Immunostimulatory nucleic acid nanoparticles (NANPs) augment protective osteoblast and osteoclast type I interferon responses to Staphylococcus aureus.

Recalcitrant staphylococcal osteomyelitis may be due, in part, to the ability of Staphylococcus aureus to invade bone cells. However, osteoclasts and osteoblasts are now recognized to shape host responses to bacterial infection and we have recently described their ability to produce IFN-ß following S. aureus infection and limit intracellular bacterial survival/propagation. Here, we have investigated the ability of novel, rationally designed, nucleic acid nanoparticles (NANPs) to induce the production of immune mediators, including IFN-ß, following introduction into bone cells. We demonstrate the successful delivery of representative NANPs into osteoblasts and osteoclasts via endosomal trafficking when complexed with lipid-based carriers. Their delivery was found to differentially induce immune responses according to their composition and architecture via discrete cytosolic pattern recognition receptors. Finally, the utility of this nanoparticle technology was supported by the demonstration that immunostimulatory NANPs augment IFN-ß production by S. aureus infected bone cells and reduce intracellular bacterial burden.

The antioxidant effect of tetrahedral framework nucleic acid-based delivery of small activating RNA targeting DJ-1 on retinal oxidative stress injury.

Age-related macular degeneration (AMD) and diabetic retinopathy (DR) are the world's leading causes of blindness. The retinal pigment epithelium (RPE) and vascular endothelial cell exposed to oxidative stress is the major cause of AMD and DR. DJ-1, an important endogenous antioxidant, its overexpression is considered as a promising antioxidant treatment for AMD and DR. Here, we modified the tetrahedral frame nucleic acids (tFNAs) with DJ-1 saRNAs as a delivery system, and synthesized a novel nanocomplex (tFNAs-DJ-1 saRNAs). In vitro studies show that tFNAs-DJ-1 saRNAs can efficiently transfer DJ-1 saRNAs to human umbilical vein endothelial cells (HUVECs) and ARPE-19s, and significantly increased their cellular DJ-1 level. Reactive oxygen species expression in H2O2-treated HUVECs and ARPE-19s were decreased, cell viability was enhanced and cell apoptosis were inhibited when tFNAs-DJ-1 saRNAs were delivered. Moreover, tFNAs-DJ-1 saRNAs preserved mitochondrial structure and function under oxidative stress conditions. In the aspect of molecular mechanism, tFNAs-DJ-1 saRNAs activated Erk and Nrf2 pathway, which might contribute to its protective effects against oxidative stress damage. To conclude, this study shows the successfully establishment of a simple but effective delivery system of DJ-1 saRNAs associated with antioxidant effects in AMD and DR, which may be a promising agent for future treatment in oxidative stress-related retinal disorders.

Nucleic Acid Materials-Mediated Innate Immune Activation for Cancer Immunotherapy.

Abnormally localized nucleic acids (NAs) are considered as pathogen associated molecular patterns (PAMPs) in innate immunity. They are recognized by NAs-specific pattern recognition receptors (PRRs), leading to the activation of associated signaling pathways and subsequent production of type I interferons (IFNs) and pro-inflammatory cytokines, which further trigger the adaptive immunity. Notably, NAs-mediated innate immune activation is highly dependent on the conformation changes, especially the aggregation of PRRs. Evidence indicates that the characteristics of NAs including their length, concentration and even spatial structure play essential roles in inducing the aggregation of PRRs. Therefore, nucleic acid materials (NAMs) with high valency of NAs and high-order structures hold great potential for activating innate and adaptive immunity, making them promising candidates for cancer immunotherapy. In recent years, a variety of NAMs have been developed and have demonstrated significant efficacy in achieving satisfactory anti-tumor immunity in multiple mouse models, exhibiting huge potential for clinical application in cancer treatment. This review aims to discuss the mechanisms of NAMs-mediated innate immune response, and summarize their applications in cancer immunotherapy.

Tetrahedral framework nucleic acids/hyaluronic acid-methacrylic anhydride hybrid hydrogel with antimicrobial and anti-inflammatory properties for infected wound healing.

Bacterial resistance and excessive inflammation are common issues that hinder wound healing. Antimicrobial peptides (AMPs) offer a promising and versatile antibacterial option compared to traditional antibiotics, with additional anti-inflammatory properties. However, the applications of AMPs are limited by their antimicrobial effects and stability against bacterial degradation. TFNAs are regarded as a promising drug delivery platform that could enhance the antibacterial properties and stability of nanodrugs. Therefore, in this study, a composite hydrogel (HAMA/t-GL13K) was prepared via the photocross-linking method, in which tFNAs carry GL13K. The hydrogel was injectable, biocompatible, and could be instantly photocured. It exhibited broad-spectrum antibacterial and anti-inflammatory properties by inhibiting the expression of inflammatory factors and scavenging ROS. Thereby, the hydrogel inhibited bacterial infection, shortened the wound healing time of skin defects in infected skin full-thickness defect wound models and reduced scarring. The constructed HAMA/tFNA-AMPs hydrogels exhibit the potential for clinical use in treating microbial infections and promoting wound healing.

Photochemical inactivation as an alternative method to produce a whole-cell vaccine for uropathogenic Escherichia coli (UPEC).

Uropathogenic Escherichia coli (UPEC) is the primary causative agent of lower urinary tract infection (UTI). UTI presents a serious health risk and has considerable secondary implications including economic burden, recurring episodes, and overuse of antibiotics. A safe and effective vaccine would address this widespread health problem and emerging antibiotic resistance. Killed, whole-cell vaccines have shown limited efficacy to prevent recurrent UTI in human trials. We explored photochemical inactivation with psoralen drugs and UVA light (PUVA), which crosslinks nucleic acid, as an alternative to protein-damaging methods of inactivation to improve whole-cell UTI vaccines. Exposure of UPEC to the psoralen drug AMT and UVA light resulted in a killed but metabolically active (KBMA) state, as reported previously for other PUVA-inactivated bacteria. The immunogenicity of PUVA-UPEC as compared to formalin-inactivated UPEC was compared in mice. Both generated high UPEC-specific serum IgG titers after intramuscular delivery. However, using functional adherence as a measure of surface protein integrity, we found differences in the properties of PUVA- and formalin-inactivated UPEC. Adhesion mediated by Type-1 and P-fimbriae was severely compromised by formalin but was unaffected by PUVA, indicating that PUVA preserved the functional conformation of fimbrial proteins, which are targets of protective immune responses. In vitro assays indicated that although they retained metabolic activity, PUVA-UPEC lost virulence properties that could negatively impact vaccine safety. Our results imply the potential for PUVA to improve killed, whole-cell UTI vaccines by generating bacteria that more closely resemble their live, infectious counterparts relative to vaccines generated with protein-damaging methods. IMPORTANCE: Lower urinary tract infection (UTI), caused primarily by uropathogenic Escherichia coli, represents a significant health burden, accounting for 7 million primary care and 1 million emergency room visits annually in the United States. Women and the elderly are especially susceptible and recurrent infection (rUTI) is common in those populations. Lower UTI can lead to life-threatening systemic infection. UTI burden is manifested by healthcare dollars spent (1.5 billion annually), quality of life impact, and resistant strains emerging from antibiotic overuse. A safe and effective vaccine to prevent rUTI would address a substantial healthcare issue. Vaccines comprised of inactivated uropathogenic bacteria have yielded encouraging results in clinical trials but improvements that enhance vaccine performance are needed. To that end, we focused on inactivation methodology and provided data to support photochemical inactivation, which targets nucleic acid, as a promising alternative to conventional protein-damaging inactivation methods to improve whole-cell UTI vaccines.

Effect of tetrahedral framework nucleic acids on the reconstruction of tendon-to-bone injuries after rotator cuff tears.

Clinicians and researchers have always faced challenges in performing surgery for rotator cuff tears (RCT) due to the intricate nature of the tendon-bone gradient and the limited long-term effectiveness. At the same time, the occurrence of an inflammatory microenvironment further aggravates tissue damage, which has a negative impact on the regeneration process of mesenchymal stem cells (MSCs) and eventually leads to the production of scar tissue. Tetrahedral framework nucleic acids (tFNAs), novel nanomaterials, have shown great potential in biomedicine due to their strong biocompatibility, excellent cellular internalisation ability, and unparalleled programmability. The objective of this research was to examine if tFNAs have a positive effect on regeneration after RCTs. Experiments conducted in a controlled environment demonstrated that tFNAs hindered the assembly of inflammasomes in macrophages, resulting in a decrease in the release of inflammatory factors. Next, tFNAs were shown to exert a protective effect on the osteogenic and chondrogenic differentiation of bone marrow MSCs under inflammatory conditions. The in vitro results also demonstrated the regulatory effect of tFNAs on tendon-related protein expression levels in tenocytes after inflammatory stimulation. Finally, intra-articular injection of tFNAs into a rat RCT model showed that tFNAs improved tendon-to-bone healing, suggesting that tFNAs may be promising tendon-to-bone protective agents for the treatment of RCTs.

Evaluation of therapeutic role of harmaline: in vitro cytotoxicity targeting nucleic acids.

Use of small molecules as valuable drugs against diseases is still an indefinable purpose due to the lack of in-detail knowledge regarding proper bio-target identification, specificity aspects, mode-mechanism of binding and proper in vitro study. Harmaline, an important beta-carboline alkaloid, shows effective anti-proliferative action against different types of human cancers and is also found to be a nucleic acid targeting natural molecule. This review sought to address the different signal pathways of apoptosis by harmaline in different cancer cell lines and simultaneously to characterize the structure activity aspects of the alkaloid with different motifs of nucleic acid to show its preference, biological efficacy and genotoxicity. The results open up new insights for the design and development of small molecule-based nucleic acid therapeutic agents.

Tetrahedral Framework Nuclear Acids Can Regulate Interleukin-17 Pathway to Alleviate Inflammation and Inhibit Heterotopic Ossification in Ankylosing Spondylitis.

Ankylosing spondylitis (AS) is a chronic systemic inflammatory disease that leads to serious spinal deformity and ankylosis. Persistent inflammation and progressive ankylosis lead to loss of spinal flexibility in patients with AS. Tetrahedral framework nucleic acids (tFNAs) have emerged as a one kind of nanomaterial composed of four specially designed complementary DNA single strands with outstanding biological properties. Results from in vivo experiments demonstrated that tFNAs treatment could inhibit inflammatory responses and heterotopic ossification to halt disease progression. In vitro, tFNAs were proved to influence the biological behavior of AS primary chondrocytes and inhibit the secretion of pro-inflammatory cytokines through interleukin-17 pathway. The osteogenic process of chondrocytes was as well inhibited at the transcriptional level to regulate the expression of related proteins. Therefore, we believe tFNAs had a strong therapeutic effect and could serve as a nonsurgical remedy in the future to help patients suffering from AS.

Novel Drug Development in Chronic Hepatitis B Infection: Capsid Assembly Modulators and Nucleic Acid Polymers.

Currently approved treatment of patients with chronic hepatitis B infection is insufficient to achieve functional cure. Numerous new compounds are identified, and among many, capsid assembly modulators (CAMs) and nucleic acid polymers (NAPs) are 2 classes of virus-directing agents in clinical development. CAMs interfere with viral pregenomic RNA encapsidation and are effective in viral load reduction but have limited effects on hepatitis B surface antigen (HBsAg). NAPs prevent HBsAg release from hepatocytes and induce intracellular degradation, leading to potent suppression of serum HBsAg when combined with nucleoside analogues and pegylated interferon demonstrated by initial data, but awaiting further confirmation studies.

Relative expression of key genes involved in nucleic acids methylation in Anopheles gambiae sensu stricto.

In vertebrates, enzymes responsible for DNA methylation, one of the epigenetic mechanisms, are encoded by genes falling into the cytosine methyltransferases genes family (Dnmt1, Dnmt3a,b and Dnmt3L). However, in Diptera, only the methyltransferase Dnmt2 was found, suggesting that DNA methylation might act differently for species in this order. Moreover, genes involved in epigenetic dynamics, such as Ten-eleven Translocation dioxygenases (TET) and Methyl-CpG-binding domain (MBDs), present in vertebrates, might play a role in insects. This work aimed at investigating nucleic acids methylation in the malaria vector Anopheles gambiae (Diptera: Culicidae) by analysing the expression of Dnmt2, TET2 and MBDs genes using quantitative real-time polymerase chain reaction (qRT-PCR) at pre-immature stages and in reproductive tissues of adult mosquitoes. In addition, the effect of two DNA methylation inhibitors on larval survival was evaluated. The qPCR results showed an overall low expression of Dnmt2 at all developmental stages and in adult reproductive tissues. In contrast, MBD and TET2 showed an overall higher expression. In adult mosquito reproductive tissues, the expression level of the three genes in males' testes was significantly higher than that in females' ovaries. The chemical treatments did not affect larval survival. The findings suggest that mechanisms other than DNA methylation underlie epigenetic regulation in An. gambiae.

Effects of Puerarin-Loaded Tetrahedral Framework Nucleic Acids on Osteonecrosis of the Femoral Head.

Osteonecrosis of the femoral head (ONFH) is recognized as a common refractory orthopedic disease that causes severe pain and poor quality of life in patients. Puerarin (Pue), a natural isoflavone glycoside, can promote osteogenesis and inhibit apoptosis of bone mesenchymal stem cells (BMSCs), demonstrating its great potential in the treatment of osteonecrosis. However, its low aqueous solubility, fast degradation in vivo, and inadequate bioavailability, limit its clinical application and therapeutic efficacy. Tetrahedral framework nucleic acids (tFNAs) are promising novel DNA nanomaterials in drug delivery. In this study, tFNAs as Pue carriers is used and synthesized a tFNA/Pue complex (TPC) that exhibited better stability, biocompatibility, and tissue utilization than free Pue. A dexamethasone (DEX)-treated BMSC model in vitro and a methylprednisolone (MPS)-induced ONFH model in vivo is also established, to explore the regulatory effects of TPC on osteogenesis and apoptosis of BMSCs. This findings showed that TPC can restore osteogenesis dysfunction and attenuated BMSC apoptosis induced by high-dose glucocorticoids (GCs) through the hedgehog and Akt/Bcl-2 pathways, contributing to the prevention of GC-induced ONFH in rats. Thus, TPC is a promising drug for the treatment of ONFH and other osteogenesis-related diseases.

Tetrahedral Framework Nucleic Acids Promote Senile Osteoporotic Fracture Repair by Enhancing Osteogenesis and Angiogenesis of Callus.

Senile osteoporotic fracture has aroused increasing attention due to high morbidity and mortality. However, to date, there is no effective therapeutic approach available. Senile osteoporosis is characterized by impaired osteogenesis and angiogenesis, osteoporotic fracture repair could also be promoted by enhancing osteogenesis and angiogenesis. Tetrahedral framework nucleic acids (tFNAs) are a multifunctional nanomaterial that have recently been extensively used in biomedical fields, which could enhance osteogenesis and angiogenesis in vitro. Therefore, we applied tFNAs to intact and femoral fractural senile osteoporotic mice, respectively, to evaluate the effects of tFNAs on senile osteoporosis and osteoporotic fracture repair regarding the osteogenesis and angiogenesis of the callus at the early healing stages and to initially explore the potential mechanism. The outcomes showed that tFNAs had no significant effects on the osteogenesis and angiogenesis of the femur and mandible in intact senile osteoporotic mice within 3 weeks after tFNA treatment, while tFNAs could promote osteogenesis and angiogenesis of callus in osteoporotic fracture repair, which may be regulated by a FoxO1-related SIRT1 pathway. In conclusion, tFNAs could promote senile osteoporotic fracture repair by enhancing osteogenesis and angiogenesis, offering a new strategy for the treatment of senile osteoporotic fracture.

In vitro PCR verification that lysozyme inhibits nucleic acid replication and transcription.

Lysozyme can kill bacteria by its enzymatic activity or through a mechanism involving its cationic nature, which can facilitate electrostatic interactions with the viral capsid, the negatively charged parts of nucleic acids, and polymerase, so binding to nucleic acids may be another biological function of lysozyme. Here, PCR was used as a research tool to detect the effects of lysozyme on the replication and transcription of nucleic acids after treatment in different ways. We found that lysozyme and its hydrolysate can enter cells and inhibit PCR to varying degrees in vitro, and degraded lysozyme inhibited nucleic acid replication more effectively than intact lysozyme. The inhibition of lysozyme may be related to polymerase binding, and the sensitivity of different polymerases to lysozyme is inconsistent. Our findings provide a theoretical basis for further explaining the pharmacological effects of lysozyme, such as antibacterial, antiviral, anticancer, and immune regulatory activities, and directions for the development of new pharmacological effects of lysozyme and its metabolites.

The nano-windmill exerts superior anti-inflammatory effects via reducing choline uptake to inhibit macrophage activation.

Macrophages' activation plays a central role during the development and progression of inflammation, while the regulation of metabolic reprogramming of macrophages has been recently identified as a novel strategy for anti-inflammatory therapies. Our previous studies have found that tetrahedral framework nucleic acid (tFNA) plays a mild anti-inflammatory effect by inhibiting macrophage activation, but the specific mechanism remains unclear. Here, by metabolomics and RNA sequencing, choline uptake is identified to be significantly repressed by decreased slc44a1 expression in tFNA-treated activated macrophages. Inspired by this result, combined with the excellent delivery capacities of tFNA, siR-slc44a1 is loaded into the tFNA to develop a new tFNA-based small interfering RNA (siRNA) delivery system named 'nano-windmill,' which exhibits a synergetic role by targeting slc44a1, finally blowing up the anti-inflammatory effects of tFNA to inhibit macrophages activation via reducing choline uptake. By confirming its anti-inflammatory effects in chronic (periodontitis) and acute (sepsis) inflammatory disease, the tFNA-based nanomedicine developed for inflammatory diseases may provide broad prospects for tFNA upgrading and various biological applications such as anti-inflammatory.

Typhaneoside-Tetrahedral Framework Nucleic Acids System: Mitochondrial Recovery and Antioxidation for Acute Kidney Injury treatment.

Acute kidney injury (AKI) is not only a worldwide problem with a cruel hospital mortality rate but also an independent risk factor for chronic kidney disease and a promoting factor for its progression. Despite supportive therapeutic measures, there is no effective treatment for AKI. This study employs tetrahedral framework nucleic acid (tFNA) as a vehicle and combines typhaneoside (Typ) to develop the tFNA-Typ complex (TTC) for treating AKI. With the precise targeting ability on mitochondria and renal tubule, increased antiapoptotic and antioxidative effect, and promoted mitochondria and kidney function restoration, the TTC represents a promising nanomedicine for AKI treatment. Overall, this study has developed a dual-targeted nanoparticle with enhanced therapeutic effects on AKI and could have critical clinical applications in the future.

Tetrahedral framework nucleic acids inhibit pathological neovascularization and vaso-obliteration in ischaemic retinopathy via PI3K/AKT/mTOR signalling pathway.

This study aimed to explore the effect and the molecular mechanism of tetrahedral framework nucleic acids (tFNAs), a novel self-assembled nanomaterial with excellent biocompatibility and superior endocytosis ability, in inhibition of pathological retinal neovascularization (RNV) and more importantly, in amelioration of vaso-obliteration (VO) in ischaemic retinopathy. tFNAs were synthesized from four single-stranded DNAs (ssDNAs). Cell proliferation, wound healing and tube formation assays were performed to explore cellular angiogenic functions in vitro. The effects of tFNAs on reducing angiogenesis and inhibiting VO were explored by oxygen-induced retinopathy (OIR) model in vivo. In vitro, tFNAs were capable to enter endothelial cells (ECs), inhibit cell proliferation, tube formation and migration under hypoxic conditions. In vivo, tFNAs successfully reduce RNV and inhibit VO in OIR model via the PI3K/AKT/mTOR/S6K pathway, while vascular endothelial growth factor fusion protein, Aflibercept, could reduce RNV but not inhibit VO. This study provides a theoretical basis for the further understanding of RNV and suggests that tFNAs might be a novel promising candidate for the treatment of blind-causing RNV.

Tetrahedral framework nucleic acids alleviate irradiation-induced salivary gland damage.

In this study, we investigated the role of tetrahedral framework nucleic acids (tFNAs) in irradiation-induced salivary gland damage in vitro and in vivo. Irradiation-damaged submandibular gland cells (SMGCs) were treated with different concentrations of tFNAs. Cell activity was measured by CCK-8 assay. Cell death was detected by Calcein-AM/PI double staining. Cell apoptosis was assessed by flow cytometry. The expression of apoptosis proteins and inflammatory cytokines were detected by western blot. Body weight, drinking volume, saliva flow rate and lag time was measured 8 weeks after irradiation. Micromorphological changes of submandibular gland were assessed by haematoxylin-eosin and masson staining. Cell proliferation, apoptosis and microvessel density of submandibular gland were evaluated by immunohistochemical staining. tFNAs could promote cell proliferation, inhibit cell apoptosis of irradiation-damaged SMGCs and reduce irradiation induced cell death. Mechanism studies revealed that tFNAs inhibited cell apoptosis through regulating the Bcl-2/Bax/Caspase-3 signalling pathway and inhibited the release of TNF-α, IL-1ß and IL-6 to reduce cell damage caused by inflammation. Animal experiments showed that tFNAs could alleviate irradiation-induced weight loss, increased water intake, decreased saliva production and prolonged salivation lag time and could ameliorate salivary gland damage. tFNAs have a positive effect on alleviating irradiation-induced salivary gland damage and might be a promising agent for the treatment of this disease.

Combined treatment of ε-polylysine and heat damages protective structures and spore inner membranes to inactivate Bacillus subtilis spores.

The sterilizing effect of a combination of heat (80, 90, and 100 °C) and ε-polylysine (ε-PL, 0.25 and 1 g/L) treatments on Bacillus subtilis spores was investigated and compared with that of conventional heat sterilization. The inactivation rate of spores and changes in their protective structure were evaluated using different methods and techniques. Changes in cell membrane's fatty acids, cell walls, proteins and nucleic acids were also analyzed. The results showed that the combined heat and ε-PL treatments significantly (p < 0.05) inactivated the Bacillus subtilis spores compared with the single heat treatment. Besides, the inactivation of spores was enhanced as the temperature and ε-PL concentration of combined treatments increased. The inactivation rate was found to be 2.18 log after heating at 90 °C for 60 min combined with the addition of 1 g/L ε-PL. Additionally, the electrical conductivity of spores' suspension and the positive region of flow cytometry significantly (p < 0.05) increased depending on temperature and ε-PL concentration of a combination treatment, indicating significant damage in the cell membranes and increased permeability. Significant changes in the spore morphology were also observed by the microscopy analysis after a combination treatment. Furthermore, the Fourier transform infrared spectra indicated a phase change in the inner membrane and alteration in the structure of peptidoglycan layer, as well as protein and nucleic acids denaturation after combined treatments. Therefore, the combined heat and ε-PL treatments can be suggested as sterilizing alternative to conventional heat sterilization in the food industry.

Effect of the variation in the extracellular concentration of l-arginine in the physiology of Leishmania (Viannia) braziliensis and its susceptibility to some antileishmanial drugs.

The knowledge about amino acid metabolism in trypanosomatids is a valuable source of new therapeutic targets. l-arginine is an essential amino acid for Leishmania parasites, and it participates in the synthesis of polyamines, a group of essential nutrients used for nucleic acids, proteins biosynthesis, and redox modulation necessary for proliferation. In the present study, we evaluated the effect of changes in the availability of this amino acid on promastigotes and intracellular amastigotes on U937 macrophages and showed that the absence of l-arginine in culture medium negatively influences the growth and infectivity of Leishmania (Viannia) braziliensis, causing a decrease in the percentage of the infected cells and parasite load tested through light microscopy. In addition, the absence of l-arginine resulted in the parasite's inability to regulate its reactive oxygen species (ROS) production, which persisted for up to 24 h by flow cytometry following the probe H2DCF-DA dye. Moreover, the differentiation of promastigote to amastigote in axenic culture was more significant at low concentrations of l-arginine suggesting that this depletion induces a stress environment to increase this transformation under axenic conditions. No association was established between the availability of l-arginine and the effectiveness of antileishmanial drugs. All these results confirm the importance of l-arginine in L. braziliensis life cycle vital processes, such as its replication and infectivity, as documented in other Leishmania species. Based on these results, we proposed that the l-arginine uptake/metabolism route is possible in exploring new antileishmanial drugs.

The antimicrobial effect of a novel peptide LL-1 on Escherichia coli by increasing membrane permeability.

BACKGROUND: The widespread use of antibiotics has led to the emergence of many drug-resistant strains; thus, the development of new antibacterial drugs is essential with antimicrobial peptides becoming the focus of research. This study assessed the antibacterial effect of a novel antimicrobial peptide, named LL-1 on Escherichia coli (E.coli) by determining the minimum inhibitory concentration (MIC) and the antibacterial curve. The interaction between LL-1 and E. coli DNA was then detected by nucleic acid gel electrophoresis. The effect of LL-1 on the E. coli cell membrane was assessed by detecting the leakage of ß-galactosidase, nucleic acid and protein. The influence of LL-1 on the intracellular ATP of E. coli was analysed by determining the concentration of intracellular ATP. Finally, the bacteria and colonies of E. coli treated with LL-1 were observed using scanning and transmission electron microscopy. RESULTS: The results suggested that the MIC value was 3.125 µg/ml, and the antibacterial effect was dose-dependent. LL-1 dose-dependently combined with E. coli DNA. LL-1 resulted in the leakage of intracellular ß-galactosidase, nucleic acid and protein, and decreased intracellular ATP concentrations of E. coli. Two MIC of LL-1 caused E. coli to shrink, resulting in a rough surface, plasmolysis, and bacterial adhesion. CONCLUSION: This study indicated that LL-1 had a good bactericidal effect on E. coli by mainly increasing the permeability of the cell membrane, leading to leakage of the intracellular content. This will lay the foundation for an in-depth study on the antibacterial mechanism of LL-1 against E. coli and its clinical application.