Drug-resistant biofilm infection is an extremely serious clinical problem, that easily leads to failure of antibiotic treatment. Although gold nanoparticles (AuNPs) as photothermal agents have been widely used in biofilm eradication, there are still challenges to be addressed, such as insignificantly redshifted absorption and slow assembly process of aggregated AuNPs. Herein, we developed an acidity-activated dispersion-to-aggregation transition to enhance the accumulation of self-complementary zwitterionic peptide-decorated AuNPs for photothermal eradication of drug-resistant biofilm infections. AuNPs were decorated with self-complementary zwitterionic peptides (ZP1 and ZP2) coupled with pH-sensitive anhydride (DMA) and pH-insensitive anhydride (SA), respectively. ZP2-decorated AuNPs with DMA modification (AuNP@ZP2(DMA)) exhibited prolonged blood circulation and enhanced accumulation in acidic biofilm microenvironment. Moreover, the electrostatic attraction between self-complementary ligands drove AuNPs to form closely packed aggregates with strong near-infrared absorption, leading to in vivo photoacoustic imaging ability and photothermal effect against drug-resistant bacteria and fungus, as well as microbial biofilms. AuNP@ZP2(DMA) with longer charge domains and a polyethylene glycol oligomer spacer showed greater photothermal antimicrobial and biofilm resistance in vitro and in vivo. This study develops an innovative acidity-activated AuNP photothermal agent, which provides an effective approach for treatment of biofilm infections.

Hypertrophic scar (HS) considerably affects the appearance and causes tissue dysfunction in patients. The low bioavailability of 5-fluorouracil poses a challenge for HS treatment. Here we show a separating microneedle (MN) consisting of photo-crosslinked GelMA and 5-FuA-Pep-MA prodrug in response to high reactive oxygen species (ROS) levels and overexpression of matrix metalloproteinases (MMPs) in the HS pathological microenvironment. In vivo experiments in female mice demonstrate that the retention of MN tips in the tissue provides a slowly sustained drug release manner. Importantly, drug-loaded MNs could remodel the pathological microenvironment of female rabbit ear HS tissues by ROS scavenging and MMPs consumption. Bulk and single cell RNA sequencing analyses confirm that drug-loaded MNs could reverse skin fibrosis through down-regulation of BCL-2-associated death promoter (BAD), insulin-like growth factor 1 receptor (IGF1R) pathways, simultaneously regulate inflammatory response and keratinocyte differentiation via up-regulation of toll-like receptors (TOLL), interleukin-1 receptor (IL1R) and keratinocyte pathways, and promote the interactions between fibroblasts and keratinocytes via ligand-receptor pair of proteoglycans 2 (HSPG2)-dystroglycan 1(DAG1). This study reveals the potential therapeutic mechanism of drug-loaded MNs in HS treatment and presents a broad prospect for clinical application.

In situ polymerization on cell membranes can decrease cell mobility, which may inhibit tumor growth and invasion. However, the initiation of radical polymerization traditionally requires exogenous catalysts or free radical initiators, which might cause side effects in normal tissues. Herein, we synthesized a Y-type diacetylene-containing lipidated peptide amphiphile (TCDA-KFFFFK(GRGDS)-YIGSR, Y-DLPA) targeting integrins and laminin receptors on murine mammary carcinoma 4T1 cells, which underwent nanoparticle-to-nanofiber morphological transformation and in situ polymerization on cell membranes. Specifically, the polymerized Y-DLPA induced 4T1 cell apoptosis and disturbed the substance exchange and metabolism. In vitro assays demonstrated that the polymerized Y-DLPA nanofibers decreased the migration capacity of 4T1 cells, potentially suppressing tumor invasion and metastasis. When administered locally to 4T1 tumor-bearing mice, the Y-DLPA nanoparticles formed a biomimetic extracellular matrix that effectively suppressed tumor growth. This study provides an in situ polymerization strategy that can serve as an effective drug-free biomaterial with low side effects for antitumor therapy.

Mild autophagy accompanied with immunogenic cell death (ICD) effect destructs immune-associated antigens, weakening the immune response against tumor growth. To address this dilemma, we develop a peptide-based bicomponent nanocarrier with encapsulation of a cellular hyperautophagy activator (STF-62247) for near-infrared (NIR) photo/immunotherapy to eliminate primary and metastatic breast tumors. The electrostatic-driven nanodrug (PPNPs@STF) with active-targeting and efficient endosomal escape can induce specific ICD effect upon NIR laser irradiation, and trigger autophagy to a mild activation state. Notably, the simultaneously released STF-62247 precisely promotes autophagy to an overactivated state, resulting in autophagic death of tumor cells and further boosting ICD-related antigen presentation. More importantly, the combined photo/immunotherapy of PPNPs@STF not only inhibits tumor cell proliferation, but also promotes dendritic cells (DCs)-associated immune response. In 4 T1 tumor-bearing mice, PPNPs@STF effectively inhibits growth of primary and distant tumors, and suppresses lung metastasis with a minimized side effect. This study provides a hyperautophagy activator-assisted strategy that can enhance ICD-based antitumor immune response for the treatment of metastatic breast cancer.

Bacterial infections exacerbate the formation of bacterial biofilms, leading to resistance to traditional drugs, persistent infection, and even threatening patient's life. Efficient antimicrobial materials against drug-resistant bacterial biofilms are highly desired. In this study, a photodynamic nanodrug with bacterial targeting was constructed by cooperative coordination of zinc ion with an antimicrobial peptide with hydrophobic tripeptides on the side chains and the photosensitizer chlorin e6. The supramolecular nanodrug with a uniform spherical structure possessed high photosensitizer loading capacity and enhanced photodynamic efficacy, which could deep penetrate and eradicate methicillin-resistant Staphylococcus aureus (MRSA) biofilms upon 655 nm laser irradiation. Furthermore, in vivo experiments verified the efficient elimination of MRSA biofilms on implanted catheters. This study provides a novel strategy to fabricate metalloprotein-inspired supramolecular photodynamic nanodrugs against drugresistant bacterial biofilms-associated infections in vivo.

Aggregated gold nanoparticles (AuNPs) that respond to the acidic microenvironment of bacterial infection sites upon near-infrared (NIR) light irradiation provide a facile approach against bacterial infection. Generally, the aggregation of AuNPs with a larger size results in a higher photothermal conversion efficiency. However, it remains challenging to construct pH-sensitive large-sized AuNPs due to their poor dispersive stability and insensitive stimuli-response. To address this challenge, zwitterionic peptide-modified AuNPs (AuNPs@ZP) with three different sizes (15, 40 and 60 nm) were fabricated to achieve pH-induced aggregation and NIR photothermal antibacterial treatment. The self-complementary zwitterionic peptide (ZP) with the amino acid sequence of CVVVAAAEEEKKK was grafted on the surface of AuNPs, which underwent a fully reversible disassembly/aggregation switching process in response to pH changes. More importantly, AuNP40nm@ZP and AuNP60nm@ZP exhibited broad spectrum and efficient antibacterial activity upon 808 nm laser irradiation, due to their excellent photothermal conversion effect. This study provides a novel self-complementary zwitterionic peptide design to drive pH-induced large-sized AuNP aggregate formation for better NIR photothermal antibacterial treatment.

Antimicrobial peptides (AMPs) potentially serve as ideal antimicrobial agents for the treatment of polymicrobial abdominal infections due to their broad-spectrum antimicrobial activity and excellent biocompatibility. However, the balance of chain length, positive charges, and hydrophobicity on the antimicrobial activity of AMPs are still far from being optimal. Herein, a series of AMPs ([KX]n-NH2, X = Ile, Leu or Phe, n = 3, 4, 5, or 6) with varied charges and hydrophobicity for the treatment of polymicrobial abdominal infections are designed. Specifically, [KI]4-NH2 peptide exhibits the best in vitro antimicrobial activity against Gram-positive and -negative bacteria, as well as fungal strains. Based on the good cell biocompatibility, [KI]4-NH2 peptide is found to have negligible in vivo toxicity at the dosage of up to 28 mg kg-1. Furthermore, great in vivo therapeutic efficacy of [KI]4-NH2 peptide against S. typhimurium is demonstrated in the mice abdominal infection model. The design of short sequence of antimicrobial peptides with a charge/hydrophobicity balanced structures provides a simple and efficient strategy for potential clinical applications of antimicrobial peptide-based biomaterials in a variety of bacterial infection diseases.

Precise control of diacetylene-containing peptide amphiphile (DPA) based supramolecular architectures is important for their in cellulo polymerization behaviors and biomedical applications. Herein, we reported two DPAs (cationic PA-NH2 and zwitterionic PA-OH) with a similar molecular structure, which exhibited completely opposite polymerization behaviors in aqueous solution and living cells. Specifically, PA-NH2 was unpolymerizable in aqueous solution but underwent in cellulo polymerization to respond to the intracellular microenvironment. On the contrary, zwitterionic PA-OH was polymerized in solution, rather than inside living cells. Based on the results of cell viability and total internal reflection fluorescent microscopy measurement, PA-OH exhibited higher affinity with cell membranes and lower cytotoxicity than those of PA-NH2. Therefore, it is suggested that the in cellulo polymerization of PA-NH2 should be responsive for greater cytotoxicity, rather than the membrane affinity. This study provides an in-depth understanding of the role of charge properties in the polymerization behavior of DPAs and seeks their potential biomedical applications.

In order to artificially regulate cell behaviors, intracellular polymerization as an emerging chemical technique has attracted much attention. Yet, it is still a challenge to achieve effective intracellular polymerization to conquer tumors in the complex cellular environment. Herein, this work develops a tumor-targeting and caspase-3 responsive nanoparticle composed of a diacetylene-containing lipidated peptide amphiphile and mitochondria-targeting photosensitizer (C3), which undergoes nanoparticle-to-nanofiber transformation and efficient in situ polymerization triggered by photodynamic treatment and activation of caspase-3. The locational nanofibers on the mitochondria membranes lead to mitochondrial reactive oxygen species (mtROS) burst and self-amplified circulation, offering persistent high oxidative stress to induce cell apoptosis. This study provides a strategy for greatly enhanced antitumor therapeutic efficacy through mtROS burst and self-amplified circulation induced by intracellular transformation and in situ polymerization.

Recently, in-situ polymerization inside living cells has attracted much attention due to the efficient cellular internalization and elevated drug retention. However, the lack of tracking of the in-situ polymerization process and the unclear effects of polymerization on cellular functions restrict its biomedical applications. Herein, we designed a Y-shaped diacetylene-containing lipidated peptide amphiphile (Y-DLPA1) with positive charges, which underwent in-situ polymerization initiated by reactive oxygen species in the intracellular microenvironment. In comparison, zwitterionic Y-DLPA2 and negatively charged Y-DLPA3 were polymerized in aqueous solution, but cannot polymerize in the intracellular microenvironment. The polymerized Y-DLPA1 with red fluorescence provides a platform to label cells for long-term tracking studies. This polymerization reaction induced tumor cell apoptosis, increased cell viscosity and decreased cell motility, which potentially inhibited tumor metastasis and served as a novel antitumor agent. This work provides a novel strategy to track in-situ polymerization process and modulate cell biofunctions.