Efficient Delivery of Bioactive Antibodies into the Cytoplasm of Living Cells by Charge-Conversional Polyion Complex Micelles

Supramolecular Genome Editing: Targeted Delivery and Endogenous Activation of CRISPR/Cas9 by Dynamic Host-Guest Recognition

We synthesize supramolecular poly(disulfide) (CPS) containing covalently attached cucurbit[7]uril (CB[7]), which is exploited not only as a carrier to deliver plasmid DNA encoding destabilized Cas9 (dsCas9), but also as a host to include trimethoprim (TMP) by CB[7] moieties through the supramolecular complexation to form TMP@CPS/dsCas9. Once the plasmid is transfected into tumor cells by CPS, the presence of polyamines can competitively trigger the decomplexation of TMP@CPS, thereby displacing and releasing TMP from CB[7] to stabilize dsCas9 that can target and edit the genomic locus of PLK1 to inhibit the growth of tumor cells. Following the systemic administration of TMP@CPS/dsCas9 decorated with hyaluronic acid (HA), tumor-specific editing of PLK1 is detected due to the elevated polyamines in tumor microenvironment, greatly minimizing off-target editing in healthy tissues and non-targeted organs. As the metabolism of polyamines is dysregulated in a wide range of disorders, this study offers a supramolecular approach to precisely control CRISPR/Cas9 functions under particular pathological contexts.

Bioresponsive Polymers for Nanomedicine-Expectations and Reality!

Bioresponsive polymers in nanomedicine have been widely perceived to selectively activate the therapeutic function of nanomedicine at diseased or pathological sites, while sparing their healthy counterparts. This idea can be described as an advanced version of Paul Ehrlich’s magic bullet concept. From that perspective, the inherent anomalies or malfunction of the pathological sites are generally targeted to allow the selective activation or sensory function of nanomedicine. Nonetheless, while the primary goals and expectations in developing bioresponsive polymers are to elicit exclusive selectivity of therapeutic action at diseased sites, this remains difficult to achieve in practice. Numerous research efforts have been undertaken, and are ongoing, to tackle this fine-tuning. This review provides a brief introduction to key stimuli with biological relevance commonly featured in the design of bioresponsive polymers, which serves as a platform for critical discussion, and identifies the gap between expectations and current reality.

Liquid Droplet Formation and Facile Cytosolic Translocation of IgG in the Presence of Attenuated Cationic Amphiphilic Lytic Peptides

Fc region binding peptide conjugated with attenuated cationic amphiphilic lytic peptide L17E trimer [FcB(L17E)₃ ] was designed for immunoglobulin G (IgG) delivery into cells. Particle-like liquid droplets were generated by mixing Alexa Fluor 488 labeled IgG (Alexa488-IgG) with FcB(L17E)₃ . Droplet contact with the cellular membrane led to spontaneous influx and distribution of Alexa488-IgG throughout cells in serum containing medium. Involvement of cellular machinery accompanied by actin polymerization and membrane ruffling was suggested for the translocation. Alexa488-IgG negative charges were crucial in liquid droplet formation with positively charged FcB(L17E)₃ . Binding of IgG to FcB(L17E)₃ may not be necessary. Successful intracellular delivery of Alexa Fluor 594-labeled anti-nuclear pore complex antibody and anti-mCherry-nanobody tagged with supernegatively charged green fluorescence protein allowed binding to cellular targets in the presence of FcB(L17E)₃ .

Mitochondrion-specific dendritic lipopeptide liposomes for targeted sub-cellular delivery

The mitochondrion is an important sub-cellular organelle responsible for the cellular energetic source and processes. Owing to its unique sensitivity to heat and reactive oxygen species, the mitochondrion is an appropriate target for photothermal and photodynamic treatment for cancer. However, targeted delivery of therapeutics to mitochondria remains a great challenge due to their location in the sub-cellular compartment and complexity of the intracellular environment. Herein, we report a class of the mitochondrion-targeted liposomal delivery platform consisting of a guanidinium-based dendritic peptide moiety mimicking mitochondrion protein transmembrane signaling to exert mitochondrion-targeted delivery with pH sensitive and charge-reversible functions to enhance tumor accumulation and cell penetration. Compared to the current triphenylphosphonium (TPP)-based mitochondrion targeting system, this dendritic lipopeptide (DLP) liposomal delivery platform exhibits about 3.7-fold higher mitochondrion-targeted delivery efficacy. Complete tumor eradication is demonstrated in mice bearing 4T1 mammary tumors after combined photothermal and photodynamic therapies delivered by the reported DLP platform.

Synergistic Interplay of Covalent and Non-Covalent Interactions in Reactive Polymer Nanoassembly Facilitates Intracellular Delivery of Antibodies

The primary impediments in developing large antibodies as drugs against intracellular targets involve their low transfection efficiency and suitable reversible encapsulation strategies for intracellular delivery with retention of biological activity. To address this, we outline an electrostatics-enhanced covalent self-assembly strategy to generate polymer-protein/antibody nanoassemblies. Through structure-activity studies, we down-select the best performing self-immolative pentafluorophenyl containing activated carbonate polymer for bioconjugation. With the help of an electrostatics-aided covalent self-assembly approach, we demonstrate efficient encapsulation of medium to large proteins (HRP, 44 kDa and β-gal, 465 kDa) and antibodies (ca. 150 kDa). The designed polymeric nanoassemblies are shown to successfully traffic functional antibodies (anti-NPC and anti-pAkt) to cytosol to elicit their bioactivity towards binding intracellular protein epitopes and inducing apoptosis.

Secondary structure drives self-assembly in weakly segregated globular protein–rod block copolymers

Imparting secondary structure to the polymer block can drive self-assembly in globular protein–helix block copolymers, increasing the effective segregation strength between blocks with weak or no repulsion.

Rational Design of Nanocarriers for Intracellular Protein Delivery

Protein/antibody therapeutics have exhibited the advantages of high specificity and activity even at an extremely low concentration compared to small molecule drugs. However, they are accompanied by unfavorable physicochemical properties such as fragile tertiary structure, large molecular size, and poor penetration of the membrane, and thus the clinical use of protein drugs is hindered by inefficient delivery of proteins into the host cells. To overcome the challenges associated with protein therapeutics and enhance their biopharmaceutical applications, various protein-loaded nanocarriers with desired functions, such as lipid nanocapsules, polymeric nanoparticles, inorganic nanoparticles, and peptides, are developed. In this review, the different strategies for intracellular delivery of proteins are comprehensively summarized. Their designed routes, mechanisms of action, and potential therapeutics in live cells or in vivo are discussed in detail. Furthermore, the perspective on the new generation of delivery systems toward the emerging area of protein-based therapeutics is presented as well.

Polymeric Micelles Loading Proteins through Concurrent Ion Complexation and pH-Cleavable Covalent Bonding for In Vivo Delivery

Protein drugs have great potential as targeted therapies, yet their application suffers from several drawbacks, such as instability, short half-life, and adverse immune responses. Thus, protein delivery approaches based on stimuli-responsive nanocarriers can provide effective strategies for selectively enhancing the availability and activation of proteins in targeted tissues. Herein, polymeric micelles with the ability of encapsulating proteins are developed via concurrent ion complexation and pH-cleavable covalent bonding between proteins and block copolymers directed to pH-triggered release of the protein payload. Carboxydimethylmaleic anhydride (CDM) is selected as the pH-sensitive moiety, since the CDMamide bond is stable at physiological pH (pH 7.4), while it cleaves at pH 6.5, that is, the pathophysiological pH of tumors and inflammatory tissues. By using poly(ethylene glycol)-poly(l-lysine) block copolymers having 45% CDM addition, different proteins with various sizes and isoelectric points are loaded successfully. By using myoglobin-loaded micelles (myo/m) as a model, the stability of the micelles in physiological conditions and the dissociation and release of functional myoglobin at pH 6.5 are successfully confirmed. Moreover, myo/m shows extended half-life in blood compared to free myoglobin and micelles assembled solely by polyion complex, indicating the potential of this system for in vivo delivery of proteins.

Granzyme B-loaded, cell-selective penetrating and reduction-responsive polymersomes effectively inhibit progression of orthotopic human lung tumor in vivo

The clinical use of protein therapeutics with intracellular targets is hampered by its in vivo fragility and low cell permeability. Here, we report that cell-selective penetrating and reduction-responsive polymersomes (CPRPs) mediate high-efficiency targeted delivery of granzyme B (GrB) to orthotopic human lung tumor in vivo. Model protein studies using FITC-labeled cytochrome C (FITC-CC) revealed efficient and high protein loading up to 17.2 wt% for CPRPs. FITC-CC-loaded CPRPs exhibited a small size of 82-90 nm, reduction-responsive protein release, as well as greatly enhanced internalization and cytoplasmic protein release in A549 lung cancer cells compared with the non-targeted FITC-CC-loaded RPs control. GrB-loaded CPRPs showed a high potency toward A549 lung cancer cells with a half maximal inhibitory concentration (IC₅₀) of 20.7 nM. Under the same condition, free GrB was essentially non-toxic. Importantly, installing cell-selective penetrating peptide did not alter the circulation time but did enhance tumor accumulation of RPs. Orthotopic A549-Luc lung tumor-bearing nude mice administered with GrB-loaded CPRPs at a dosage of 2.88 nmol GrB equiv./kg showed complete tumor growth inhibition with little body weight loss throughout the treatment period, resulting in significantly improved survival rate over the non-targeted and non-treated controls. These cell-selective penetrating and reduction-responsive polymersomes provide a targeted protein therapy for cancers.

Fabrication of Charge-Conversion Nanoparticles for Cancer Imaging by Flash Nanoprecipitation

Traditional charge-conversion nanoparticles (NPs) need the breakage of acid-labile groups on the surface, which impedes the rapid response to the acidic microenvironment. Here, we developed novel rodlike charge-conversion NPs with amphiphilic dextran- b-poly(lactic- co-glycolic acid), poly(2-(dimethylamino) ethylmethylacrylate)- b-poly(ε-caprolactone), and an aggregation-induced emission-active probe through flash nanoprecipitation (FNP). These NPs exhibit reversible negative-to-positive charge transition at a slightly acidic pH relying on the rapid protonation/deprotonation of polymers. The size and the critical charge-conversion pH can be further tuned by varying the flow rate and polymer ratio. Consequently, the charge conversion endows NPs with resistance to protein adsorption at physiological pH and enhanced internalization to cancer cells under acidic conditions. Ex vivo imaging on harvest organs shows that charge-conversion NPs were predominantly distributed in tumors after intravenous administration to mice due to the robust response of NPs to the acidic microenvironment in tumor tissue, whereas control NPs or free probes were broadly accumulated in tumor, liver, kidney, and lung. These results suggest the great potential of the current FNP strategy in the facile and generic fabrication of charge-conversion NPs for tumor-targeting delivery of drugs or fluorescent probes.

Transduction Methods for Cytosolic Delivery of Proteins and Bioconjugates into Living Cells

The human organism and its constituting cells rely on interplay between multiple proteins exerting specific functions. Progress in molecular biotechnologies has facilitated the production of recombinant proteins. When administrated to patients, recombinant proteins can provide important healthcare benefits. To date, most therapeutic proteins must act from the extracellular environment, with their targets being secreted modulators or extracellular receptors. This is because proteins cannot passively diffuse across the plasma membrane into the cytosol. To expand the scope of action of proteins for cytosolic targets (representing more than 40% of the genome) effective methods assisting protein cytosolic entry are being developed. To date, direct protein delivery is extremely tedious and inefficient in cultured cells, even more so in animal models of pathology. Novel techniques are changing this limitation, as recently developed in vitro methods can robustly convey large amount of proteins into cell cultures. Moreover, advances in protein formulation or protein conjugates are slowly, but surely demonstrating efficiency for targeted cytosolic entry of functional protein in vivo in tumor xenograft models. In this review, various methods and recently developed techniques for protein transport into cells are summarized. They are put into perspective to address the challenges encountered during delivery.

Dual-pH Sensitive Charge-Reversal Polypeptide Micelles for Tumor-Triggered Targeting Uptake and Nuclear Drug Delivery

A novel dual-pH sensitive charge-reversal strategy is designed to deliver antitumor drugs targeting to tumor cells and to further promote the nuclei internalization by a stepwise response to the mildly acidic extracellular pH (≈6.5) of a tumor and endo/lysosome pH (≈5.0). Poly(L-lysine)-block-poly(L-leucine) diblock copolymer is synthesized and the lysine amino residues are amidated by 2,3-dimethylmaleic anhydride to form β-carboxylic amide, making the polypeptides self-assemble into negatively charged micelles. The amide can be hydrolyzed when exposed to the mildly acidic tumor extracellular environment, which makes the micelles switch to positively charged and they are then readily internalized by tumor cells. A nuclear targeting Tat peptide is further conjugated to the polypeptide via a click reaction. The Tat is amidated by succinyl chloride to mask its positive charge and cell-penetrating function and thus to inhibit nonspecific cellular uptake. After the nanoparticles are internalized into the more acidic intracellular endo/lysosomes, the Tat succinyl amide is hydrolyzed to reactivate the Tat nuclear targeting function, promoting nanoparticle delivery into cell nuclei. This polypeptide nanocarrier facilitates tumor targeting and nuclear delivery simultaneously by simply modifying the lysine amino residues of polylysine and Tat into two different pH-sensitive β-carboxylic amides.

Nanostructural systems developed with positive charge generation to drug delivery

The surface charge of a nanostructure plays a critical role in modulating blood circulation time, nanostructure-cell interaction, and intracellular events. It is unfavorable to have positive charges on the nanostructure surface before arriving at the disease site because positively charged nanostructures interact strongly with blood components, resulting in rapid clearance from the blood, and suboptimal targeted accumulation at the tumor site. Once at the tumor site, however, the positive charge on the nanostructure surface accelerates uptake by tumor cells and promotes the release of payloads from the lysosomes to the cytosol or nucleus inside cells. Thus, the ideal nanocarrier systems for drug delivery would maintain a neutral or negatively charged surface during blood circulation but would then generate a positive surface charge after accumulation at the tumor site or inside the cancer cells. This Progress Report focuses on the design and application of various neutral or negatively charged nanostructures that can generate a positive charge in response to the tumor microenvironment or an external stimulus.

Natural polypeptide-based supramolecular nanogels for stable noncovalent encapsulation

Supramolecular nanogel, a physically cross-linked nanosize hydrogel, spontaneously self-assembles in aqueous solution via secondary interactions and is thus of great interest in nanomedicine as a drug carrier. We developed a versatile method for supramolecular nanogel self-assembled by electrostatic interaction between positive surfactant micelles and negative polypeptides. Core-shell-like structures of supramolecular nanogels provide stable hydrophobic pockets that prevent simple diffusion of hydrophobic guest molecules, resulting in high encapsulation stability. The size of the supramolecular nanogels can be systematically controlled by varying the size of the surfactant micelles. Furthermore, noncovalently encapsulated dye molecules can be released in response to matrix metalloproteinases highly overexpressed in tumor tissues, potentially providing tumor-triggered targeting.

Temperature-modulated noncovalent interaction controllable complex for the long-term delivery of etanercept to treat rheumatoid arthritis

The clinical applications of etanercept (Enbrel), an emerging therapeutic protein for rheumatoid arthritis (RA), are limited by its instability and low bioavailability. In this study, a long-term and efficient therapeutic nanocomplex formulation for RA treatment was developed in the form of a temperature-modulated noncovalent interaction controllable (TMN) complex based on a temperature-sensitive amphiphilic polyelectrolyte (succinylated pullulan-g-oligo(L-lactide); SPL). The TMN complexes were prepared by simply mixing the negatively charged SPL copolymer and the positively charged etanercept via electrostatic interaction at 4 °C below the polymer's clouding temperature (CT), and the resulting complex demonstrated significantly improved salt and serum stability with increased hydrophobic interactions at temperatures (physiological condition, 37.5 °C) above the CT. An in vitro study of the bioactivity of etanercept indicated that the TMN complex improves the long-term stability of etanercept in an aqueous environment because of the exposure of the functional active site and the molecular chaperone-like effect of the hydrophobic copolymer. This formulation possessed prolonged in vivo pharmacokinetic parameters. In a collagen-induced arthritis RA rat model, we verified the outstanding therapeutic effect of the TMN complexes. These results imply that this approach would be widely applied to protein and peptide delivery systems.

In situ forming reduction-sensitive degradable nanogels for facile loading and triggered intracellular release of proteins

In situ forming reduction-sensitive degradable nanogels were designed and developed based on poly(ethylene glycol)-b-poly(2-(hydroxyethyl) methacrylate-co-acryloyl carbonate) (PEG-P(HEMA-co-AC)) block copolymers for efficient loading as well as triggered intracellular release of proteins. PEG-P(HEMA-co-AC) copolymers were prepared with controlled Mn of 9.1, 9.5, and 9.9 kg/mol and varying numbers of AC units per molecule of 7, 9 and 11, respectively (denoted as copolymer 1, 2, and 3) by reversible addition-fragmentation chain transfer copolymerization. These copolymers were freely soluble in phosphate buffer but formed disulfide-cross-linked nanogels with defined sizes ranging from 72.5 to 124.1 nm in the presence of cystamine via ring-opening reaction with cyclic carbonate groups. The sizes of nanogels decreased with increasing AC units as a result of increased cross-linking density. Dynamic light scattering studies showed that these nanogels though stable at physiological conditions were rapidly dissociated in response to 10 mM dithiothreitol (DTT). Interestingly, FITC-labeled cytochrome C (FITC-CC) could be readily loaded into nanogels with remarkable loading efficiencies (up to 98.2%) and loading contents (up to 48.2 wt.%). The in vitro release studies showed that release of FITC-CC was minimal under physiological conditions but significantly enhanced under reductive conditions in the presence of 10 mM DTT with about 96.8% of FITC-CC released in 22 h from nanogel 1. In contrast, protein release from 1,4-butanediamine cross-linked nanogels (reduction-insensitive control) remained low under otherwise the same conditions. MTT assays showed that these nanogels were nontoxic to HeLa cells up to a tested concentration of 2 mg/mL. Confocal microscopy results showed that nanogel 1 delivered and released FITC-CC into the perinuclei region of HeLa cells following 8 h incubation. CC-loaded reductively degradable nanogels demonstrated apparently better apoptotic activity than free CC as well as reduction-insensitive controls. These in situ forming, surfactant and oil-free, and reduction-sensitive degradable nanogels are highly promising for targeted protein therapy.