Protein Delivery System Containing a Nickel-Immobilized Polymer for Multimerization of Affinity-Purified His-Tagged Proteins Enhances Cytosolic Transfer

Rational design of diblock copolymer enables efficient cytosolic protein delivery

Polymer-mediated cytosolic protein delivery demonstrates a promising strategy for the development of protein therapeutics. Here, we propose a new designed diblock copolymer which realizes efficient cytosolic protein delivery both in vitro and in vivo. The polymer contains one protein-binding block composed of phenylboronic acid (PBA) and N-(3-dimethylaminopropyl) (DMAP) pendant units for protein binding and endosomal escape, respectively, followed by the response to ATP enriched in the cytosol which triggers the protein release. The other block is PEG designed to improve particle size control and circulation in vivo. By optimizing the block composition, sequence and length of the copolymer, the optimal one (BP20) was identified with the binding block containing 20 units of both PBA and DMAP, randomly distributed along the chain. When mixed with proteins, the BP20 forms stable nanoparticles and mediates efficient cytosolic delivery of a wide range of proteins including enzymes, toxic proteins and CRISPR/Cas9 ribonucleoproteins (RNP), to various cell lines. The PEG block, especially when further modified with folic acid (FA), enables tumor-targeted delivery of Saporin in vivo, which significantly suppresses the tumor growth. Our results shall inspire the design of novel polymeric vehicles with robust capability for cytosolic protein delivery, which holds great potential for both biological research and therapeutic applications.

Cysteine-independent CRISPR-Associated Protein Labeling for Presentation and Co-delivery of Molecules Toward Genetic and Epigenetic Regulations

Labeling of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) associated proteins (Cas) remains an immense challenge for their genome engineering applications. To date, cysteine-mediated bioconjugation is the most efficient strategy for labeling Cas proteins. However, introducing a cysteine residue in the protein at the right place might be challenging without perturbing the enzymatic activity. We report a method that does not require cysteine residues for small molecule presentation on the CRISPR-associated protein SpCas9 for in vitro protein detection, probing cellular protein expression, and nuclear co-delivery of molecules in mammalian cells. We repurposed a simple protein purification tag His6 peptide for non-covalent labeling of molecules on the CRISPR enzyme SpCas9. The small molecule labeling enabled us to rapidly detect SpCas9 in a biochemical assay. We demonstrate that small molecule labeling can be utilized for probing bacterial protein expression in realtime. Furthermore, we coupled SpCas9's nuclear-targeting ability in co-delivering the presenting small molecules to the mammalian cell nucleus for prospective genome engineering applications. Furthermore, we demonstrate that the method can be generalized to label oligonucleotides for multiplexing CRISPR-based genome editing and template-mediated DNA repair applications. This work paves the way for genomic loci-specific bioactive small molecule and oligonucleotide co-delivery toward genetic and epigenetic regulations.

Intracellular Protein Delivery: Approaches, Challenges, and Clinical Applications

Protein biologics are powerful therapeutic agents with diverse inhibitory and enzymatic functions. However, their clinical use has been limited to extracellular applications due to their inability to cross plasma membranes. Overcoming this physiological barrier would unlock the potential of protein drugs for the treatment of many intractable diseases. In this review, we highlight progress made toward achieving cytosolic delivery of recombinant proteins. We start by first considering intracellular protein delivery as a drug modality compared to existing Food and Drug Administration-approved drug modalities. Then, we summarize strategies that have been reported to achieve protein internalization. These techniques can be broadly classified into 3 categories: physical methods, direct protein engineering, and nanocarrier-mediated delivery. Finally, we highlight existing challenges for cytosolic protein delivery and offer an outlook for future advances.

Guanidine-modified albumin-MMAE conjugates with enhanced endocytosis ability

Aiming to address the insufficient endocytosis ability of traditional albumin drug conjugates, this paper reports elegant guanidine modification to improve efficacy for the first time. A series of modified albumin drug conjugates were designed and synthesized with different structures, including guanidine (GA), biguanides (BGA) and phenyl (BA), and different quantities of modifications. Then, the endocytosis ability and in vitro/vivo potency of albumin drug conjugates were systematically studied. Finally, a preferred conjugate A4 was screened, which contained 15 BGA modifications. Conjugate A4 maintains spatial stability similar to that of the unmodified conjugate AVM and could significantly enhance endocytosis ability (p*** = 0.0009) compared with the unmodified conjugate AVM. Additionally, the in vitro potency of conjugate A4 (EC50 = 71.78 nmol in SKOV3 cells) was greatly enhanced (approximately 4 times) compared with that of the unmodified conjugate AVM (EC50 = 286.00 nmol in SKOV3 cells). The in vivo efficacy of conjugate A4 completely eliminated 50% of tumors at 33 mg/kg, which was significantly better than the efficacy of conjugate AVM at the same dose (P** = 0.0026). In addition, theranostic albumin drug conjugate A8 was designed to intuitively realize drug release and maintain antitumor activity similar to conjugate A4. In summary, the guanidine modification strategy could provide new ideas for the development of new generational albumin drug conjugates.

Engineering Nucleotidoproteins for Base-Pairing-Assisted Cytosolic Delivery and Genome Editing

Protein therapeutics targeting intracellular machineries hold profound potential for disease treatment, and hence robust cytosolic protein delivery technologies are imperatively demanded. Inspired by the super-negatively charged, nucleotide-enriched structure of nucleic acids, adenylated pro-proteins (A-proteins) with dramatically enhanced negative surface charges have been engineered for the first time via facile green synthesis. Then, thymidine-modified polyethyleneimine is developed, which exhibits strong electrostatic attraction, complementary base pairing, and hydrophobic interaction with A-proteins to form salt-resistant nanocomplexes with robust cytosolic delivery efficiencies. The acidic endolysosomal environment enables traceless restoration of the A-proteins and consequently promotes the intracellular release of the native proteins. This strategy shows high efficiency and universality for a variety of proteins with different molecular weights and isoelectric points in mammalian cells. Moreover, it enables highly efficient delivery of CRISPR-Cas9 ribonucleoproteins targeting fusion oncogene EWSR1-FLI1, leading to pronounced anti-tumor efficacy against Ewing sarcoma. This study provides a potent and versatile platform for cytosolic protein delivery and gene editing, and may benefit the development of protein pharmaceuticals.

Bioactivated and PEG-Protected Circa 2 nm Gold Nanoparticles for in Cell Labelling and Cryo-Electron Microscopy

Advances in cryo-electron microscopy (EM) enable imaging of protein assemblies within mammalian cells in a near native state when samples are preserved by cryogenic vitrification. To accompany this progress, specialized EM labelling protocols must be developed. Gold nanoparticles (AuNPs) of 2 nm are synthesized and functionalized to bind selected intracellular targets inside living human cells and to be detected in vitreous sections. As a proof of concept, thioaminobenzoate-, thionitrobenzoate-coordinated gold nanoparticles are functionalized on their surface with SV40 Nuclear Localization Signal (NLS)-containing peptides and 2 kDa polyethyleneglycols (PEG) by thiolate exchange to target the importin-mediated nuclear machinery and facilitate cytosolic diffusion by shielding the AuNP surface from non-specific binding to cell components, respectively. After delivery by electroporation into the cytoplasm of living human cells, the PEG-coated AuNPs diffuse freely in the cytoplasm but do not enter the nucleus. Incorporation of NLS within the PEG coverage promotes a quick nuclear import of the nanoparticles in relation to the density of NLS onto the AuNPs. Cryo-EM of vitreous cell sections demonstrate the presence of 2 nm AuNPs as single entities in the nucleus. Biofunctionalized AuNPs combined with live-cell electroporation procedures are thus potent labeling tools for the identification of macromolecules in cellular cryo-EM.

The Dawn of a New Era: Targeting the "Undruggables" with Antibody-Based Therapeutics

The high selectivity and affinity of antibodies toward their antigens have made them a highly valuable tool in disease therapy, diagnosis, and basic research. A plethora of chemical and genetic approaches have been devised to make antibodies accessible to more "undruggable" targets and equipped with new functions of illustrating or regulating biological processes more precisely. In this Review, in addition to introducing how naked antibodies and various antibody conjugates (such as antibody-drug conjugates, antibody-oligonucleotide conjugates, antibody-enzyme conjugates, etc.) work in therapeutic applications, special attention has been paid to how chemistry tools have helped to optimize the therapeutic outcome (i.e., with enhanced efficacy and reduced side effects) or facilitate the multifunctionalization of antibodies, with a focus on emerging fields such as targeted protein degradation, real-time live-cell imaging, catalytic labeling or decaging with spatiotemporal control as well as the engagement of antibodies inside cells. With advances in modern chemistry and biotechnology, well-designed antibodies and their derivatives via size miniaturization or multifunctionalization together with efficient delivery systems have emerged, which have gradually improved our understanding of important biological processes and paved the way to pursue novel targets for potential treatments of various diseases.

Piperazine-modified dendrimer achieves efficient intracellular protein delivery via caveolar endocytosis bypassing the endo-lysosomal pathway

Intracellular protein delivery has been a major challenge due to various physiological barriers including low proteolytic stability and poor membrane permeability of the biologics. Nanoparticles were widely proposed to deliver cargo proteins into cells by endocytosis, however, the materials and complexes with proteins are often entrapped in endosomes and subject to lysosome degradation. In this study, we report a piperazine modified dendrimer for stabilizing the complexes via a combination of electrostatic interaction and hydrophobic interactions. The complexes show rapid cell internalization and the loaded proteins are released into the cytosols as early as half an hour post incubation. Mechanism study suggests that the complexes are endocytosed into cells via caveolae-based pathways, which could be inhibited by inhibitors such as genistein, filipin III, brefeldin A and nystatin. The phenylpiperazine-modified polymer enables the delivery of cargo proteins with reserved bioactivity and show high permeability in three-dimensional cell spheroids. The results prove the beneficial roles of phenylpiperazine ligands in polymer-mediated cytosolic protein delivery systems. STATEMENT OF SIGNIFICANCE: We synthesized a list of piperazine and derivatives modified dendrimers as cytosolic protein delivery vectors via facile reactions. Phenylpiperazine modification enables the efficient protein binding through the combination of electrostatic, hydrogen bonding and hydrophobic interactions. Phenylpiperazine modified dendrimers were internalized into the cells via a caveolae-based endo/lysosome-independent path and could release the cargo proteins into the cytosols as early as half an hour post incubation. Phenylpiperazine modified dendrimers delivered cargo proteins with reserved bioactivity and showed high permeability in three-dimensional cell spheroids.

Histidine-based coordinative polymers for efficient intracellular protein delivery via enhanced protein binding, cellular uptake, and endosomal escape

Polymers are one of the most promising protein delivery carriers; however, their applications are hindered by low delivery efficacy owing to their undesirable performance in protein binding, cellular uptake and endosomal escape. Here, we designed a series of histidine-based coordinative polymers for efficient intracellular protein delivery. Coordination of metal ions such as Ni²⁺, Zn²⁺, and Cu²⁺ with histidine residues on a polymer greatly improved its performance in protein binding, complex stability, cellular uptake and endosomal escape, therefore achieving highly improved protein delivery efficacy. Among the coordinative polymers, the Zn²⁺-coordinated one exhibited the highest cellular uptake, while the Cu²⁺-coordinated one exhibited the highest endosomal escape. The Ni²⁺-coordinated polymer formed large-sized aggregates with cargo proteins and showed insufficient protein release after endocytosis. The results obtained in this study provided new insight into the development of coordinative polymer-based protein delivery systems.

A Cu+ /Thiourea Dendrimer Achieves Excellent Cytosolic Protein Delivery via Enhanced Cell Uptake and Endosome Escape

Intracellular protein delivery has attracted considerable attention in the development of protein-based therapeutics, however, the design of highly efficient materials for robust delivery of native proteins remains challenging. This study proposes a Cu⁺ -based coordination polymer for cytosolic protein delivery with high efficacy and robustness. The phenylthiourea grafted dendrimer is coordinated with cuprous ions to prepare the polymeric carrier, which efficiently bind cargo proteins via a combination of coordination, ionic and hydrophobic interactions. The incorporation of Cu⁺ ions in the polymer greatly improves its cellular uptake and endosomal escape. The cuprous-based coordination polymer successfully delivered a variety of structurally diverse proteins into various cell lines with reserved bioactivities. This study provides a new type of coordination polymers for cytosolic delivery of biomacromolecules.

Coacervate-mediated novel pancreatic cancer drug Aleuria Aurantia lectin delivery for augmented anticancer therapy

Background

Pancreatic cancer, one of the cancers with the highest mortality rate, has very limited clinical treatment. Cancer cells express abnormal glycans on the surface, and some lectins with a high affinity for the glycans induce apoptosis in cancer. In this study, the efficacy of Aleuria Aurantia lectin (AAL) for the treatment of pancreatic cancer was evaluated and the efficacy improvement through AAL delivery with mPEGylated coacervate (mPEG-Coa) was investigated.

Methods

AAL was treated with pancreatic cancer cells, PANC-1, and the expression level of caspase-3 and subsequent apoptosis was analyzed. In particular, the anticancer efficacy of AAL was compared with that of concanavalin A, one of the representative anticancer lectins. Then, methoxypolyethylene glycol-poly(ethylene arginylaspartate diglyceride), a polycation, was synthesized, and an mPEG-Coa complex was prepared with polyanion heparin. The AAL was incorporated into the mPEG-Coa and the release kinetics of the AAL from the mPEG-Coa and the cargo protection capacity of the mPEG-Coa were evaluated. Finally, improved anticancer ability through Coa-mediated AAL delivery was assessed.

Results

These results indicated that AAL is a potential effective pancreatic cancer treatment. Moreover, mPEG-Coa rapidly released AAL at pH 6.5, an acidic condition in the cancer microenvironment. The initial rapid release of AAL effectively suppressed pancreatic cancer cells, and the continuous supply of AAL through the Coa transporter effectively inhibited proliferation recurrence of cancer cells.

Conclusion

AAL is a potential novel drug for the treatment of pancreatic cancer therapeutic agent. In addition, a continuous supply of drugs above the therapeutic threshold using mPEG-Coa could improve therapeutic efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00282-6.

Gold Nanoparticle-Mediated Gene Therapy

Gold nanoparticles (AuNPs) have gained increasing attention as novel drug-delivery nanostructures for the treatment of cancers, infections, inflammations, and other diseases and disorders. They are versatile in design, synthesis, modification, and functionalization. This has many advantages in terms of gene editing and gene silencing, and their application in genetic illnesses. The development of several techniques such as CRISPR/Cas9, TALEN, and ZFNs has raised hopes for the treatment of genetic abnormalities, although more focused experimentation is still needed. AuNPs, however, have been much more effective in trending research on this subject. In this review, we highlight recently well-developed advancements that are relevant to cutting-edge gene therapies, namely gene editing and gene silencing in diseases caused by a single gene in humans by taking an edge of the unique properties of the AuNPs, which will be an important outlook for future research.

Anionic amphiphilic calixarenes for peptide assembly and delivery

Shape-persistent macrocycles enable superior control on molecular self-assembly, allowing the preparation of well-defined nanostructures with new functions. Here, we report on anionic amphiphilic calixarenes of conic shape and their self-assembly behavior in aqueous media for application in intracellular delivery of peptides. Newly synthesized calixarenes bearing four phosphonate groups and two or four long alkyl chains were found to form micelles of ∼ 10 nm diameter, in contrast to an analogue with short alkyl chains. These amphiphilic calixarenes are able to complex model (oligo-lysine) and biologically relevant (HIV-1 nucleocapsid peptide) cationic peptides into small nanoparticles (20-40 nm). By contrast, a control anionic calixarene with short alkyl chains fails to form small nanoparticles with peptides, highlighting the importance of micellar assembly of amphiphilic calixarenes for peptide complexation. Cellular studies reveal that anionic amphiphilic calixarenes exhibit low cytotoxicity and enable internalization of fluorescently labelled peptides into live cells. These findings suggest anionic amphiphilic macrocycles as promising building blocks for the preparation of peptide delivery vehicles.

Reactive oxygen species-responsive branched poly (β-amino ester) with robust efficiency for cytosolic protein delivery

Protein therapy targeting the intracellular machinery holds great potentials for disease treatment, and therefore, effective cytosolic protein delivery technologies are highly demanded. Herein, we developed reactive oxygen species (ROS)-degradable, branched poly(β-amino ester) (PBAE) with built-in phenylboronic acid (PBA) in the backbone and terminal-pendent arginine for the efficient cytosolic protein delivery. The PBAE could form stable and cell-ingestible nanocomplexes (NCs) with proteins via electrostatic interaction, nitrogen-boronate (N-B) coordination, and hydrogen bonding, while it can be degraded into small segments by the over-produced H₂O₂ in tumor cells to enable cytoplasmic protein release. As thus, PBAE exhibited high efficiency in delivering varieties of proteins with distinct molecular weights (12.4-430 kDa) and isoelectric points (4.7-10.5) into tumor cells, including enzymes, toxins, and antibodies. Moreover, PBAE mediated efficient delivery of saporin into tumor cells in vivo, provoking pronounced anti-tumor outcomes. This study provides a robust and versatile platform for cytosolic protein delivery, and the elaborately tailored PBAE may find promising applications for protein-based biological research and disease management. STATEMENT OF SIGNIFICANCE: Cytosolic delivery of native proteins holds great therapeutic potentials, which however, is limited by the lack of robust delivery carriers that can simultaneously feature strong protein encapsulation yet effective intracellular protein release. Herein, ROS-degradable, branched poly(β-amino ester) (PBAE) with backbone-embedded phenylboronic acid (PBA) and terminal-pendent arginine was developed to synchronize these two processes. PBA and arginine moieties allowed PBAE to encapsulate proteins via N-B coordination, electrostatic interaction, hydrogen bonding, and salt bridging, while PBA could be oxidized by over-produced H₂O₂ inside cancer cells to trigger PBAE degradation and intracellular protein release. As thus, the top-performing PBAE mediated efficient cytosolic delivery of various proteins including enzymes, toxins, and antibodies. This study provides a powerful platform for cytosolic protein delivery, and may find promising utilities toward intracellular protein therapy against cancer and other diseases such as inflammation.

A general carbon dot-based platform for intracellular delivery of proteins

The shortcomings of proteins, such as poor stability in biological environments, the impermeability of the membrane and the susceptibility to enzymolysis, restrict their potential applications. Therefore, constructing universal nanocarriers for intracellular delivery of a variety of proteins remains a great challenge. In this work, gallic acid (GA) and L-lysine were used as starting materials to synthesize carbon dots (CDs). The CDs were used as carriers to interact with bovine serum albumin (BSA), enhanced green fluorescent protein (EGFP) and glucose oxidase (GOx) via supramolecular interaction to construct CDs-protein nanocomposites CDs-BSA, CDs-EGFP and CDs-GOx. Furthermore, CDs-EGFP and CDs-GOx can achieve intracellular protein delivery and maintain 89% of the biological activity of GOx. In this work, the latency of CDs is projected as a universal platform for effective intracellular delivery of proteins.

Tailoring Hyperbranched Poly(β-amino ester) as a Robust and Universal Platform for Cytosolic Protein Delivery

Cytosolic protein delivery is a prerequisite for protein-based biotechnologies and therapeutics on intracellular targets. Polymers that can complex with proteins to form nano-assemblies represent one of the most important categories of materials, because of the ease of nano-fabrication, high protein loading efficiency, no need for purification, and maintenance of protein bioactivity. Stable protein encapsulation and efficient intracellular liberation are two critical yet opposite processes toward cytosolic delivery, and polymers that can resolve these two conflicting challenges are still lacking. Herein, hyperbranched poly(β-amino ester) (HPAE) with backbone-embedded phenylboronic acid (PBA) is developed to synchronize these two processes, wherein PBA enhanced protein encapsulation via nitrogen-boronate (N-B) coordination while triggered polymer degradation and protein release upon oxidation by H₂ O₂ in cancer cells. Upon optimization of the branching degree, charge density, and PBA distribution, the best-performing A2-B3-C2-S₂ -P₂ is identified, which mediates robust delivery of various native proteins/peptides with distinct molecular weights (1.6-430 kDa) and isoelectric points (4.1-10.3) into cancer cells, including enzymes, toxins, antibodies, and CRISPR-Cas9 ribonucleoproteins (RNPs). Moreover, A2-B3-C2-S₂ -P₂ mediates effective cytosolic delivery of saporin both in vitro and in vivo to provoke remarkable anti-tumor efficacy. Such a potent and universal platform holds transformative potentials for protein pharmaceuticals.

“Spear and Shield in One” Nanochaperone Enables Protein to Navigate Multiple Biological Barriers for Enhanced Tumor Synergistic Therapy

Protein therapeutics have been viewed as powerful candidates for cancer treatment by virtue of highly specific bioactivity and minimized adverse effects. However, the intracellular delivery of protein drugs remains enormously...

Genetic and Covalent Protein Modification Strategies to Facilitate Intracellular Delivery

Protein-based therapeutics represent a rapidly growing segment of approved disease treatments. Successful intracellular delivery of proteins is an important precondition for expanded in vivo and in vitro applications of protein therapeutics. Direct modification of proteins and peptides for improved cytosolic translocation are a promising method of increasing delivery efficiency and expanding the viability of intracellular protein therapeutics. In this Review, we present recent advances in both synthetic and genetic protein modifications for intracellular delivery. Active endocytosis-based and passive internalization pathways are discussed, followed by a review of modification methods for improved cytosolic delivery. After establishing how proteins can be modified, general strategies for facilitating intracellular delivery, such as chemical supercharging or inclusion of cell-penetrating motifs, are covered. We then outline protein modifications that promote endosomal escape. We finally examine the delivery of two potential classes of therapeutic proteins, antibodies and associated antibody fragments, and gene editing proteins, such as cas9.

Polymer nano-systems for the encapsulation and delivery of active biomacromolecular therapeutic agents

Biomacromolecular therapeutic agents, particularly proteins, antigens, enzymes, and nucleic acids are emerging as powerful candidates for the treatment of various diseases and the development of the recent vaccine based on mRNA highlights the enormous potential of this class of drugs for future medical applications. However, biomacromolecular therapeutic agents present an enormous delivery challenge compared to traditional small molecules due to both a high molecular weight and a sensitive structure. Hence, the translation of their inherent pharmaceutical capacity into functional therapies is often hindered by the limited performance of conventional delivery vehicles. Polymer drug delivery systems are a modular solution able to address those issues. In this review, we discuss recent developments in the design of polymer delivery systems specifically tailored to the delivery challenges of biomacromolecular therapeutic agents. In the future, only in combination with a multifaceted and highly tunable delivery system, biomacromolecular therapeutic agents will realize their promising potential for the treatment of diseases and for the future of human health.

Efficient Delivery of Antibodies Intracellularly by Co-Assembly with Hexahistidine-Metal Assemblies (HmA)

PURPOSE

There has been a substantial global market for antibodies, which are based on extracellular targets. Binding intracellular targets by antibodies will bring new chances in antibody therapeutics and a huge market increase. We aim to evaluate the efficiency of a novel delivery system of His6-metal assembly (HmA) in delivering intracellular antibodies and biofunctions of delivered antibodies.

METHODS

In this study, the physicochemical properties of HmA@Antibodies generated through co-assembling with antibodies and HmA were well characterized by dynamic light scatter. The cytotoxicity of HmA@Antibodies was investigated by Cell Counting Kit-8 (CCK-8). The endocytic kinetics and lysosome escape process of HmA@Antibodies were studied by flow cytometry and fluorescent staining imaging, respectively. Compared to the commercialized positive control, the intracellular delivery efficiency by HmA@Antibodies and biofunctions of delivered antibodies were evaluated by fluorescent imaging and CCK-8.

RESULTS

Various antibodies (IgG, anti-β-tubulin and anti-NPC) could co-assemble with HmA under a gentle condition, producing nano-sized (~150 nm) and positively charged (~+30 eV) HmA@Antibodies particles with narrow size distribution (PDI ~ 0.15). HmA displayed very low cytotoxicity to divers cells (DCs, HeLa, HCECs, and HRPE) even after 96 h for the feeding concentration ≤100 μg mL-1, and fast escape from endosomes. In the case of delivery IgG, the delivery efficiency into alive cells of HmA was better than a commercial protein delivery reagent (PULSin). For cases of the anti-β-tubulin and anti-NPC, HmA showed comparable delivery efficiency to their positive controls, but HmA with ability to deliver these antibodies into alive cells was still superior to positive controls delivering antibodies into dead cells through punching holes.

CONCLUSION

Our results indicate that this strategy is a feasible way to deliver various antibodies intracellularly while preserving their functions, which has great potential in various applications and treating many refractory diseases by intracellular antibody delivery.

Efficient delivery of cytosolic proteins by protein-hexahistidine-metal co-assemblies

Proteins play key roles in most biological processes, and protein dysfunction can cause various diseases. Over the past few decades, tremendous development has occurred in the protein therapeutic market due to the high specificity, low side effects, and low risk of proteins. Currently, all protein drugs on the market are based on extracellular targeting; more than 70% of intracellular targets remain un-druggable. Efficient delivery of cytosolic proteins is of significance for protein drugs, advanced biotechnology and molecular cell biology. Herein, we developed a co-assembly strategy for protein-hexahistidine-metal for intracellular protein delivery. Based on the coordinative interaction between His₆ and metal ions, various proteins were encapsulated in situ into nanosized and positively charged protein encapsulation particles(Protein@HmA) through a co-assembly process with a high loading capacity and loading efficiency. Protein@HmA was able to deliver proteins with diverse physicochemical properties through multiple endocytosis pathways, and the protein could quickly escape from endosomes. In addition, the bioactivity of the loaded protein during co-assembly and the intracellular delivery processes were well preserved and could be properly exerted inside cells. Our results demonstrate that this strategy should be a valuable platform for protein delivery and has huge potential in protein-based theranostics. STATEMENT OF SIGNIFICANCE: Intracellular targets with protein drugs may provide a new way for the treatment of many refractory disease. Herein, we developed a co-assembly strategy for protein-hexahistidine-metal for efficient intracellular protein delivery. Based on the coordinative interaction between His₆ and metal ions, various proteins were encapsulated in situ into nanosized and positively charged particles (Protein@HmA) with a high loading efficiency. Protein@HmA was able to deliver different proteins through multiple endocytosis pathways, and the protein could quickly escape from endosomes. In addition, the bioactivity of the loaded protein during co-assembly and the intracellular delivery processes were well preserved and could be properly exerted inside cells. This strategy should be a valuable platform for protein delivery and has huge potential in protein-based theranostics.

Cytosolic protein delivery via metabolic glycoengineering and bioorthogonal click reactions

Cytosolic protein delivery holds great potential for the development of protein-based biotechnologies and therapeutics. Currently, cytosolic protein delivery is mainly achieved with the assistance of various carriers. Herein, we present a universal and effective strategy for carrier-free cytosolic protein delivery via metabolic glycoengineering and bioorthogonal click reactions. Ac₄ManNAz (AAM), an azido-modified N-acetylmannosamine analogue, was first employed to label tumor cell surfaces with abundant azido groups via glycometabolism. Then, proteins including RNase A, cytochrome C (Cyt C), and bovine serum albumin (BSA) were covalently modified with dibenzocyclooctyne (DBCO). Based on the highly efficient bioorthogonal click reactions between DBCO and azido, DBCO-modified proteins could be efficiently internalized by azido-labeled cancer cells. RNase A-DBCO could largely maintain its enzymatic activity and, thus, led to notable anti-tumor efficacy in HeLa and B16F10 cells in vitro and in B16F10 xenograft tumors in vivo. This study therefore provides a simple and powerful approach for carrier-free protein delivery and would have broad applicability in anti-tumor protein therapy.

Different Biological Activities of Histidine-Rich Peptides Are Favored by Variations in Their Design

The protein transduction and antimicrobial activities of histidine-rich designer peptides were investigated as a function of their sequence and compared to gene transfection, lentivirus transduction and calcein release activities. In membrane environments, the peptides adopt helical conformations where the positioning of the histidine side chains defines a hydrophilic angle when viewed as helical wheel. The transfection of DNA correlates with calcein release in biophysical experiments, being best for small hydrophilic angles supporting a model where lysis of the endosomal membrane is the limiting factor. In contrast, antimicrobial activities show an inverse correlation suggesting that other interactions and mechanisms dominate within the bacterial system. Furthermore, other derivatives control the lentiviral transduction enhancement or the transport of proteins into the cells. Here, we tested the transport into human cell lines of luciferase (63 kDa) and the ribosome-inactivating toxin saporin (30 kDa). Notably, depending on the protein, different peptide sequences are required for the best results, suggesting that the interactions are manifold and complex. As such, designed LAH4 peptides assure a large panel of biological and biophysical activities whereby the optimal result can be tuned by the physico-chemical properties of the sequences.

Metal-Protein Hybrid Materials with Desired Functions and Potential Applications

Metal nanohybrids are fast emerging functional nanomaterials with advanced structures, intriguing physicochemical properties, and a broad range of important applications in current nanoscience research. Significant efforts have been devoted toward design and develop versatile metal nanohybrid systems. Among numerous biological components, diverse proteins offer avenues for making advanced multifunctional systems with unusual properties, desired functions, and potential applications. This review discusses the rational design, properties, and applications of metal-protein nanohybrid materials fabricated from proteins and inorganic components. The construction of functional biomimetic nanohybrid materials is first briefly introduced. The properties and functions of these hybrid materials are then discussed. After that, an overview of promising application of biomimetic metal-protein nanohybrid materials is provided. Finally, the key challenges and outlooks related to this fascinating research area are also outlined.

Nanodrug with dual-sensitivity to tumor microenvironment for immuno-sonodynamic anti-cancer therapy

Although a combination with photodynamic therapy (PDT) is a potential means to improve the immune checkpoint blockade (ICB)-based anticancer immunotherapy, this strategy is subjected to the extremely poor light penetration in melanoma. Herein, we develop a lipid (LP)-based micellar nanocarrier encapsulating sonosensitizer chlorin e6 (Ce6) in the core, conjugating anti-PD-L1 antibody (aPD-L1) to the interlayer through MMP-2-cleavable peptide, and bearing a PEG coating sheddable at low pH value (≈6.5) of tumor microenvironment. The unique nanocarrier design allows a tumor-targeting delivery to activate the anti-tumor immunity and meanwhile to reduce immune-related adverse effects (irAEs). Moreover, a sonodynamic therapy (SDT) is triggerable by using ultrasonic insonation to produce tumor-killing reactive oxygen species (ROS), thereby bypassing the poor light penetration which restricts PDT in melanoma. A combination of SDT with aPD-L1 immunotherapy effectively promotes tumor infiltration and activation of cytotoxic T cells, which resulted in robust anti-cancer immunity and long-term immune memory to effectively suppress melanoma growth and postoperative recurrence. This strategy for tumor-targeting codelivery of immune checkpoint inhibitors and SDT agents could be readily extended to other tumor types for better immunotherapeutic outcome and reduced irAEs.

Rescue the retina after the ischemic injury by polymer-mediated intracellular superoxide dismutase delivery

Oxidative stress is a hallmark of the pathophysiogenesis of retinal ischemia. The direct delivery of antioxidant enzymes such as superoxide dismutase (SOD) into retinal cells provides a promising option for the down-regulation of oxidative stress in retinal ischemia, however, efficient intracellular protein delivery remains a major challenge for this application. Here, a boronic acid-rich polymer was used for the intracellular delivery of SOD both in vitro and in vivo. The polymer assembled with SOD into uniform nanoparticles with high binding affinity, and transported the cargo protein into several cell lines with maintained bioactivity and low cytotoxicity. We investigated the intraocular biodistribution, therapeutic efficacy and safety of the SOD nanoformulation in a retinal ischemia/reperfusion (I/R) injury model. After intravitreal injection, the nanoparticles rapidly diffused through the vitreous and penetrated into retinal ganglion cells (RGCs). Compared to free SOD, the nanoformulation exhibited much enhanced therapeutic efficacy with reduced RGC apoptosis and protected retinal function. Enzymatic results confirmed that the SOD nanoformulation reduced malondialdehyde expression and increased glutathione level in the ocular tissues, and thereby down-regulated oxidative stress and prevented RGC loss. Overall, this work offers a new therapeutic option for the treatment of retinal ischemic disorders by direct delivery of antioxidant proteins.

Bifunctional and Bioreducible Dendrimer Bearing a Fluoroalkyl Tail for Efficient Protein Delivery Both In Vitro and In Vivo

Rational design of stimuli-responsive polymers for cytosolic protein delivery with robust efficiency is of great importance but remains a challenging task. Here, we reported a bioreducible and amphiphilic dendrimer bearing a fluoroalkyl tail for this purpose. The fluorolipid was conjugated to the focal point of a cysteamine-cored polyamidoamine dendrimer via disulfide bond, while phenylboronic acid moieties were decorated on dendrimer surface for efficient protein binding. The yielding polymer showed high protein binding capability and complex stability and could efficiently release the cargo proteins in a glutathione-responsive manner. The designed polymer was effective in the delivery of various membrane-impermeable proteins into living cells with reserved bioactivities. In addition, the polymer efficiently delivered a toxin protein saporin into 4T1 breast cancer cells and inhibited the tumor growth in vivo after intravenous injection. The developed polymer in this study is a promising vector for the delivery of membrane-impermeable proteins to treat various diseases.

On Complex Coacervate Core Micelles: Structure-Function Perspectives

The co-assembly of ionic-neutral block copolymers with oppositely charged species produces nanometric colloidal complexes, known, among other names, as complex coacervates core micelles (C3Ms). C3Ms are of widespread interest in nanomedicine for controlled delivery and release, whilst research activity into other application areas, such as gelation, catalysis, nanoparticle synthesis, and sensing, is increasing. In this review, we discuss recent studies on the functional roles that C3Ms can fulfil in these and other fields, focusing on emerging structure-function relations and remaining knowledge gaps.

Direct Functional Protein Delivery with a Peptide into Neonatal and Adult Mammalian Inner Ear In Vivo

The aim of this study was to study an antimicrobial peptide (AMP), aurein 1.2, which substantially increased protein delivery directly into multiple mammalian inner-ear cell types in vivo. Different concentrations of aurein 1.2 with superpositively charged GFP (+36 GFP) protein fused with Cre recombinase were delivered to postnatal day 1-2 (P1-2) and adult cochleae of Cre reporter transgenic mice with various delivery methods. By cochleostomy at different concentrations of aurein 1.2-+36 GFP (1 μM, 5 μM, 22.5 μM, and 50 μM, respectively), the tdTomato (tdT) expression was observed in outer hair cells (OHCs; 20.77%, 23.02%, 76.36%, and 92.47%, respectively) and inner hair cells (IHCs; 14.90%, 44.50%, 89.59%, and 96.13%, respectively) in the cochlea. The optimal concentration was 22.5 μM with the highest transfection efficiency and the lowest cytotoxicity. Wide-spread tdT signals were detected in the cochlear-supporting cells, utricular-supporting cells, auditory nerve, and spiral ligament in neonatal and adult mice. Compared to cochleostomy, injection through the round window membrane (RWM) also produced highly efficient tdT+ labeled cells with less cell loss. In summary, the peptide aurein 1.2 fused with +36 GFP dramatically expanded the target cells with increased efficiency in direct protein delivery in the inner ear. Aurein 1.2-+36 GFP has the potential to be developed as protein-based therapy in regeneration and genome editing in the mammalian inner ear.

How Computational Chemistry and Drug Delivery Techniques Can Support the Development of New Anticancer Drugs

The early and late development of new anticancer drugs, small molecules or peptides can be slowed down by some issues such as poor selectivity for the target or poor ADME properties. Computer-aided drug design (CADD) and target drug delivery (TDD) techniques, although apparently far from each other, are two research fields that can give a significant contribution to overcome these problems. Their combination may provide mechanistic understanding resulting in a synergy that makes possible the rational design of novel anticancer based therapies. Herein, we aim to discuss selected applications, some also from our research experience, in the fields of anticancer small organic drugs and peptides.

Protein@Inorganic Nanodumpling System for High-Loading Protein Delivery with Activatable Fluorescence and Magnetic Resonance Bimodal Imaging Capabilities

Efficient protein delivery into the target cell is highly desirable for protein therapeutics. Current approaches for protein delivery commonly suffer from low-loading protein capacity, poor specificity for target cells, and invisible protein release. Herein, we report a protein@inorganic nanodumpling (ND) system as an intracellular protein delivery platform. Similar to a traditional Chinese food, the dumpling, ND consists of a protein complex "filling" formed by metal-ion-directed self-assembly of protein cargos fused to histidine-rich green fluorescent proteins (H₃₉GFPs), which are further encapsulated by an external surface "wrapper" of manganese dioxide (MnO₂) via in situ biomineralization. This ND structure allows for a high loading capacity (>63 wt %) for protein cargos with enhanced stability. NDs can be targeted and internalized into cancer cells specifically through folic acid receptors by surface-tailored folic acid. The protein cargo release is in a bistimuli-responsive manner, triggered by an either reductive or acidic intracellular microenvironment. Moreover, the MnO₂ nanowrapper is an efficient fluorescence quencher for inner fused GFPs and also a "switch-on" magnetic resonance imaging (MRI) agent via triggered release of Mn²⁺ ions, which enables activatable fluorescence/MRI bimodal imaging of protein release. Finally, the ND is highly potent and specific to deliver functional protein ribonuclease A (RNase A) into cultured target cells and the tumor site in a xenografted mouse model, eliminating the tumor cells with high therapeutic efficacy. Our approach provides a promising alternative to advance protein-based cancer therapeutics.

Boronic acid-engineered gold nanoparticles for cytosolic protein delivery

Boronic acid-engineered gold nanoparticles for effective cytosolic protein delivery with the help of hypertonicity.

Carboxylated branched poly(β-amino ester) nanoparticles enable robust cytosolic protein delivery and CRISPR-Cas9 gene editing

Efficient cytosolic protein delivery is necessary to fully realize the potential of protein therapeutics. Current methods of protein delivery often suffer from low serum tolerance and limited in vivo efficacy. Here, we report the synthesis and validation of a previously unreported class of carboxylated branched poly(β-amino ester)s that can self-assemble into nanoparticles for efficient intracellular delivery of a variety of different proteins. In vitro, nanoparticles enabled rapid cellular uptake, efficient endosomal escape, and functional cytosolic protein release into cells in media containing 10% serum. Moreover, nanoparticles encapsulating CRISPR-Cas9 ribonucleoproteins (RNPs) induced robust levels of gene knock-in (4%) and gene knockout (>75%) in several cell types. A single intracranial administration of nanoparticles delivering a low RNP dose (3.5 pmol) induced robust gene editing in mice bearing engineered orthotopic murine glioma tumors. This self-assembled polymeric nanocarrier system enables a versatile protein delivery and gene editing platform for biological research and therapeutic applications.

A modular approach for cytosolic protein delivery: metal ion-induced self-assembly of gold nanoclusters as a general platform

We developed a versatile and modular method for cytosolic protein delivery through metal ion-induced co-assembly of gold nanoclusters and proteins into supramolecular assemblies. The versatility and high efficiency of this strategy to assemble and deliver various proteins into living cells were demonstrated. Importantly, the activity of proteins was maintained during the delivery. This modular approach provides an exciting and promising new nano-platform for cytosolic protein delivery.

Cytosolic delivery of inhibitory antibodies with cationic lipids

Antibodies can be developed to directly inhibit almost any protein, but their inability to enter the cytosol limits inhibitory antibodies to membrane-associated or extracellular targets. Developing a cytosolic antibody delivery system would offer unique opportunities to directly inhibit and study intracellular protein function. Here we demonstrate that IgG antibodies that are conjugated with anionic polypeptides (ApPs) can be complexed with cationic lipids originally designed for nucleic acid delivery through electrostatic interactions, enabling close to 90% cytosolic delivery efficiency with only 500 nM IgG. The ApP is fused to a small photoreactive antibody-binding domain (pAbBD) that can be site-specifically photocrosslinked to nearly all off-the-shelf IgGs, enabling easy exchange of cargo IgGs. We show that cytosolically delivered IgGs can inhibit the drug efflux pump multidrug resistance-associated protein 1 (MRP1) and the transcription factor NFκB. This work establishes an approach for using existing antibody collections to modulate intracellular protein function.

Engineered Polymeric Materials for Biological Applications: Overcoming Challenges of the Bio-Nano Interface

Nanomedicine has generated significant interest as an alternative to conventional cancertherapy due to the ability for nanoparticles to tune cargo release. However, while nanoparticletechnology has promised significant benefit, there are still limited examples of nanoparticles inclinical practice. The low translational success of nanoparticle research is due to the series ofbiological roadblocks that nanoparticles must migrate to be effective, including blood and plasmainteractions, clearance, extravasation, and tumor penetration, through to cellular targeting,internalization, and endosomal escape. It is important to consider these roadblocks holistically inorder to design more effective delivery systems. This perspective will discuss how nanoparticlescan be designed to migrate each of these biological challenges and thus improve nanoparticledelivery systems in the future. In this review, we have limited the literature discussed to studiesinvestigating the impact of polymer nanoparticle structure or composition on therapeutic deliveryand associated advancements. The focus of this review is to highlight the impact of nanoparticlecharacteristics on the interaction with different biological barriers. More specific studies/reviewshave been referenced where possible.

Biocompatible gold nanoclusters: synthetic strategies and biomedical prospects

The latest advances concerning ultra-small gold nanoparticles (≤2 nm) commonly known as gold nanoclusters (AuNCs) are reviewed and discussed in the context of biological and biomedical applications (labeling, delivery, imaging and therapy). A great diversity of synthetic methods has been developed and optimized aiming to improve the chemical structures and physicochemical properties of the resulting AuNCs. The main synthetic approaches were surveyed with emphasis on methods leading to water-soluble AuNCs since aqueous solutions are the preferred media for biological applications. The most representative and recent experimental results are discussed in relationship to their potential for biomedical applications.

Artificial Cellulosome Complex from the Self-Assembly of Ni-NTA-Functionalized Polymeric Micelles and Cellulases

Polymer-protein core-shell nanoparticles have been explored for enzyme immobilization. This work reports on the development of functional polymeric micelles for immobilizing His6 -tagged cellulases with controlled spatial orientation of enzymes, resulting in "artificial cellulosomes" for effective cellulose hydrolysis. Poly(styrene)-b-poly(styrene-alt-maleic anhydride) was prepared through one-pot reversible addition-fragmentation chain-transfer polymerization and modified with nitrilotriacetic acid (NTA) to afford an amphiphilic block copolymer. The self-assembled polymer was mixed with a solution of NiSO4 to form Ni-NTA-functionalized micelles, which could successfully capture His6 -tagged cellulases and form hierarchically structured core-shell nanoparticles with cellulases as the corona. Because the anchored enzymes are site-specifically oriented and in close proximity, synergistic catalysis that results in over twofold activity enhancement has been achieved.

A boronic acid-rich dendrimer with robust and unprecedented efficiency for cytosolic protein delivery and CRISPR-Cas9 gene editing

Cytosolic protein delivery is of central importance for the development of protein-based biotechnologies and therapeutics; however, efficient intracellular delivery of native proteins remains a challenge. Here, we reported a boronic acid-rich dendrimer with unprecedented efficiency for cytosolic delivery of native proteins. The dendrimer could bind with both negatively and positively charged proteins and efficiently delivered 13 cargo proteins into the cytosol of living cells. All the delivered proteins kept their bioactivities after cytosolic delivery. The dendrimer ensures efficient intracellular delivery of Cas9 protein into various cell lines and showed high efficiency in CRISPR-Cas9 genome editing. The rationally designed boronic acid-rich dendrimer permits the development of an efficient platform with high generality for the delivery of native proteins.

Hexahistidine-metal assemblies: A promising drug delivery system

It is of considerable interest to construct an ideal drug delivery system (i.e., high drug payload, minimal cytotoxicity, rapid endocytosis, and lysosomal escape) under mild conditions for disease treatment, tissue engineering, bioimaging, etc. Inspired by the coordinative interactions between histidine and metal ions, we present the facile synthesis of hexahistidine (His₆)-metal assembly (HmA) particles under mild conditions for the first time. The HmA particles presented a high loading capacity, a wide variety of loadable drugs, minimal cytotoxicity, quick internalization, the ability to bypass the lysosomes, and rapid intracellular drug release. In addition, HmA encapsulation largely improved the antitumor ability of camptothecin (CPT) relative to free CPT. By capitalizing on these promising features in drug delivery, HmA will have great potential in various biomedical fields. STATEMENT OF SIGNIFICANCE: It is of considerable interest to construct an ideal drug delivery system (i.e., high drug payload, minimal cytotoxicity, rapid endocytosis, and lysosomal escape) under mild conditions. Inspired by the coordinative interactions between histidine and metal ions, we present for the first time the facile synthesis of Hexahistidine (His₆)-metal assembly (HmA) particles under mild conditions. The HmA particles exhibited a high loading capacity, a wide variety of loadable drugs, minimal cytotoxicity, quick internalization, the ability to bypass the lysosomes, and rapid intracellular drug release. By capitalizing on these promising features in drug delivery, HmA will have great potential in various biomedical fields.