Self-Assembly of Peptides as an Alluring Approach toward Cancer Treatment and Imaging

Cancer is a severe threat to humans, as it is the second leading cause of death after cardiovascular diseases and still poses the biggest challenge in the world of medicine. Due to its higher mortality rates and resistance, it requires a more focused and productive approach to provide the solution for it. Many therapies promising to deliver favorable results, such as chemotherapy and radiotherapy, have come up with more negatives than positives. Therefore, a new class of medicinal solutions and a more targeted approach is of the essence. This review highlights the alluring properties, configurations, and self-assembly of peptide molecules which benefit the traditional approach toward cancer therapy while sparing the healthy cells in the process. As targeted drug delivery systems, self-assembled peptides offer a wide spectrum of conjugation, biocompatibility, degradability-controlled responsiveness, and biomedical applications, including cancer treatment and cancer imaging.

Covalent drugs based on small molecules and peptides for disease theranostics

Biomacromolecules, such as proteins, nucleic acids and polysaccharides, are widely distributed in the human body, and some of them have been recognized as the targets of drugs for disease theranostics. Drugs typically act on targets in two ways: non-covalent bond and covalent bond. Non-covalent bond-based drugs have some disadvantages, such as structural instability and environmental sensitivity. Covalent interactions between drugs and targets have a longer action time, higher affinity and controllability than non-covalent interactions of conventional drugs. With the development of artificial intelligence, covalent drugs have received more attention and have been developed rapidly in pharmaceutical research in recent years. From the perspective of covalent drugs, this review summarizes the design methods and the effects of covalent drugs. Finally, we discuss the application of covalent peptide drugs and expect to provide a new reference for cancer treatment.

In vivo assembly enhanced binding effect augments tumor specific ferroptosis therapy

Emerging evidence indicates that the activation of ferroptosis by glutathione peroxidase 4 (GPX4) inhibitors may be a prominent therapeutic strategy for tumor suppression. However, the wide application of GPX4 inhibitors in tumor therapy is hampered due to poor tumor delivery efficacy and the nonspecific activation of ferroptosis. Taking advantage of in vivo self-assembly, we develop a peptide-ferriporphyrin conjugate with tumor microenvironment specific activation to improve tumor penetration, endocytosis and GPX4 inhibition, ultimately enhancing its anticancer activity via ferroptosis. Briefly, a GPX4 inhibitory peptide is conjugated with an assembled peptide linker decorated with a pH-sensitive moiety and ferriporphyrin to produce the peptide-ferriporphyrin conjugate (Gi-F-CAA). Under the acidic microenvironment of the tumor, the Gi-F-CAA self-assembles into large nanoparticles (Gi-F) due to enhanced hydrophobic interaction after hydrolysis of CAA, improving tumor endocytosis efficiency. Importantly, Gi-F exhibits substantial inhibition of GPX4 activity by assembly enhanced binding (AEB) effect, augmenting the oxidative stress of ferriporphyrin-based Fenton reaction, ultimately enabling antitumor properties in multiple tumor models. Our findings suggest that this peptide-ferriporphyrin conjugate design with AEB effect can improve the therapeutic effect via induction of ferroptosis, providing an alternative strategy for overcoming chemoresistance.

Sonoactivated Cascade Fenton Reaction Enhanced by Synergistic Modulation of Electron-Hole Separation for Improved Tumor Therapy

Chemodynamic therapy (CDT) is an emerging targeted treatment technique for tumors via the generation of highly cytotoxic hydroxyl radical (·OH) governed by tumor microenvironment-assisted Fenton reaction. Despite high effectiveness, it faces limitations like low reaction efficiency and limited endogenous H2 O2 , compromising its therapeutic efficacy. This study reports a novel platform with enhanced CDT performance by in situ sono-activated cascade Fenton reaction. A piezoelectric g-C3 N4 (Au-Fe-g-C3 N4 ) nanosheet is developed via sono-activated synergistic effect/H2 O2 self-supply mediated cascade Fenton reaction, realizing in situ ultrasound activated cascade Fenton reaction kinetics by synergistic modulation of electron-hole separation. The nanosheets consist of piezoelectric g-C3 N4 nanosheet oxidizing H2 O to highly reactive H2 O2 from the valence band, Fe3+ /Fe2+ cycling activated by conduction band to generate ·OH, and Au nanoparticles that lower the bandgap and further adopt electrons to generate more 1 O2 , resulting in improved CDT and sonodynamic therapy (SDT). Moreover, the Au-Fe-g-C3 N4 nanosheet is further modified by the targeted peptide to obtain P-Au-Fe-g-C3 N4 , which inhibits tumor growth in vivo effectively by generating reactive oxygen species (ROS). These results demonstrated that the sono-activated modulation translates into a high-efficiency CDT with a synergistic effect using SDT for improved anti-tumor therapy.

Intrinsic Strain-Mediated Ultrathin Ceria Nanoantioxidant

Metal oxide nanozymes have emerged as the most efficient and promising candidates to mimic antioxidant enzymes for treatment of oxidative stress-mediated pathophysiological disorders, but the current effectiveness is unsatisfactory due to insufficient catalytic performance. Here, we report for the first time an intrinsic strain-mediated ultrathin ceria nanoantioxidant. Surface strain in ceria with variable thicknesses and coordinatively unsaturated Ce sites was investigated by theoretical calculation analysis and then was validated by preparing ∼1.2 nm ultrathin nanoplates with ∼3.0% tensile strain in plane/∼10.0% tensile strain out of plane. Compared with nanocubes, surface strain in ultrathin nanoplates could enhance the covalency of the Ce-O bond, leading to increasing superoxide dismutase (SOD)-mimetic activity by ∼2.6-fold (1533 U/mg, in close proximity to that of natural SOD) and total antioxidant activity by ∼2.5-fold. As a proof of concept, intrinsic strain-mediated ultrathin ceria nanoplates could boost antioxidation for improved ischemic stroke treatment in vivo, significantly better than edaravone, a commonly used clinical drug.

Cell membrane-specific self-assembly of peptide nanomedicine induces tumor immunogenic death to enhance cancer therapy

Immunogenic cell death (ICD), as an unusual cell death pattern, mediates cancer cells to release a series of damage-associated molecular patterns (DAMPs), and is widely used in the field of cancer immunotherapy. Injuring the cell membrane can serve as a novel ICD initiation strategy. In this study, a peptide nanomedicine (PNpC) is designed using the fragment CM11 of cecropin, which is effective in disrupting cell membranes because of its α-helical structure. PNpC self-assembles in situ in the presence of high levels of alkaline phosphatase (ALP) on the tumor cell membrane, transforming from nanoparticles to nanofibers, which reduces the cellular internalization of the nanomedicine and increases the interaction between CM11 and tumor cell membranes. Both in vitro and in vivo results indicate that PNpC plays a significant role in killing tumor cells by triggering ICD. The ICD induced by the destruction of the cancer cell membrane is accompanied by the release of DAMPs, which promotes the maturation of DCs and facilitates the presentation of tumor-associated antigens (TAA), resulting in the infiltration of CD8+ T cells. We believe that PNpC can trigger ICD while killing cancer cells, providing a new reference for cancer immunotherapy.

Reversible covalent nanoassemblies for augmented nuclear drug translocation in drug resistance tumor

The drug efflux by P-glycoprotein (P-gp) is the primary contributor of multidrug resistance (MDR), which eventually generates insufficient nuclear drug accumulation and chemotherapy failure. In this paper, reversible covalent nanoassemblies on the basis of catechol-functionalized methoxy poly (ethylene glycol) (mPEG-dop) and phenylboronic acid-modified cholesterol (Chol-PBA) are successfully synthesized for delivery of both doxorubicin (DOX, anti-cancer drug) and tariquidar (TQR, P-glycoprotein inhibitor), which shows efficient nuclear DOX accumulation for overcoming tumor MDR. Through naturally forming phenylboronate linkage in physiological circumstances, Chol-PBA is able to bond with mPEG-dop. The resulting conjugates (PC) could self-assemble into reversible covalent nanoassemblies by dialysis method, and transmission electron microscopy analysis reveals the PC distributes in nano-scaled spherical particles before and after drug encapsulation. Under the assistance of Chol, PC can enter into lysosome of tumor cells via low-density lipoprotein (LDL) receptor-mediated endocytosis. Then the loaded TQR and DOX are released in acidic lysosomal compartments, which inhibit P-gp mediated efflux and elevate nuclear accumulation of DOX, respectively. At last, this drug loaded PC nanoassemblies show significant tumor suppression efficacy in multidrug-resistant tumor models, which suggests great potential for addressing MDR in cancer therapy.

An Ultrasound-Induced Self-Clearance Hydrogel for Male Reversible Contraception

Nearly half of pregnancies worldwide are unintended mainly due to failure of contraception, resulting in negative effects on women's health. Male contraception techniques, primarily condoms and vasectomy, play a crucial role in birth control, but cannot be both highly effective and reversible at the same time. Herein, an ultrasound (US)-induced self-clearance hydrogel capable of real-time monitoring is utilized for in situ injection into the vas deferens, enabling effective contraception and noninvasive recanalization whenever needed. The hydrogel is composed of (i) sodium alginate (SA) conjugated with reactive oxygen species (ROS)-cleavable thioketal (SA-tK), (ii) titanium dioxide (TiO₂), which can generate a specific level of ROS after US treatment, and (iii) calcium chloride (CaCl₂), which triggers the formation of the hydrogel. For contraception, the above mixture agents are one-time injected into the vas deferens, which can transform from liquid to hydrogel within 160 s, thereby significantly physically blocking the vas deferens and inhibiting movability of sperm. When fertility is needed, a noninvasive remedial ultrasound can make TiO₂ generate ROS, which cleaves SA-tK to destroy the network of the hydrogel. Owing to the recanalization, the refertility rate is restored to 100%. Meanwhile, diagnostic ultrasound (D-US, 22 MHz) can monitor the occlusion and recanalization process in real-time. In summary, the proposed hydrogel contraception can be a reliable, safe, and reversible male contraceptive strategy that addresses an unmet need for men to control their fertility.

Skin-like wound dressings with on-demand administration based on in situ peptide self-assembly for skin regeneration

Burn injuries without the normal skin barrier usually cause skin wound infections, and wound dressings are necessary. Although various dressings with antibacterial ability have already been developed, the biosafety and administration mode are still bottleneck problems for further application. Herein, we designed skin-like wound dressings based on silk fibroin (SF), which are modified with the gelatinase-cleavable self-assembled/antibacterial peptide (GPLK) and epidermal growth factor (EGF). When a skin wound is infected, the gelatinase over-secreted by bacteria can cut the GPLK peptides, leading to the in situ self-assembly of peptides and the resultant high-efficiency sterilization. Compared with the commercial antibacterial dressing, the SF-GPLK displayed a faster wound healing rate. When a skin wound is not infected, the GPLK peptides remain in the SF, realizing good biosafety. Generally, the EGF can be released to promote wound healing and skin regeneration in both cases. Therefore, skin-like SF-GPLK wound dressings with on-demand release of antibacterial peptides provide a smart administration mode for clinical wound management and skin regeneration.

Intracellular Self-Immolative Polyprodrug with Near-Infrared Light Guided Accumulation and in Vivo Visualization of Drug Release

The selective accumulation and real-time monitoring of drug release at tumor site are the key bottlenecks to the clinical translation of polyprodrug. Herein, an intracellular self-immolative polyprodrug (PMTO) is exploited, which not only shows the enhanced cellular internalization and selective accumulation in tumor site under the mild hyperthermia triggered by laser irradiation, but also possesses the self-monitoring drug release ability in vivo. The polyprodrug amphiphiles are synthesized by sequential esterification reaction, and hydrophilic poly(ethylene glycol) serves as blocking agent. On account of the mild hyperthermia produced by PMTO under the laser irradiation at tumor site, the cell membranous permeability increases, resulting in the enhanced cellular internalization and drug accumulation in tumor. After internalized by cells, the self-immolative PMTO nanoparticles can release free mitoxantrone (MTO) in intracellular reductive environment, and ratiometric photoacoustic imaging based on distinct signals between MTO and PMTO is presented to trace the drug release in vivo. Finally, this self-monitoring polyprodrug presents significant tumor suppression efficacy, which exhibits great potential for guiding the clinical medication in cancer treatment.

In Vivo Self-Assembly Induced Cell Membrane Phase Separation for Improved Peptide Drug Internalization

Therapeutic peptides have been widely concerned, but their efficacy is limited by the inability to penetrate cell membranes, which is a key bottleneck in peptide drugs delivery. Herein, an in vivo self-assembly strategy is developed to induce phase separation of cell membrane that improves the peptide drugs internalization. A phosphopeptide KYp is synthesized, containing an anticancer peptide [KLAKLAK]₂ (K) and a responsive moiety phosphorylated Y (Yp). After interacting with alkaline phosphatase (ALP), KYp can be dephosphorylated and self-assembles in situ, which induces the aggregation of ALP and the protein-lipid phase separation on cell membrane. Consequently, KYp internalization is 2-fold enhanced compared to non-responsive peptide, and IC₅₀ value of KYp is approximately 5 times lower than that of free peptide. Therefore, the in vivo self-assembly induced phase separation on cell membrane promises a new strategy to improve the drug delivery efficacy in cancer therapy.

Regulating Twisted Skeleton to Construct Organ-Specific Perylene for Intensive Cancer Chemotherapy

The systemic use of pharmaceutical drugs for cancer patients is a compromise between desirable therapy and side effects because of the intrinsic shortage of organ-specific pharmaceutical drug. Design and construction of pharmaceutical drug to achieve the organ-specific delivery is thus desperately desirable. We herein regulate perylene skeleton to effect organ-specificity and present an example of lung-specific distribution on the basis of bay-twisted PDIC-NC. We further demonstrate that PDIC-NC can target into mitochondria to act as cellular respiration inhibitor, inducing insufficient production of adenosine triphosphate, promoting endogenous H₂ O₂ and ^. OH burst, elevating calcium overload, efficiently triggering the synergistic apoptosis, autophagy and endoplasmic reticulum stress of lung cancer cells. The antitumor performance of PDIC-NC is verified on in vivo xenografted, metastasis and orthotopic lung cancer, presenting overwhelming evidences for potentially clinical application. This study contributes a proof-of-concept demonstration of twisted perylene to well attain lung-specific distribution, and meanwhile achieves intensive lung cancer chemotherapy.

Hybrid Plasmonic Nanodumbbells Engineering for Multi-Intensified Second Near-Infrared Light Induced Photodynamic Therapy

Photodynamic therapy (PDT) has shown great potential in infection treatment. However, the shallow depth of the short wavelength light and the low reactive oxygen species (ROS) production hinder its development. A strategy that can achieve a second near-infrared (NIR-II) light that is a long wavelength induced multi-intensified antibacterial PDT is most critical. Herein, hybrid plasmonic Au/CdSe_xS_y with precise Ag doping (ACA) nanodumbbells are rationally designed for ideal NIR-II light induced antibacterial PDT. Plasmonic Au nanorods extend the photocatalytic activity of ACA to NIR-II regions, which provides a basis for NIR-II light induced PDT. More importantly, multi-intensified PDT can be realized by the following creativities: (i) elaborate design of as-synthesized nanodumbbells that allows for electron holes to be redistributed in different regions simultaneously, (ii) the efficient hot-electrons injection that benefits from the ratio tailoring of anions ratio of Se and S, and (iii) the dopant Ag level inhibiting the combination of electron holes. The nanodumbbells create effective hot-electrons injection and a separation of electron holes, which provides great convenience for the production of ROS and allows NIR-II light induced PDT for the inhibition of bacteria and biofilms. As a result, comparably, our well-defined ACA hybrid nanodumbbells can generate about 40-fold superoxide radicals (·O₂^-) and more hydroxyl radicals (·OH). Therefore, the MIC value of the as-synthesized nanodumbbells is lower than the value of 1/16 of core-shell ACA. In vivo results further demonstrate that our nanodumbbells exhibit excellent PDT efficacy.

Ultrasound-Activated Cascade Effect for Synergistic Orthotopic Pancreatic Cancer Therapy

In some malignant tumor, especially for pancreatic tumor, poor solid-tumor penetration of nanotherapeutics impedes their treatment efficacy. Herein, we develop a polymer-peptide conjugate with the deep tissue penetration ability, which undergoes a cascade process under ultrasound (US), including (1) the singlet oxygen ¹O₂ is generated by P18, (2) the thioketal bond is cleaved by the ¹O₂, (3) the departure of PEG chains leads to the in situ self-assembly, and (4) the resultant self-assembled PK nanoparticles show considerable cellular internalization. Owing to the synergistic effect of US on increasing the membrane permeability, the endocytosis and lysosome escape of PK nanoparticles are further enhanced effectively, resulting in the improved therapeutic efficacy. Thanks to the high tissue-penetrating depth and spatial precision of US, PTPK presents enhanced tumor inhibition in an orthotopic pancreatic tumor model. Therefore, the US-activated cascade effect offers a novel perspective for precision medicine and disease theranostics.

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PPCs in single molecule state present remarkable solid-tumor penetrability

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US induced in situ self-assembly of PPCs is verified

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Assembled nanoparticles and US synergistically contribute to the cellular internalization

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US-activated cascade effect leads to effective inhibition of pancreatic tumor growth

Near-Infrared Laser-Triggered In Situ Dimorphic Transformation of BF2-Azadipyrromethene Nanoaggregates for Enhanced Solid Tumor Penetration

The shape of a drug delivery system impacts its in vivo behavior such as circulation time, accumulation, and penetration. Considering the advantages of functional dyes in bioapplications, we synthesize a class of nanoaggregates based on BF₂-azadipyrromethene (aza-BODIPY) dyes, which can realize long blood circulation and deep tumor penetration simultaneously in vivo through morphological transformation modulated by a near-infrared (NIR) laser. First, when the temperature increases, the wormlike nanofibers of the aza-BODIPY-1 aggregate, possessing a long blood circulation time, can be transformed into spherical nanoparticles, which are conducive to increasing the penetration in the solid tumor. Second, without any postmodification, the nanofibers exhibit an outstandingly narrow absorption band in the NIR spectral range, so that they possess ideal photothermal properties. Through 655 nm laser irradiation, the intrinsic photothermal effect causes a local temperature increase to ∼48 °C, realizing the transformation of 1-NFs to 1-NPs. Third, the morphological transformation is real-time detected by photoacoustic (PA) imaging. By monitoring the change of the PA signal at a specific wavelength, the in vivo deformation process of nanomaterials can be traced. Consequently, the in situ morphology transformation of aza-BODIPY-based nanomaterials can simultaneously realize long blood circulation and deep penetration, resulting in the enhanced antitumor outcome.

Photothermal-Promoted Morphology Transformation in Vivo Monitored by Photoacoustic Imaging

The in situ construction of the nanoassembly has been demonstrated to improve the performance of bioactive molecules, but the control of the morphology of nanomaterials in vivo still remains a tremendous challenge. Herein, a photothermal-promoted morphology transformation (PMT) strategy is developed to accelerate the formation of nanomaterials for improving the biological performance of drug molecules. Compared with the spontaneous process, the rate of transformation increases by ∼4 times in the PMT process. Owing to increased assembly rate, the tumor accumulation of drugs is ∼2-fold than that without photo irradiation, which inhibits tumor growth effectively. More importantly, the chemical reassembly process in vitro and in vivo is monitored by the advanced ratiometric photoacoustic image, confirming the photoinduced transformation acceleration. Through the noninvasively artificial control on assembly dynamics in vivo, the PMT strategy provides a new insight for developing the intelligent theranostics.

Recent progress of therapeutic peptide based nanomaterials: from synthesis and self-assembly to cancer treatment

This review has described the synthesis, self-assembly and the anti-cancer application of therapeutic peptides and their conjugates, particularly polymer–peptide conjugates (PPCs).

Programmable Construction of Peptide-Based Materials in Living Subjects: From Modular Design and Morphological Control to Theranostics

Self-assembled nanomaterials show potential high efficiency as theranostics for high-performance bioimaging and disease treatment. However, the superstructures of pre-assembled nanomaterials may change in the complicated physiological conditions, resulting in compromised properties and/or biofunctions. Taking advantage of chemical self-assembly and biomedicine, a new strategy of "in vivo self-assembly" is proposed to in situ construct functional nanomaterials in living subjects to explore new biological effects. Herein, recent advances on peptide-based nanomaterials constructed by the in vivo self-assembly strategy are summarized. Modular peptide building blocks with various functions, such as targeting, self-assembly, tailoring, and biofunctional motifs, are employed for the construction of nanomaterials. Then, self-assembly of these building blocks in living systems to construct various morphologies of nanostructures and corresponding unique biological effects, such as assembly/aggregation-induced retention (AIR), are introduced, followed by their applications in high-performance drug delivery and bioimaging. Finally, an outlook and perspective toward future developments of in vivo self-assembled peptide-based nanomaterials for translational medicine are concluded.

Site-Specific Construction of Long-Term Drug Depot for Suppression of Tumor Recurrence

Local tumor recurrence after surgical resection is a critical concern in cancer therapy, and the current treatments, such as postsurgical chemotherapy, still show undesired side effects. Here a nonimplant strategy (transformation induced localization, TIL) is presented to in situ construct long-term retentive drug depots, wherein the sustained drug release from fibrous drug depots results in highly efficient suppression of postsurgical local tumor relapse. The peptide-based prodrug nanoparticles show favorable tumor targeting and instantly reorganize into fibrous nanostructures under overexpressed enzyme, realizing the construction of long-term drug depot in the tumor site. After the resection surgery, the remnant cancer cells are still inhibited by the sustained drug release from the fibrous prodrug depot, effectively preventing postsurgical local recurrences. This TIL strategy shows great potential in cancer recurrence therapy and offers a novel perspective for constructing functional biomaterials in vivo.

Tumor Microenvironmental pH and Enzyme Dual Responsive Polymer-Liposomes for Synergistic Treatment of Cancer Immuno-Chemotherapy

Despite recent advances in tumor treatment through cancer immunotherapy, the efficacy of this approach remains to be improved. Looking forward to high rates of objective clinical response, cancer immunotherapy combined with chemotherapy has gained increasing attention recently. Here, we constructed liposomes with matrix metalloproteinases (MMPs) responsive moiety and PD-L1 inhibitor conjugate combine with low dose chemotherapy to achieve enhanced antitumor efficacy. Upon introduction of the pH-responsive polymer to LPDp, the coassembly could be almost stable in physiological conditions and tumor microenvironments and release the loaded cargos at the lysosome. MMP-2 enzyme extracellularly secreted by the B16F10 cells could cleave the cross-linker and liberate the PD-L1 inhibitor effectively disrupting the PD-1/PD-L1 interaction in vitro. Low dose DOX encapsulated in the LPDp was capable of sensitizing B16F10 cells to CTLs by inducing overexpression of M6PR on tumor cell membranes. In comparison with free PD-L1 inhibitor, LPDp improved the biodistribution and on-demand release of the peptide inhibitor in tumor regions following administration. LPDp achieved the optimal tumor suppression efficiency (∼78.7%), which demonstrated the significantly enhanced antitumor effect ( P < 0.01) than that of LPp (∼57.5%) as well as that of LD (<40%), attributing to synergistic contribution from the substantial increase in M6PR expression on tumor cells and the blockade of immune checkpoints. This strategy provides a strong rationale for combining standard-of-care chemotherapy with relative nontoxic and high specific immunotherapy.

Near-Infrared Laser-Driven in Situ Self-Assembly as a General Strategy for Deep Tumor Therapy

Nanotherapeutics have encountered some bottleneck problems in cancer therapy, such as poor penetration and inefficient accumulation in tumor site. We herein developed a novel strategy for deep tissue penetration in molecular level and near-infrared (NIR) laser guided in situ self-assembly to solve these challenges. For the proof-of-concept study, we synthesized the polymer-peptide conjugates (PPCs) composed of (i) poly(β-thioester) as thermoresponsive backbone, (ii) functional peptides (cytotoxic peptide and cell-penetrating peptide), and (iii) the NIR molecule with photothermal property. The PPCs in the molecular level with small size (<10 nm) can penetrate deeply into the interior of the tumor at body temperature. Under the irradiation of NIR laser, the temperature rise induced by photothermal molecules led to the intratumoral self-assembly of thermoresponsive PPCs. The resultant spherical nanoparticles can accumulate in tumor and enter cells effectively, inducing cell apoptosis by destroying mitochondria membrane. Through the site-specific size control, a variety of merits of PPCs are realized including deep tumor penetration, enhanced accumulation, and cellular internalization in vivo. Taking advantage of the NIR guided in situ assembly strategy, numerous polymeric or nanoscaled therapeutics with high anticancer activity can be exploited.

High-Performance Identification of Human Bladder Cancer Using a Signal Self-Amplifiable Photoacoustic Nanoprobe

Cancer diagnostics has been an important research field, and identification of small lesions that are less noticeable plays a vital role in thoroughly removing the tumor, thereby reducing the recurrence rate of cancer. Herein, we synthesized a signal self-amplifiable photoacoustic (PA) liposomal nanoprobe composed by ammonium hydrogen carbonate (AHC) payload and aggregated purpurin-18 (P18) within the bilayer. Under PA laser irradiation, P18 aggregates efficiently generated local heat, leading to the launch of wide-band ultrasonic emission. In parallel, the heat also triggered the decomposition of AHC and production of CO₂ bubbles, which consequently dramatically amplified the acoustic signal. For clinical translation, by decorating bladder cancer (BC) specific CD44v6 antibody onto nanoprobe, we were capable of utilizing this high sensitive and specific PA probe for human BC tissue imaging. The results indicated that small tumor lesion (<5 mm) was identified and the tumor-to-normal tissue ratio was ∼18 folds enhancement by using this PA probe, which rendered the tumor boundary distinct. All together, we developed a new strategy for exploring high-performance imaging probes, which might potentially benefit for the imaging-guided surgery in clinics.

A self-destructive nanosweeper that captures and clears amyloid β-peptides

Cerebral amyloid β-peptide (Aβ) accumulation resulting from an imbalance between Aβ production and clearance is one of the most important causes in the formation of Alzheimer's disease (AD). In order to preserve the maintenance of Aβ homeostasis and have a notable AD therapy, achieving a method to clear up Aβ plaques becomes an emerging task. Herein, we describe a self-destructive nanosweeper based on multifunctional peptide-polymers that is capable of capturing and clearing Aβ for the effective treatment of AD. The nanosweeper recognize and bind Aβ via co-assembly through hydrogen bonding interactions. The Aβ-loaded nanosweeper enters cells and upregulates autophagy thus promoting the degradation of Aβ. As a result, the nanosweeper decreases the cytotoxicity of Aβ and rescues memory deficits of AD transgenic mice. We believe that this resourceful and synergistic approach has valuable potential as an AD treatment strategy.

Synthesis of Self-Assembled Porphyrin Nanoparticle Photosensitizers

The use of nanoparticles as a potential building block for photosensitizers has recently become a focus of interest in the field of photocatalysis and photodynamic therapy. Porphyrins and their derivatives are effective photosensitizers due to extended π-conjugated electronic structure, high molar absorption from visible to near-infrared spectrum, and high singlet oxygen quantum yields as well as chemical versatility. In this paper, we report a synthesis of self-assembled porphyrin nanoparticle photosensitizers using zinc meso-tetra(4-pyridyl)porphyrin (ZnTPyP) through a confined noncovalent self-assembly process. Scanning electron microscopy reveals formation of monodisperse cubic nanoparticles. UV-vis characterizations reveal that optical absorption of the nanoparticles exhibits a red shift due to noncovalent self-assembly of porphyrins, which not only effectively increase intensity of light absorption but also extend light absorption broadly covering visible light for enhanced photodynamic therapy. Electron spin-resonance spectroscopy (ESR) studies show the resultant porphyrin nanoparticles release a high yield of singlet oxygen. Nitric oxide (NO) coordinates to central metal Zn ions to form stabilized ZnTPyP@NO nanoparticles. We show that under light irradiation ZnTPyP@NO nanoparticles release highly reactive peroxynitrite molecules that exhibit enhanced antibacterial photodynamic therapy (APDT) activity. The ease of the synthesis of self-assembled porphyrin nanoparticles and light-triggered release of highly reactive moieties represent a completely different photosensitizer system for APDT application.

Enzyme-sensitive cytotoxic peptide–dendrimer conjugates enhance cell apoptosis and deep tumor penetration

Cytotoxic peptide conjugated PAMAM dendrimers with MMP2-sensitive PEG for efficient tumor penetration, cellular internalization and mitochondria disruption.

Reconfigurable Peptide Nanotherapeutics at Tumor Microenvironmental pH

Peptide nanomaterials have recently attracted considerable interest in the biomedical field. However, their poor bioavailability and less powerful therapeutic efficacy hamper their further applications. Herein, we discovered reconfigurable and activated nanotherapeutics in the tumor microenvironment. Two peptides, that is, a pH-responsive peptide HLAH and a matrix metalloprotease-2 (MMP2)-sensitive peptide with a poly(ethylene glycol) (PEG) terminal were conjugated onto the hydrophobic poly(β-thioester)s backbones to gain the copolymer P-S-H. The therapeutic activity of the HLAH peptide could be activated in tumors owing to its reconfiguration under microenvironmental pH. The resultant copolymers self-assembled into nanoparticles under physiological condition, with HLAH in cores protected by PEG shells. The moderate size (∼100 nm) and negative potential enabled the stable circulation of P-S-H in the bloodstream. Once arrived at the tumor site, the P-S-H nanoparticles were stimulated by overexpressed MMP2 and acidic pH, and subsequently the shedding of the PEG shell and protonation of the HLAH peptide induced the reassembly of nanoparticles, resulting in the formation of nanoparticles with activated cytotoxic peptides on the surface. In vivo experiments demonstrated that the reorganized nanoassembly contained three merits: (1) effective accumulation in the tumor site, (2) enhanced antitumor capacity, and (3) no obvious toxic effect at the treatment dose. This on-site reorganization strategy provides an avenue for developing high-performance peptide nanomaterials in cancer treatment.

An "On-Site Transformation" Strategy for Treatment of Bacterial Infection

To date, numerous nanosystems have been developed as antibiotic replacements for bacterial infection treatment. However, these advanced systems are limited owing to their nontargeting accumulation and the consequent side effects. Herein, transformable polymer-peptide biomaterials have been developed that enable specific accumulation in the infectious site and long-term retention, resulting in enhanced binding capability and killing efficacy toward bacteria. The polymer-peptide conjugates are composed of a chitosan backbone and two functional peptides, i.e., an antimicrobial peptide and a poly(ethylene glycol)-tethered enzyme-cleavable peptide (CPC-1). The CPC-1 initially self-assembles into nanoparticles with pegylated coronas. Upon the peptides are cleaved by the gelatinase secreted by a broad spectrum of bacterial species, the resultant compartments of nanoparticles spontaneously transformed into fibrous nanostructures that are stabilized by enhanced chain-chain interaction, leading to exposure of antimicrobial peptide residues for multivalent cooperative electrostatic interactions with bacterial membranes. Intriguingly, the in situ morphological transformation also critically improves the accumulation and retention of CPC-1 in infectious sites in vivo, which exhibits highly efficient antibacterial activity. This proof-of-concept study demonstrates that pathological environment-driven smart self-assemblies may provide a new idea for design of high-performance biomaterials for disease diagnostics and therapeutics.

[Experience of Sun's procedure for chronic type B dissection with aortic arch involvement]

Objective: To study the surgical treatment of chronic type B dissection with aortic arch involvement using Sun's procedure. Methods: Between February 2009 and December 2015, 29 patients [20 males, 9 females, with a mean age of (41±12) years, range 24-64 years] with type B dissection with aortic arch involvement underwent Sun's procedure. Sixteen patient had a history of hypertension. Marfan syndrome was observed in 9 cases, coronary artery disease in 3 cases, mitral regurgitation in 3 patients, cerebrovascular disease in one patient. Twenty-two patients suffered proximal aortic arch disease, 4 cases experienced history of aortic root procedure and 2 subjects had history of pregnancy. Four patients had aortic arch malformation. Results: One case suffered from massive cerebral infarction after surgery and died in another hospital. Concomitant procedures included mitral valve replacement in 3 cases, coronary artery bypass grafting in 3 patients, reconstruction of the right aberrant subclavian artery in one patient. Ventilator support exceeding 24 hours obseved in 2 patients. One of them recieved continuous renal replacement therapy and recovered before discharge. Spinal cord injury was obseved in one case, brain infarction in one patient and pericardial drainage in one case. Two patients required tracheotomy. During 12-94 (43±23) months' follow-up, thoracoabdominal aortic replacment was performed in 4 patients, thoracic endovascular aortic repair (TEVAR) in 2 subjects and repair of perivalvular leakage in one patient. Conclusions: Sun's procedure obtained satisfactory results in patients with chronic type B dissection with aortic arch involvement. Concomitant repair of proximal aortic arch lesions and distal type B dissection can be adopted using Sun's procedure.

In Situ Monitoring Intracellular Structural Change of Nanovehicles through Photoacoustic Signals Based on Phenylboronate-Linked RGD-Dextran/Purpurin 18 Conjugates

The stimuli-responsive polymeric nanocarriers have been studied extensively, and their structural changes in cells are important for the controlled intracellular drug release. The present work reported RGD-dextran/purpurin 18 conjugates with pH-responsive phenylboronate as spacer for monitoring the structural change of nanovehicles through ratiometric photoacoustic (PA) signal. Phenylboronic acid modified purpurin 18 (NPBA-P18) could attach onto the RGD-decorated dextran (RGD-Dex), and the resulting RGD-Dex/NPBA-P18 (RDNP) conjugates with different molar ratios of RGD-Dex and NPBA-P18 were prepared. When the moles of NPBA-P18 were equivalent to more than triple of RGD-Dex, the single-stranded RDNP conjugates could self-assemble into nanoparticles in aqueous solution due to the fairly strong hydrophobicity of NPBA-P18. The pH-responsive aggregations of NPBA-P18 were investigated by UV-vis, fluorescence, and circular dichroism spectra, as well as transmission electron microscope. Based on distinct PA signals between monomeric and aggregated state, ratiometric PA signal of I₇₅₀/I₇₁₀ could be presented to trace the structural change progress. Compared with RDNP single chains, the nanoparticles exhibited effective cellular internalization through endocytosis pathway. Furthermore, the nanoparticles could form well-ordered aggregates responding to intracellular acidic environment, and the resulting structural change was also monitored by ratiometric PA signal. Therefore, the noninvasive PA approach could provide a deep insight into monitoring the intracellular structural change process of stimuli-responsive nanocarriers.

An in Situ Intracellular Self-Assembly Strategy for Quantitatively and Temporally Monitoring Autophagy

Autophagy plays a crucial role in the metabolic process. So far, conventional methods are incapable of rapid, precise, and real-time monitoring of autophagy in living objects. Herein, we describe an in situ intracellular self-assembly strategy for quantitative and temporal determination of autophagy in living objectives. The intelligent building blocks (DPBP) are composed by a bulky dendrimer as a carrier, a bis(pyrene) derivative (BP) as a signal molecule, and a peptide linker as a responsive unit that can be cleaved by an autophagy-specific enzyme, i.e., ATG4B. DPBP maintains the quenched fluorescence with monomeric BP. However, the responsive peptide is specifically tailored upon activation of autophagy, resulting in self-aggregation of BP residues which emit a 30-fold enhanced fluorescence. By measuring the intensity of fluorescent signal, we are able to quantitatively evaluate the autophagic level. In comparison with traditional techniques, such as TEM, Western blot, and GFP-LC3, the reliability and accuracy of this method are finally validated. We believe this in situ intracellular self-assembly strategy provides a rapid, effective, real-time, and quantitative method for monitoring autophagy in living objects, and it will be a useful tool for autophagy-related fundamental and clinical research.

One-pot synthesis of pH-responsive hyperbranched polymer–peptide conjugates with enhanced stability and loading efficiency for combined cancer therapy

Nanoparticles as drug-delivery systems have received significant attention due to their merits such as prolonged circulation time and passive targeting of a tumor site.

In Situ Construction and Characterization of Chlorin-Based Supramolecular Aggregates in Tumor Cells

We demonstrate in situ construction and characterization of supramolecular aggregates from chlorin p6 (Cp6) molecules in tumor cells. Fully deprotonated Cp6 molecules in neutral condition were partially protonated inside the acidic lysosomes of cells and significantly increased the hydrophobicity of them that resulted in simultaneous formation of J-type aggregates. Importantly, the formation of J-aggregates was fully characterized in artificial tissues by UV-vis, circular dichroism (CD) and transmission electron microscope (TEM) techniques. Compared to the monomers, the J-aggregates exhibited 55-fold enhanced thermal conversion efficiency (η) at the optimal excitation wavelength (690 nm). The remarkably increased heat effect contributed to the stronger photoacoustic (PA) signals, leading to at least 2 orders of magnitude increase of the tumor-to-normal tissue ratio (T/N), which was defined as the PA signal ratio between tumor site and surrounding normal tissue. We envision that this proof-of-concept study will open a new way to develop tumor environment-induced self-assembly for variable biomedical applications.

Bio-orthogonally Deciphered Binary Nanoemitters for Tumor Diagnostics

Bioinspired design concept has been recognized as one of the most promising strategies for discovering new biomaterials. However, smart biomaterials that are of growing interests in biomedical field need biological processability to meet their emergent applications in vivo. Herein, a new bio-orthogonally deciphered approach has been demonstrated for modulating optical properties of nanomaterials in living systems. The self-assembled nanoemitters based on cyanine-pyrene molecule 1 with inert optical property are designed and prepared. The structure and optical feature of the nanoemitters 1 can be efficiently and reliably modulated by a unique bio-orthogonal mechanism with abundant glutathione (GSH) as an activator. As a result, the self-assembled nanoemitters 1 spontaneously exhibits binary emissions for high-performance tumor imaging in vivo. We believe that this bio-orthogonally deciphered strategy opens a new avenue for designing variable smart biomaterials or devices in biomedical applications.

pH-Sensitive Polymeric Nanoparticles Modulate Autophagic Effect via Lysosome Impairment

In drug delivery systems, pH-sensitive polymers are commonly used as drug carriers, and significant efforts have been devoted to the aspects of controlled delivery and release of drugs. However, few studies address the possible autophagic effects on cells. Here, for the first time, using a fluorescent autophagy-reporting cell line, this study evaluates the autophagy-induced capabilities of four types of pH-sensitive polymeric nanoparticles (NPs) with different physical properties, including size, surface modification, and pH-sensitivity. Based on experimental results, this study concludes that pH-sensitivity is one of the most important factors in autophagy induction. In addition, this study finds that variation of concentration of NPs could cause different autophagic effect, i.e., low concentration of NPs induces autophagy in an mTOR-dependent manner, but high dose of NPs leads to autophagic cell death. Identification of this tunable autophagic effect offers a novel strategy for enhancing therapeutic effect in cancer therapy through modulation of autophagy.

Self-Assembled ROS-Sensitive Polymer-Peptide Therapeutics Incorporating Built-in Reporters for Evaluation of Treatment Efficacy

One of the major challenges in current cancer therapy is to maximize therapeutic effect and evaluate tumor progression under the scheduled treatment protocol. To address these challenges, we synthesized the cytotoxic peptide (KLAKLAK)2 (named KLAK) conjugated amphiphilic poly(β-thioester)s copolymers (H-P-K) composed of reactive oxygen species (ROS) sensitive backbones and hydrophilic polyethylene glycol (PEG) side chains. H-P-K could self-assemble into micelle-like nanoparticles by hydrophobic interaction with copolymer backbones as cores and PEG and KLAK as shells. The assembled polymer-peptide nanoparticles remarkably improved cellular internalization and accumulation of therapeutic KLAK in cells. Compared to free KLAK peptide, the antitumor activity of H-P-K was significantly enhanced up to ∼400 times, suggesting the effectiveness of the nanoscaled polymer-peptide conjugation as biopharmaceuticals. The higher antitumor activity of nanoparticles was attributed to the efficient disruption of mitochondrial membranes and subsequent excessive ROS production in cells. To realize the ROS monitoring and treatment evaluation, we encapsulated squaraine (SQ) dyes as built-in reporters in ROS-sensitive H-P-K micelles. The overgenerated ROS around mitochondria stimulated the swelling of nanoparticles and subsequent release of SQ, which formed H-aggregates and significantly increased the photoacoustic (PA) signal. We believed that this self-assembled polymer-peptide nanotherapeutics incorporating built-in reporters has great potential for high antitumor performance and in situ treatment evaluation.

A General Strategy for Facile Synthesis and In Situ Screening of Self-Assembled Polymer-Peptide Nanomaterials

A universal strategy for efficient, mild, and purification-free synthesis and in situ screening of functional polymer-peptide nanomaterials is described. More than 1000 polymer-peptide conjugates (PPCs) with various chemical structures, compositions, and therapeutic efficacy are created. According to this strategy, the structure-function relationship of the PPCs is revealed, and the antitumor efficacies of the top performing PPCs are evaluated in vivo.

Oxidation and temperature dual responsive polymers based on phenylboronic acid and N-isopropylacrylamide motifs

Oxidation and temperature dual responsive copolymers using ROS as a target for drug delivery have been demonstrated.

A Peptide-Network Weaved Nanoplatform with Tumor Microenvironment Responsiveness and Deep Tissue Penetration Capability for Cancer Therapy

Novel core-shell tumor-penetrating vesicles consisting of a nanovesicle core with tumor-penetrating ligands and enzymatically degradable polymeric peptides anchored covalently to the core to form a thin polymeric shell are evaluated as drug-delivery systems. This delivery platform demonstrates an enhanced therapeutic efficacy attributed to the synergistic contributions from matrix metalloproteinase (MMP)-responsive drug release as well as improved tumor accumulation and penetration in the tumor microenvironment.

pH-Sensitive polymer assisted self-aggregation of bis(pyrene) in living cells in situ with turn-on fluorescence

Supramolecular self-assemblies with various nanostructures in organic and aqueous solutions have been prepared with desired functions. However, in situ construction of self-assembled superstructures in physiological conditions to achieve expected biological functions remains a challenge. Here, we report a supramolecular system to realize the in situ formation of nanoaggregates in living cells. The bis(pyrene) monomers were dispersed inside of hydrophobic domains of pH-sensitive polymeric micelles and delivered to the lysosomes of cells. In the acidic lysosomes, the bis(pyrene) monomers were released and self-aggregated with turn-on fluorescence. We envision this strategy for in situ construction of supramolecular nanostructures in living cells will pave the way for molecular diagnostics in the future.

Self-assembled autophagy-inducing polymeric nanoparticles for breast cancer interference in-vivo

A peptide-conjugated poly(β-amino ester) that self-assembles into micelle-like nanoparticles is prepared by a convenient and modular supramolecular approach. The polymer-beclin-1 (P-Bec1) nanoparticles display enhanced cytotoxicity to breast cancer cells through induction of autophagy. This approach overcomes two major limitations of the haploinsufficient tumor suppressor Bec1 compared to small-molecule drugs: poor delivery to tumors owing to enzymatic degradation, and unstable, non-specific bio-distribution and targeting in the tumor tissues.