Tricyclic cell-penetrating peptides for efficient delivery of functional antibodies into cancer cells

Strategies and challenges of cytosolic delivery of proteins

The cytosolic delivery of therapeutic proteins represents a promising strategy for addressing diseases caused by protein dysfunction. Despite significant advances, efficient delivery remains challenging due to barriers such as cell membrane impermeability, endosomal sequestration and protein instability. This review summarises recent progress in protein delivery systems, including physical, chemical and biological approaches, with a particular focus on strategies that enhance endosomal escape and targeting specificity. We further discuss the clinical translatability of these approaches and propose future directions for improving delivery efficiency and safety, ultimately unlocking the therapeutic potential of intracellular proteins.

Engineering IgG antibodies for intracellular targeting and drug delivery

Enabling immunoglobulin G (IgG)-format antibodies to autonomously internalize and localize in the cytosol of targeted cells-referred to as cytosol-penetrating antibodies (cytotransmab, CT)-is challenging yet highly promising. A primary barrier to cytosolic access for CT is limited endosomal escape. Herein, we developed a second-generation (2G) CT, named in2CT4.1, featuring an endosomal acidic pH-responsive endosomal escape motif (R-W/E motif) with Arg-Trp pairs and a Glu patch in the CH3 and CL domains of IgG1/κ antibody. This motif selectively destabilizes endosomal membranes at endosomal acidic pH to facilitate cytosolic access while remaining inactive at neutral pH. The 2G CT, in2CT4.1, achieves efficient cytosolic localization at nanomolar concentrations, demonstrating approximately 3-fold higher endosomal escape efficiency compared to the first-generation CT. The potential of 2G CT is validated by engineering a cytosolic α-tubulin-targeting CT via an α-tubulin-specific variable domain in in2CT4.1. Additionally, the 2G CT effectively delivers the catalytic domain of diphtheria toxin to the cytosol of epidermal growth factor receptor-overexpressing tumor cells, resulting in near-complete suppression of tumor growth in a xenograft mouse model. These results establish 2G CT as a versatile platform for targeting cytosolic proteins and delivering therapeutic payloads, with broad potential in targeted cancer therapy and other applications.

In Vivo Interrogation of Cell-Penetrating Peptide Function: Accumulation in Tumors and the Potential as a Specific PET Probe

We aimed to evaluate the biodistribution and specificity of 68Ga-DOTA-TAT and RHO-TAT using MGC-803 and HT-29 tumor cells as well as tumor-xenografted nude mice and to demonstrate its application in positron emission tomography (PET) imaging. The in vitro evaluation of 68Ga-DOTA-TAT was assessed in MGC-803 and HT-29 cell lines, and the in vivo evaluation of 68Ga-DOTA-TAT was also performed in mice bearing MGC-803 or HT-29 tumors, respectively. Fluorescence microscopy was also employed to evaluate the specificity of RHO-TAT in vitro in MGC-803 and HT-29 cells as well as ex vivo in tumor slices of the corresponding tumor models. The in vivo imaging differences between 68Ga-DOTA-TAT and 18F-FDG in MGC-803 and HT-29 tumors were also studied. The biodistribution and micro-PET results demonstrated significant uptake of 68Ga-DOTA-TAT in non-FDG-avid MGC-803 tumors, whereas there was negligible uptake in FDG-avid HT-29 tumors. RHO-TAT showed superior fluorescence microscopy imaging effects in MGC-803 cells and tumor slices but not in HT-29 cells and tumor slices, which were consistent with the in vivo results. 68Ga-DOTA-TAT combined with 18F-FDG can be applied noninvasively in cancers with PET imaging for potential patient selection and stratification. We demonstrated a higher binding of 68Ga-DOTA-TAT and RHO-TAT to MGC-803 cells as well as to non-FDG-avid MGC-803 xenografted tumors and a lower binding to HT-29 cells and FDG-avid xenografted tumors. These results suggest that TAT has the potential to be a ligand for targeting certain tumors.

Intracellular delivery of proteins for live cell imaging

The majority of cellular functions are regulated by intracellular proteins, and regulating their interactions can unlock fundamental insights in biology and open new avenues for drug discovery. Because the vast majority of intracellular targets remain undruggable, there is significant current interest in developing protein-based agents especially monoclonal antibodies due to their specificity, availability, and established screening/engineering methods. However, efficient delivery of proteins into the cytoplasm has been a major challenge in biological engineering and drug discovery. We previously reported a platform technology based on a Coomassie blue-cholesterol conjugate (CB-tag) capable of delivering small proteins directly into the cytoplasm. Here, we report a new generation of CB-tag that can bring proteins with a wide size range into the cytoplasm, bypassing endosomal sequestration. Remarkably, intracellular targets with distinct structures were visualized. Overall, the new CB-tag demonstrated a robust ability in protein delivery with broad applications ranging from live-cell immunofluorescence to protein-based therapeutic development.

Sustainable Materials Enabled Terahertz Functional Devices

Terahertz (THz) devices, owing to their distinctive optical properties, have achieved myriad applications in diverse domains including wireless communication, medical imaging therapy, hazardous substance detection, and environmental governance. Concurrently, to mitigate the environmental impact of electronic waste generated by traditional materials, sustainable materials-based THz functional devices are being explored for further research by taking advantages of their eco-friendliness, cost-effective, enhanced safety, robust biodegradability and biocompatibility. This review focuses on the origins and distinctive biological structures of sustainable materials as well as succinctly elucidates the latest applications in THz functional device fabrication, including wireless communication devices, macromolecule detection sensors, environment monitoring sensors, and biomedical therapeutic devices. We further highlight recent applications of sustainable materials-based THz functional devices in hazardous substance detection, protein-based macromolecule detection, and environmental monitoring. Besides, this review explores the developmental prospects of integrating sustainable materials with THz functional devices, presenting their potential applications in the future.

Efficient Synthesis of Cleavable Cell-Penetrating Peptide-Cargo Conjugate via Low-Equivalent of Cell-Penetrating Peptide Activated by 2,2'-Dithiodipyridine

Cell-penetrating peptides (CPPs) are favored for protein delivery due to their efficiency, rapidity, and low toxicity. However, conjugation of CPPs to proteins often requires significant amounts of CPPs to ensure yields, which also may result in increased protein dimer formation. Herein, it is reported that the use of low equivalents 2,2'-dithiodipyridine (DPDS)-activated CPP for conjugation cargo allows for high-conversion-rate CPP-cargo conjugates. Using this strategy, high-conversion-rate conjugates of cyclic deca-arginine peptide (cR10) with ubiquitin (Ub) and UbcH7 are obtained using only low equivalents of cR10. Furthermore, three CPPs are successfully conjugated to cargo via DPDS, and their successful cytosolic delivery is confirmed through fluorescence imaging.

Reprogramming of Glucose Metabolism by Nanocarriers to Improve Cancer Immunotherapy: Recent Advances and Applications

Although immunotherapy has made significant progress in cancer treatment, its limited responsiveness has greatly hindered widespread clinical application. The Warburg effect in tumor cells creates a tumor microenvironment (TME) characterized by hypoxia, low glucose levels, and high lactate levels, which severely inhibits the antitumor immune response. Consequently, targeting glucose metabolism to reprogram the TME is considered an effective strategy for reversing immunosuppression and immune evasion. Numerous studies have been conducted on enhancing cancer immunotherapy efficacy through the delivery of glucose metabolism modulators via nanocarriers. This review provides a comprehensive overview of the glucose metabolic characteristics of tumors and their impacts on the immune system, as well as nanodelivery strategies targeting glucose metabolism to enhance immunotherapy. These strategies include inhibiting key glycolytic enzymes, blocking glucose and lactate transporters, and utilizing glucose oxidase and lactate oxidase. Furthermore, this article reviews recent advancements in synergistic antitumor therapy involving glucose metabolism-targeted therapy combined with other treatments, such as chemotherapy, radiotherapy (RT), phototherapy, and immunotherapy. Finally, we discuss the limitations and future prospects of nanotechnology targeting glucose metabolism therapy, hoping to provide new directions and ideas to improve cancer immunotherapy.

Injectable ECM-mimetic dynamic hydrogels abolish ferroptosis-induced post-discectomy herniation through delivering nucleus pulposus progenitor cell-derived exosomes

Discectomy-induced ferroptosis of nucleus pulposus cells (NPCs) contributes to postoperative lumbar disc herniation (LDH) recurrence and intervertebral disc degeneration (IDD). We discover that nucleus pulposus progenitor cells (NPPCs) could imprint ferroptosis resistance into NPCs through exosome-dependent intercellular transmission of miR-221-3p. Based on these findings, we first develop synthetically-tailored NPPC-derived exosomes with enhanced miR-221-3p expression and NPC uptake capacity, which are integrated into an injectable hydrogel based on extracellular matrix (ECM) analogues. The ECM-mimetic hydrogel (HACS) serves as a biomimetic filler for the post-operative care of herniated discs, which could be facilely injected into the discectomy-established nucleus pulposus (NP) cavity for localized treatment. HACS-mediated in-situ exosome release in the NP cavity enables marked ferroptosis inhibition in NPCs that not only prevents LDH recurrence but also reverses the IDD symptoms, leading to robust restoration of NP structure and functions. In summary, this study offers a promising approach for treating disc herniation.

Mechanistic Insights into the Tools for Intracellular Protein Delivery

Proteins are an important therapeutic modality in modern medicine. However, their inherent inability to traverse cell membranes essentially limits their application to extracellular targets. Recent advances in intracellular protein delivery have enabled access to traditionally "undruggable" intracellular targets and paved the way to precisely modulate cellular functions. This Review provides a comprehensive examination of the key mechanisms and emerging technologies that facilitate the transport of functional proteins across cellular membranes. Delivery methods are categorized into physical, chemical, and biological approaches, each with distinct advantages and limitations. Physical methods enable direct protein entry but often pose challenges related to invasiveness and technical complexity. Chemical strategies offer customizable solutions with enhanced control over cellular targeting and uptake, yet may face issues with cytotoxicity and scalability. Biological approaches leverage naturally occurring processes to achieve efficient intracellular transport, though regulatory and production consistency remain hurdles. By highlighting recent advancements, challenges, and opportunities within each approach, this review underscores the potential of intracellular protein delivery technologies to unlock new therapeutic pathways and transform drug development paradigms.

Tumor Microenvironment pH-Sensitive Peptidomimetics for Targeted Anticancer Drug Delivery

Cell-penetrating peptides (CPPs) are known for their effective intracellular transport of bioactives such as therapeutic proteins, peptides, nucleic acid, and small molecule drugs. However, the excessive cationic charges that promote their membrane permeability result in nonselective delivery and cellular toxicity. In this study, we report a decamer cell-penetrating peptidomimetic, Hkd, designed to selectively deliver anticancer drugs into tumor cells in response to the acidic microenvironment. The pH-sensitive histidine (H) imidazole side chain undergoes protonation in acidic environments, facilitating membrane permeability. The rigid cyclic dipeptide (CDP) core (kd) of Hkd has multiple hydrogen bond donor and acceptor sites, enabling selective interaction-driven cellular uptake. Pharmacokinetic studies revealed the excellent serum stability of Hkd. Cellular uptake studies of Hkd showed improved uptake at a lower pH than physiological pH. Conjugation of Hkd to the anticancer drug camptothecin (Cpt) reduced nonselective drug transport to normal cells while effectively delivering the drug into cancerous cells at the tumor microenvironment pH and retaining the therapeutic potential of the drug. The systematic design of pH-sensitive peptidomimetics offers a viable method to overcome the challenges of stability and selectivity faced by traditional highly cationic CPPs, potentially expanding the application range of this delivery system.

Guanidyl-rich α-helical polypeptide enables efficient cytosolic pro-protein delivery and CRISPR-Cas9 genome editing

Intracellular delivery of proteins has attracted significant interest in biological research and cancer treatment, yet it continues to face challenges due to the lack of effective delivery approaches. Herein, we developed an efficient strategy via cationic α-helical polypeptide-mediated anionic proprotein delivery. The protein was reversibly modified with adenosine triphosphate via dynamic covalent chemistry to prepare an anionic proprotein (A-protein) with abundant phosphate groups. A guanidyl-decorated α-helical polypeptide (LPP) was employed not only to encapsulate A-protein through electrostatic attraction and hydrogen bonding, forming stable nanocomplexes, but also to enhance cell membrane penetration due to its rigid α-helical conformation. Consequently, this strategy mediated the effective delivery of various proteins with different isoelectric points and molecular weights, including α-chymotrypsin, bovine serum albumin, ribonuclease A, cytochrome C, saporin, horseradish peroxidase, β-galactosidase, and anti-phospho-Akt, into cancer cells. More importantly, it enabled efficient delivery of CRISPR-Cas9 ribonucleoproteins to elicit robust polo-like kinase 1 genome editing for inhibiting cancer cell growth. This rationally designed protein delivery system may benefit the development of intracellular protein-based cancer therapy.

Staudinger Reaction-Responsive Coacervates for Cytosolic Antibody Delivery and TRIM21-Mediated Protein Degradation

A low-molecular-weight compound whose structure strikes a fine balance between hydrophobicity and hydrophilicity may form coacervates via liquid-liquid phase separation in an aqueous solution. These coacervates may encapsulate and convoy proteins across the plasma membrane into the cell. However, releasing the cargo from the vehicle to the cytosol is challenging. Here, we address this issue by designing phase-separating coacervates, which are disassembled by the bioorthogonal Staudinger reaction. We constructed and selected triphenylphosphine-based compounds that formed phase-separated coacervates in an aqueous solution. Reacting the coacervates with azides resulted in microdroplet dissolution, so they received the name Staudinger Reaction-Responsive Coacervates, SR-Coa. SR-Coa could encapsulate proteins, including antibodies, and translocate them across the plasma membrane into the cell. Further treatment of the cell with ethyl azidoacetate induced the cargo dispersion from the puncta to the cytosolic distribution. We showcased an application of the SR-Coa/ethyl azidoacetate system in facilitating the translocation of the EGFR/antibody complex into the cell, which induced EGFR degradation via the TRIM21-dependent pathway both in vitro and in vivo. Besides the membrane protein EGFR, this system could also degrade endogenous protein EZH2. Taken together, here we report a strategy of controlling molecular coacervates by a bioorthogonal reaction in the cell for cytosolic protein delivery and demonstrate its use in promoting targeted protein degradation via the proteasome-dependent pathway.

Enhancing DNA Vaccine Delivery Through Stearyl-Modified Cell-Penetrating Peptides: Improved Antigen Expression and Immune Response In Vitro and In Vivo

BACKGROUND

Inefficient cellular uptake is a significant limitation to the efficacy of DNA vaccines. In this study, we introduce S-Cr9T, a stearyl-modified cell-penetrating peptide (CPP) designed to enhance DNA vaccine delivery by forming stable complexes with plasmid DNA, thereby protecting it from degradation and promoting efficient intracellular uptake.

METHODS AND RESULTS

In vitro studies showed that S-Cr9T significantly improved plasmid stability and transfection efficiency, with optimal performance at an N/P ratio of 0.25. High-content imaging revealed that the S-Cr9T-plasmid complex stably adhered to the cell membrane, leading to enhanced plasmid uptake and transfection. In vivo, S-Cr9T significantly increased antigen expression and triggered a robust immune response, including a threefold increase in IFN-γ secretion and several hundred-fold increases in antibody levels compared to control groups.

CONCLUSIONS

These findings underscore the potential of S-Cr9T to enhance DNA vaccine efficacy, offering a promising platform for advanced gene therapy and vaccination strategies.

Rapid and unbiased enrichment of extracellular vesicles via a meticulously engineered peptide

Extracellular vesicles (EVs) have garnered significant attention in biomedical applications. However, the rapid, efficient, and unbiased separation of EVs from complex biological fluids remains a challenge due to their heterogeneity and low abundance in biofluids. Herein, we report a novel approach to reconfigure and modify an artificial insertion peptide for the unbiased and rapid isolation of EVs in 20 min with ∼80% recovery in neutral conditions. Moreover, the approach demonstrates exceptional anti-interference capability and achieves a high purity of EVs comparable to standard ultracentrifugation and other methods. Importantly, the isolated EVs could be directly applied for downstream protein and nucleic acid analyses, including proteomics analysis, exome sequencing analysis, as well as the detection of both epidermal growth factor receptor (EGFR) and V-Ki-ras2 Kirsten Rat Sarcoma Viral Oncogene Homologue (KRAS) gene mutation in clinical plasma samples. Our approach offers great possibilities for utilizing EVs in liquid biopsy, as well as in various other biomedical applications.

Cell-Penetrating Peptide Induced Superstructures Triggering Highly Efficient Antibacterial Activity

To endow non-antibacterial molecules with highly efficient bactericide activity is an important but challenging issue. Herein, a kind of cell-penetrating peptide octa-arginine (R8) is found to be effective in activating antibacterial ability when assembling with anionic surfactant sodium dodecyl sulfate (SDS), while individual R8 or SDS shows poor or no antibacterial ability. By combined electrostatic, hydrogen bond, and hydrophobic interactions, R8 and SDS associate into wormlike micelle and lamellar structure by forming supramolecular self-assembling units, depending on their charge ratio (CR). The lamellar aggregates show particularly high antibacterial activities against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Interestingly, E. coli and S. aureus are killed by membrane-disrupting and membrane-penetrating mechanisms, respectively. Furthermore, in vivo experiments evidence that the R8/SDS lamellar aggregates accelerate the recovery of bacteria-infected wounds, wherein the reduced inflammation and promoted angiogenesis are clearly presented. This study proves that highly efficient bactericidal activity is triggered by the synergistic action of penetrating peptide and anionic amphiphiles, thus providing a new strategy to realize highly efficient and targetable antibacterial application.

Polysaccharide-Based Coacervate Microgel Bearing Cationic Peptides That Achieve Dynamic Cell-Membrane Structure Alteration and Facile Cytosolic Infusion of IgGs

Conjugates of the biocompatible polysaccharide pullulan with a cell membrane permeabilizing peptide L17E (PL-L17Es) were prepared with the aim of producing complex coacervates with pronounced intracellular antibody (IgG) delivery activity and stable structures. Coacervates with diameters of a few μm were formed simply by mixing PL-L17Es with IgG labeled with negatively charged fluorescent moieties of Alexa Fluor 488 [IgG(AF488)]. The coacervate resulted in a pronounced cytosolic infusion of IgG(AF488) and IgG binding to the target proteins inside the cell. The droplet structures were maintained even under high salt conditions, and the fluorescence in the droplet was not recovered after photobleaching, suggesting the formation of complex coacervate microgels. Dynamic changes in cell membrane structure to entrap the coacervate microgels were captured by confocal and electron microscopy, resulting in cytosolic IgG infusion. The use of M-lycotoxin instead of L17E resulted in a coacervate microgel with marked IgG delivery activity even in the presence of serum. Successful IgG delivery to primary hepatocytes, undifferentiated induced pluripotent stem (iPS) cells, and iPS cell-derived intestinal epithelial cells was also achieved. The construction of complex coacervate microgels with design flexibility and the validity of intracellular IgG delivery with high salt stability were thus demonstrated.

Strategies to boost antibody selectivity in oncology

Antibodies in oncology are being equipped with toxic cargoes and effector functions that can kill cells at very low concentrations. A key challenge is that most targets on cancer cells are also present on at least some healthy cells. Shared targets can result in off-tumor binding and compromise the safety and potential of therapeutic candidates. In this review, we survey strategies that can help direct biologics to cancer sites more selectively. These strategies are becoming increasingly feasible thanks to advances in molecular design and engineering. The objective is to create therapeutics that exploit changes in cancer and leverage the human body infrastructure, enabling therapeutics that discriminate not just self from non-self but diseased from healthy tissue.

Orthogonal DNA Self-Assembly-Based Expansion Microscopy Platform for Amplified, Multiplexed Biomarker Imaging

Expansion microscopy (ExM) facilitates nanoscale imaging under conventional microscopes, but it frequently encounters challenges such as fluorescence losses, low signal-to-noise ratio (SNR), and limited detection throughput. To address these issues, a method of orthogonal DNA self-assembly-based ExM (o-DAExM) platform is developed, which employs hybridization chain reaction instead of conventional fluorescence labeling units, showcasing signal amplification efficacy, enhancement of SNR, and expandable multiplexing capability at any stage of the ExM process. In this work, o-DAExM has been applied to compare with immunofluorescence-based ExM for cellular cytoskeleton imaging, and the resolved nanoscale spatial distributions of cytoskeleton show outstanding performance and reliability of o-DAExM. Furthermore, the study demonstrates the utility of o-DAExM in accurately revealing exosome heterogeneous information and multiplexed analysis of protein targets in single cells, which provides infinite possibilities in super-resolution imaging of cells and other samples. Therefore, o-DAExM offers a straightforward expansion and signal labeling method, highlighting future prospects to study nanoscale structures and functional networks in biological systems.

A cell-penetrating NS5B-specific nanobody inhibits bovine viral diarrhea virus replication

Bovine viral diarrhea virus (BVDV) causes one of the significant devastating diseases for the cattle industry worldwide. The virus can cross the placenta and result in the persistent infection of the fetus, which has hampered the efficacy and the development of vaccines. Hence, efficient antiviral strategies are urgently needed. In our previous work, a specific nanobody Nb1 against nonstructural protein 5 (NS5B) was successfully isolated, and the replication of BVDV was significantly reduced in the MDBK cell line stably expressing Nb1. Nevertheless, the Nb1 protein itself cannot enter the cells autonomously, which has severely hampered the application of the Nb1. In this work, Nb1fuses with a trans-activating transduction (TAT) peptide to form the TAT-Nb1. The TAT-Nb1 was expressed in Escherichia coli, and then purified by Ni-nitrilotriacetic acid (Ni-NTA) resin. We showed that TAT successfully delivered Nb1 into the MDBK cells, and the TAT-Nb1 efficiently inhibited the replication of BVDV in a dose-and time-dependent manner. Furthermore, the recognition site of Nb1 to NS5B was identified as NS5Baa186-487 by the yeast two-hybrid assay. In summary, this study indicates that the TAT-Nb1 can potentially to be an antiviral drug against BVDV infection, and this research may accelerate the process of Nb1 for clinical use.

Spotlight on HIV-derived TAT peptide as a molecular shuttle in drug delivery

HIV-derived TAT peptide, with a high penetration rate into cells and its nonimmunogenic and minimally toxic nature, is an attractive tool for enhancing the biodistribution of drugs and their systemic administration. Despite the presence of numerous promising preclinical investigations illustrating its capability to specifically target distinct tissues and deliver a diverse range of pharmacological agents, the efficacy of various clinical trials incorporating TAT has been impeded by several considerable obstacles. Hence, there is much need for an in-depth investigation concerning the application of TAT in drug delivery mechanisms. In this review, we have elucidated the structure of TAT and its utility in the proficient delivery of various types of bioactive molecules.

Antibody-Directing Antibody Conjugates (ADACs) Enabled by Orthogonal Click Chemistry for Targeted Intracellular Delivery

Using orthogonal click chemistries for efficient nanoscale self-assembly, a new antibody-directing antibody conjugate (ADAC) nanogel is generated. In this system, one of the antibodies is displayed on the nanogel surface to specifically recognize cell-surface epitopes while the other antibody is encapsulated inside the nanogel core. The system is programmed to release the latter antibody in its functional form in the cytosolic environment of a specific cell to engage intracellular targets. ADACs offer a potential solution to harness the advantages seen with antibody-drug conjugates (ADCs) to deliver therapeutic cargos to specific tissues, but with the added capability of carrying biologics as the cargo. In this manuscript, this potential is demonstrated through delivery of antibodies against intracellular targets in specific cells. This platform offers new avenues for precise therapeutic interventions and the potential to address previously "undruggable" cellular targets.

Design of peptide therapeutics as protein-protein interaction inhibitors to treat neurodegenerative diseases

Peptide therapeutics are an emerging class of drugs to treat neurodegenerative diseases by inhibiting protein-protein interactions (PPIs). Nerinetide has recently emerged as a promising therapeutic for the treatment of ischemic stroke and Alzheimer's Disease (AD). The design of this potent neuroprotective agent includes a cell penetrating peptide sequence that achieves delivery into neurons and a protein-protein inhibitory sequence that achieves inhibition of protein complex formation through mimicry. In this study, we deconstruct the nerinetide sequence and study the relationship between plasma stability, intraneuronal delivery and drug efficacy to provide design guidelines for the development of next generation, peptidic PPI inhibitors to treat neurodegenerative diseases.

Green synthesis of highly fluorescent carbon quantum dots from almond resin for advanced theranostics in biomedical applications

Fluorescent Carbon Quantum Dots (CQDs) are being used in medical applications, particularly in theranostics. These Carbon Quantum Dots have been gaining more attention lately due to their potential as an effective replacement for hazardous synthetic organic dyes in a variety of biomedical applications, including live cell imaging and diagnostics. In this study, highly fluorescent Carbon Quantum Dots by one pot microwave based green route with a size of less than 10 nm, was prepared from commercially available almond resin, Prunus dulcis and conjugated with honey as additional reagent for surface functionalization. They exhibit a deep blue emission on excitation at 350 nm with an elevated quantum yield at 61%. They possess atomic nature and basic features such as high photo-stability, varying fluorescence, greater biocompatibility, and better water solubility. These fluorescent labels exhibit faster cellular invagination without disturbing the cell stability. The CQDs present cell imaging capacity with multi-coloration for visualizing the fine architecture of the nucleus naming, the nuclear membrane and nucleolus, which is linked with their varied, surface structures such as amphiphilic property and higher positive charges. These characteristics with minimal invasion have made carbon quantum dots to become the spotlight in theranostics. They can be used as alternatives to synthetic dyes for fluorescence- related cell-imaging. The intriguing fact about this approach is that it opens the possibility of combining therapy and diagnostics into one unit, which can alter how some diseases are handled and, in turn, transform the field of healthcare.

Molecular Imaging of p53 in Mouse Models of Cancer Using a Radiolabeled Antibody TAT Conjugate with SPECT

Mutations of p53 protein occur in over half of all cancers, with profound effects on tumor biology. We present the first-to our knowledge-method for noninvasive visualization of p53 in tumor tissue in vivo, using SPECT, in 3 different models of cancer. Methods: Anti-p53 monoclonal antibodies were conjugated to the cell-penetrating transactivator of transcription (TAT) peptide and a metal ion chelator and then radiolabeled with 111In to allow SPECT imaging. 111In-anti-p53-TAT conjugates were retained longer in cells overexpressing p53-specific than non-p53-specific 111In-mIgG (mouse IgG from murine plasma)-TAT controls, but not in null p53 cells. Results: In vivo SPECT imaging showed enhanced uptake of 111In-anti-p53-TAT, versus 111In-mIgG-TAT, in high-expression p53R175H and medium-expression wild-type p53 but not in null p53 tumor xenografts. The results were confirmed in mice bearing genetically engineered KPC mouse-derived pancreatic ductal adenocarcinoma tumors. Imaging with 111In-anti-p53-TAT was possible in KPC mice bearing spontaneous p53R172H pancreatic ductal adenocarcinoma tumors. Conclusion: We demonstrate the feasibility of noninvasive in vivo molecular imaging of p53 in tumor tissue using a radiolabeled TAT-modified monoclonal antibody.

An injectable adhesive hydrogel for photothermal ablation and antitumor immune activation against bacteria-associated oral squamous cell carcinoma

Pathogenic bacteria are closely associated with the occurrence, development and metastasis of oral squamous cell carcinoma (OSCC). Antibacterial therapy has been considered an enhancement strategy to suppress bacteria-associated tumors and promote anti-tumor immune responses. Herein, we developed an injectable adhesive hydrogel, PNIPAM/DL@TIR, for the in situ photothermal ablation and robust stimulation of antitumor immunity against OSCC colonized by Porphyromonas gingivalis (Pg), one of the major oral pathogenic bacteria. PNIPAM/DL@TIR, composed of poly(N-isopropylacrylamide), demethylated lignin, and TAT peptide-conjugated IR820, was prepared using a simple dissolve-dry-swell solvent exchange method. Upon 808 nm laser irradiation, PNIPAM/DL@TIR exerted photothermal effects to ablate Pg-colonized OSCC and generate dual tumor and bacterial antigens. Owing to its large number of catechol groups, PNIPAM/DL@TIR efficiently captured these antigens to form an in situ antigen repository, thereby eliciting robust and durable antitumor immune responses. Proteomic analysis revealed that the captured antigens comprised both tumor neoantigens and bacterial antigens. The catechol groups endowed PNIPAM/DL@TIR with antioxidant activity, which was also conducive to stimulating antitumor immunity. Altogether, this study develops an injectable adhesive hydrogel and provides a combination strategy for treating bacteria-associated OSCC. STATEMENT OF SIGNIFICANCE: In this study, we developed an injectable adhesive hydrogel, PNIPAM/DL@TIR, for in situ photothermal ablation and robust stimulation of antitumor immunity against OSCC colonized by Porphyromonas gingivalis, one of the major oral pathogenic bacteria. PNIPAM/DL@TIR, which consists of poly(N-isopropylacrylamide), demethylated lignin, and TAT peptide-conjugated IR820 exhibited outstanding photothermal performance. Owing to the presence of catechol groups, PNIPAM/DL@TIR has good bioadhesive properties and can capture protein antigens to form in situ antigen repository, thus initiating robust and long-term antitumor immune responses. In addition, PNIPAM/DL@TIR exhibited strong antioxidant activity that is favorable for promoting antitumor immunity. In the mouse model of OSCC with bacterial infection, PNIPAM/DL@TIR not only ablated the primary tumors upon NIR laser irradiation, but also induced tumor and bacterial vaccination in situ to suppress distant tumors and lung metastasis.

Impact of Cellular Crowding on Protein Structural Dynamics Investigated by EPR Spectroscopy

The study of how the intracellular medium influences protein structural dynamics and protein-protein interactions is a captivating area of research for scientists aiming to comprehend biomolecules in their native environment. As the cellular environment can hardly be reproduced in vitro, direct investigation of biomolecules within cells has attracted growing interest in the past two decades. Among magnetic resonances, site-directed spin labeling coupled to electron paramagnetic resonance spectroscopy (SDSL-EPR) has emerged as a powerful tool for studying the structural properties of biomolecules directly in cells. Since the first in-cell EPR experiment was reported in 2010, substantial progress has been made, and this Review provides a detailed overview of the developments and applications of this spectroscopic technique. The strategies available for preparing a cellular sample and the EPR methods that can be applied to cells will be discussed. The array of spin labels available, along with their strengths and weaknesses in cellular contexts, will also be described. Several examples will illustrate how in-cell EPR can be applied to different biological systems and how the cellular environment affects the structural and dynamic properties of different proteins. Lastly, the Review will focus on the future developments expected to expand the capabilities of this promising technique.

An approach for the intracellular delivery of IgG via enzymatic ligation with a cell-permeable attenuated cationic amphiphilic lytic peptide

Achieving effective intracellular delivery of therapeutic molecules such as antibodies (IgG) is a challenge in biomedical research and pharmaceutical development. Conjugation of IgG with a cell-penetrating peptide is a rational approach. Here, not only the efficacy of the conjugates in internalizing into cells, but also the physicochemical property of the conjugates allowing their solubilized states in solution without forming aggregates are critical. In this study, we have shown that the first requirement can be addressed using a cell-permeable attenuated cationic amphiphilic lytic (CP-ACAL) peptide, L17ER4. The second requirement can be addressed by ligation of IgG to L17ER4 using sortase A, where the use of a linker of appropriate chain length is also important. For evaluation, the intracellular delivery efficacy was studied using conjugate structures with different orientations and conjugation modes of L17ER4 in ligation to a model protein, green fluorescent protein fused to a nuclear localization signal (NLS-EGFP). The effect of tetraarginine positioning in the L17ER4 sequence was also investigated. Following these studies, an optimized peptide sequence containing L17ER4 was ligated to an anti-green fluorescent protein (GFP) IgG bearing a sortase A recognition sequence. Treatment of the cells with the conjugate of anti-GFP IgG and L17ER4 resulted in a high efficiency of cytosolic translocation of the conjugate and the binding to the target protein in the cell without significant aggregate formation. The feasibility of the d-form of L17ER4 as a CP-ACAL was also confirmed.

Intracellular delivery strategies using membrane-interacting peptides and proteins

While the cellular cytosol and organelles contain attractive targets for disease treatments, it remains a challenge to deliver therapeutic biomacromolecules to these sites. This is due to the selective permeability of the plasma and endosomal membranes, especially for large and hydrophilic therapeutic cargos such as proteins and nucleic acids. In response, many different delivery systems and molecules have been devised to help therapeutics cross these barriers to reach cytosolic targets. Among them are peptide and protein-based systems, which have several advantages over other natural and synthetic materials including their ability to interact with cell membranes. In this review, we will describe recent advances and current challenges of peptide and protein strategies that leverage cell membrane association and modulation to enable cytosolic delivery of biomacromolecule cargo. The approaches covered here include peptides and proteins derived from or inspired by natural sequences as well as those designed de novo for delivery function.

Identifying Cell-Penetrating Peptides for Effectively Delivering Antimicrobial Molecules into Streptococcus suis

Cell-penetrating peptides (CPPs) are promising carriers to effectively transport antisense oligonucleotides (ASOs), including peptide nucleic acids (PNAs), into bacterial cells to combat multidrug-resistant bacterial infections, demonstrating significant therapeutic potential. Streptococcus suis, a Gram-positive bacterium, is a major bacterial pathogen in pigs and an emerging zoonotic pathogen. In this study, through the combination of super-resolution structured illumination microscopy (SR-SIM), flow cytometry analysis, and toxicity analysis assays, we investigated the suitability of four CPPs for delivering PNAs into S. suis cells: HIV-1 TAT efficiently penetrated S. suis cells with low toxicity against S. suis; (RXR)4XB had high penetration efficiency with inherent toxicity against S. suis; (KFF)3K showed lower penetration efficiency than HIV-1 TAT and (RXR)4XB; K8 failed to penetrate S. suis cells. HIV-1 TAT-conjugated PNA specific for the essential gyrase A subunit gene (TAT-anti-gyrA PNA) effectively inhibited the growth of S. suis. TAT-anti-gyrA PNA exhibited a significant bactericidal effect on serotypes 2, 4, 5, 7, and 9 strains of S. suis, which are known to cause human infections. Our study demonstrates the potential of CPP-ASO conjugates as new antimicrobial compounds for combating S. suis infections. Furthermore, our findings demonstrate that applying SR-SIM and flow cytometry analysis provides a convenient, intuitive, and cost-effective approach to identifying suitable CPPs for delivering cargo molecules into bacterial cells.

Finding ways into the cytosol: Peptide-mediated approaches for delivering proteins into cells

The delivery of functional proteins, including antibodies, into cells opens up many opportunities to regulate cellular events, with significant implications for studies in chemical biology and therapeutics. The inside of cells is isolated from the outside by the cell membrane. The hydrophilic nature of proteins prevents direct permeation of proteins through the cell membrane by passive diffusion. Therefore, delivery routes using endocytic uptake followed by endosomal escape have been explored. Alternatively, delivery concepts using transient permeabilization of cell membranes or effective promotion of endocytic uptake and endosomal escape using modified membrane-lytic peptides have been reported in recent years. Non-canonical protein delivery concepts, such as the use of liquid droplets or coacervates, have also been proposed. This review highlights some of the topics in peptide-mediated intracellular protein delivery.

Covalent conjugation and non-covalent complexation strategies for intracellular delivery of proteins using cell-penetrating peptides

Therapeutic proteins provided new opportunities for patients and high sales volumes. However, they are formulated for extracellular targets. The lipophilic barrier of the plasma membrane renders the vast array of intracellular targets out of reach. Peptide-based delivery systems, namely cell-penetrating peptides (CPPs), have few safety concerns, and low immunogenicity, with control over administered doses. This study investigates CPP-based protein delivery systems by classifying them into CPP-protein "covalent conjugation" and CPP: protein "non-covalent complexation" categories. Covalent conjugates ensure the proximity of the CPP to the cargo, which can improve cellular uptake and endosomal escape. We will discuss various aspects of covalent conjugates through non-cleavable (stable) or cleavable bonds. Non-cleavable CPP-protein conjugates are produced by recombinant DNA technology to express the complete fusion protein in a host cell or by chemical ligation of CPP and protein, which ensures stability during the delivery process. CPP-protein cleavable bonds are classified into pH-sensitive and redox-sensitive bonds, enzyme-cleavable bonds, and physical stimuli cleavable linkers (light radiation, ultrasonic waves, and thermo-responsive). We have highlighted the key characteristics of non-covalent complexes through electrostatic and hydrophobic interactions to preserve the conformational integrity of the CPP and cargo. CPP-mediated protein delivery by non-covalent complexation, such as zippers, CPP adaptor methods, and avidin-biotin technology, are featured. Conclusively, non-covalent complexation methods are appropriate when a high number of CPP or protein samples are to be screened. In contrast, when the high biological activity of the protein is critical in the intracellular compartment, conjugation protocols are preferred.

Remodeling of anti-tumor immunity with antibodies targeting a p53 mutant

BACKGROUND

p53, the most frequently mutated gene in cancer, lacks effective targeted drugs.

METHODS

We developed monoclonal antibodies (mAbs) that target a p53 hotspot mutation E285K without cross-reactivity with wild-type p53. They were delivered using lipid nanoparticles (LNPs) that encapsulate DNA plasmids. Western blot, BLI, flow cytometry, single-cell sequencing (scRNA-seq), and other methods were employed to assess the function of mAbs in vitro and in vivo.

RESULTS

These LNP-pE285K-mAbs in the IgG1 format exhibited a robust anti-tumor effect, facilitating the infiltration of immune cells, including CD8+ T, B, and NK cells. scRNA-seq revealed that IgG1 reduces immune inhibitory signaling, increases MHC signaling from B cells to CD8+ T cells, and enriches anti-tumor T cell and B cell receptor profiles. The E285K-mAbs were also produced in the dimeric IgA (dIgA) format, whose anti-tumor activity depended on the polymeric immunoglobulin receptor (PIGR), a membrane Ig receptor, whereas that of IgG1 relied on TRIM21, an intracellular IgG receptor.

CONCLUSIONS

Targeting specific mutant epitopes using DNA-encoded and LNP-delivered mAbs represents a potential precision medicine strategy against p53 mutants in TRIM21- or PIGR-positive cancers.

Homologous polydopamine ameliorates haemolysis of melittin for enhancing its anticancer efficacy

Despite exhibiting potent anticancer activity, the strong hemolytic properties of melittin (MEL) significantly restrict its delivery efficiency and clinical applications. To address this issue, we have devised a strategy wherein homologous dopamine (DA), an essential component of bee venom, is harnessed as a vehicle for the synthesis of MEL-polydopamine (PDA) nanoparticles (MP NPs). The ingenious approach lies in the fact that MEL is a basic polypeptide, and the polymerization of DA is also conducted under alkaline conditions, indicating the distinctive advantages of PDA in MEL encapsulation. Furthermore, MP NPs are modified with folic acid to fabricate tumor-targeted nanomedicine (MPF NPs). MPF NPs can ameliorate the hemolysis of MEL in drug delivery and undergo degradation triggered by high levels of reactive oxygen species (ROS) within solid tumors, thereby facilitating MEL release and subsequent restoration of anticancer activity. After cellular uptake, MPF NPs induce cell apoptosis through the PI3K/Akt-mediated p53 signaling pathway. The tumor growth inhibitory rate of MPF NPs in FA receptor-positive 4T1 and CT26 xenograft mice reached 78.04% and 81.66%, which was significantly higher compared to that in FA receptor-negative HepG2 xenograft mice (45.79%). Homologous vehicles provide a new perspective for nanomedicine design.

Sulfonium-Stapled Peptides-Based Neoantigen Delivery System for Personalized Tumor Immunotherapy and Prevention

Neoantigen peptides hold great potential as vaccine candidates for tumor immunotherapy. However, due to the limitation of antigen cellular uptake and cross-presentation, the progress with neoantigen peptide-based vaccines has obviously lagged in clinical trials. Here, a stapling peptide-based nano-vaccine is developed, comprising a self-assembly nanoparticle driven by the nucleic acid adjuvant-antigen conjugate. This nano-vaccine stimulates a strong tumor-specific T cell response by activating antigen presentation and toll-like receptor signaling pathways. By markedly improving the efficiency of antigen/adjuvant co-delivery to the draining lymph nodes, the nano-vaccine leads to 100% tumor prevention for up to 11 months and without tumor recurrence, heralding the generation of long-term anti-tumor memory. Moreover, the injection of nano-vaccine with signal neoantigen eliminates the established MC-38 tumor (a cell line of murine carcinoma of the colon without exogenous OVA protein expression) in 40% of the mice by inducing potent cytotoxic T lymphocyte infiltration in the tumor microenvironment without substantial systemic toxicity. These findings represent that stapling peptide-based nano-vaccine may serve as a facile, general, and safe strategy to stimulate a strong anti-tumor immune response for the neoantigen peptide-based personalized tumor immunotherapy.

Dual-mRNA Delivery Using Tumor Cell Lysate-Based Multifunctional Nanoparticles as an Efficient Colon Cancer Immunogene Therapy

Background

Messenger RNA (mRNA)-based immunogene therapy holds significant promise as an emerging tumor therapy approach. However, the delivery efficiency of existing mRNA methods and their effectiveness in stimulating anti-tumor immune responses require further enhancement. Tumor cell lysates containing tumor-specific antigens and biomarkers can trigger a stronger immune response to tumors. In addition, strategies involving multiple gene therapies offer potential optimization paths for tumor gene treatments.

Methods

Based on the previously developed ideal mRNA delivery system called DOTAP-mPEG-PCL (DMP), which was formed through the self-assembly of 1.2-dioleoyl-3-trimethylammonium-propane (DOTAP) and methoxypoly (ethylene glycol)-b-poly (ε-caprolactone) (mPEG-PCL), we introduced a fused cell-penetrating peptide (fCPP) into the framework and encapsulated tumor cell lysates to form a novel nanovector, termed CLSV system (CLS: CT26 tumor cell lysate, V: nanovector). This system served a dual purpose of facilitating the delivery of two mRNAs and enhancing tumor immunogene therapy through tumor cell lysates.

Results

The synthesized CLSV system had an average size of 241.17 nm and a potential of 39.53 mV. The CLSV system could not only encapsulate tumor cell lysates, but also deliver two mRNAs to tumor cells simultaneously, with a transfection efficiency of up to 60%. The CLSV system effectively activated the immune system such as dendritic cells to mature and activate, leading to an anti-tumor immune response. By loading Bim-encoded mRNA and IL-23A-encoded mRNA, CLSV/Bim and CLSV/IL-23A complexes were formed, respectively, to further induce apoptosis and anti-tumor immunity. The prepared CLSV/dual-mRNA complex showed significant anti-cancer effects in multiple CT26 mouse models.

Conclusion

Our results suggest that the prepared CLSV system is an ideal delivery system for dual-mRNA immunogene therapy.

Cellular Uptake of Cell-Penetrating Peptides Activated by Amphiphilic p-Sulfonatocalix[4]arenes

We report the synthesis of a series of amphiphilic p-sulfonatocalix[4]arenes with varying alkyl chain lengths (CX4-Cn) and their application as efficient counterion activators for membrane transport of cell-penetrating peptides (CPPs). The enhanced membrane activity is confirmed with the carboxyfluorescein (CF) assay in vesicles and by the direct cytosolic delivery of CPPs into CHO-K1, HCT 116, and KTC-1 cells enabling excellent cellular uptake of the CPPs into two cancer cell lines. Intracellular delivery was confirmed by fluorescence microscopy after CPP entry into live cells mediated by CX4-Cn, which was also quantified after cell lysis by fluorescence spectroscopy. The results present the first systematic exploration of structure-activity relationships for calixarene-based counterion activators and show that CX4-Cn are exceptionally effective in cellular delivery of CPPs. The dodecyl derivative, CX4-C12, serves as best activator. A first mechanistic insight is provided by efficient CPP uptake at 4 °C and in the presence of the endocytosis inhibitor dynasore, which indicates a direct translocation of the CPP-counterion complexes into the cytosol and highlights the potential benefits of CX4-Cn for efficient and direct translocation of CPPs and CPP-conjugated cargo molecules into the cytosol of live cells.

Reversible Assembly of Proteins and Phenolic Polymers for Intracellular Protein Delivery with Serum Stability

The design of intracellular delivery systems for protein drugs remains a challenge due to limited delivery efficacy and serum stability. Herein, we propose a reversible assembly strategy to assemble cargo proteins and phenolic polymers into stable nanoparticles for this purpose using a heterobifunctional adaptor (2-formylbenzeneboronic acid). The adaptor is easily decorated on cargo proteins via iminoboronate chemistry and further conjugates with catechol-bearing polymers to form nanoparticles via boronate diester linkages. The nanoparticles exhibit excellent serum stability in culture media but rapidly release the cargo proteins triggered by lysosomal acidity and GSH after endocytosis. In a proof-of-concept animal model, the strategy successfully transports superoxide dismutase to retina via intravitreal injection and efficiently ameliorates the oxidative stress and cellular damage in the retina induced by ischemia-reperfusion (I/R) with minimal adverse effects. The reversible assembly strategy represents a robust and efficient method to develop serum-stable systems for the intracellular delivery of biomacromolecules.

Uptake pathways of cell-penetrating peptides in the context of drug delivery, gene therapy, and vaccine development

Cell-penetrating peptides have been extensively utilized for the purpose of facilitating the intracellular delivery of cargo that is impermeable to the cell membrane. The researchers have exhibited proficient delivery capabilities for oligonucleotides, thereby establishing cell-penetrating peptides as a potent instrument in the field of gene therapy. Furthermore, they have demonstrated a high level of efficiency in delivering several additional payloads. Cell penetrating peptides (CPPs) possess the capability to efficiently transport therapeutic molecules to specific cells, hence offering potential remedies for many illnesses. Hence, their utilization is imperative for the improvement of therapeutic vaccines. In contemporary studies, a plethora of cell-penetrating peptides have been unveiled, each characterized by its own distinct structural attributes and associated mechanisms. Although it is widely acknowledged that there are multiple pathways through which particles might be internalized, a comprehensive understanding of the specific mechanisms by which these particles enter cells has to be fully elucidated. The absorption of cell-penetrating peptides can occur through either direct translocation or endocytosis. However, it is worth noting that categories of cell-penetrating peptides are not commonly linked to specific entrance mechanisms. Furthermore, research has demonstrated that cell-penetrating peptides (CPPs) possess the capacity to enhance antigen uptake by cells and facilitate the traversal of various biological barriers. The primary objective of this work is to examine the mechanisms by which cell-penetrating peptides are internalized by cells and their significance in facilitating the administration of drugs, particularly in the context of gene therapy and vaccine development. The current study investigates the immunostimulatory properties of numerous vaccine components administered using different cell-penetrating peptides (CPPs). This study encompassed a comprehensive discussion on various topics, including the uptake pathways and mechanisms of cell-penetrating peptides (CPPs), the utilization of CPPs as innovative vectors for gene therapy, the role of CPPs in vaccine development, and the potential of CPPs for antigen delivery in the context of vaccine development.

Nucleus-targeting DNase I self-assembly delivery system guided by pirarubicin for programmed multi-drugs release and combined anticancer therapy

The cell nucleus serves as the pivotal command center of living cells, and delivering therapeutic agents directly into the nucleus can result in highly efficient anti-tumor eradication of cancer cells. However, nucleus-targeting drug delivery is very difficult due to the presence of numerous biological barriers. Here, three antitumor drugs (DNase I, ICG: indocyanine green, and THP: pirarubicin) were sequentially triggered protein self-assembly to produce a nucleus-targeting and programmed responsive multi-drugs delivery system (DIT). DIT consisted of uniform spherical particles with a size of 282 ± 7.7 nm. The acidic microenvironment of tumors and near-infrared light could successively trigger DIT for the programmed release of three drugs, enabling targeted delivery to the tumor. THP served as a nucleus-guiding molecule and a chemotherapy drug. Through THP-guided DIT, DNase I was successfully delivered to the nucleus of tumor cells and killed them by degrading their DNA. Tumor acidic microenvironment had the ability to induce DIT, leading to the aggregation of sufficient ICG in the tumor tissues. This provided an opportunity for the photothermal therapy of ICG. Hence, three drugs were cleverly combined using a simple method to achieve multi-drugs targeted delivery and highly effective combined anticancer therapy.

Mitocytosis Mediated by an Enzyme-Activable Mitochondrion-Disturbing Polymer-Drug Conjugate Enhances Active Penetration in Glioblastoma Therapy

The application of nanomedicines for glioblastoma (GBM) therapy is hampered by the blood-brain barrier (BBB) and the dense glioblastoma tissue. To achieve efficient BBB crossing and deep GBM penetration, this work demonstrates a strategy of active transcellular transport of a mitochondrion-disturbing nanomedicine, pGBEMA22-b-pSSPPT9 (GBEPPT), in the GBM tissue through mitocytosis. GBEPPT is computer-aided designed and prepared by self-assembling a conjugate of an amphiphilic block polymer and a drug podophyllotoxin (PPT). When GBEPPT is delivered to the tumor site, overexpressed γ-glutamyl transpeptidase (GGT) on the brain-blood endothelial cell, or the GBM cell triggered enzymatic hydrolysis of γ-glutamylamide on GBEPPT to reverse its negative charge to positive. Positively charged GBEPPT rapidly enter into the cell and target the mitochondria. These GBEPPT disturb the homeostasis of mitochondria, inducing mitocytosis-mediated extracellular transport of GBEPPT to the neighboring cells via mitosomes. This intracellular-to-intercellular delivery cycle allows GBEPPT to penetrate deeply into the GBM parenchyma, and exert sustainable action of PPT released from GBEPPT on the tumor cells along its penetration path at the tumor site, thus improving the anti-GBM effect. The process of mitocytosis mediated by the mitochondrion-disturbing nanomedicine may offer great potential in enhancing drug penetration through malignant tissues, especially poorly permeable solid tumors.

Liquid Droplet-Mediated Formulation of Lipid Nanoparticles Encapsulating Immunoglobulin G for Cytosolic Delivery

Antibodies are promising biopharmaceuticals that offer new therapeutic options for diseases. Since antibodies are membrane impermeable, approaches that allow immunoglobulin Gs (IgGs) to access intracellular therapeutic targets would open new horizons in antibody therapies. Lipid nanoparticles (LNPs) are among the classes of vectors that deliver biopharmaceuticals into cells. Using liquid droplets formed by IgG and polyglutamate, we report here a unique approach to forming LNPs containing IgG via liquid droplets formed in the presence of polyglutamic acid (polyE). The addition of polyE promoted the formation of smaller LNPs with cationic lipids than in its absence, and the formed LNPs were much more efficient in cytosolic IgG delivery and targeting of cellular proteins. This approach also allows for the encapsulation of intact IgG without the need for chemical or sequence modification. The intracellularly delivered IgG retained its target binding ability, as demonstrated by labeling of nuclear pore complex and HRas-GFP and inhibition of antiapoptotic cell death by phosphorylated Akt protein in live cells.

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

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

Cell-Penetrating Peptide-Bismuth Bicycles

Cell-penetrating peptides (CPPs) play a significant role in the delivery of cargos into human cells. We report the first CPPs based on peptide-bismuth bicycles, which can be readily obtained from commercially available peptide precursors, making them accessible for a wide range of applications. These CPPs enter human cells as demonstrated by live-cell confocal microscopy using fluorescently labelled peptides. We report efficient sequences that demonstrate increased cellular uptake compared to conventional CPPs like the TAT peptide (derived from the transactivating transcriptional activator of human immunodeficiency virus 1) or octaarginine (R8 ), despite requiring only three positive charges. Bicyclization triggered by the presence of bismuth(III) increases cellular uptake by more than one order of magnitude. Through the analysis of cell lysates using inductive coupled plasma mass spectrometry (ICP-MS), we have introduced an alternative approach to examine the cellular uptake of CPPs. This has allowed us to confirm the presence of bismuth in cells after exposure to our CPPs. Mechanistic studies indicated an energy-dependent endocytic cellular uptake sensitive to inhibition by rottlerin, most likely involving macropinocytosis.

E3MPH16: An efficient endosomolytic peptide for intracellular protein delivery

To facilitate the introduction of proteins, such as antibodies, into cells, a variety of delivery peptides have been engineered. These peptides are typically highly cationic and somewhat hydrophobic, enabling cytosolic protein delivery at the cost of causing cell damage by rupturing membranes. This balance between delivery effectiveness and cytotoxicity presents obstacles for their real-world use. To tackle this problem, we designed a new endosome-disruptive cytosolic delivery peptide, E3MPH16, inspired by mastoparan X (MP). E3MPH16 was engineered to incorporate three Glu (E3) and 16 His (H16) residues at the N- and C-termini of MP, respectively. The negative charges of E3 substantially mitigate the cell-surface damage induced by MP. The H16 segment is known to enhance cell-surface adsorption and endocytic uptake of the associated molecules. With these modifications, E3MPH16 was successfully trapped within endosomes. The acidification of endosomes is expected to protonate the side chains of E3 and H16, enabling E3MPH16 to rupture endosomal membranes. As a result, nearly 100% of cells achieved cytosolic delivery of a model biomacromolecule, Alexa Fluor 488-labeled dextran (10 kDa), via endosomal escape by co-incubation with E3MPH16. The delivery process also suggested the involvement of macropinocytosis and caveolae-mediated endocytosis. With the assistance of E3MPH16, Cre recombinase and anti-Ras-IgG delivered into HEK293 cells and HT1080 cells enabled gene recombination and inhibited cell proliferation, respectively. The potential for in vivo application of this intracellular delivery method was further validated by topically injecting the green fluorescent protein fused with a nuclear localization signal (NLS-GFP) along with E3MPH16 into Colon-26 tumor xenografts in mice.

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.

Bioactive Phosphorus Dendrimers as a Universal Protein Delivery System for Enhanced Anti-inflammation Therapy

Nanocarrier-based cytoplasmic protein delivery offers opportunities to develop protein therapeutics; however, many delivery systems are positively charged, causing severe toxic effects. For enhanced therapeutics, it is also of great importance to design nanocarriers with intrinsic bioactivity that can be integrated with protein drugs due to the limited bioactivity of proteins alone for disease treatment. We report here a protein delivery system based on anionic phosphite-terminated phosphorus dendrimers with intrinsic anti-inflammatory activity. A phosphorus dendrimer termed AK-137 with optimized anti-inflammatory activity was selected to complex proteins through various physical interactions. Model proteins such as bovine serum albumin, ribonuclease A, ovalbumin, and fibronectin (FN) can be transfected into cells to exert their respective functions, including cancer cell apoptosis, dendritic cell maturation, or macrophage immunomodulation. Particularly, the constructed AK-137@FN nanocomplexes display powerful therapeutic effects in acute lung injury and acute gout arthritis models by integrating the anti-inflammatory activity of both the carrier and protein. The developed anionic phosphite-terminated phosphorus dendrimers may be employed as a universal carrier for protein delivery and particularly utilized to deliver proteins and fight different inflammatory diseases with enhanced therapeutic efficacy.

Chemical Modification of Cytochrome C for Acid-Responsive Intracellular Apoptotic Protein Delivery for Cancer Eradication

Delivering bioactive proteins into cells without carriers presents significant challenges in biomedical applications due to limited cell membrane permeability and the need for targeted delivery. Here, we introduce a novel carrier-free method that addresses these challenges by chemically modifying proteins with an acid-responsive cell-penetrating peptide (CPP) for selective intracellular delivery within tumours. Cytochrome C, a protein known for inducing apoptosis, served as a model for intracellular delivery of therapeutic proteins for cancer treatment. The CPP was protected with 2,3-dimethyl maleic anhydride (DMA) and chemically conjugated onto the protein surface, creating an acid-responsive protein delivery system. In the acidic tumour microenvironment, DMA deprotects and exposes the positively charged CPP, enabling membrane penetration. Both in vitro and in vivo assays validated the pH-dependent shielding mechanism, demonstrating the modified cytochrome C could induce apoptosis in cancer cells in a pH-selective manner. These findings provide a promising new approach for carrier-free and tumour-targeted intracellular delivery of therapeutic proteins for a wide range of potential applications.

Amplified Targeted Drug Delivery Independent of Target Number through Alternative Administration of Two Matched Nanoparticles

Targeting nanoparticles (NPs) based on the specific binding of ligands with molecular targets provides a promising tool for tissue-selective drug delivery. However, the number of molecular targets on the cell surface is limited, hindering the number of NPs that can bind and, thus, limiting the therapeutic outcome. Although several strategies have been developed to enhance drug delivery, such as enhancing drug loading and circulation time or increasing the enhanced permeability and retention effect of nanocarriers, none have resolved this issue. Herein, we designed a simple method for amplified and targeted drug delivery using two matched NPs. One NP was aptamer-functionalized to specifically bind to target cells, while the other was aptamer-complementary DNA-functionalized to specifically bind to aptamer-NPs. Alternate administration of the two matched NPs enables their continuous accumulation in the disease site despite their limited molecular targets. As a proof of concept, the method was tested in a breast cancer model and significantly enhanced chemotherapy of tumor cells in vitro and in vivo. The potential applications of this method in a brain injury model were also demonstrated. Overall, the study describes a method for amplified targeted drug delivery independent of the target number.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.