A polymeric nanocarrier with a tumor acidity-activatable arginine-rich (R9) peptide for enhanced drug delivery

Advanced Biomaterials Derived from Functional Polyphosphoesters: Synthesis, Properties, and Biomedical Applications

Polyphosphoesters (PPEs) represent an innovative class of biodegradable polymers, with the phosphate ester serving as the core repeating unit of their polymeric backbone. Recently, biomaterials derived from functionalized PPEs have garnered significant interest in biomedical applications because of their commendable biocompatibility, biodegradability, and the capacity for functional modification. This review commences with a brief overview of synthesis methodologies and the distinctive properties of PPEs, including thermoresponsiveness, degradability, stealth effect, and biocompatibility. Subsequently, the review delves into the latest applications of PPEs-based nanocarriers for drug or gene delivery and PPEs-based polymeric prodrugs and scaffolds in the biomedical field, presenting several illustrative examples for each application. By encapsulating the advancements of recent years, this review aims to offer an enhanced understanding and serve as a reference for the synthesis and biomedical applications of functional PPEs.

Peptide-based non-viral gene delivery: A comprehensive review of the advances and challenges

Gene therapy is the most effective treatment option for diseases, but its effectiveness is affected by the choice and design of gene carriers. The genes themselves have to pass through multiple barriers in order to enter the cell and therefore require additional vectors to carry them inside the cell. In gene therapy, peptides have unique properties and potential as gene carriers, which can effectively deliver genes into specific cells or tissues, protect genes from degradation, improve gene transfection efficiency, and enhance gene targeting and biological responsiveness. This paper reviews the research progress of peptides and their derivatives in the field of gene delivery recently, describes the obstacles encountered by foreign materials to enter the interior of the cell, and introduces the following classes of functional peptides that can carry materials into the interior of the cell, and assist in transmembrane translocation of carriers, thus breaking through endosomal traps to enable successful entry of genetic materials into the nucleus of the cell. The paper also discusses the combined application of peptide vectors with other vectors to enhance its transfection ability, explores current challenges encountered by peptide vectors, and looks forward to future developments in the field.

Cell-Penetrating and Enzyme-Responsive Peptides for Targeted Cancer Therapy: Role of Arginine Residue Length on Cell Penetration and In Vivo Systemic Toxicity

For the improved delivery of cancer therapeutics and imaging agents, the conjugation of cell-penetrating peptides (CPPs) increases the cellular uptake and water solubility of agents. Among the various CPPs, arginine-rich peptides have been the most widely used. Combining CPPs with enzyme-responsive peptides presents an innovative strategy to target specific intracellular enzymes in cancer cells and when combined with the appropriate click chemistry can enhance theranostic drug delivery through the formation of intracellular self-assembled nanostructures. However, one drawback of CPPs is their high positive charge which can cause nonspecific binding, leading to off-target accumulation and potential toxicity. Hence, balancing cell-specific penetration, toxicity, and biocompatibility is essential for future clinical efficacy. We synthesized six cancer-specific, legumain-responsive RnAANCK peptides containing one to six arginine residues, with legumain being an asparaginyl endopeptidase that is overexpressed in aggressive prostate tumors. When conjugated to Alexa Fluor 488, R1-R6AANCK peptides exhibited a concentration- and time-dependent cell penetration in prostate cancer cells, which was higher for peptides with higher R values, reaching a plateau after approximately 120 min. Highly aggressive DU145 prostate tumor cells, but not less aggressive LNCaP cells, self-assembled nanoparticles in the cytosol after the cleavage of the legumain-specific peptide. The in vivo biocompatibility was assessed in mice after the intravenous injection of R1-R6AANCK peptides, with concentrations ranging from 0.0125 to 0.4 mmol/kg. The higher arginine content in R4-6 peptides showed blood and urine indicators for the impairment of bone marrow, liver, and kidney function in a dose-dependent manner, with instant hemolysis and morbidity in extreme cases. These findings underscore the importance of designing peptides with the optimal arginine residue length for a proper balance of cell-specific penetration, toxicity, and in vivo biocompatibility.

Multi-Functional Polymer Nanoparticles with Enhanced Adipocyte Uptake and Adipocytolytic Efficacy

Multi-functional polymer nanoparticles have been widely utilized to improve cellular uptake and enhance therapeutic efficacy. In this study, it is hypothesized that the cellular uptake of poly(D,L-lactide-co-glycolide) (PLG) nanoparticles loaded with calcium carbonate minerals into adipocytes can be improved by covalent modification with nona-arginine (R9 ) peptide. It is further hypothesized that the internalization mechanism of R9 -modified PLG nanoparticles by adipocytes may be contingent on the concentration of R9 peptide present in the nanoparticles. R9 -modified PLG nanoparticles followed the direct penetration mechanism when the concentration of R9 peptide in the nanoparticles reached 38 µM. Notably, macropinocytosis is the major endocytic mechanism when the R9 peptide concentration is ≤ 26 µM. The endocytic uptake of the nanoparticles effectively generated carbon dioxide gas at an endosomal pH, resulting in significant adipocytolytic effects in vitro, which are further supported by the findings in an obese mouse model induced by high-fat diet. Gas-generating PLG nanoparticles, modified with R9 peptide, demonstrated localized reduction of adipose tissue (reduction of 13.1%) after subcutaneous injection without significant side effects. These findings highlight the potential of multi-functional polymer nanoparticles for the development of effective and targeted fat reduction techniques, addressing both health and cosmetic considerations.

Fabrication of a new photoluminescent and pH-responsive nanocomposite based on a hyperbranched polymer prepared from amino acid for targeted drug delivery applications

In this study, the Fe₃O₄ nanoparticles were encapsulated in the hyperbranched poly _L-lysine citramid (HBPLC). The Fe₃O₄-HBPLC nanocomposite modified with _L-arginine and quantum dots (QDs) to obtain Fe₃O₄-HBPLC-Arg/QDs as a new photoluminescent and magnetic nanocarrier for the pH-responsive release and targeted delivery of Doxorubicin (DOX). The prepared magnetic nanocarrier was fully characterized using different techniques. Its various potential as a magnetic nanocarrier was evaluated. The in-vitro drug release studies exhibited that the prepared nanocomposite has pH-responsive behavior. The antioxidant study revealed good antioxidant properties of the nanocarrier. Also, the nanocomposite revealed excellent photoluminescence with a quantum yield of 48.5 %. Cellular uptake studies showed that Fe₃O₄-HBPLC-Arg/QD has high cell uptake in MCF-7 cells and can be used for bioimaging applications. In-vitro cytotoxicity, colloidal stability, and enzymatic degradability studies revealed that the prepared nanocarrier is non-toxic (with cell viability of 94%), stabile and biodegradable (about 37%). The nanocarrier was hemocompatible with 8% hemolysis. Also, according to the apoptosis and MTT assays, the Fe₃O₄-HBPLC-Arg/QD-DOX induced greater toxicity and cellular apoptosis against breast cancer cells about 47.0 %.

One New Acid-Activated Hybrid Anticancer Peptide by Coupling with a Desirable pH-Sensitive Anionic Partner Peptide

Anticancer peptides (ACPs) are promising antitumor resources, and developing acid-activated ACPs as more effective and selective antitumor drugs would represent new progress in cancer therapy. In this study, we designed a new class of acid-activated hybrid peptides LK-LE by altering the charge shielding position of the anionic binding partner LE based on the cationic ACP LK and investigated their pH response, cytotoxic activity, and serum stability, in hoping to achieve a desirable acid-activatable ACP. As expected, the obtained hybrid peptides could be activated and exhibit a remarkable antitumor activity by rapid membrane disruption at acidic pH, whereas its killing activity could be alleviated at normal pH, showing a significant pH response compared with LK. Importantly, this study found that the peptide LK-LE3 with the charge shielding in the N-terminal of LK displayed notably low cytotoxicity and more stability, demonstrating that the position of charge masking is extremely important for the improvement of peptide toxicity and stability. In short, our work opens a new avenue to design promising acid-activated ACPs as potential targeting agents for cancer treatment.

Membrane Internalization Mechanisms and Design Strategies of Arginine-Rich Cell-Penetrating Peptides

Cell-penetrating peptides (CPPs) have been discovered to deliver chemical drugs, nucleic acids, and macromolecules to permeate cell membranes, creating a novel route for exogenous substances to enter cells. Up until now, various sequence structures and fundamental action mechanisms of CPPs have been established. Among them, arginine-rich peptides with unique cell penetration properties have attracted substantial scientific attention. Due to the positively charged essential amino acids of the arginine-rich peptides, they can interact with negatively charged drug molecules and cell membranes through non-covalent interaction, including electrostatic interactions. Significantly, the sequence design and the penetrating mechanisms are critical. In this brief synopsis, we summarize the transmembrane processes and mechanisms of arginine-rich peptides; and outline the relationship between the function of arginine-rich peptides and the number of arginine residues, arginine optical isomers, primary sequence, secondary and ternary structures, etc. Taking advantage of the penetration ability, biomedical applications of arginine-rich peptides have been refreshed, including drug/RNA delivery systems, biosensors, and blood-brain barrier (BBB) penetration. Understanding the membrane internalization mechanisms and design strategies of CPPs will expand their potential applications in clinical trials.

Construction of Folate-Conjugated and pH-Responsive Cell Membrane Mimetic Mixed Micelles for Desirable DOX Release and Enhanced Tumor-Cellular Target

Smart multifunctional polymeric micelles are in urgent demand for future cancer diagnosis and therapy. In this paper, doxorubicin (DOX)-loaded folic acid (FA)-targeting and pH-responsive cell membrane mimetic mixed micelles of P(DMAEMA-co-MaPCL) (PCD) and FA-P(MPC-co-MaPCL) (PMCF) (mass ratio 5/5) were prepared by a dialysis method. The micelle size, morphology, X-ray powder diffraction (XRD), pH responsiveness, in vitro DOX release, cytotoxicity, and cellular uptake were studied in detail. The results indicated that DOX could be efficiently loaded into mixed micelles (PDMCF micelles), and the DOX-loaded mixed micelles (DOX@PDMCF micelles) exhibited a size of 150 nm and pH-responsive DOX release in an extended period. Furthermore, the DOX@PDMCF micelles could efficiently suppress the proliferation of tumor cells, HeLa and MCF-7 cells. Our data suggest that the DOX@PDMCF micelles have the potential to be applied in tumor therapy, especially for treating various folate receptor overexpressed tumors.

Phosphorylcholine zwitterionic shell-detachable mixed micelles for enhanced cancerous cellular uptakes and increased DOX release

To further enhance the cancerous cellular uptakes and increase the drug release of the drug loaded micelles, herein, we fabricated a series of mixed micelles with different mass ratios using two amphiphilic copolymers P(DMAEMA-co-MaPCL) and PCL-SS-PMPC. The mixed micelles showed a prolonged circulation time due to the zwitterionic shells in a physiological environment (pH 7.4). In addition, because of the protonation of tertiary amine groups in PDMAEMA and the breakage of the disulfide bond in PMPC-SS-PCL in a tumor microenvironment, the mixed micelles aggregated, which led to enhanced cancerous cellular penetration and increased DOX release. Moreover, cytotoxicity assay showed that the mixed micelles had good biocompatibility to L929, HeLa and MCF-7 cells, even at a concentration of up to 1 mg mL^-1. Furthermore, enhanced antitumour activity and cellular uptake of HeLa and MCF-7 cells were detected after loading with DOX, which was determined by confocal laser scanning microscopy (CLSM) and flow cytometry (FC), especially for the DOX@MIX 3 micelles (20% mass ratio of the P(DMAEMA-co-MaPCL)). Therefore, the mixed strategy provides a simple and efficient ways to promote anticancer drug delivery.

Autophagy responsive intra-intercellular delivery nanoparticles for effective deep solid tumor penetration

Deep tumor cells (cells in the center of solid tumors) play a crucial role in drug tolerance, metastasis, recurrence and microenvironment immune suppression. However, their deep location endows them with an untouched abdomen and makes them refractory to current treatments. Herein, we exploited the characteristic of higher autophagy in deep tumor cells than in superficial tumor cells and designed autophagy-responsive multifunctional nanoparticles (PGN) to enhance drug accumulation in deep tumor cells. PGNs were prepared by densely coating poly (lactic-co-glycolic acid) (PLGA) with cationic autophagy-responsive cell-penetrating peptide (GR9) and anionic 2,3-dimethylmaleic anhydride (DMA)-modified DSPE-PEG. The suitable nanoparticle size (122.4 nm) and charge-neutral surface (0.21 mV) of the NPs enabled long blood circulation. The hydrolysis of surface-anchored anionic DMA in the acidic microenvironment led to the exposure of the GR9 peptide and enhance tumor penetration. Once the PGN arrived in deep tumor cells with strong autophagy, GR9 was cut off by an autophagy shear enzyme, and the nanoparticles remained in the cells to undergo degradation. Furthermore, we prepared docetaxel (DTX) and chloroquine (CQ) loaded d-PGN. CQ inhibits autophagosome fusion with lysosomes, resulting in autophagosome accumulation, which further enhances the sensitivity of d-PGN to autophagy and their deep tumor retention. In vivo experiments showed that drug-loaded d-PGN achieved excellent antitumor efficacy with a peak inhibition rate of 82.1%. In conclusion, autophagy-responsive multifunctional nanoparticles provide a novel potential strategy for solid tumor treatment.

Recent advances in polymeric core-shell nanocarriers for targeted delivery of chemotherapeutic drugs

The treatment effect of chemotherapeutics is often impeded by nonspecific biodistribution and limited biocompatibility. Polymeric core-shell nanocarriers (PCS NCs) composed of a polymer core and at least one shell have been widely applied for cancer therapy and have shown great potential in selectively delivering chemotherapeutic drugs to tumor sites. These PCS NCs can effectively ameliorate the delivery efficiency and therapeutic index of anticarcinogens by prolonging drug residence in the bloodstream, enhancing tumor tissue drug penetration, facilitating cellular drug uptake, controlling the spatiotemporal release of payloads, or codelivering two or more bioactive agents. This review summarizes recently published literature on using PCS NCs to transport chemotherapeutic drugs with poor aqueous solubility and discusses their design principles, structural features, functional properties, and potential limitations.

Nuclear delivery of dual anti-cancer drugs by molecular self-assembly

Nanomedicines generally suffer from poor accumulation in tumor cells, low anti-tumor efficacy, and drug resistance. In order to address these problems, we introduced a novel nanomedicine based on dual anti-cancer drugs, which showed good cell nuclear accumulation properties. The novel nanomedicine consisted of three components: (1) dual anti-cancer drugs, 10-hydroxycamptothecin (HCPT) and chlorambucil (CRB), whose targets are located in the cell nucleus, (2) a nuclear localizing dodecapeptide, PMI peptide (TSFAEYWNLLSP), which could activate p53 by binding with MDM2 and MDMX located in the cell nucleus, and (3) an efficient self-assembling tripeptide FFY. Our nanomedicine exhibited enhanced cellular uptake and nuclear accumulation properties, thus achieving an excellent anti-cancer capacity both in vitro and in vivo. Our study will provide an inspiration for the development of novel multifunctional nanomaterials for cancer diagnosis and therapy.

An effective polymeric nanocarrier that allows for active targeting and selective drug delivery in cell coculture systems

In this manuscript, we report the development of a versatile, robust, and stable targeting nanocarrier for active delivery. This nanocarrier is based on bifunctionalized polymeric nanoparticles conjugated to a monoclonal antibody that allows for active targeting of either (i) a fluorophore for tracking or (ii) a drug for monitoring specific cell responses. This nanodevice can efficiently discriminate between cells in coculture based on the expression levels of cell surface receptors. As a proof of concept, we have demonstrated efficient delivery using a broadly established cell surface receptor as the target, the epidermal growth factor receptor (EGFR), which is overexpressed in several types of cancers. Additionally, a second validation of this nanodevice was successfully carried out using another cell surface receptor as the target, the cluster of differentiation 147 (CD147). Our results suggest that this versatile nanocarrier can be expanded to other cell receptors and bioactive cargoes, offering remarkable discrimination efficiency between cells with different expression levels of a specific marker. This work supports the ability of nanoplatforms to boost and improve the progress towards personalized medicine.

Dual Peptide-Modified Nanoparticles Improve Combination Chemotherapy of Etoposide and siPIK3CA Against Drug-Resistant Small Cell Lung Carcinoma

Small cell lung carcinoma (SCLC) is a highly aggressive form of malignancy with rapid recurrence and poor prognosis. The dual peptide-modified nanoparticles (NPs) for improving chemotherapy against drug-resistant small cell lung carcinoma cells has been developed. In this study, the SCLC targeting ligand, antagonist G peptide (AG), and cell-penetrating peptide, TAT, modified NPs were used to encapsulate both anticancer drugs etoposide (ETP) and PIK3CA small-interfering RNA (siPIK3CA). The ETP@NPs and siRNA@NPs had particle size 201.0 ± 1.9-206.5 ± 0.7 nm and 155.3 ± 12.4-169.1 ± 11.2 nm, respectively. The lyophilized ETP@NPs and siRNA@NPs maintained their particle size and zeta potential during 28-day storage without severe aggregation or dissociation. Either ETP@NPs or siRNA@NPs significantly reduced the IC₅₀ of drugs by 2.5-5.5 folds and 2.4-3.9 folds, respectively, as compared to free ETP and siRNA/PEI nanocomplex in drug-resistant CD133(+) H69 cells. Herein, the IC₅₀ of dual-peptide modified ETP@NPs and siRNA@NPs were prominently lower than single-peptide modified NPs. The synergistic effect (CI < 1) was further observed in co-treatment of ETP and siPIK3CA particularly delivered by dual-peptide modified NPs.

A cascade dual-targeted nanocarrier for enhanced alectinib delivery to ALK-positive lung cancer

A polymeric nanocarrier with a cascade of magnetic and TAT targeting enhanced the therapeutic efficacy of alectinib towards ALK-positive lung cancer.