Carriers For Protein Delivery Research Articles

Dual-responsive nanocarriers for efficient cytosolic protein delivery and CRISPR-Cas9 gene therapy of inflammatory skin disorders.

Developing protein drugs that can target intracellular sites remains a challenge due to their inadequate membrane permeability. Efficient carriers for cytosolic protein delivery are required for protein-based drugs, cancer vaccines, and CRISPR-Cas9 gene therapies. Here, we report a screening process to identify highly efficient materials for cytosolic protein delivery from a library of dual-functionalized polymers bearing both boronate and lipoic acid moieties. Both ligands were found to be crucial for protein binding, endosomal escape, and intracellular protein release. Polymers with higher grafting ratios exhibit remarkable efficacies in cytosolic protein delivery including enzymes, monoclonal antibodies, and Cas9 ribonucleoprotein while preserving their activity. Optimal polymer successfully delivered Cas9 ribonucleoprotein targeting NLRP3 to disrupt NLRP3 inflammasomes in vivo and ameliorate inflammation in a mouse model of psoriasis. Our study presents a promising option for the discovery of highly efficient materials tailored for cytosolic delivery of specific proteins and complexes such as Cas9 ribonucleoprotein.

Tough, self-healing and injectable dynamic nanocomposite hydrogel based on gelatin and sodium alginate

Biomacromolecules based injectable and self-healing hydrogels possessing high mechanical properties have widespread potential in biomedical field. However, dynamic features are usually inversely proportional to toughness. It is challenging to simultaneously endow these properties to the dynamic hydrogels. Here, we fabricated an injectable nanocomposite hydrogel (CS-NPs@OSA-l-Gtn) stimultaneously possessing excellent autonomous self-healing performance and high mechanical strength by doping chitosan nanoparticles (CS-NPs) into dynamic polymer networks of oxidized sodium alginate (OSA) and gelatin (Gtn) in the presence of borax. The synergistic effect of the multiple reversible interactions combining dynamic covalent bonds (i.e., imine bond and borate ester bond) and noncovalent interactions (i.e., electrostatic interaction and hydrogen bond) provide effective energy dissipation to endure high fatigue resistance and cyclic loading. The dynamic hydrogel exhibited excellent mechanical properties like maximum 2.43 MPa compressive strength, 493.91 % fracture strain, and 89.54 kJ/m3 toughness. Moreover, the integrated hydrogel after injection and self-healing could withstand 150 successive compressive cycles. Besides, the bovine serum albumin embedded in CS-NPs could be sustainably released from the nanocomposite hydrogel for 12 days. This study proposes a novel strategy to synthesize an injectable and self-healing hydrogel combined with excellent mechanical properties for designing high-strength natural carriers with sustained protein delivery.

Polyelectrolyte nanoparticles based on poly[N-(2-hydroxypropyl)methacrylamide-block-poly(N-(3-aminopropyl)methacrylamide] copolymers for delivery of heparin-binding proteins

In addition to the delivery of therapeutic nucleic acids and low-molecular weight drugs, polyelectrolyte nanoparticles (NPs) have recently been studied as carriers for protein delivery. However, the stability of NPs during isolation steps, which ensures their easy redispersion, needs to be solved empirically for individual systems using cryoprotectants and stabilizers. To avoid the use of additives, we studied the formation of polyelectrolyte NPs consisting of a newly synthesized polycationic diblock copolymer based on poly(N-(2-hydroxypropyl)methacrylamide)-block-poly(N-(3-aminopropyl)methacrylamide) (p(HPMA-b-APMA) and heparin (Hep). The p(APMA) blocks electrostatically complexed with Hep, and the p(HPMA) blocks formed a neutral corona of NPs, limiting NP aggregation. Self-assembly was monitored through the changes in size and zeta potential of the formed NPs, which depended on the copolymer composition and the concentration of polyelectrolyte solutions. The interactions between the NP components were analysed by FTIR spectroscopy, and XPS analysis indicated the presence of p(HPMA) blocks on the surface of the NPs. The encapsulation of the model chemokine CXCL12 and basic fibroblast growth factor (FGF-2) was driven by their specific bioaffinity for Hep, resulting in a high 90 % entrapment efficiency and increased protein stability. CXCL12 was released over 48 h, while FGF-2 exhibited a sustained release of up to 38 % over four weeks. In addition, the released CXCL12 effectively stimulated the migration of macrophages and T-lymphocyte cells, indicating the preserved protein bioactivity. Considering the proven noncytotoxic performance of the NPs towards fibroblasts and mesenchymal stem cells, the polyelectrolyte NPs of p(HPMA-b-APMA) and Hep loaded with heparin-binding proteins can be considered as promising candidates for the controlled delivery of bioactive proteins in biomedical applications.

Efficient intracellular and in vivo delivery of toxin proteins by a ROS-responsive polymer for cancer therapy.

Rational design of efficient cytosolic protein delivery carriers holds enormous promise for biotherapeutics development. Several delivery systems have been developed during the past decades, while tailoring the balance between extracellular protein binding and intracellular cargo release is still challenging. In this study, we synthesized a series of oxygen-sensitive reactive polymers, rich in boron, by radical polymerization and post-modification for cytosolic protein delivery in vitro and in vivo. The introduction of boronate building blocks into the polymer scaffold significantly enhanced its protein binding affinity, and the polymer/protein complexes with high stability were obtained by tailoring the molecular ratios between the boronate ligands and the amine groups. The lead material screened from the polymer library exhibited efficient protein delivery efficacy that can release cargo proteins in cytosol in a reactive oxygen species responsive manner, which enables intracellular delivery of proteins with maintained bioactivity. In addition, the polymer-based nanoformulations efficiently delivered saporin, a toxin protein, into osteosarcoma cells and tumor tissues, and exhibited high therapeutic efficacy in an osteosarcoma mouse model. The synthesized polymer in this study can be developed as a promising nanocarrier for cytosolic delivery of protein therapeutics to treat a variety of diseases.

Calcination-free nanoarchitectonics of mesoporous conducting polymer@silica hybrids with ultra-large pores and their enhanced protein adsorption capacity

The nanohybrids of mesoporous conducting polymer@silica with ultra-large pore size are successfully in-situ synthesised from 3,4-propylenedioxythiophene (ProDOT) derived cationic surfactant and silica precursor assisted by co-solvent n-butanol at high temperature without any template removal process. The ultra-large mesopores pores are created in the nanohybrids without calcination step through an integrated approach of simple polymerisation and rearrangement of the conducting and hydrophobic monomeric unit, ProDOT unit followed by the pore swelling with the co-solvent and high-temperature hydrothermal treatment. By controlling the hydrothermal temperature and the amount of co-solvent, the pore size can be expanded from 11.6 nm to 27 nm. The prepared nanohybrid with ultra large pores exhibits a high adsorption capacity for large-sized protein (bovine serum albumin, BSA), and the adsorption capacity can be controlled with the adjustment of the pore size. The adsorption capacity of a nanohybrid with 27 nm is 166 mg/g, which is almost twice that of a nanohybrid with 11.6 nm (75 mg/g). The mesoporous conducting polymer@silica nanohybrids can be applied as a carrier for protein delivery or the support for enzymatic catalysis or biosensors.

ROS-responsive polypeptides for intracellular protein delivery and CRISPR/Cas9 gene editing

Protein therapeutics have emerged as a rapidly growing class of medicine in recent years due to the high potency and specificity. However, protein drugs acting on intracellular targets are currently unavailable due to their membrane impermeability. There is a great demand to develop efficient carriers for intracellular protein delivery. Here, we reported a reactive oxygen species responsive material based on biodegradable polypeptide for this purpose. Boronate moieties were decorated on polypeptides via a p-hydroxybenzylcarbamate self-immolative spacer. The modified polypeptide could catch cargo proteins via ionic interaction and nitrogen/boronate coordination to form uniform nanoparticles, and efficiently release the bound proteins under hydrogen peroxide (H2O2) through the oxidation of boronate ligands. The lead polymer efficiently delivered diverse cargo proteins enter living cells and retained their protein activity. In addition, it efficiently transported Cas9 ribonucleoprotein (RNP) into cells for CRISPR/Cas9 gene editing and achieved liver repair against acetaminophen (APAP)-induced liver injury in mice. The results provided a facile strategy to construct efficient, responsive and biodegradable polymers for cytosolic protein delivery.

Transdermal Delivery of Antigenic Protein Using Ionic Liquid-Based Nanocarriers for Tumor Immunotherapy.

Transdermal drug delivery systems (TDDSs) may be useful for preventing various diseases including cancer. However, the stratum corneum (SC) inhibits the permeation of foreign particles into the skin. To obtain an effective TDDS, we developed a protein-containing nanocarrier (PCNC) comprising an antigenic protein (ovalbumin/OVA) stabilized by a combination of surfactants, i.e., a lipid-based surface-active ionic liquid and Tween-80. The PCNC was lyophilized to remove water and cyclohexane and then dispersed in isopropyl myristate. It is biocompatible both in vitro and in vivo, and is suitable for use in a therapeutic TDDS. The skin permeability of the PCNC was significantly (p < 0.0001) enhanced, and the transdermal distribution and transdermal flux of the OVA delivery system were 25 and 28 times greater, respectively, than those of its aqueous formulation. The PCNC disrupted the order of lipid orientation in the skin's SC and increased intercellular protein delivery. It demonstrated effective antitumor activity, drastically (p < 0.001) suppressed tumor growth, increased mouse survival rates, and significantly (p < 0.001) stimulated the OVA-specific tumor immune response. The PCNC also increased the number of cytotoxic T cells expressing CD8 antibodies on their surfaces (CD8 + T-cells) in the tumor microenvironment. These findings suggest that PCNCs may be promising biocompatible carriers for transdermal antigenic protein delivery in tumor immunotherapy.

Controlled synthesis of PEGylated polyelectrolyte nanogels as efficient protein carriers

Designing rational carriers for protein encapsulation and delivery is of great interest in a wide range of applications. Herein, we develop a type of PEGylated polyelectrolyte nanogel that enables efficient protein loading, protection and intracellular delivery. Our design relies on a one pot process involving cooperative electrostatic assembly and polymerization, which constructs polyion complex (PIC) micelles containing cross-linked cationic PDMAEMA network associated with anionic PAA. Further removing PAA chains leads to core–shell nanogels with a cationic network surrounded by poly (ethylene glycol) (PEG) blocks. The established strategy allows to fabricate well-defined nanogels with regulated size and swelling ability depending on pH, salt concentration and cross-link degree. More notably, the abundant positive charges and the thermo-response of PDMAEMA network realize sufficient encapsulation and protection of BSA proteins, while the PEG blocks endow appreciable biocompatibility and successful intracellular protein delivery. Our study establishes a facile and robust approach for preparing core–shell polyelectrolyte nanogels with regulated size and properties, as well as prominent capabilities for protein encapsulation and delivery.

A Preparation Technique of Fine S/O/W Emulsions for Protein Delivery Formed with Solid Fat.

The improvement in the stability of solid-in-oil-in-water (S/O/W) emulsions, which are used as carriers for protein delivery, was investigated. For this purpose, emulsions were prepared using trimyristin, a solid fat, as the oil phase, and using the membrane emulsification and solvent evaporation methods. The samples were made into stable fine emulsions using polyvinyl alcohol, a hydrophilic polymer, as an emulsifier, and by controlling the particle size uniformly. The S/O/W emulsions prepared by this method showed almost no leakage of encapsulated proteins and exhibited controlled release in an intestinal environment.

PH-Sensitive Polymer-Based Carriers as a Useful Approach for Oral Delivery of Therapeutic Protein: A Review.

There are many proteins and enzymes in the human body, and their dysfunction can lead to the emergence of a disease. The use of proteins as a drug is common in various diseases such as diabetes. Proteins are hydrophilic molecules whose spatial structure is critical to their correct function. There are different ways for the administration of proteins. Protein structures are degraded by gastric acid and enzymes in the gastrointestinal tract and have a slight ability to permeate from the gastrointestinal epithelium due to their large hydrophilic nature. Therefore, their oral use has limitations. Since the oral route for the administration of drugs is one of the best and easiest routes for patients, many studies have been done to increase the stability, penetration, and ultimately, the bioavailability of proteins through oral administration. One of the studied strategies for oral delivery of protein is the use of pH-sensitive polymer-based carriers. These carriers use different pH-sensitive polymers, such as eudragit®, chitosan, dextran, and alginate. The use of pH-sensitive polymer- based carriers by protecting the protein from stomach acid (low pH) and degrading enzymes, increasing permeability and maintaining the spatial structure of the protein, leads to increased bioavailability. In this review, we focus on the various polymers used to prepare pH-sensitive polymer- based carriers for the oral delivery of proteins.

Preparation of Chitosan Nanoparticles as a Capable Carrier for Antigen Delivery and Antibody Production.

Background: Chitosan (CS) nanoparticles have attracted considerable attention as a non-viral and cationic carrier for delivery of therapeutic proteins and antigens and offer non-invasive routes of administration such as oral, nasal and ocular routes, and also show adjuvant characteristics for vaccines. Objectives: Preparation and formulation of CS nanoparticles as a capable carrier with immunoadjuvant properties to enhance the bioavailability of antigen and produce antibody with high affinity.Materials and Methods: CS nanoparticles were produced by ionic gelation process of sodium tripolyphosphate (TPP) with CS. Particle size and morphology of nanoparticles were determined using Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) and also direct observation under light microscope. The influence of the initial BSA concentration and CS concentration on loading efficiency and release behavior was evaluated. The ε-toxin (derived from Clostridium perfringens type D) was loaded on CS nanoparticles and the complex was injected hypodermically into the rabbits for once. The anti ε-toxin antibody level in blood serum was evaluated using Dot Blot and ELISA methods.Results: The CS nanoparticles in different groups have a particle diameter (Z-average) in approximate ranges of 200-400, 300-600, 450-800 nm and a positive Zeta potential (32.4 - 48.6 mv). Optimum loading efficiency was achieved for CS at a concentration of 0.5 mg.mL-1 and TPP of 1.0 mg.mL-1. The results showed that the toxin-CS complex produces antitoxin at levels more than twice as high the control. Conclusion: The CS nanoparticles can be used as a good biodegradable carrier for protein and antigen delivery.

All-Peptide-Based Polyion Complex Vesicles: Facile Preparation and Encapsulation of the Protein in Active Form.

The polyion complex vesicle (PICsome) is a promising platform for bioactive molecule delivery as well as nanoreactor systems. In addition to anionic and cationic charged blocks, a hydrophilic poly(ethylene glycol) (PEG) block is mostly employed for PICsome formation; however, the long-term safety of the PEG component in vivo is yet to be clarified. In this study, we developed novel PEG-free PICsome comprising all peptide components. Instead of the PEG block, we selected the sarcosine (Sar) oligomer as a hydrophilic block and fused it with anionic oligo(l-glutamic acid). Mixing the Sar-containing anionic peptide with cationic oligo(l-lysine) resulted in the formation of stable vesicles. The peptide-based PICsome was able to encapsulate a model protein in its hollow structure. After modification of the surface with a cell-penetrating peptide, the protein-encapsulated PICsome was successfully delivered into plant cells, indicating its promised for application as a biocompatible carrier for protein delivery.

Enhancing the Solubility and Transdermal Delivery of Drugs Using Ionic Liquid‐In‐Oil Microemulsions

AbstractThe development of hydrophobic drug and protein delivery carriers remains a challenge. To synthesize L‐(‐)‐carnitine‐based ionic liquid (IL), this study applies the density functional theory to investigate the hydrogen bonds and van der Waals force that govern L‐(‐)‐carnitine‐based IL formation. An ionic liquid‐in‐oil microemulsion (IL/O ME) is then developed to facilitate the transdermal delivery of proteins and increase the solubility of drugs. IL/O ME is prepared using isopropyl myristate (IPM), Tween 80/Span 20, and L‐(‐)‐carnitine‐based IL. The skin permeation studies conducted using mouse skin show that the insulin permeation percentage of the developed IL/O ME is 3.55 folds higher than that of phosphate‐buffered saline and 2.91 folds better than that of a hydrophilic L‐(‐)‐carnitine‐based IL. In addition, the solubility of two drug molecules, that is, rosiglitazone and bezafibrate, in IL/O ME is at least 49.28 folds higher than their solubility in water or IPM. Therefore, IL/O ME can significantly improve the solubility of drugs and increase the permeability of proteins (e.g., insulin), thus demonstrating a promising potential as a delivery carrier.

Development of an M cell targeted nanocomposite system for effective oral protein delivery: preparation, in vitro and in vivo characterization

BackgroundThere is a strong need for non-invasive and patient-friendly delivery systems of protein drugs for long-term therapy. However, oral delivery of protein drugs is a big challenge due to many barriers including instability in the gastrointestinal (GI) tract and low permeability. To overcome the absorption barriers in GI tract and improve the patient compliance, this study aimed to develop an M cell targeted-nanocomposite delivery system of protein drugs.ResultsAn aminoclay-protein core complex (AC-Ins) was prepared by using insulin as a model protein and then sequentially coated with Ulex europaeus agglutinin 1 (UEA-1) for M-cell targeting and the pH sensitive polymer, Eudragit® L100 (EUAC-Ins). All nanoparticles were obtained with a high entrapment efficiency (> 90%) and their structural characteristics were confirmed by Fourier transform-infrared spectroscopy, energy dispersive X-ray spectroscopy, and circular dichroism. Among the developed nanoparticles, EUAC-Ins effectively suppressed drug release at pH 1.2, while rapidly released drugs at pH 6.8 due to dissolution of the outer coating layer. The conformational stability of insulin entrapped in EUAC-Ins was well maintained in the presence of proteolytic enzymes. Compared to free insulin, EUAC-Ins increased the membrane transport of insulin by 4.4-fold in M cells. In parallel, oral administration of EUAC-Ins in mice enhanced insulin uptake by 4.1-fold in the intestinal Peyer’s patches and 2.6-fold in intestinal epithelium tissues with normal villi, compared to free insulin. Orally administered EUAC-Ins decreased significantly the blood glucose level in diabetic mice, while the effect of oral insulin solution was negligible.ConclusionAn M cell targeted-ternary nanocomposite system obtained by dual coating of the aminoclay-protein core complex with UEA-1 and a pH dependent polymer is promising as an effective oral protein delivery carrier.

Co-delivery of proteins and small molecule drugs for mitochondria-targeted combination therapy.

Herein, we report the first use of gluthathione (GSH)-responsive nanogel-based carriers for mitochondria-targeted delivery of functional proteins and antibodies. We further demonstrated the successful co-encapsulation of a protein and small molecule (RNase A/Doxorubicin) in dual-cargo nanocapsules for mitochondria-targeted combination therapy.

Preparation and Evaluation of 6-Maleimidohexanoic Acid Grafted Chitosan Nanoparticles as a Novel Carrier for Intranasal Protein Delivery

In this study, 6-maleimidohexanoic acid grafted chitosan nanoparticles (MHA-CS NPs) were prepared and evaluated the efficiency of intranasal protein delivery as compared with well-known chitosan nanoparticles (CS NPs). Fluorescein isothiocyanate labelled with bovine serum albumin (FITC-BSA) was used as a model protein. The results indicated that both CS NPs and MHA-CS NPs were positively charged NPs before and after protein loading. The condition for optimal protein loading was 1:6 mass ratio of protein/NPs at 1 h incubation period. The optimal formulations of CS NPs and MHA-CS NPs were evaluated on porcine mucosa as ex vivo. The mucoadhesive and permeation properties of FITC-BSA loaded MHA-CS NPs showed a greater than FITC-BSA loaded CS NPs and FITC-BSA solution, respectively. These ex vivo studies present the potential of MHA-CS NPs as a novel carrier for intranasal protein delivery that will be a candidate for in vivo study.

Nanoporous Microsponge Particles (NMP) of Polysaccharides as Universal Carriers for Biomolecules Delivery.

Different polysaccharides—namely dextran, carboxymethyl dextran, alginate, and hyaluronic acid—were compared for the synthesis of nanoporous microsponges particles (NMPs) obtained from a one-pot self-precipitation/cross-linking process. The morphologies and sizes of the NMPs were evaluated comparatively with respect to polymer-to-polymer and cross-linker solvents (water-based vs. DMSO). We found that the radial distribution of the polymer in the near-spherical NMPs was found to peak either at the core or in the corona of the particle, depending both on the specific polymer or the solvent used for the formation of NMPs. The NMP porosity and the swelling capability were evaluated via scanning electron microscopy (SEM). The degradation study indicated that after 10 h incubation with a reducing agent, approximately 80% of the NMPs were disassembled into soluble polysaccharide chains. The adsorption and release capacity of each type of NMP were evaluated using fluorescently labeled bovine serum albumin and lysozyme as model proteins, highlighting a release time typically much longer than the corresponding adsorption time. The dependence of the adsorption-release performance on pH was demonstrated as well. Confocal microscopy images allowed us to probe the different distribution of labeled proteins inside the NMP. The safety and non-cytotoxicity of NMPs were evaluated after incubation with fibroblast 3T3 cells and showed that all types of NMPs did not adversely affect the cell viability for concentrations up to 2.25 μg/mL and an exposure time up to 120 h. Confocal microscopy imaging revealed also the effective interaction between NMPs and fibroblast 3T3 cells. Overall, this study describes a rapid, versatile, and facile approach for preparing a universal non-toxic, nanoporous carrier for protein delivery under physiological conditions.

Antimicrobial pH-sensitive protein carrier based on modified xanthan gum

Proteins have poor absorption efficiency through the gastrointestinal (GI) tract due to their physical and chemical instabilities and short half-life. The aim of the present study was to encapsulate bovine serum albumin (BSA) protein in an efficient potentially biodegradable pH-sensitive carrier based on crosslinked xanthan gum-g-poly (N-vinyl imidazole) for delivery in the intestines. The structure of crosslinked grafts was characterized with different analysis techniques: FTIR, XRD, TGA and FE-SEM/EDX. BSA uptake and release from loaded grafts were performed in two different pH media, acidic (pH 1.2) and slightly alkaline (pH 7.4) solutions, imitating the simulated gastric and intestinal pH, respectively, within various time intervals at body temperature (37 °C). The results showed that the swelling rate and the accumulative BSA release % were faster in pH 7.4 medium than in pH 1.2 medium. The BSA release results revealed that BSA release mechanism in both media followed non-Fickian release. The structural integrity of released BSA was elucidated with SDS-PAGE analysis and the obtained data confirmed that BSA was released without any deformation in its structure. Cytotoxicity of crosslinked grafts was studied against normal cell line by neutral red uptake assay test and the obtained results showed that the prepared grafted carriers possesses good biocompatibility and considered as safe carriers for protein delivery. In addition, investigation of their antimicrobial activities against Aspergillus niger and Staphylococcus aureus confirmed that they can be used as antimicrobial protein carriers to transfer the proteins through GI tract.

Tailoring guanidyl-rich polymers for efficient cytosolic protein delivery

Cytosolic protein delivery is important for the development of protein therapeutics towards intracellular targets. Guanidyl polymers exhibit high binding affinity with cargo proteins, and thus were designed as carriers for intracellular protein delivery. However, the structure-activity relationship and mechanism of these polymers in cytosolic protein delivery remained to be investigated. In this study, we synthesized a total number of eighteen guanidyl-rich polymers by grafting various guanidyl containing compounds onto a polyethylenimine scaffold. The investigated guanidyl analogues were consisted of a guanidyl group and a hydrophobic component including cyclohexane, benzene, and alkanes with various chain lengths. It is surprising that only the polymers with both benzene and guanidyl possessed high efficiency in cytosolic protein delivery. Further results showed that all the synthesized polymers have efficient protein binding in water and high cellular uptake, but these polymers except the benzene-guanidyl based one enter the cytosol of cells without carrying their cargo proteins, suggesting poor stability of the polymer/protein complexes in culture medium. Paired guanidinium-π interactions between the ligands on benzene-guanidyl polymers are critical to the stabilization of polymer/protein complexes. In addition, a lead polymer in the library exhibited robust delivery efficacy to various cargo proteins, while maintaining their bioactivity after cell internalization. The results suggest that complex stability is a critical factor in polymer-mediated intracellular protein delivery systems, and provide new insights to guide design of polymeric protein vehicles.

Poly(L-Glutamic Acid)-Based Brush Copolymers: Fabrication, Self-assembly, and Evaluation as Efficient Nanocarriers for Cationic Protein Drug Delivery.

Protein drugs were considered to be the first choice to treat many human diseases, but their clinical application was usually limited by their short half-life and lack of validated targeted therapy. Here, a series of folate-functionalized poly(ethylene glycol)-b-(poly(2-aminoethyl-L-glutamate)-g-poly(L-glutamic acid))s (FA-PEG-b-(PELG-g-PLGA)s) were designed as tumor-targeted carriers for cationic protein delivery. Compared with traditional copolymers consisting of PEG and linear charged hydrophilic blocks, FA-PEG-b-(PELG-g-PLGA) with brush-like polyelectrolyte segments were beneficial to improving their electrostatic interactions with loading protein molecules, thus increasing drug-loading stability and protecting encapsulated proteins from degradation. The designed polymer brushes could efficiently encapsulate cytochrome C (CytC), a cationic model protein, to form polyion complex (PIC) micelles with an average particle size of approximately 200nm. An in vitro drug release study showed that the drug-loading stability of the formed PIC micelles was largely improved. The functionalization of the block copolymer carriers with a targeting folate group enhanced the tumor cell growth inhibition and total apoptotic rates induced by CytC. Our results shed light on the unique advantages of brush-like polymer carriers in delivering cationic proteins, and the poly(L-glutamic acid)-based linear-brush diblock copolymers could be applied as a versatile delivery platform for molecular targeting in cancer therapy.