNPs, confirming their excellent circulation time and preferential accumulation at the tumor site, which is attributed to the enhanced permeability and retention effect. Moreover, the cage structure significantly promotes the photosensitizing effect of porSMNs by inhibiting the π-π stacking interactions of the photosensitizers, ablating of the tumors without relapse by taking advantage of photodynamic therapy.

Macrotheranostic Probe with Disease-Activated Near-Infrared Fluorescence, Photoacoustic, and Photothermal Signals for Imaging-Guided Therapy

Theranostics provides opportunities for precision cancer therapy. However, theranostic probes that simultaneously turn on their diagnostic signal and pharmacological action only in respond to a targeted biomarker have been less exploited. We herein report the synthesis of a macrotheranostic probe that specifically activates its near-infrared fluorescence (NIRF), photoacoustic (PA), and photothermal signals in the presence of a cancer-overexpressed enzyme for imaging-guided cancer therapy. Superior to the small-molecule counterpart probe, the macrotheranostic probe has ideal biodistribution and renal clearance, permitting passive targeting of tumors, in situ activation of multimodal signals, and effective photothermal ablation. Our study thus provides a macromolecular approach towards activatable multimodal phototheranostics.

pH triggered re-assembly of nanosphere to nanofiber: The role of peptide conformational change for enhanced cancer therapy

pH-triggered conformational change and subsequent re-assembly of nanostructures provide a new strategy in nanomedicine for controlled drug release and enhanced therapy. Here, we reported the development of a novel pH-responsive nano-assembly as a drug carrier from peptide amphiphile (PA) consisting of mimicking peptide and stearic acid moieties. The mimicking peptide is a basic 17-amino acid peptide derived from antennapedia homeodomain, and undergoes a conformational transition of the secondary structure from β-sheet at pH7.4 to α-helix at pH5.0. Such transition therefore leads to simultaneous evolution of the self-assembled structure of PA from nanosphere to nanofiber, promotes assemblies retention and then release drugs in the cytoplasm of tumor cell. In vitro studies showed that the doxorubicin (Dox)-loaded PA nanoparticle (PA@Dox) could be uptaken efficiently by the cell due to the membrane penetrating capability of the mimicking peptide and subsequently the released Dox further induce apoptosis of murine colon carcinoma CT26 (MCCC) cell. In a mouse xenograft model of MCCC, administration of PA@Dox via lateral tail vein injection could remarkably retard the tumor growth. The overall results suggested that the PA-based nanocarriers adopting the novel strategy of pH-triggered secondary structural change could enhance therapeutic efficacy and be used as a promising platform for potential development of new generation of drug carriers for cancer therapy.

Glutathione-responsive paclitaxel dimer nanovesicles with high drug content

Paclitaxel dimers containing mono thioether linkers can self-assemble into hollow nanovesicles that exhibit comparable cytotoxicity to Taxol.

Micelles with Sheddable Dendritic Polyglycerol Sulfate Shells Show Extraordinary Tumor Targetability and Chemotherapy in Vivo

Cancer nanomedicines are typically stealthed by a poly(ethylene glycol) layer that is important to obtain extended blood circulation and elevated tumor accumulation. PEG stealth, however, also leads to poor tumor cell selectivity and uptake thereby reducing treatment efficacy. Here, we report that biodegradable micelles with sheddable dendritic polyglycerol sulfate (dPGS) shells show an unusual tumor targetability and chemotherapy in vivo. The self-assembly of dPGS-SS-poly(ε-caprolactone) amphiphilic block copolymer with an M_n of 4.8-3.7 kg mol^-1 affords negatively charged and small sized micelles (dPGS-SS-PCL Ms). dPGS-SS-PCL Ms reveal a low cytotoxicity, decent doxorubicin (DOX) loading, and accelerated drug release under a reductive condition. Notably, DOX-loaded dPGS-SS-PCL Ms exhibit a high tolerable dosage of more than 40 mg kg^-1, a long plasma half-life of ca. 2.8 h, and an extraordinary tumor accumulation. Intriguingly, therapeutic results demonstrate that DOX-loaded dPGS-SS-PCL Ms induce complete tumor suppression, significantly improved survival rate, and diminishing adverse effects as compared to free drug (DOX·HCl) in MCF-7 human mammary carcinoma models. Dendritic polyglycerol sulfate with a superior tumor homing ability appears to be an attractive alternative to PEG in formulating targeted cancer nanomedicines.

Facile preparation of hybrid core-shell nanorods for photothermal and radiation combined therapy

The hybrid platinum@iron oxide core-shell nanorods with high biocompatibility were synthesized and applied for combined therapy. These hybrid nanorods exhibit a good photothermal effect on cancer cells upon irradiation with a NIR laser. Furthermore, due to the presence of a high atomic number element (platinum core), the hybrid nanorods show a synergistic effect between photothermal and radiation therapy. Therefore, the as-prepared core-shell nanorods could play an important role in facilitating synergistic therapy between photothermal and radiation therapy to achieve better therapeutic efficacy.

Polymer-based nanoparticles for protein delivery: design, strategies and applications

Therapeutic proteins have attracted significant attention as they perform vital roles in various biological processes. Polymeric nanoparticles can offer not only physical protection from environmental stimuli but also targeted delivery of such proteins to specific sites, enhancing their therapeutic efficacy.

Long-term and oxidative-responsive alginate–deferoxamine conjugates with a low toxicity for iron overload

Long-term and oxidative-responsive alginate–deferoxamine conjugates.