β-Galactosidase-activated near-infrared AIEgen for ovarian cancer imaging in vivo

Near-infrared (NIR) aggregation induced-emission luminogens (AIEgens) circumvent the noisome aggregation-caused quenching (ACQ) effect in physiological milieu, thus holding high promise for real-time and sensitive imaging of biomarkers in vivo. β-Galactosidase (β-Gal) is a biomarker for primary ovarian carcinoma, but current AIEgens for β-Gal sensing display emissions in the visible region and have not been applied in vivo. We herein propose an NIR AIEgen QM-TPA-Gal and applied it for imaging β-Gal activity in vitro and in ovarian tumor model. After being internalized by ovarian cancer cells (e.g., SKOV3), the hydrophilic nonfluorescent QM-TPA-Gal undergoes hydrolyzation by β-Gal to yield hydrophobic QM-TPA-OH, which subsequently aggregates into nanoparticles to turn NIR fluorescence "on" through the AIE mechanism. In vitro experimental results indicate that QM-TPA-Gal has a sensitive and selective response to β-Gal with a limit of detection (LOD) of 0.21 U/mL. Molecular docking simulation confirms that QM-TPA-Gal has a good binding ability with β-Gal to allow efficient hydrolysis. Furthermore, QM-TPA-Gal is successfully applied for β-Gal imaging in SKOV3 cell and SKOV3-bearing living mouse models. It is anticipated that QM-TPA-Gal could be applied for early diagnosis of ovarian cancers or other β-Gal-associated diseases in near future.

Intracellular Nitroreductase-Triggered "On" and "Enhanced" Photoacoustic Signals for Sensitive Imaging of Tumor Hypoxia

Current molecular photoacoustic (PA) probes are designed with either stimulus-turned "on" or assembly-enhanced signals to trace biological analytes/events. PA probes based on the nature-derived click reaction between 2-cyano-6-aminobenzothiazole (CBT) and cysteine (Cys) (i.e., CBT-Cys click reaction) possess both "turn-on" and "enhanced" PA signals; and thus, should have higher sensitivity. Nevertheless, such PA probes, particularly those for sensitive imaging of tumor hypoxia, remain scarce. Herein, a PA probe NI-Cys(StBu)-Dap(IR780)-CBT (NI-C-CBT) is rationally designed, which after being internalized by hypoxic tumor cells, is cleaved by nitroreductase under the reduction condition to yield cyclic dimer C-CBT-Dimer to turn the PA signal "ON" and subsequently assembled into nanoparticles C-CBT-NPs with additionally enhanced PA signal ("Enhanced"). NI-C-CBT exhibits 1.7-fold "ON" and 3.2-fold overall "Enhanced" PA signals in vitro. Moreover, it provides 1.9-fold and 2.8-fold overall enhanced PA signals for tumor hypoxia imaging in HeLa cells and HeLa tumor-bearing mice, respectively. This strategy is expected to be widely applied to design more "smart" PA probes for sensitive imaging of important biological events in vivo in near future.

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.

Three-in-One Peptide Prodrug with Targeting, Assembly and Release Properties for Overcoming Bacterium-Induced Drug Resistance and Potentiating Anti-Cancer Immune Response

The presence of bacteria in tumor results in chemotherapeutic drug resistance and weakens the immune response in colorectal cancer. To overcome bacterium-induced chemotherapeutic drug resistance and potentiate antitumor immunity, herein a novel molecule Biotin-Lys(SA-Cip-OH)-Lys(SA-CPT)-Phe-Phe-Nap (Biotin-Cip-CPT-Nap) is rationally designed containing four functional motifs (i.e., a biotin motif for targeting, Phe-Phe(-Nap) motif for self-assembly, ciprofloxacin derivative (Cip-OH) motif for antibacterial effect, and camptothecin (CPT) motif for chemotherapy). Using the designed molecule, a novel strategy of intracellular enzymatic nanofiber formation and synergistic antibacterium-enhanced chemotherapy and immunotherapy is achieved. Under endocytosis mediated by highly expressed biotin receptor in colorectal cancer cell membrane and the catalysis of highly expressed carboxylesterase in the cytoplasm, this novel molecule can be transformed into Biotin-Nap, which self-assembled into nanofibers. Meanwhile, antibiotic Cip-OH and chemotherapeutic drug CPT are released, overcoming bacterium-induced drug resistance and enhancing the therapeutic efficacy of immunotherapy towards colorectal cancer. This work offers a feasible strategy for the design of novel multifunctional prodrugs to improve the efficiency of colorectal cancer treatment.

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.

Dual Aggregations of a Near-Infrared Aggregation-Induced Emission Luminogen for Enhanced Imaging of Alzheimer's Disease

Aggregation-induced emission (AIE) enables "Turn-On" imaging generally through single aggregation of the AIE luminogen (AIEgen). Dual aggregrations of the AIEgen might further enhance the imaging intensity and the consequent sensitivity. Herein, we rationally designed a near-infrared (NIR) AIEgen Ac-Trp-Glu-His-Asp-Cys(StBu)-Pra(QMT)-CBT (QMT-CBT) which, upon caspase1 (Cas1) activation, underwent a CBT-Cys click reaction to form cyclic dimers QMT-Dimer (the first aggregation) and assembled into nanoparticles (the second aggregation), turning the AIE signal "on" for enhanced imaging of Alzheimer's disease (AD). Molecular dynamics simulations validated that the fluorogen QMT in QMT-NPs stacked much tighter with each other than in the single aggregates of the control compound Ac-Trp-Glu-His-Asp-Cys(tBu)-Pra(QMT)-CBT (QMT-CBT-Ctrl). Dual aggregations of QMT rendered 1.9-, 1.7-, and 1.4-fold enhanced fluorescence intensities of its single aggregation in vitro, in cells, and in a living AD mouse model, respectively. We anticipate this smart fluorogen to be used for sensitive diagnosis of AD in the clinic in the near future.

Assembly drives regioselective azide-alkyne cycloaddition reaction

Azide-alkyne cycloaddition reaction is a very common organic reaction to synthesize nitrogen-containing heterocycles. Once catalyzed by Cu(I) or Ru(II), it turns out to be a click reaction and thus is widely applied in chemical biology for labeling. However, besides their poor regioselectivity towards this reaction, these metal ions are not biologically friendly. Hence, it is an urgent need to develop a metal-free azide-alkyne cycloaddition reaction for biomedical applications. In this work, we found that, in the absence of metal ions, supramolecular self-assembly in an aqueous solution could realize this reaction with excellent regioselectivity. Nap-Phe-Phe-Lys(azido)-OH firstly self-assembled into nanofibers. Then, Nap-Phe-Phe-Gly(alkynyl)-OH at equivalent concentration approached to react with the assembly to yield the cycloaddition product Nap-Phe-Phe-Lys(triazole)-Gly-Phe-Phe-Nap to form nanoribbons. Due to space confinement effect, the product was obtained with excellent regioselectivity. Employing the excellent properties of supramolecular self-assembly, we are applying this strategy to realize more reactions without metal ion catalysis.

Enzymatic Self-Assembly of Adamantane-Peptide Conjugate for Combating Staphylococcus aureus Infection

Staphylococcus aureus (S. aureus) remains a leading cause of bacterial infections. However, eradication of S. aureus infections with common antibiotics is increasingly difficult due to outbreaks of drug resistance. Therefore, new antibiotic classes and antibacterial strategies are urgently in demand. Herein, it is shown that an adamantane-peptide conjugate, upon dephosphorylation by alkaline phosphatase (ALP) constitutively expressed on S. aureus, generates fibrous assemblies in situ to combat S. aureus infection. By attaching adamantane to a phosphorylated tetrapeptide Nap-Phe-Phe-Lys-Tyr(H2 PO3 )-OH, the rationally designed adamantane-peptide conjugate Nap-Phe-Phe-Lys(Ada)-Tyr(H2 PO3 )-OH (Nap-FYp-Ada) is obtained. Upon bacterial ALP activation, Nap-FYp-Ada is dephosphorylated and self-assembles into nanofibers on the surface of S. aureus. As revealed by cell assays, the assemblies of adamantane-peptide conjugates interact with cell lipid membrane and thereby disrupt membrane integrity to kill S. aureus. Animal experiments further demonstrate the excellent potential of Nap-FYp-Ada in the treatment of S. aureus infection in vivo. This work provides an alternative approach to design antimicrobial agents.

Caspase-3-Triggered Intracellular Gadolinium Nanoparticle Formation for T1-Weighted Magnetic Resonance Imaging of Apoptosis In Vivo

Apoptosis, with a hallmark of upregulated protease Caspase-3, has been frequently imaged with various probes to reveal the therapeutic efficiencies of different drugs. However, activatable molecular probes with programmable self-assembling behaviors that enable enhanced T₁-weighted magnetic resonance imaging (MRI) of apoptosis remain scarce. Herein, taking advantage of a CBT-Cys click reaction, we rationally designed a Caspase-3-activatable self-assembling probe Ac-Asp-Glu-Val-Asp-Cys(StBu)-Lys(DOTA(Gd))-CBT (DEVDC_S-Gd-CBT) for apoptosis imaging in vivo. After Caspase-3 cleavage in apoptotic cells, DEVDC_S-Gd-CBT underwent CBT-Cys click reaction to form a cyclic dimer, which self-assembled into Gd nanoparticles. With this probe, enhanced T₁-weighted MR images of apoptosis were achieved at low magnetic fields in vitro, in cis-dichlorodiamineplatinum-induced apoptotic cells and in tail-amputation-simulated apoptotic zebrafish. We anticipate that the smart probe DEVDC_S-Gd-CBT could be applied for T₁-weighted MRI of apoptosis-related diseases in the clinic in the future.

Tandem Guest-Host-Receptor Recognitions Precisely Guide Ciprofloxacin to Eliminate Intracellular Staphylococcus aureus

Staphylococcus aureus (S. aureus) is able to hide within host cells to escape immune clearance and antibiotic action, causing life-threatening infections. To boost the therapeutic efficacy of antibiotics, new intracellular delivery approaches are urgently needed. Herein, by rational design of an adamantane (Ada)-containing antibiotic-peptide precursor Ada-Gly-Tyr-Val-Ala-Asp-Cys(StBu)-Lys(Ciprofloxacin)-CBT (Cip-CBT-Ada), we propose a strategy of tandem guest-host-receptor recognitions to precisely guide ciprofloxacin to eliminate intracellular S. aureus. Via guest-host recognition, Cip-CBT-Ada is decorated with a β-cyclodextrin-heptamannoside (CD-M) derivative to yield Cip-CBT-Ada/CD-M, which is able to target mannose receptor-overexpressing macrophages via multivalent ligand-receptor recognition. After uptake, Cip-CBT-Ada/CD-M undergoes caspase-1 (an overexpressed enzyme during S. aureus infection)-initiated CBT-Cys click reaction to self-assemble into ciprofloxacin nanoparticle Nano-Cip. In vitro and in vivo experiments demonstrate that, compared with ciprofloxacin or Cip-CBT-Ada, Cip-CBT-Ada/CD-M shows superior intracellular bacteria elimination and inflammation alleviation efficiency in S. aureus-infected RAW264.7 cells and mouse infection models, respectively. This work provides a supramolecular platform of tandem guest-host-receptor recognitions to precisely guide antibiotics to eliminate intracellular S. aureus infection efficiently.

Apoptosis-Amplified Assembly of Porphyrin Nanofiber Enhances Photodynamic Therapy of Oral Tumor

Oral squamous cell carcinoma (OSCC) is the most common oral cancer, having high recurrence and metastasis features. In addition to surgery, photodynamic therapy (PDT) is considered as another effective approach for OSCC treatment. The water solubility of currently available PDT photosensitizers (PSs) is poor, lowering their singlet oxygen (¹O₂) yield and consequent PDT efficiency. Strategies of PS assembly have been reported to increase ¹O₂ yield, but it is still possible to further enhance PDT efficiency. In this work, we utilized apoptosis to amplify the assembly of porphyrin nanofibers for enhanced PDT of OSCC. A water-soluble porphyrin derivative, Ac-Asp-Glu-Val-Asp-Asp-TPP (Ac-DEVDD-TPP), was designed for this purpose. Upon caspase-3 (Casp3, an activated enzyme during apoptosis) cleavage and laser irradiation, Ac-DEVDD-TPP was converted to D-TPP, which spontaneously self-assembled into porphyrin nanofibers, accompanied by 1.4-fold and 2.1-fold ¹O₂ generations in vitro and in cells, respectively. The as-formed porphyrin nanofiber induced efficient cell apoptosis and pyroptosis. In vivo experiments demonstrated that, compared with the scrambled control compound Ac-DEDVD-TPP, Ac-DEVDD-TPP led to 6.2-fold and 1.3-fold expressions of Casp3 in subcutaneous and orthotopic oral tumor models, respectively, and significantly suppressed the tumors. We envision that our strategy of apoptosis-amplified porphyrin assembly might be applied for OSCC treatment in the clinic in the near future.

Facile Label-Free Three-Input Molecular Keypad Lock

Featured with molecule-level data encryption, molecular keypad locks show attractive merits in information security. Most of the previous multiple-input locks use fluorescence as output but are impeded by inefficient/labile prequenching or highly synthetic complexity/difficulty of the fluorophore-containing processor molecules. We herein propose a facile three-input molecular keypad lock, which is simple in synthesis and label free but capable of in situ generation of a fluorescent moiety (dityrosine) for background-free fluorescence readout. A nonfluorescent ("Locked") tyrosine derivate _zY_pc was easily synthesized as the processor. The correct "password" (i.e., UV → ALP → TYR, ABC) stepwise converted _zY_pc to a dityrosine-containing product, exhibiting a bright blue fluorescence output ("Open"). In contrast, wrongly permutated inputs failed to open this lock. This device shows potential to be extended as a more advanced keypad lock with better security.

Enzymatic Nanosphere-to-Nanofiber Transition and Autophagy Inducer Release Promote Tumor Chemotherapy

Chemotherapy has remained an effective and predominant cancer treatment for the past decades, but is hampered by its low response rate and severe systemic toxicity. Combination chemotherapies are proposed to address these issues, yet their therapeutic outcomes are still far from satisfactory. Thus, it is urgent to develop novel strategies to promote tumor chemosensitivity while reducing toxic side effects of chemotherapeutics. Herein, employing a rationally designed peptide conjugate Nap-Phe-Phe-Lys(SA-AZD8055)-Tyr(H₂ PO₃ )-OH (Nap-AZD-Yp), a novel approach of simultaneous intracellular nanofiber formation and autophagy inducer release is proposed for selectively sensitizing tumor to chemotherapy. Upon sequential catalyses of alkaline phosphatase and carboxylesterase, Nap-AZD-Yp undergoes nanosphere-to-nanofiber transition accompanied by autophagy inducer AZD8055 release in cancer cells. Cell experiments show enhanced endocytosis of anticancer drug doxorubicin and inhibition of cell migration due to the intracellular nanofiber formation. The released AZD8055 further activates excessive autophagy of cancer cells, sensitizing them to chemotherapy. Animal experiment results suggest Nap-AZD-Yp can significantly enhance the therapeutic effects of doxorubicin on tumors while mitigate its toxic adverse effects on normal tissues. It is anticipated that the "smart" concept in this work c be widely employed to develop novel combinational therapies for the treatment of cancers and other diseases in near future.

Granzyme B Turns Nanoparticle Fluorescence "On" for Imaging Cytotoxic T Lymphocyte Activity in Vivo

Cytotoxic T lymphocytes (CTLs) are important immune cells, and their activation is a key step for cancer immunotherapy. Precise evaluation of CTL activity in vivo provides a powerful tool for monitoring cancer-immunotherapeutic outcomes, yet it faces tremendous challenges. Herein, by rationally designing a near-infrared (NIR) fluorescence probe Cys(StBu)-Ile-Glu-Phe-Asp-Lys(Cy5.5)-CBT (Cy5.5-CBT) and employing a reduction-instructed CBT-Cys click condensation reaction, we developed the fluorescence "dual quenched" nanoparticles Cy5.5-CBT-NPs for imaging of granzyme B (GraB), a biomarker tightly associated with the tumoricidal activity of CTLs. Upon GraB cleavage, Cy5.5-CBT-NPs disassembled, subtly turning the fluorescence signal "on". With this fluorescence "turn-on" property, Cy5.5-CBT-NPs enabled sensitive and real-time monitoring of GraB-mediated CTL responses against cancer cells in vitro. Animal experiments demonstrated that, at 16 h post injection, the fluorescence imaging signal of Cy5.5-CBT-NPs showed a 3.1-fold increase on the tumor sites of mice treated by an immune-activating drug S-(2-boronoethyl)-L-cysteine hydrochloride. We envision that Cy5.5-CBT-NPs may provide a powerful tool for noninvasive and sensitive evaluation of immunotherapeutic efficacy of cancer in the near future.

FAP-α-Instructed Coumarin Excimer Formation for High Contrast Fluorescence Imaging of Tumor

Emissive excimers, which are formed by planar polycyclic aromatic fluorophores (e.g., coumarin), enable high contrast tumor imaging. However, it is still challenging to "turn on" excimer fluorescence in physiological dilute solutions. The biocompatible CBT-Cys click condensation reaction enables both intra- and intermolecular aggregations of the as-loaded fluorophores on the probe molecules, which may promote the generation of emissive excimers in a synergistic manner. As a proof-of-concept, we herein design a fluorescence probe Cbz-Gly-Pro-Cys(StBu)-Lys(coumarin)-CBT (Cbz-GPC(StBu)K(Cou)-CBT), which can be activated by FAP-α under tumor-inherent reduction conditions, undergo a CBT-Cys click reaction, and self-assemble into coumarin nanoparticle Cou-CBT-NP to "turn on" the excimer fluorescence. In vitro and in vivo studies validate that this "smart" probe realizes efficient excimer fluorescence imaging of FAP-α-overexpressed tumor cells with high contrast and enhanced accumulation, respectively. We anticipate that this probe can be applied for diagnosis of FAP-α-related diseases in the clinic in near future.

Salt-Inducible Kinase 2-Triggered Release of Its Inhibitor from Hydrogel to Suppress Ovarian Cancer Metastasis

Salt-inducible kinase 2 (SIK2) is a promising target for ovarian cancer therapy due to its critical role in tumorigenesis and progression. Currently available SIK2 inhibitors have shown remarkable therapeutic effects on ovarian cancers in preclinical studies. However, direct administration of the SIK2 inhibitors may bring significant off-target effect, limiting their clinical applications. In this work, by rational design of a hydrogelator Nap-Phe-Phe-Glu-Glu-Leu-Tyr-Arg-Thr-Gln-Ser-Ser-Ser-Asn-Leu-OH (Nap-S) to coassemble a SIK2 inhibitor HG-9-91-01 (HG), a SIK2-responsive supramolecular hydrogel (Gel Nap-S+HG) for local administration and SIK2-responsive release of HG is reported to efficiently suppress ovarian cancer metastasis. Under the activation of SIK2 overexpressed in ovarian cancers, Nap-S in the hydrogel is phosphorylated to yield hydrophilic Nap-Phe-Phe-Glu-Glu-Leu-Tyr-Arg-Thr-Gln-Ser(H2 PO3 )-Ser-Ser-Asn-Leu (Nap-Sp), triggering the disassembly of the hydrogel and a responsive release of the inhibitor. Cell experiments indicate that sustained release of HG from Gel Nap-S+HG induce a prominent therapeutic effect on cancer cells by inhibiting SIK2 and phosphorylation of their downstream signaling molecules. Animal experiments demonstrate that, compared with those tumor model mice treated with free HG, Gel Nap-S+HG-treatment mice show an enhanced inhibition on ovarian tumor growth and metastasis. It is anticipated that the Gel Nap-S+HG can be applied for ovarian cancer therapy in clinic in the near future.

Trident Molecule with Nanobrush-Nanoparticle-Nanofiber Transition Property Spatially Suppresses Tumor Metastasis

Metastasis-induced high mortality of cancers urgently demands new approaches to simultaneously inhibit primary tumor metastasis and distant tumor growth. Herein, by rational design of a trident molecule Nap-Phe-Phe-Lys(SA-CPT)-Lys(SA-HCQ)-Tyr(H₂PO₃)-OH (Nap-CPT-HCQ-Yp) with three functional "spears" (i.e., a phosphotyrosine motif for enzymatic self-assembly, camptothecin (CPT) motif for chemotherapy, and hydroxychloroquine (HCQ) motif for autophagy inhibition) and nanobrush-nanoparticle-nanofiber transition property, we propose a novel strategy of intracellular enzymatic nanofiber formation and synergistic autophagy inhibition-enhanced chemotherapy and immunotherapy for spatial suppression of tumor metastasis. Under sequential alkaline phosphatase catalysis and carboxylesterase hydrolysis, Nap-CPT-HCQ-Yp undergoes nanobrush-nanoparticle-nanofiber transition, accompanied by the releases of CPT and HCQ. The formed intracellular nanofibers effectively inhibit the metastasis and invasion behaviors of cancer cells. Meanwhile, the released CPT and HCQ synergistically induce a prominent therapeutic effect through autophagy inhibition-enhanced chemotherapy. Furthermore, chemotherapy of Nap-CPT-HCQ-Yp enhances immunogenic cell death, resulting in the activation of toxic T-cells. Finally, a combination of checkpoint blockade therapy and Nap-CPT-HCQ-Yp-mediated chemotherapy elicits systemic antitumor immunity, thereby achieving efficient inhibitions of primary tumors as well as distant tumors in a breast tumor model. Our work offers a simple and feasible strategy for the design of "smart" multifunctional prodrugs to spatially suppress tumor metastasis.

ROS Turn Nanoparticle Fluorescence on for Imaging Staphylococcus aureus Infection In Vivo

Direct, noninvasive, and real-time imaging of Staphylococcus aureus (S. aureus) infection is of great value for quick diagnosis of related disease in clinic, but remains challenging. Herein, employing a rationally designed near-infrared fluorescence probe Cys(StB u)-EDA-Thioketal-Lys(Cy5.5)-CBT (TK-CBT) and a CBT-Cys click reaction, the fluorescence-quenched nanoparticles TK-CBT-NPs are facilely prepared. Upon oxidation by the abundant reactive oxygen species in S. aureus-infected macrophages, TK-CBT-NPs are fractured, turning the fluorescence "on" for imaging infections in vitro and in vivo. Specifically, TK-CBT-NPs show a 6.1-fold fluorescence imaging signal enhancement of the macrophages that are infected by S. aureus for 20 h in vitro. At 4 h postinjection, TK-CBT-NPs show a 2.8-fold fluorescence imaging signal enhancement of the sites in mice that are infected by S. aureus for 24 h. It is anticipated that TK-CBT-NPs could be applied for diagnosis of S. aureus infections in clinic in the near future.

Intracellular Self-Assembly of Peptide Conjugates for Tumor Imaging and Therapy

Intracellular self-assembly (ISA) is a versatile and powerful strategy for in situ constructing sophisticated and functional supramolecular nanostructures, which has been widely applied in biomedicine and biomedical engineering. Among the common building blocks for ISA, peptides have attracted increasingly attention due to their intrinsic bioactivity, biocompatibility, and biodegradability. Particularly, by conjugating functional motifs (e.g., probes or drugs) to peptides to yield the peptide conjugates, the latter show enhanced stability and efficiency, and probably new functions. In recent years, employing ISA of peptide conjugates for tumor imaging and treatment has achieved great progresses. Therefore, the recent progress of ISA of peptide conjugates is summarized in this progress report. Moreover, several examples of ISA of peptide conjugates for other important imaging or therapeutic applications are also introduced. Finally, a brief perspective on remaining challenges and potential directions for future research in this area is presented.

Multistimulus Responsive Biointerfaces with Switchable Bioadhesion and Surface Functions

Stimuli-responsive biointerfaces can serve as dynamic tools for modulation of biointerfacial interactions. Considering the complexity of biological environments, surfaces with multistimulus responsive switchable bioactivity are of great interest. In the work reported herein, a multistimulus responsive biointerface with on-off switchable bioadhesion (protein adsorption, bacterial adhesion, and cell adhesion) and surface functions in response to change in temperature, pH, or sugar content is developed. This surface is based on a silicon modified with a copolymer containing a thermoresponsive component (poly(N-isopropylacrylamide)) and a component, phenylboronic acid, that can form pH-responsive and sugar-responsive dynamic boronate ester bonds with diol-containing molecules. It is shown that biointeractions including protein adsorption and release, bacteria and cell attachment and detachment on this surface can be regulated by changing temperature, pH, and sugar content of the medium, either individually or all three simultaneously. Furthermore, this surface can switch between two different functions, namely between killing and releasing bacteria, by introduction of a diol-containing biocidal compound. Compared to switchable surfaces that are responsive to only one stimulus, our multistimulus responsive surface is better adapted to respond to the multifunctional complexities of the biological environment and thus has potential for use in numerous biomedical and biotechnology applications.

Structure-Activity Relationship of Peptide-Conjugated Chloramphenicol for Inhibiting Escherichia coli

Intravenous administration of a prodrug, chloramphenicol succinate (CLsu), is ineffective. Recently, we have shown that conjugation of diglycine of CLsu (CLsuGG) not only increases the antibiotic efficacy against Escherichia coli but also reduces adverse drug effects against bone marrow stromal cells. Here, we report the synthesis of structural analogues of CLsuGG and their activities against E. coli. These analogues reveal several trends: (i) except the water-insoluble analogues, the attachment of peptides to CLsu enhances the efficacy of the prodrugs; (ii) negative charges, high steric hindrance in the side chains, or a rigid diester decreases the activities of prodrugs in comparison to CLsuGG; (iii) dipeptides apparently increase the efficacy of the prodrugs most effectively; and so forth. This work suggests that conjugating peptides to CLsu effectively modulates the properties of prodrugs. The structure-activity relationship of these new conjugates may provide useful insights for expanding the pool of antibiotics.

Diglycine Enables Rapid Intrabacterial Hydrolysis for Activating Anbiotics against Gram-negative Bacteria

Antimicrobial drug resistance demands novel approaches for improving the efficacy of antibiotics, especially against Gram-negative bacteria. Herein, we report that conjugating a diglycine (GG) to an antibiotic prodrug drastically accelerates intrabacterial ester-bond hydrolysis required for activating the antibiotic. Specifically, the attachment of GG to chloramphenicol succinate (CLsu) generates CLsuGG, which exhibits about an order of magnitude higher inhibitory efficacy than CLsu against Escherichia coli. Further studies reveal that CLsuGG undergoes rapid hydrolysis, catalyzed by intrabacterial esterases (e.g., BioH and YjfP), to generate chloramphenicol (CL) in E. coli. Importantly, the conjugate exhibits lower cytotoxicity to bone marrow stromal cells than CL. Structural analogues of CLsuGG indicate that the conjugation of GG to an antibiotic prodrug is an effective strategy for accelerating enzymatic prodrug hydrolysis and enhancing the antibacterial efficacy of antibiotics.

Two-in-One Platform for High-Efficiency Intracellular Delivery and Cell Harvest: When a Photothermal Agent Meets a Thermoresponsive Polymer

Efficient intracellular delivery of exogenous macromolecules is a key operation in biological research and for clinical applications. Moreover, under particular in vitro or ex vivo conditions, harvesting the engineered cells that maintain good viability is also important. However, none of the methods currently available is truly satisfactory in all respects. Herein, a "two-in-one" platform based on a polydopamine/poly( N-isopropylacrylamide) (PDA/PNIPAAm) hybrid film is developed, showing high efficiency in both cargo delivery and cell harvest without compromising cell viability. Due to the strong photothermal effect of PDA in response to near-infrared irradiation, this film can deliver diverse molecules to a number of cell types (including three hard-to-transfect cells) with an efficiency of ∼99% via membrane-disruption mechanism. Moreover, due to the thermoresponsive properties of PNIPAAm, the cells are harvested from the film without compromising viability by simply decreasing the temperature. A proof-of-concept experiment demonstrates that, using this platform, "recalcitrant" endothelial cells can be transfected by the functional ZNF580 gene and the harvested transfected cells can be recultured with high retention of viability and improved migration. In general, this "two-in-one" platform provides a reliable, universally applicable approach for both intracellular delivery and cell harvest in a highly efficient and nondestructive way, with great potential for use in a wide range of biomedical applications.

Abstract P3-03-08: Not presented

This abstract was not presented at the conference.

Citation Format: Liang Y, Chen X, Zhan W, Zhu Y, Wu J, Huang O, He J, Zhu L, Li Y, Chen W, Shen K. Not presented [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-08.

Fabrication of Supramolecular Bioactive Surfaces via β-Cyclodextrin-Based Host-Guest Interactions

Supramolecular host-guest interactions provide a facile and versatile basis for the construction of sophisticated structures and functional assemblies through specific molecular recognition of host and guest molecules to form inclusion complexes. In recent years, these interactions have been exploited as a means of attaching bioactive molecules and polymers to solid substrates for the fabrication of bioactive surfaces. Using a common host molecule, β-cyclodextrin (β-CD), and various guest molecules as molecular building blocks, we fabricated several types of bioactive surfaces with multifunctionality and/or function switchability via host-guest interactions. Other groups have also taken this approach, and several intelligent designs have been developed. The results of these investigations indicate that, compared to the more common covalent bonding-based methods for attachment of bioactive ligands, host-guest based methods are simple, more broadly ("universally") applicable, and allow convenient renewal of bioactivity. In this Spotlight on Applications, we review and summarize recent developments in the fabrication of supramolecular bioactive surfaces via β-CD-based host-guest interactions. The main focus is on the work from our laboratory, but highlights on work from other groups are included. Applications of the materials are also emphasized. These surfaces can be categorized into three types based on: (i) self-assembled monolayers, (ii) polymer brushes, and (iii) multilayered films. The host-guest strategy can be extended from material surfaces to living cell surfaces, and work along these lines is also reviewed. Finally, a brief perspective on the developments of supramolecular bioactive surfaces in the future is presented.

Reply to Comment on 'Nanoscale mapping of optical band gaps using monochromated electron energy loss spectroscopy'

We respond to the comment by Thomas Walther and reaffirm the findings of our original article.

Recombinant phosphoglucomutase and CAMP factor as potential subunit vaccine antigens induced high protection against Streptococcus iniae infection in flounder (Paralichthys olivaceus)

AIMS

The aim of this study was to screen vaccine candidates from virulence factors of Streptococcus iniae in flounder model.

METHODS AND RESULTS

The immunogenicity of recombinant phosphoglucomutase (rPGM) and rCAMP factor was confirmed by Western blot. The percentage of surface membrane immunoglobulin-positive (sIg⁺ ) lymphocytes in peripheral blood leucocytes, the specific and total serum IgM and the activity of acid phosphatase (ACP) and peroxidase (POD) in flounder were determined with flow cytometry, ELISA and commercial enzyme activity kits, respectively, after intraperitoneal immunization with rPGM and rCAMP factor. The results showed that rPGM and rCAMP factor could induce significant rise in sIg⁺ lymphocytes, specific serum IgM and activities of ACP and POD. Additionally, the relative percent survival rate of the vaccinated flounder was 64 and 54% in challenge experiment using S. iniae, respectively. These results indicated that rPGM and rCAMP factor could evoke humoural and innate immune response in flounder and provide high-efficiency immunoprotection against S. iniae infection.

CONCLUSIONS

Phosphoglucomutase (PGM) and CAMP factor were promising vaccine candidates against S. iniae in flounder.

SIGNIFICANCE AND IMPACT OF THE STUDY

Phosphoglucomutase and CAMP factor have the potential to be vaccine candidates, which provide important information for us to develop the effective subunit vaccines, especially the multivaccine, against S .iniae in aquaculture.

Sweet Switch: Sugar-Responsive Bioactive Surfaces Based on Dynamic Covalent Bonding

Smart bioactive surfaces that can modulate interactions with biological systems are of great interest. In this work, a surface with switchable bioactivity in response to sugars has been developed. It is based on dynamic covalent bonding between phenylboronic acid (PBA) and secondary hydroxyls on the "wide" rim of β-cyclodextrin (β-CD). The system reported consists of gold surface modified with PBA-containing polymer brushes and a series of functional β-CD derivatives conjugated to diverse bioactive ligands (CD-X). CD-X molecules are attached to the surface to give specified bioactivity such as capture of a specific protein or killing of attached bacteria. Subsequent treatment with cis-diol containing biomolecules having high affinity for PBA (e.g. fructose) leads to the release of CD-X together with the captured proteins, killed bacteria, and so forth from the surface. The surface bioactivity is thereby "turned off". Effectively, this constitutes an on-off bioactivity switch in a mild and noninvasive way, which has the potential in the design of dynamic bioactive surfaces for biomedical applications.

A facile method to prepare a versatile surface coating with fibrinolytic activity, vascular cell selectivity and antibacterial properties

Clot and thrombus formation on surfaces that come into contact with blood is still the most serious problem for blood contacting devices. Despite many years of continuous efforts in developing hemocompatible materials, it is still of great interest to develop multifunctional materials to enable vascular cell selectivity (to favor rapid endothelialization while inhibiting smooth muscle cell proliferation) and improve hemocompatibility. In addition, biomaterial-associated infections also cause the failure of biomedical implants and devices. However, it remains a challenging task to design materials that are multifunctional, since one of their functions will usually be compromised by the introduction of another function. In the present work, the gold substrate was first layer-by-layer (LbL) deposited with a multilayered polyelectrolyte film containing chitosan (positively charged) and a copolymer of sodium 4-vinylbenzenesulfonate (SS) and the "guest" adamantane monomer 1-adamantan-1-ylmethyl methacrylate (P(SS-co-Ada), negatively charged) via electro-static interactions, referred to as Au-LbL. The chitosan and P(SS-co-Ada) were intended to provide, respectively, resistance to bacteria and heparin-like properties. Then, "host" β-cyclodextrin derivatives bearing seven lysine ligands (CD-L) were immobilized on the Au-LbL surface by host-guest interactions between adamantane residues and CD-L, referred to as Au-LbL/CD-L. Finally, a versatile surface coating with fibrinolytic activity (lysis of nascent clots), vascular cell selectivity and antibacterial properties was developed.

A supramolecular approach for versatile biofunctionalization of magnetic nanoparticles

A convenient and versatile approach for biofunctionalization of magnetic nanoparticles was developed based on supramolecular host–guest interaction.

Smart Biointerface with Photoswitched Functions between Bactericidal Activity and Bacteria-Releasing Ability

Smart biointerfaces with capability to regulate cell-surface interactions in response to external stimuli are of great interest for both fundamental research and practical applications. Smart surfaces with "ON/OFF" switchability for a single function such as cell attachment/detachment are well-known and useful, but the ability to switch between two different functions may be seen as the next level of "smart". In this work reported, a smart supramolecular surface capable of switching functions reversibly between bactericidal activity and bacteria-releasing ability in response to UV-visible light is developed. This platform is composed of surface-containing azobenzene (Azo) groups and a biocidal β-cyclodextrin derivative conjugated with seven quaternary ammonium salt groups (CD-QAS). The surface-immobilized Azo groups in trans form can specially incorporate CD-QAS to achieve a strongly bactericidal surface that kill more than 90% attached bacteria. On irradiation with UV light, the Azo groups switch to cis form, resulting in the dissociation of the Azo/CD-QAS inclusion complex and release of dead bacteria from the surface. After the kill-and-release cycle, the surface can be easily regenerated for reuse by irradiation with visible light and reincorporation of fresh CD-QAS. The use of supramolecular chemistry represents a promising approach to the realization of smart, multifunctional surfaces, and has the potential to be applied to diverse materials and devices in the biomedical field.

Nanoscale mapping of optical band gaps using monochromated electron energy loss spectroscopy

Using monochromated electron energy loss spectroscopy in a probe-corrected scanning transmission electron microscope we demonstrate band gap mapping in ZnO/ZnCdO thin films with a spatial resolution below 10 nm and spectral precision of 20 meV.

Supramolecular Platform with Switchable Multivalent Affinity: Photo-Reversible Capture and Release of Bacteria

Surfaces having dynamic control of interactions at the biological system-material interface are of great scientific and technological interest. In this work, a supramolecular platform with switchable multivalent affinity was developed to efficiently capture bacteria and on-demand release captured bacteria in response to irradiation with light of different wavelengths. The system consists of a photoresponsive self-assembled monolayer containing azobenzene (Azo) groups as guest and β-cyclodextrin (β-CD)-mannose (CD-M) conjugates as host with each CD-M containing seven mannose units to display localized multivalent carbohydrates. Taking the advantage of multivalent effect of CD-M, this system exhibited high capacity and specificity for the capture of mannose-specific type 1-fimbriated bacteria. Moreover, ultraviolet (UV) light irradiation caused isomerization of the Azo groups from trans-form to cis-form, resulting in the dissociation of the host-guest Azo/CD-M inclusion complexes and localized release of the captured bacteria. The capture and release process could be repeated for multiple cycles, suggesting good reproducibility. This platform provides the basis for development of reusable biosensors and diagnostic devices for the detection and measurement of bacteria and exhibits great potential for use as a standard protocol for the on-demand switching of surface functionalities.

A hemocompatible polyurethane surface having dual fibrinolytic and nitric oxide generating functions

Thrombus formation remains a serious problem in developing blood compatible materials. Despite continuous, intensive efforts over many years to prepare surfaces that prevent clotting, such surfaces have not been achieved; indeed it seems that surface-induced clotting is inevitable. An alternative approach is to accept that clotting will occur and to design surfaces so that small, nascent clots will be lysed before they can cause harm. The generation of plasmin, as in the fibrinolytic system, may be adopted for this purpose. The vascular endothelium (the inner surface of intact blood vessels) releases nitric oxide (NO) on a continuous basis. NO protects against platelet activation and aggregation, and also has an anti-proliferative effect on smooth muscle cells (SMCs). Based on these two important functions of the vascular system, the approach of constructing a fibrinolytic surface that generates NO is developed in the present work. Poly(oligo(ethylene glycol) methyl ether methacrylate-co-6-amino-2-(2-methacylamido)-hexanoic acid) (poly(OEGMA-co-LysMA)) was attached to a vinyl-functionalized polyurethane (PU) surface by graft polymerization giving a surface (PU-POL) with protein-resistant properties (via poly(OEGMA)) and clot lysing properties (via poly(LysMA)). Selenocystamine, which catalyzes S-nitrosothiol decomposition to generate NO in the vasculature, was then immobilized on the PU-POL surface via covalent attachment. A dual functioning surface with fibrinolytic activity (lysis of nascent clots) and NO releasing ability (inhibition of platelet adhesion and SMC adhesion as well as proliferation) was thereby constructed.

A multifunctional surface for blood contact with fibrinolytic activity, ability to promote endothelial cell adhesion and inhibit smooth muscle cell adhesion

A multifunctional surface with fibrinolytic activity, the ability to promote endothelial cell and inhibit smooth muscle cell adhesion was realized.

A reusable supramolecular platform for the specific capture and release of proteins and bacteria

A re-usable supramolecular platform with the capability of high-efficiency capture and on-demand release of specific proteins and bacteria was developed.

Multifunctional and Regenerable Antibacterial Surfaces Fabricated by a Universal Strategy

Development of a versatile strategy for antibacterial surfaces is of great scientific interest and practical significance. However, few methods can be used to fabricate antibacterial surfaces on substrates of different chemistries and structures. In addition, traditional antibacterial surfaces may suffer problems related to the attached dead bacteria. Herein, antibacterial surfaces with multifunctionality and regenerability are fabricated by a universal strategy. Various substrates are first deposited with multilayered films containing guest moieties, which can be further used to incorporate biocidal host molecules, β-cyclodextrin (β-CD) derivatives modified with quaternary ammonium salt groups (CD-QAS). The resulting surfaces exhibit strong biocidal activity to kill more than 95% of attached pathogenic bacteria. Notably, almost all the dead bacteria can be easily removed from the surfaces by simple immersion in sodium dodecyl sulfate, and the regenerated surfaces can be treated with new CD-QAS for continued use. Moreover, when another functional β-CD derivative molecule is co-incorporated together with CD-QAS, the surfaces exhibit both functions simultaneously, and neither specific biofunction and antibacterial activity is compromised by the presence of the other. These results thus present a promising way to fabricate multifunctional and regenerable antibacterial surfaces on diverse materials and devices in the biomedical fields.

Percutaneous laser ablation for treatment of locally recurrent papillary thyroid carcinoma <15 mm

AIM

To evaluate the efficacy and safety of ultrasound-guided percutaneous laser ablation (PLA) for recurrent papillary thyroid carcinomas (PTC) <15 mm in the neck.

MATERIALS AND METHODS

A retrospective study was conducted in 21 patients with 27 recurrent PTC lesions who underwent PLA. The extent of ablation was assessed by contrast-enhanced ultrasonography (CEUS) after PLA. Measurement of the volume of tumour and serum thyroglobulin, and clinical evaluation were performed at 7 days, and 1, 3, 6, and 12 months, and every 6 months thereafter.

RESULTS

The procedure was well tolerated. Of 21 patients, 18 were successfully treated in a single session. Incomplete ablation was detected by CEUS in three patients, and a second ablation was performed. The mean largest diameter and the average baseline volume were reduced from 7.5±2.8 mm and 105.4±114 mm³ to 0.4±1 mm and 0.8±2.4 mm³ at the final follow-up.

CONCLUSIONS

Ultrasound-guided PLA is effective for the treatment of recurrent PTCs with a comparable success rate to radio-iodine therapy, and it may become a primary choice of treatment for recurrent PTCs in selected patients who are ineligible for surgery and/or prefer not to have further surgery.

A Smart Antibacterial Surface for the On-Demand Killing and Releasing of Bacteria

For various human healthcare and industrial applications, endowing surfaces with the capability to not only efficiently kill bacteria but also release dead bacteria in a rapid and repeatable fashion is a promising but challenging effort. In this work, the synergistic effects of combining stimuli-responsive polymers and nanomaterials with unique topographies to achieve smart antibacterial surfaces with on-demand switchable functionalities are explored. Silicon nanowire arrays are modified with a pH-responsive polymer, poly(methacrylic acid), which serves as both a dynamic reservoir for the controllable loading and release of a natural antimicrobial lysozyme and a self-cleaning platform for the release of dead bacteria and the reloading of new lysozyme for repeatable applications. The functionality of the surface can be simply switched via step-wise modification of the environmental pH and can be effectively maintained after several kill-release cycles. These results offer a new methodology for the engineering of surfaces with switchable functionalities for a variety of practical applications in the biomedical and biotechnology fields.

Overexpression of ZWF1 and POS5 improves carotenoid biosynthesis in recombinant Saccharomyces cerevisiae

Recombinant Saccharomyces cerevisiae expressing exogenous carotenogenic genes can synthesize carotenoids. NADPH is a key cofactor for carotenoid biosynthesis, while glucose-6-phosphate dehydrogenase (Zwf1) and an NADH kinase (Pos5) are the two main NADPH-supplying sources in S. cerevisiae. Here, the effect of ZWF1 and POS5 overexpression on carotenoid yield in recombinant S. cerevisiae was explored. The initial carotenogenic strain Sc-EYBIH+I which expressed crtE, crtYB, crtI, cHMG1 and another copy of crtI could synthesize 1·35 ± 0·13 mg l(-1) of lycopene and 0·32 ± 0·02 mg l(-1) of β-carotene. When ZWF1 was overexpressed (Sc-EYBIZH+I), glucose-6-phosphate dehydrogenase activity increased by 103-fold, the transcription level of crtE and crtI increased significantly, the lycopene and β-carotene yield increased to 2·29 ± 0·06 and 0·38 ± 0·02 mg l(-1) respectively. When POS5 was overexpressed (Sc-EYBIPH+I), NAD kinase activity increased by 5·5-fold, the transcription level of crtE, crtYB and crtI increased obviously, the lycopene and β-carotene yield increased to 2·50 ± 0·11 and 0·53 ± 0·03 mg l(-1) respectively. Therefore, improvement of NADPH supply contributed to carotenoids biosynthesis in S. cerevisiae and overexpression of POS5 was more effective than overexpression of ZWF1. This study provides a new strategy for enhancing carotenoid biosynthesis.

SIGNIFICANCE AND IMPACT OF THE STUDY

NADPH is a key cofactor for carotenoid biosynthesis. Glucose-6-phosphate dehydrogenase (Zwf1) and an NADH kinase (Pos5) are effective NADPH-supplying sources in Saccharomyces cerevisiae. When ZWF1 and POS5 were overexpressed in a carotenoid-producing S. cerevisiae strain individually, the total yield of lycopene and β-carotene increased by 59·9% and 81·4%, respectively, and the final product β-carotene yield increased by 18·8% and 65·6% respectively. This suggests the improvement of NADPH supply as a useful strategy for carotenoids biosynthesis.

Regulation of Protein Binding Capability of Surfaces via Host-Guest Interactions: Effects of Localized and Average Ligand Density

The protein binding capability of biomaterial surfaces can significantly affect subsequent biological responses, and appropriate ligand presentation is often required to guarantee the best functions. Herein, a new facile method for regulating this capability by varying the localized and average ligand density is presented. Binding between lysine and plasminogen relevant to a fibrinolysis system was chosen as a model. We integrated different lysine-modified β-cyclodextrin (β-CD) derivatives onto bioinert copolymer brushes via host-guest interactions. The localized and average lysine density can be conveniently modulated by changing the lysine valency on β-CD scaffolds and by diluting lysine-persubstituted β-CD with pure β-CD, respectively. Both the plasminogen adsorption and the plasminogen binding affinity were enhanced by lysine-persubstituted β-CD compared with those of lysine-monosubstituted β-CD, which is possibly due to the higher localized lysine density and the multivalent binding of plasminogen on lysine-persubstituted β-CD surfaces. With a change in the ratio of lysine-persubstituted β-CD to β-CD, the average lysine density can be tuned, leading to the linear regulation of the adsorption of plasminogen on surfaces.

A theranostic prodrug delivery system based on Pt(IV) conjugated nano-graphene oxide with synergistic effect to enhance the therapeutic efficacy of Pt drug

Due to their high NIR-optical absorption and high specific surface area, graphene oxide and graphene oxide-based nanocomposites have great potential in both drug delivery and photothermal therapy. In the work reported herein we successfully integrate a Pt(IV) complex (c,c,t-[Pt(NH3)2Cl2(OH)2]), PEGylated nano-graphene oxide (PEG-NGO), and a cell apoptosis sensor into a single platform to generate a multifunctional nanocomposite (PEG-NGO-Pt) which shows potential for targeted drug delivery and combined photothermal-chemotherapy under near infrared laser irradiation (NIR), and real-time monitoring of its therapeutic efficacy. Non-invasive imaging using a fluorescent probe immobilized on the GO shows an enhanced therapeutic effect of PEG-NGO-Pt in cancer treatment via apoptosis and cell death. Due to the enhanced cytotoxicity of cisplatin and the highly specific tumor targeting of PEG-NGO-Pt at elevated temperatures, this nanocomposite displays a synergistic effect in improving the therapeutic efficacy of the Pt drug with complete destruction of tumors, no tumor recurrence and minimal systemic toxicity in comparison with chemotherapy or photothermal treatment alone, highlighting the advantageous effects of integrating Pt(IV) with GO for anticancer treatment.