Intra-Lysosomal Peptide Assembly for the High Selectivity Index against Cancer

Radiopharmaceuticals and their applications in medicine

Radiopharmaceuticals involve the local delivery of radionuclides to targeted lesions for the diagnosis and treatment of multiple diseases. Radiopharmaceutical therapy, which directly causes systematic and irreparable damage to targeted cells, has attracted increasing attention in the treatment of refractory diseases that are not sensitive to current therapies. As the Food and Drug Administration (FDA) approvals of [177Lu]Lu-DOTA-TATE, [177Lu]Lu-PSMA-617 and their complementary diagnostic agents, namely, [68Ga]Ga-DOTA-TATE and [68Ga]Ga-PSMA-11, targeted radiopharmaceutical-based theranostics (radiotheranostics) are being increasingly implemented in clinical practice in oncology, which lead to a new era of radiopharmaceuticals. The new generation of radiopharmaceuticals utilizes a targeting vector to achieve the accurate delivery of radionuclides to lesions and avoid off-target deposition, making it possible to improve the efficiency and biosafety of tumour diagnosis and therapy. Numerous studies have focused on developing novel radiopharmaceuticals targeting a broader range of disease targets, demonstrating remarkable in vivo performance. These include high tumor uptake, prolonged retention time, and favorable pharmacokinetic properties that align with clinical standards. While radiotheranostics have been widely applied in tumor diagnosis and therapy, their applications are now expanding to neurodegenerative diseases, cardiovascular diseases, and inflammation. Furthermore, radiotheranostic-empowered precision medicine is revolutionizing the cancer treatment paradigm. Diagnostic radiopharmaceuticals play a pivotal role in patient stratification and treatment planning, leading to improved therapeutic outcomes in targeted radionuclide therapy. This review offers a comprehensive overview of the evolution of radiopharmaceuticals, including both FDA-approved and clinically investigated agents, and explores the mechanisms of cell death induced by radiopharmaceuticals. It emphasizes the significance and future prospects of theranostic-based radiopharmaceuticals in advancing precision medicine.

Benzo-pyrrolidinyl substituted silicon phthalocyanines: A novel two-photon lysosomal nanoprobe for in vitro photodynamic therapy

Lysosomes are pivotal in diverse physiological phenomena, encompassing autophagy, apoptosis, and cellular senescence. The demand for precise tumors treatment has led to the development of specific lysosome-targeting probes capable of elucidating lysosomal dynamics and facilitating targeted cell death. In this research, we report the synthesis and characterization of a novel benzopyrrolidinyl-substituted silicon phthalocyanine (Py-SiPc), designed for selective lysosome labeling and Fluorescence imaging-guided in vitro photodynamic therapy. Furthermore, we encapsulated Py-SiPc within a biocompatible nanocarrier, dipalmitoylphosphatidylethanolamine-polyethylene glycol 2000 (DSPE), to create water-soluble nanoparticles (DSPE@Py-SiPc). These nanoparticles exhibit exceptional lysosome labeling capabilities, as evidenced by bioimaging techniques. Upon exposure to laser irradiation, DSPE@Py-SiPc efficiently induces the production of reactive oxygen species, impairing lysosomal function and triggering lysosomal-mediated cell death. The DSPE@Py-SiPc system emerges as a promising photosensitizer.

Design and Applications of Supramolecular Peptide Hydrogel as Artificial Extracellular Matrix

Supramolecular peptide hydrogels (SPHs) consist of peptides containing hydrogelators and functional epitopes, which can first self-assemble into nanofibers and then physically entangle together to form dynamic three-dimensional networks. Their porous structures, excellent bioactivity, and high dynamicity, similar to an extracellular matrix (ECM), have great potential in artificial ECM. The properties of the hydrogel are largely dependent on peptides. The noncovalent interactions among hydrogelators drive the formation of assemblies and further transition into hydrogels, while bioactive epitopes modulate cell-cell and cell-ECM interactions. Therefore, SPHs can support cell growth, making them ideal biomaterials for ECM mimics. This Review outlines the classical molecular design of SPHs from hydrogelators to functional epitopes and summarizes the recent advancements of SPHs as artificial ECMs in nervous system repair, wound healing, bone and cartilage regeneration, and organoid culture. This emerging SPH platform could provide an alternative strategy for developing more effective biomaterials for tissue engineering.

Host-Guest Adduct as a Stimuli-Responsive Prodrug: Enzyme-Triggered Self-Assembly Process of a Short Peptide Within Mitochondria to Induce Cell Apoptosis

To address the issue of nonspecific biodistribution of a chemotherapeutic drug, stable [2]pseudorotaxane complexes (PK@CAOPP and PR@CAOPP) are used to demonstrate a proof of concept. Cationic -PPh3 + moiety in CAOPP allows specific localization of the PK@CAOPP/ PR@CAOPP in the mitochondrial membrane (MM). Electrostatic interaction between the cationic LysinePK or ArgininePR moiety and the negatively charged phosphoesterCAOPP functionality in CAOPP favours strong adduct formation. The ALP-induced hydrolytic cleavage of the phosphoester moiety in cancer cells triggers dephosphorylation and releases PK/ PR moiety from PK@CAOPP/PR@CAOPP. PK or PR, derived from the Phe-Phe dipeptide, formed fibril-like molecular aggregates in the MM to induce dysfunction, depolarization, ROS generation and apoptotic MCF7 cell death. Such phenomena were not observed in ALP-negative HEK293 normal cells. These propositions were confirmed through control studies using NBDK and PE, other guest molecules. Smaller size and inclusion of the short peptides (PK or PR) within the hydrophobic interior of CAOPP, were attributed to their stability in blood serum. Thus, we have demonstrated the use of supramolecular adducts as a potential therapeutic option for treating cancer cells without affecting healthy cells. The efficacy was also established with an in-vivo MCF7 tumour xenograft model using Balb/c nude mice.

Matrix metalloproteinase 2-responsive dual-drug-loaded self-assembling peptides suppress tumor growth and enhance breast cancer therapy

Conventional chemotherapeutic agents are limited by their lack of targeting and penetration and their short retention time, and chemotherapy might induce an immune suppressive environment. Peptide self-assembly can result in a specific morphology, and the resulting morphological changes are stimuli responsive to the external environment, which is important for drug permeation and retention of encapsulated chemotherapeutic agents. In this study, a polypeptide (Pep1) containing the peptide sequences PLGLAG and RGD that is responsive to matrix metalloproteinase 2 (MMP-2) was successfully developed. Pep1 underwent a morphological transformation from a spherical structure to aggregates with a high aspect ratio in response to MMP-2 induction. This drug delivery system (DI/Pep1) can transport doxorubicin (DOX) and indomethacin (IND) simultaneously to target tumor cells for subsequent drug release while extending drug retention within tumor cells, which increases immunogenic cell death and facilitates the immunotherapeutic effect of CD4+ T cells. Ultimately, DI/Pep1 attenuated tumor-associated inflammation, enhanced the body's immune response, and inhibited breast cancer growth by combining the actions of DOX and IND. Our research offers an approach to hopefully enhance the effectiveness of cancer treatment.

Fibroblast Growth Factor Receptor 1-Specific Dehydrogelation to Release Its Inhibitor for Enhanced Lung Tumor Therapy

Fibroblast growth factor receptor 1 (FGFR1) is emerging as a promising molecular target of lung cancer, and various FGFR1 inhibitors have exhibited significant therapeutic effects on lung cancer in preclinical research. Due to their low targeting ability or bioavailability, direct administration of these inhibitors may cause side effects. Herein, a hydrogelator, Nap-Phe-Phe-Phe-Glu-Thr-Glu-Leu-Tyr-OH (Nap-Y), was rationally designed to coassemble with an FGFR1 inhibitor nintedanib (Nin) to form a peptide hydrogel Gel Y/Nin for localized administration and FGFR1-triggered release of Nin. Upon specific phosphorylation by FGFR1 overexpressed on lung cancer cells, Nap-Y in Gel Y/Nin is converted to the hydrophilic product Nap-Phe-Phe-Phe-Glu-Thr-Glu-Leu-Tyr(H2PO3)-OH (Nap-Yp), leading to dehydrogelation of the gel and subsequent Nin release. In vitro experiments demonstrate that the release of Nin in a sustained manner from Gel Y/Nin significantly suppresses the survival, migration, and invasion of A549 cells by inhibiting FGFR1 expression and its phosphorylation function on downstream signaling molecules. Nude mouse studies show that Gel Y/Nin exhibits enhanced therapeutic efficacy on lung tumor than free Nin. We anticipate that Gel Y/Nin will be utilized for lung cancer treatment in clinical settings in the near future.

Amino Acid-Derived Supramolecular Assembly and Soft Materials

Amino acids (AAs), serving as the primary monomer of peptides and proteins, are widely present in nature. Benefiting from their inherent advantages, such as chemical diversity, low cost, ease of modification, chirality, biosafety, and bio-absorbability, AAs have been extensively exploited to create self-assembled nanostructures and supramolecular soft materials. In this review article, we systematically describe the recent progress regarding amino acid-derived assembly and functional soft materials. A brief background and several classified assemblies of AAs and their derivatives (chemically modified AAs) are summarized. The key non-covalent interactions to drive the assembly of AAs are emphasized based on the reported systems of self-assembled and co-assembled AAs. We discuss the molecular design of AAs and the general rules behind the hierarchical nanostructures. The resulting soft materials with interesting properties and potential applications are demonstrated. The conclusion and remarks on AA-based supramolecular assemblies are also presented from the viewpoint of chemistry, materials, and bio-applications.

Design of an Acidic pH-Activated NIR Fluorescent Convertible Rhodamine-Hemicyanine Probe-Peptide Conjugate for Living Cancer Cell Active Targeted Selective Tracking of Lysosomes

We have synthesized an acidic pH-activatable dual targeting ratiometric fluorescent probe-peptide conjugate using the SPPS protocol on Rink amide AM resin. Living carcinoma cell specific active targeting, successive cell penetration, and selective staining of lysosomes are accomplished. Real-time monitoring of lysosomes, 3D, and multicolor cancer cell imaging are also attained. The de novo design consists of the integration of multifunctionality into a single molecular scaffold, e. g., RGDS peptide residue to target cancer cell surface overexpressed receptor αVβ3 integrin, live-cell penetrating organic unsymmetrical rhodamine-hemicyanine chromophore comprising a lysosome targeting morpholine group, and an acidic pH openable spiro-lactam ring for a visible-to-NIR switchable ratiometric response. Water-soluble fluorescent probe-peptide conjugate exhibits intramolecular spirolactamization at basic pH through Arg amide N. The visible spirolactam state predominantly exists at physiological and basic pH and can be switched to the highly conjugated NIR open amide state (λem=735 nm) through spiro-lactam ring opening triggered by acidic pH with a huge bathochromic shift (Δλabs=336 nm, ΔλFL=265 nm). Moreover, pH-sensitive ratiometric optical switching is achieved. This in situ acidic cancer cell lysosome activatable multifunctional fluorophore-peptide conjugate shows augmented molar absorptivity, enhanced quantum yield, and improved fluorescence lifetime at acidic lysosomal pH; negligible cytotoxicity; and dual targeted ratiometric imaging capability of living cancer cell selective lysosomes with a pKa value of 5.1.

Self-Assembly in Living Cells: Bottom-Up Syntheses in Natural Factory

In situ self-assembly in living systems is referred to as the processes that regulate assembly by stimuli-responsive reactions at target sites under physiological conditions. Due to the advantages of precisely forming well-defined nanostructures at pathological lesions, in situ-formed assemblies with tailored bioactivity are promising for the development of next-generation biomedical agents. In this Perspective, we summarize the progress of in situ self-assembly of peptides in living cells with an emphasis on the state-of-the-art strategies regulating assembly processes, establishing complexity within assembly systems, and exploiting their applications in biomedicines. We also provide our forward conceiving perspectives on the challenges in the development of in situ assembly in living cells to demonstrate its great potential in creating biomaterials for healthcare in the future.

Folic Acid-Functionalized β-Cyclodextrin for Delivery of Organelle-Targeted Peptide Chemotherapeutics in Cancer

Recent emphasis on the design of drug delivery systems typically involves the effective transport of a pharmaceutical substance to the disease site with the desired therapeutic efficacy and minimal cytotoxicity. Organelle-targeted peptides have become an integral part of designing an important class of prodrug/prodrug assemblies for new supramolecular therapeutics owing to their favorable biocompatibility, synthetic ease, tunability of their aggregation behavior, and desired functionalization for site-specificity. However, it is still limited due to the low selectivity. We designed a folic acid-functionalized β-cyclodextrin (FA-CD) as a delivery platform for specific and selective delivery of organelle-targeted (such as microtubule, lysosome, and mitochondria) peptide chemotherapeutics to the folate receptor (FR) overexpressing cancer cell lines. Low toxicity was found for the FA-CD and organelle-targeted peptide inclusion complex in FR-negative normal cells, but superior inhibition of tumor growth with no in vivo toxicity was found for the inclusion complex in the xenograft tumor model.

Subcellular targeting strategies for protein and peptide delivery

Cytosolic delivery of proteins and peptides provides opportunities for effective disease treatment, as they can specifically modulate intracellular processes. However, most of protein-based therapeutics only have extracellular targets and are cell-membrane impermeable due to relatively large size and hydrophilicity. The use of organelle-targeting strategy offers great potential to overcome extracellular and cell membrane barriers, and enables localization of protein and peptide therapeutics in the organelles. Although progresses have been made in the recent years, organelle-targeted protein and peptide delivery is still challenging and under exploration. We reviewed recent advances in subcellular targeted delivery of proteins/peptides with a focus on targeting mechanisms and strategies, and highlight recent examples of active and passive organelle-specific protein and peptide delivery systems. This emerging platform could open a new avenue to develop more effective protein and peptide therapeutics.

Enzyme-instructed intramitochondrial polymerization for enhanced anticancer treatment without the development of drug-resistance

Intracellular polymerization in living cells motivated chemists to generate polymeric structures with a multitude of possibilities to interact with biomacromolecules. However, out-of-control of the intracellular chemical reactions would be an obstacle restricting its application, providing the toxicity of non-targeted cells. Here, we reported intracellular thioesterase-mediated polymerization for selectively occurring polymerization using disulfide bonds in cancer cells. The acetylated monomers did not form disulfide bonds even under an oxidative environment, but they could polymerize into the polymeric structure after cleavage of acetyl groups only when encountered activity of thioesterase enzyme. Furthermore, acetylated monomers could be self-assembled with doxorubicin, providing doxorubicin loaded micelles for efficient intracellular delivery of drug and monomers. Since thioesterase enzymes were overexpressed in cancer cells specifically, the micelles were disrupted under activity of the enzyme and the polymerization could occur selectively in the cancer mitochondria. The resulting polymeric structures disrupted the mitochondrial membrane, thus activating the cellular death of cancer cells with high selectivity. This strategy selectively targets diverse cancer cells involving drug-resistant cells over normal cells. Moreover, the mitochondria targeting strategy overcomes the development of drug resistance even with repeated treatment. This approach provides a way for selective intracellular polymerization with desirable anticancer treatment.

Clustering of the Membrane Protein by Molecular Self-Assembly Downregulates the Signaling Pathway for Cancer Cell Inhibition

This work reports a cyclic peptide appended self-assembled scaffold that recognizes the membrane protein EGFR and arrests the EGFR signaling through multivalent interactions by assembly-induced aggregation. When incubated with cells, the oligomers of PAD-1 first recognize the overexpressed EGFR on cancer cell membranes for arresting EGFR, which then initiates cellular uptake through endocytosis. The accumulation of PAD-1 and EGFR in the lysosome results in the formation of nanofibers, leading to the lysosomal membrane permeabilization (LMP). These processes disrupt the homeostasis of EGFR and inhibit the downstream signaling transduction of EGFR for cancer cell survival. Moreover, LMP induced the release of protein aggregates that could generate endoplasmic reticulum (ER) stress, resulting in cancer cell death selectively. In vivo studies indicate the efficient antitumor efficiency of PAD-1 in tumor-bearing mice. As a first example, this work provides an alternative strategy for controlling protein behavior for tuning cellular events in living cells.

In Vivo Self-Sorting of Peptides via In Situ Assembly Evolution

Despite significant progress achieved in artificial self-sorting in solution, operating self-sorting in the body remains a considerable challenge. Here, we report an in vivo self-sorting peptide system via an in situ assembly evolution for combined cancer therapy. The peptide E3C16-SS-EIY consists of two disulfide-connected segments, E3C16SH and SHEIY, capable of independent assembly into twisted or flat nanoribbons. While E3C16-SS-EIY assembles into nanorods, exposure to glutathione (GSH) leads to the conversion of the peptide into E3C16SH and SHEIY, thus promoting in situ evolution from the nanorods into self-sorted nanoribbons. Furthermore, incorporation of two ligand moieties targeting antiapoptotic protein XIAP and organellar endoplasmic reticulum (ER) into the self-sorted nanoribbons allows for simultaneous inhibition of XIAP and accumulation surrounding ER. This leads to the cytotoxicity toward the cancer cells with elevated GSH levels, through activating caspase-dependent apoptosis and inducing ER dysfunction. In vivo self-sorting of E3C16-SS-EIY decorated with ligand moieties is thoroughly validated by tissue studies. Tumor-bearing mouse experiments confirm the therapeutic efficacy of the self-sorted assemblies for inhibiting tumor growth, with excellent biosafety. Our findings demonstrate an efficient approach to develop in vivo self-sorting systems and thereby facilitating in situ formulation of biomedical agents.

Assembly of Glycopeptides in Living Cells Resembling Viral Infection for Cargo Delivery

Self-assembly in living cells represents one versatile strategy for drug delivery; however, it suffers from the limited precision and efficiency. Inspired by viral traits, we here report a cascade targeting-hydrolysis-transformation (THT) assembly of glycosylated peptides in living cells holistically resembling viral infection for efficient cargo delivery and combined tumor therapy. We design a glycosylated peptide via incorporating a β-galactose-serine residue into bola-amphiphilic sequences. Co-assembling of the glycosylated peptide with two counterparts containing irinotecan (IRI) or ligand TSFAEYWNLLSP (PMI) results in formation of the glycosylated co-assemblies SgVEIP, which target cancer cells via β-galactose-galectin-1 association and undergo galactosidase-induced morphological transformation. While GSH-reduction causes release of IRI from the co-assemblies, the PMI moieties release p53 and facilitate cell death via binding with protein MDM2. Cellular experiments show membrane targeting, endo-/lysosome-mediated internalization and in situ formation of nanofibers in cytoplasm by SgVEIP. This cascade THT process enables efficient delivery of IRI and PMI into cancer cells secreting Gal-1 and overexpressing β-galactosidase. In vivo studies illustrate enhanced tumor accumulation and retention of the glycosylated co-assemblies, thereby suppressing tumor growth. Our findings demonstrate an in situ assembly strategy mimicking viral infection, thus providing a new route for drug delivery and cancer therapy in the future.

Lysosomal Peptide Self-Assembly to Control Cell Behavior

Lysosomes are membrane-enclosed organelles that play key roles in degrading and recycling cellular debris, cellular signaling, and energy metabolism processes. Confinement of amphiphilic peptides in the lysosome to construct functional nanostructures through noncovalent interactions is an emerging approach to tune the homeostasis of lysosome. After briefly introducing the importance of lysosome and its functions, we discuss the advantages of lysosomal nanostructure formation for disease therapy. We next discuss the strategy for triggering the self-assembly of peptides in the lysosome, followed by a concise outlook of the future perspective about this emerging research direction.

From cells to subcellular organelles: Next-generation cancer therapy based on peptide self-assembly

Due to the editability, functionality, and excellent biocompatibility of peptides, in situ self-assembly of peptides in cells is a powerful strategy for biomedical applications. Subcellular organelle targeting of peptides assemblies enables more precise drug delivery, enhances selectivity to disease cells, and mitigates drug resistance, providing an effective strategy for disease diagnosis and therapy. This reviewer first introduces the triggering conditions, morphological changes, and intracellular locations of self-assembling peptides. Then, the functions of peptide assemblies are summarized, followed by a comprehensive understanding of the interactions between peptide assemblies and subcellular organelles. Finally, we provide a brief outlook and the remaining challenges in this field.

Acid-assisted self-assembly of pyrene-capped tyrosine ruptures lysosomes to induce cancer cell apoptosis

Induced lysosomal membrane permeabilization (LMP) by peptide self-assembly has emerged as an effective platform for lysosome-targeted cancer therapy. In this study, we shift this strategical paradigm and present an innovative approach to LMP induction through amino acid-based self-assembly. Pyrene-capped tyrosine (Py-Tyr), as a proof-of-concept molecule, is designed with acidity-responsive self-assembly. Under acidic conditions (pH 4), Py-Tyr is protonated with reduced charge repulsion, and self-assembles into micrometer-scaled aggregates, which exceed the biological size of lysosomes. Cell experiments showed that Py-Tyr specifically accumulates in lysosomes and induces lysosome rupture, leading to the release of cathepsin B into the cytoplasm for subsequent apoptosis activation in cancer cells. This study capitalizes on the concept of amino acid assembly for efficient LMP induction, providing a simple and versatile platform for precise and effective therapeutic interventions in cancer therapy.

In Situ Nanofiber Formation Blocks AXL and GAS6 Binding to Suppress Ovarian Cancer Development

Anexelekto (AXL) is an attractive molecular target for ovarian cancer therapy because of its important role in ovarian cancer initiation and progression. To date, several AXL inhibitors have entered clinical trials for the treatment of ovarian cancer. However, the disadvantages of low AXL affinity and severe off-target toxicity of these inhibitors limit their further clinical applications. Herein, by rational design of a nonapeptide derivative Nap-Phe-Phe-Glu-Ile-Arg-Leu-Arg-Phe-Lys (Nap-IR), a strategy of in situ nanofiber formation is proposed to suppress ovarian cancer growth. After administration, Nap-IR specifically targets overexpressed AXL on ovarian cancer cell membranes and undergoes a receptor-instructed nanoparticle-to-nanofiber transition. In vivo and in vitro experiments demonstrate that in situ formed Nap-IR nanofibers efficiently induce apoptosis of ovarian cancer cells by blocking AXL activation and disrupting subsequent downstream signaling events. Remarkably, Nap-IR can synergistically enhance the anticancer effect of cisplatin against HO8910 ovarian tumors. It is anticipated that the Nap-IR can be applied in clinical ovarian cancer therapy in the near future.

In situ peptide assemblies for bacterial infection imaging and treatment

Bacterial infections, especially antibiotic-resistant ones, remain a major threat to human health. Advances in nanotechnology have led to the development of numerous antimicrobial nanomaterials. Among them, in situ peptide assemblies, formed by biomarker-triggered self-assembly of peptide-based building blocks, have received increasing attention due to their unique merits of good spatiotemporal controllability and excellent disease accumulation and retention. In recent years, a variety of "turn on" imaging probes and activatable antibacterial agents based on in situ peptide assemblies have been developed, providing promising alternatives for the treatment and diagnosis of bacterial infections. In this review, we introduce representative design strategies for in situ peptide assemblies and highlight the bacterial infection imaging and treatment applications of these supramolecular materials. Besides, current challenges in this field are proposed.

Artificial Peptide-Protein Necrosomes Promote Cell Death

The presence of disordered region or large interacting surface within proteins significantly challenges the development of targeted drugs, commonly known as the "undruggable" issue. Here, we report a heterogeneous peptide-protein assembling strategy to selectively phosphorylate proteins, thereby activating the necroptotic signaling pathway and promoting cell necroptosis. Inspired by the structures of natural necrosomes formed by receptor interacting protein kinases (RIPK) 1 and 3, the kinase-biomimetic peptides are rationally designed by incorporating natural or D -amino acids, or connecting D -amino acids in a retro-inverso (DRI) manner, leading to one RIPK3-biomimetic peptide PR3 and three RIPK1-biomimetic peptides. Individual peptides undergo self-assembly into nanofibrils, whereas mixing RIPK1-biomimetic peptides with PR3 accelerates and enhances assembly of PR3. In particular, RIPK1-biomimetic peptide DRI-PR1 exhibits reliable binding affinity with protein RIPK3, resulting in specific cytotoxicity to colon cancer cells that overexpress RIPK3. Mechanistic studies reveal the increased phosphorylation of RIPK3 induced by RIPK1-biomimetic peptides, elucidating the activation of the necroptotic signaling pathway responsible for cell death without an obvious increase in secretion of inflammatory cytokines. Our findings highlight the potential of peptide-protein hybrid aggregation as a promising approach to address the "undruggable" issue and provide alternative strategies for overcoming cancer resistance in the future.