Peptides For Intracellular Delivery Research Articles

Engineered Polymeric Nanovector for Intracellular Peptide Delivery in Antitumor Therapy.

This study aimed to deliver a polypeptide from the Bax-BH3 domain (BHP) through the synthesis of self-assembled amphiphile nanovectors (NVs) and to assess their potential for cancer therapeutic applications and biological safety in vitro and in vivo. These findings provide valuable options for cancer intervention and a novel approach for the rational design of therapeutics. We studied the antitumor activity of BHP by preparing RGDfK-PHPMA-b-Poly (MMA-alt-(Rhob-MA)) (RPPMMRA) and encapsulating it in BHP-NV. We also performed a series of characterizations and property analyses of RPPMMRA, including its size, stability, and drug-carrying capacity. The biocompatibility of RPPMMRA was evaluated in terms of cytotoxicity and hemolytic effects. The pro-apoptotic capacity of BHP was evaluated in vitro using mitochondrial membrane potential, flow cytometry, and apoptosis visualization techniques. The potential therapeutic effects of BHP on tumors were explored using reverse molecular docking. We also investigated the in vivo proapoptotic effect of BHP-NV in a nude mouse tumor model. NVs were successfully prepared with hydrated particle sizes ranging from 189.6 nm to 256.6 nm, spherical overall, and were able to remain stable in different media for 72 h with drug loading up to 15.2%. The NVs were be successfully internalized within 6 h with good biocompatibility. Neither BHP nor NV showed significant toxicity when administered alone, however, BHP-NV demonstrated significant side effects in vitro and in vivo. The apoptosis rate increased significantly from 14.13% to 66.34%. Experiments in vivo showed that BHP-NV exhibited significant apoptotic and tumor-suppressive effects. A targeted fluorescent NV with high drug delivery efficiency and sustained release protected the active center of BHP, constituting BHP-NV for targeted delivery. RPPMMRA demonstrated excellent biocompatibility, stability, and drug loading ability, whereas and BHP-NV demonstrated potent antitumor effects in vivo and in vitro.

A Versatile Platform for the Tumor‐Targeted Intracellular Delivery of Peptides, Proteins, and siRNA

AbstractThe efficient delivery of biologics into cells provide unique opportunities to modulate intracellular targets not druggable by conventional small molecules. The supercharged polypeptide (SCP) has become a novel intracellular delivery system due to their special advantages, including enhanced delivery efficiency and serum tolerance. However, owing to their cationic charge and non‐specificity characteristics, the in vivo application of SCP is limited. Here, an activatable SCP (ASCP) with a pH‐sensitive charge shielding sequence (CSS), a protease cleavage site, and SCP are engineered. This system shows the potential to reduce the non‐specific binding and effectively deliver various cargo (peptide, protein, small molecule, and siRNA) into the cytosol not only in vitro but also in vivo. Furthermore, an ASCP fusion protein is designed to co‐delivery of peptide (KLA)/siRNA (IKBKE) with different tumorigenesis pathways to triple negative breast cancer (TNBC) for optimal therapeutic outcomes. It is believed that ASCP delivery system will facilitate the development of bioactive molecules for use against intracellular targets. This simple yet versatile delivery system can also pave the way for the co‐delivery of multiple therapeutic cargos to address the emerging needs of combination cancer therapy.

Tetrahedral framework nucleic acids-based delivery promotes intracellular transfer of healing peptides and accelerates diabetic would healing.

ObjectivesPeptide‐based therapeutics are natural candidates to desirable wound healing. However, enzymatic surroundings largely limit its stability and bioavailability. Here, we developed a tetrahedral framework nucleic acids(tFNA)‐based peptide delivery system, that is, p@tFNAs, to address deficiencies of healing peptide stability and intracellular delivery in diabetic wound healing.Materials and MethodsAGEs (advanced glycation end products) were used to treat endothelial cell to simulate cell injury in diabetic microenvironment. The effects and related mechanisms of p@tFNAs on endothelial cell proliferation, migration, angiogenesis and ROS (reactive oxygen species) production have been comprehensively studied. The wound healing model in diabetic mice was photographically and histologically investigated in vivo.ResultsEfficient delivery of healing peptide by the framework(tFNA) was verified. p@tFNAs helped overcome the angiogenic obstacles induced by AGEs via ERK1/2 phosphorylation. In the meantime, p@tFNA exhibited its antioxidative property to achieve ROS balance. As a result, p@tFNA improved angiogenesis and diabetic wound healing in vitro and in vivo.ConclusionsOur findings demonstrate that p@tFNA could be a novel therapeutic strategy for diabetic wound healing. Moreover, a new method for intracellular delivery of peptides was also constructed.

Development of DNA aptamers specific for small therapeutic peptides using a modified SELEX method.

Aptamers are short single-stranded DNA or RNA oligonucleotides capable of binding with high affinity and specificity to target molecules. Because of their durability and ease of synthesis, aptamers are used in a wide range of biomedical fields, including the diagnosis of diseases and targeted delivery of therapeutic agents. The aptamers were selected using a process called systematic evolution of ligands by exponential enrichment (SELEX), which has been improved for various research purposes since its development in 1990. In this protocol, we describe a modified SELEX method that rapidly produces high aptamer screening yields using two types of magnetic beads. Using this method, we isolated an aptamer that specifically binds to an antimicrobial peptide. We suggest that by conjugating a small therapeutic-specific aptamer to a gold nanoparticle-based delivery system, which enhances the stability and intracellular delivery of peptides, aptamers selected by our method can be used for the development of therapeutic agents utilizing small therapeutic peptides.

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.

A manganese (II)-based coordinative dendrimer with robust efficiency in intracellular peptide delivery

Peptides have gained increasing interests as drug candidates in modern pharmaceutical industry, however, the development of peptide drugs acting on intracellular targets is limited due to their membrane impermeability. Here, we reported the use of metal-terpyridine based coordinative dendrimer for cytosolic peptide delivery. Among the investigated transition metal ions, Mn2+-coordinated polymer showed the highest delivery efficiency due to balanced peptide binding and release. It showed robust efficiency in the delivery of peptides with different charge property and hydrophobicity into various primary cells. The efficiency of Mn2+-terpyridine based polymer is superior to cell penetrating peptides such as oligoarginines. The material also delivered an autophagy-inducing peptide derived from Beclin-1 into cells and efficiently induced autophagy in the cells. This study provides a promising alternative to cell penetrating peptides for cytosolic peptide delivery.

Design of Polymeric Carriers for Intracellular Peptide Delivery in Oncology Applications.

In recent decades, peptides, which can possess high potency, excellent selectivity, and low toxicity, have emerged as promising therapeutics for cancer applications. Combined with an improved understanding of tumor biology and immuno-oncology, peptides have demonstrated robust antitumor efficacy in preclinical tumor models. However, the translation of peptides with intracellular targets into clinical therapies has been severely hindered by limitations in their intrinsic structure, such as low systemic stability, rapid clearance, and poor membrane permeability, that impede intracellular delivery. In this Review, we summarize recent advances in polymer-mediated intracellular delivery of peptides for cancer therapy, including both therapeutic peptides and peptide antigens. We highlight strategies to engineer polymeric materials to increase peptide delivery efficiency, especially cytosolic delivery, which plays a crucial role in potentiating peptide-based therapies. Finally, we discuss future opportunities for peptides in cancer treatment, with an emphasis on the design of polymer nanocarriers for optimized peptide delivery.

Endosomal Escape of Peptide-Photosensitizer Conjugates Is Affected by Amino Acid Sequences near the Photosensitizer.

Cell-penetrating peptides (CPPs) are widely used for the intracellular delivery of peptides and proteins, but CPP fusion peptides and proteins are often transported by endocytosis and trapped in endosomes. Photochemical internalization (PCI) is a method for the endosomal escape of the trapped peptide or protein and release into the cytosol using light and photosensitizers. In PCI, endosomal membranes are thought to be destabilized by singlet oxygen (1O2) photogenerated from photosensitizers localized in endosomes. We previously developed CPP-cargo-photosensitizer (PS) conjugates able to photodependently enter the cytosol via the PCI mechanism. For example, TatU1A-PS (a covalent complex of Tat [CPP], U1A RNA-binding protein [cargo], and PS) can photodependently deliver RNAs into the cytosol, and TatBim-PS (a covalent complex of Tat, Bim [cargo], and PS) can photoinduce apoptosis in mammalian cells. However, for many newly created conjugates, the induction of PCI has been insufficient. We hypothesized that the amino acid linker sequence (XX) adjacent to the photosensitizer is an important determinant of PCI efficiency. In this study, using CPP-cargo-XX-PS platforms, we examined the relationship between PCI efficiency and the linker amino acid sequence near the photosensitizer. We found that hydrophobic FF and LL linkers enhanced the PCI efficiencies of both TatBim-XX-PS and TatU1A-XX-PS. The effectiveness of the linker depended, in part, on both the cargo moiety and the photosensitizer. These results may guide the design of CPP-cargo-PS conjugates conferring broad target functions for PCI and photodynamic therapy.

Boronic acid-rich dendrimer for efficient intracellular peptide delivery

Interests in intracellular peptide delivery have continued to grow, significantly fueled by the importance of peptides and their mimetics in modern cell biology and pharmaceutical industry. However, efficient intracellular delivery of membrane-impermeable peptides of different polarities remains a challenging task. In this study, we develop a general and robust strategy for intracellular peptide delivery by using a boronic acid-rich dendrimer. The designed material is capable of transporting peptides with different polarities and charge properties into the cytosol of various cell lines without inducing additional cytotoxicity. The transduction efficacy and proteolytic stability of cargo peptides delivered by the boronic acid-rich dendrimer are much superior to peptides conjugated with cell penetrant peptides such as octaarginine. In addition, the bioactivities of pro-apoptotic peptides are maintained after intracellular delivery. This study provides a versatile and robust platform for the intracellular delivery of membrane-impermeable peptides.

Abstract LB-075: Structural stabilization of protein fragments by membrane anchoring for generation of cell-permeable protein mimetics

Abstract Targeting protein-protein interactions can provide plentiful opportunities for the discovery of novel drug candidates and powerful chemical biology tools. However, the majority of these interactions are ‘undruggable”, and we still know very little about the structural mechanisms and functions for the vast majority of them. We have developed a rational approach that allows for the straightforward development of cell-permeable metabolically stable inhibitors of protein-protein interactions. The approach is based on structural stabilization of peptides by membrane anchoring. Biophysical data suggests that proximity to the membrane facilitates interactions of hydrophobic side chains of amphiphilic peptides with the bilayer and stabilizes natural fold of not only helical but also stretched and hairpin-type peptides. Membrane tethering is achieved through straightforward derivatization of peptides with fatty acids of appropriate length that depends on peptide's hydrophobicity. Lipidation facilitates cell entry and allows intracellular delivery of peptides up to 14-16 residues long. Negative charges can interfere with the entry, while positive charges generally have little effect. Wide applicability of this method was confirmed by generation of selective and highly potent dominant negative inhibitors of RAS oncogenes, β-catenin, STAT1, STAT3 and STAT5 N-domains, Il10R1, IFNGR1 and other non-druggable targets. Rational design of inhibitors can be accomplished even in the absence of the target tertiary structure by using conservation of certain sequence parts during the evolution. High throughput generation of selective chemical biology tools allows for effective interrogation of protein-protein interactions leading to discovery of mechanistic details of molecular signaling that could not be obtained with the help of genetic approaches. Citation Format: Nadya Tarasova, Karen Stefanisko, Lyuba Khavrutskii, Sergey Tarasov. Structural stabilization of protein fragments by membrane anchoring for generation of cell-permeable protein mimetics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-075.

Macroporous silica nanoparticles for delivering Bcl2-function converting peptide to treat multidrug resistant-cancer cells

The abundance of B cell lymphoma gene 2 (Bcl-2) is closely correlated with the resistance of cancer cells to chemotherapeutic agents, and a peptide derived from orphan nuclear receptor Nur77 can convert Bcl-2 from a protector to a killer of cancer cells. However, successful application of the Bcl-2-converting peptide to treat drug-resistant cancer cells depends on an efficient delivery carrier. Mesoporous silica nanoparticles (MSNs) have been extensively studied as promising candidates for small molecule drug delivery. However, the effective encapsulation and intracellular delivery of peptides using small pore-sized MSNs still remain a great technical challenge. In this paper, an effective delivery platform for Bcl-2-converting peptide was fabricated by us to treat multidrug resistant-cancer cells via tuning the surface functionality of macroporous silica nanoparticles. The resulting large-sized pore silica nanoparticles, especially those modified with thiol group, exhibited the high Bcl-2-converting peptide-loading efficiency of over 40%. Moreover, the peptide induced MCF7/DOX cells into apoptotic status by penetrating cytomembrane into mitochondria and being bound with Bcl-2 to expose the BH3 domain with the aid of various surface functionalities-decorated MSNs. In particular, amine-modified surface of MSNs caused the greater influence on the cell apoptosis-inducing effects of peptide in comparison with other functionalities-modified ones. Taken together, our study, for the first time, demonstrates a special approach towards pore size and surface functionality-collectively modulated silica-based nanostructural material for effective delivery of bio-macromolecules (e.g., Bcl-2-converting peptide) to treat the multidrug resistant-cancer cells with elevated Bcl-2 levels.

Excipients for the lyoprotection of MAPKAP kinase 2 inhibitory peptide nano-polyplexes

Herein, excipients are investigated to ameliorate the deleterious effects of lyophilization on peptide-polymer nano-polyplex (NP) morphology, cellular uptake, and bioactivity. The NPs are a previously-described platform technology for intracellular peptide delivery and are formulated from a cationic therapeutic peptide and the anionic, pH-responsive, endosomolytic polymer poly(propylacrylic acid) (PPAA). These NPs are effective when formulated and immediately used for delivery into cells and tissue, but they are not amenable to reconstitution following storage as a lyophilized powder due to aggregation. To develop a lyophilized NP format that facilitates longer-term storage and ease of use, MAPKAP kinase 2 inhibitory peptide-based NPs (MK2i-NPs) were prepared in the presence of a range of concentrations of the excipients sucrose, trehalose, and lactosucrose prior to lyophilization and storage. All excipients improved particle morphology post-lyophilization and significantly improved MK2i-NP uptake in human coronary artery smooth muscle cells relative to lyophilized NPs without excipient. In particular, MK2i-NPs lyophilized with 300 mM lactosucrose as an excipient demonstrated a 5.23 fold increase in cellular uptake (p < 0.001), a 2.52 fold increase in endosomal disruption (p < 0.05), and a 2.39 fold increase in ex vivo bioactivity (p < 0.01) compared to MK2i-NPs lyophilized without excipients. In sum, these data suggest that addition of excipients, particularly lactosucrose, maintains and even improves the uptake and therapeutic efficacy of peptide-polymer NPs post-lyophilization relative to freshly-made formulations. Thus, the use of excipients as lyoprotectants is a promising approach for the long-term storage of biotherapeutic NPs and poises this NP platform for clinical translation.

Intracellular delivery of peptide drugs using viral nanoparticles of bacteriophage P22: covalent loading and cleavable release.

Peptides have great potential in the treatment of various diseases because of their high specificity and safety. However, their application has been limited by the lack of appropriate delivery techniques. In this study, we have demonstrated the intracellular delivery of peptides using viral nanoparticles (VNPs) of bacteriophage P22 through covalent loading of two different peptides with synergistic cytotoxic effects and controllable release triggered by Cathepsin B, a highly over-expressed protease in many tumors. Fluorescence imaging of the intracellular localization of the P22 VNPs and the peptides evidenced that the delivery system could be transported as designed. Cell Counting Kit-8 (CCK-8) assay and flow cytometry analysis revealed the cytotoxic effects of the peptides on MDA-MB-231 tumor cells. These results have confirmed the feasibility of genetically fusing cargo peptides to the capsid protein of P22 and cleavable release thereafter. This study may be instructive for the design of drug delivery systems and multifunctional theranostic devices based on P22 VNPs.

Enhanced intracellular peptide delivery by multivalent cell-penetrating peptide with bioreducible linkage

Multivalent cell-penetrating peptides (CPPs) have been reported to show enhancement in cellular uptake and endosomolytic activity. However, its application was limited to trans-delivery of cargo which is lower in cellular uptake efficiency of cargo than cis-delivery. Here, we tried the cis-delivery of cargo with multivalent CPP by preparing bioreducible dimeric CPP–cargo with apoptotic activity using TatBim peptide, a fusion of Tat CPP and Bim peptide derived from Bim apoptosis-inducing protein. Dimeric TatBim was almost twice as highly internalized by cells and significantly induced apoptosis compared to monomeric TatBim. Contribution of bioreducible linkage of dimeric TatBim towards apoptotic activity was also confirmed.

Delivery of Non-Native Cargo into Mammalian Cells Using Anthrax Lethal Toxin.

The intracellular delivery of peptide and protein therapeutics is a major challenge due to the plasma membrane, which acts as a barrier between the extracellular environment and the intracellular milieu. Over the past two decades, a nontoxic PA/LFN delivery platform derived from anthrax lethal toxin has been developed for the transport of non-native cargo into the cytosol of cells in order to understand the translocation process through a protective antigen (PA) pore and to probe intracellular biological functions. Enzyme-mediated ligation using sortase A and native chemical ligation are two facile methods used to synthesize these non-native conjugates, inaccessible by recombinant technology. Cargo molecules that translocate efficiently include enzymes from protein toxins, antibody mimic proteins, and peptides of varying lengths and non-natural amino acid compositions. The PA pore has been found to effectively convey over 30 known cargos other than native lethal factor (LF; i.e., non-native) with diverse sequences and functionalities on the LFN transporter protein. All together these studies demonstrated that non-native cargos must adopt an unfolded or extended conformation and contain a suitable charge composition in order to efficiently pass through the PA pore. This review provides insight into design parameters for the efficient delivery of new cargos using PA and LFN.

Abstract 5326: Intracellular bacterial delivery of a NIPP1-peptide kills tumor cells

Abstract Protein phosphatase-1 (PP1) is a cancer target because it is involved in many cell signaling pathways. Its activity is tightly regulated by its interaction partners, mainly via the RVxF-binding motif. RVxF-containing peptides deregulate PP1 and have therapeutic potential as antagonists of increased cancer kinase signaling. Because PP1 is responsible for more than half of the dephosphorylations on Ser/Thr sites, it is essential in all eukaryotic cells and it is difficult to target systemically. Moreover, delivering peptides to cells extracellularly is inefficient because of poor cell permeability and proteolytic instability. To specifically transport therapeutic peptides into cancer cells, we engineered bacteria to be intracellular delivery vectors. A bacterial delivery system (BDS) was designed by creating a strain that lyses after cell invasion and releases its contents into the cytoplasm of cancer cells. A BDS strain was then manipulated to express a peptide containing the RVxF motif of Nuclear Inhibitor of PP1 (NIPP1; AA 142-224). The therapeutic potential of this strain was tested on MCF-7 cell monolayers and on 3D tumor tissue. The BDS was cloned by inserting the bacterial phage lysis gene E under the control of the sseJ promoter, a Salmonella promoter that is activated after cell invasion. The specificity of the sseJ promoter was tested by inserting GFP under its control and infecting MCF-7 cancer cells with Salmonella containing the plasmid. All intracellular bacteria expressed GPF after 4 hours of infection, while no fluorescence was measured in the bacteria outside the mammalian cells. After infection, the created BDS lysed in 78% of invaded cells. BDS delivery of the NIPP1-peptide to MCF-7 cancer cells killed 41% of infected cells while infection with control, empty BDS did not result in any death. When treating tumor tissue with BDS expressing NIPP1-peptide, 39% of tumor tissue was killed after 9.5 hours, compared to 8% when treated with BDS alone. These results indicate that targeting phosphatases with intracellular peptide delivery by bacteria is feasible and reduces tumor tissue viability. Citation Format: Nele Van Dessel, Neil S. Forbes. Intracellular bacterial delivery of a NIPP1-peptide kills tumor cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5326. doi:10.1158/1538-7445.AM2015-5326

Effective Delivery of Endogenous Antioxidants Ameliorates Diabetic Nephropathy.

BackgroundDiabetic nephropathy (DN) is thought to be partially due to the injury of renal cells and the renal micro-environment by free radicals. Free radial scavenging agents that inhibit free radical damage may well prevent the development of underlying conditions such as mesangial expansion (by inhibiting extracellular matrix expression) in these patients.MethodsUsing techniques for intra-cellular delivery of peptides, we made metallothionein (MT) and superoxide dismutase (SOD), potent endogenous antioxidants, readily transducible into cell membrane and tested their protective effect against the development of DN in OLETF rats. Herein, we study antioxidant peptides for their ability to prevent oxidative damage to primary rat mesangial cells (MCs), which are important constituents of renal glomeruli.ResultsIntraperitoneal administration of these antioxidants resulted in delivery to the kidney and decreased ROS and the expression of downstream signals in renal cells and postponed the usual progression to DN. In in vitro experiments, MT and SOD were efficiently transferred to MCs, and the increased removal of ROS by MT and SOD was proportional to the degree of scavenging enzymes delivered. MT and SOD decreased three major oxidative injuries (hyperglycemia, AGE and ROS exposure) and also injuries directly mediated by angiotensin II in MCs while changing downstream signal transduction.ConclusionsThe protective effects of MT and SOD for the progression of DN in experimental animals may be associated with the scavenging of ROS by MT and SOD and correlated changes in signal transduction downstream. Concomitant administration of these antioxidant peptides may prove to be a new approach for the prevention and therapy of DN.

Improved intracellular delivery of peptide- and lipid-nanoplexes by natural glycosides

Targeted nanocarriers undergo endocytosis upon binding to their membrane receptors and are transported into cellular compartments such as late endosomes and lysosomes. In gene delivery the genetic material has to escape from the cellular compartments into the cytosol. The process of endosomal escape is one of the most critical steps for successful gene delivery. For this reason synthetic lipids with fusogenic properties such as 2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) are integrated into the nanocarriers.In this study we show that a natural, plant derived glycoside (SO1861) from Saponaria officinalis L. greatly improves the efficacy of lipid based as well as non-lipid based targeted nanoplexes consisting of a targeted K16 peptide with a nucleic acid binding domain and plasmid-DNA, minicircle-DNA or small interfering RNA (siRNA). By confocal live cell imaging and single cell analyses, we demonstrate that SO1861 augments the escape of the genetic cargo out of the intracellular compartments into the cytosol. Co-localisation experiments with fluorescence labelled dextran and transferrin indicate that SO1861 induces the release of the genetic cargo out of endosomes and lysosomes. However, the transduction efficacy of a lentivirus based gene delivery system was not augmented.In order to design receptor-targeted nanoplexes (LPD) with improved functional properties, SO1861 was integrated into the lipid matrix of the LPD. The SO1861 sensitized LPD (LPDS) were characterized by dynamic light scattering and transmission electron microscopy. Compared to their LPD counterparts the LPDS-nanoplexes showed a greatly improved gene delivery. As shown by differential scanning calorimetry SO1861 can be easily integrated into the lipid bilayer of glycerophospholipid model membranes. This underlines the great potential of SO1861 as a new transfection multiplier for non-viral gene delivery systems.

Effective delivery of a rationally designed intracellular peptide drug with gold nanoparticle-peptide hybrids.

A novel gold nanoparticle-peptide hybrid strategy was developed to intracellularly deliver a potent PKCδ inhibitor peptide for the treatment of acute lung injury. The gold nanoparticle-peptide hybrids showed good stability with high uptake, and demonstrated in vitro and in vivo efficacy. Our formulation strategy shows great promise in intracellular delivery of peptides.

A novel cell-penetrating peptide to facilitate intercellular transport of fused proteins

Cell-based delivery of cell penetrating peptides (CPPs) could represent a new platform for intracellular peptide delivery to local tissues. Expressed CPPs, coupled to a secretory signal peptide (SP), can support intercellular transport. However, low secretion efficiency, which may correlate with the positive charge of most CPPs, has emerged as one of the main impediments for efficient intercellular transport. We have reported that a modified Tat-based CPP (Tatm) with reduced positive charge is secreted efficiently, but its transduction activity was greatly reduced. We now show that a triple repeat of Tatm (Tatm3x) with an elongated α-helical amphipathic structure enhances transduction activity and simultaneously retains its secretion efficacy, although passage through the secretory pathway reduces its cell-penetrating activity. SP-Tatm3x supports intercellular transport of fused fluorescent proteins, as well as cell entry and function of a pro-apoptotic peptide. In addition, SP-Tatm3x largely escapes RNA inhibition, which is identified as another potential impediment to CPP-mediated intercellular transport. Expression of SP-Tatm3x in heparan sulfate proteoglycan-negative cells further improves its transduction activity. These results demonstrate the feasibility of intercellular transport of proteins, but further work is needed to better understand the reduction of cell-penetrating activity associated with secretion of CPP-fusion proteins.