Catheter with light-induced in-situ self-polymerized silver-loaded zwitterionic hydrogel coating with enhanced antibacterial and antithrombotic functions

Abstract

This invention relates to a catheter with a photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating that enhances antibacterial and antithrombotic functions. The catheter comprises a hydrogel matrix loaded / coated / attached to the catheter surface. This hydrogel matrix is ​​subjected to self-polymerization of SBMA monomers under ultraviolet light irradiation using MBA as a crosslinking agent, forming a three-dimensional crosslinked network while simultaneously embedding Ag NPs within the hydrogel matrix. This catheter exhibits both antibacterial and antithrombotic functions.

Description

Technical Field

[0001] This invention relates to new medical materials, specifically to a catheter with a photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating that enhances antibacterial and antithrombotic functions. Background Technology

[0002] With the rapid development of interventional therapy, blood purification, and long-term indwelling catheter technology, medical catheters have been widely used in clinical scenarios such as vascular access establishment, urinary drainage, and intravascular drug delivery. However, existing catheters still face three major challenges:

[0003] (1) High risk of thrombosis. After catheter implantation, platelets and fibrinogen are rapidly induced to adhere to / aggregate, and the incidence of thrombosis can be as high as 33–66%. This process not only leads to catheter blockage, but may also cause life-threatening complications such as pulmonary embolism. At the same time, the formation of thrombi provides a favorable substrate for subsequent microbial colonization.

[0004] (2) Insufficient antibacterial efficacy. Thrombi forming on the catheter surface significantly promote bacterial adhesion and aggregation and accelerate biofilm formation. Biofilms make pathogens more resistant to host immune defenses and antimicrobial drugs, becoming a persistent source of catheter-related bloodstream infection (CRBSI) and further exacerbating thrombosis progression. Even within 7 days after implantation, the infection rate can still reach 20–40%, forming a vicious cycle of "thrombosis-infection".

[0005] (3) Poor tissue compatibility. Catheters made of bioinert polymers such as silicone rubber and polyurethane will continuously exert physical, chemical and mechanical stimulation on the vascular endothelium, inducing chronic inflammation and delaying endothelial repair, thereby further increasing the risk of thrombosis.

[0006] The aforementioned problems severely limit the clinical performance and lifespan of medical catheters.

[0007] Currently, antithrombotic and antibacterial surface modification strategies for medical catheters can be broadly categorized into two types: active bactericidal strategies and passive antifouling strategies. Active bactericidal strategies typically involve introducing antibacterial components (such as antibiotics, antimicrobial peptides, silver nanoparticles, and anticoagulants) onto the device surface, achieving bactericidal action or inhibition of platelet activation through in-situ release. Among these, silver nanoparticles (AgNPs) are considered ideal candidates for catheter antibacterial modification due to their broad-spectrum antibacterial activity, multi-target mechanism of action, and low likelihood of inducing drug resistance. However, such systems still have key limitations: silver-based coatings often focus more on "bactericidal" functions but are insufficient in inhibiting thrombus adhesion and blocking initial bacterial attachment. Once a fouling layer forms on the surface, bacteria can still adhere and form biofilms. Furthermore, some silver coatings exhibit insufficient adhesion strength under dynamic fluid shear conditions, easily leading to particle detachment or inactivation, affecting long-term stability and clinical reliability. Simultaneously, the potential cytotoxicity and biosafety issues of silver necessitate a precise balance between antibacterial efficacy and biocompatibility.

[0008] Therefore, it is extremely urgent to develop a catheter that is both antibacterial and anti-adhesion. Summary of the Invention

[0009] This invention aims to overcome the aforementioned shortcomings and provides a novel pSBMA-A hydrogel coating. Catheters based on this coating can effectively prevent catheter-related infections and thrombotic complications. The specific solution is as follows:

[0010] This invention provides a catheter with a photo-initiated in-situ self-polymerized silver-loaded zwitterionic hydrogel coating, characterized in that it comprises a hydrogel matrix loaded / coated / attached to the surface of the catheter;

[0011] The hydrogel matrix is ​​formed by using MBA as a crosslinking agent to initiate the self-polymerization of SBMA monomers under ultraviolet light irradiation, forming a three-dimensional crosslinked network while embedding Ag NPs within the hydrogel matrix.

[0012] Furthermore, the conduit with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating provided by the present invention is further characterized in that: the method for preparing the hydrogel matrix is ​​as follows:

[0013] S1. Under light-protected conditions, stir SBMA, MBA and photoinitiator continuously at room temperature until completely dissolved;

[0014] S2. Add Ag NPs precursor colloidal solution, stir for 30-60 min, and then disperse to obtain the target hydrogel matrix.

[0015] Furthermore, the photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating of the conduit provided by the present invention is characterized in that: the mass ratio of SBMA:MBA is 10-100:1.

[0016] The amount of photoinitiator used is 0.1-0.5 wt% of the total material.

[0017] The concentration of Ag NPs was 0.01-0.08 mM.

[0018] Furthermore, the catheter with a photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating provided by the present invention is further characterized in that the surface of the catheter is also pretreated with PDA.

[0019] Furthermore, the photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating of the conduit provided by the present invention is further characterized in that: the surface of the conduit is also pretreated with BP.

[0020] Furthermore, the conduit with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating provided by the present invention is further characterized in that:

[0021] The catheter pretreatment method is as follows:

[0022] S1. Clean and dry the PVC conduit;

[0023] S2. Immerse the cleaned catheter in BP solution for 5-30 minutes;

[0024] S3. Add to Tris-HCl buffer containing dopamine and stir overnight at room temperature;

[0025] S4. Dry in an oven at a temperature not exceeding 60°C for 10-25 min to obtain a pretreated conduit with a PVC-BP-PDA coating.

[0026] Furthermore, the photoinitiated in-situ self-polymerizing silver-loaded zwitterionic hydrogel coating catheter provided by the present invention is further characterized in that: the concentration of the BP solution is 5-20 wt%;

[0027] Tris-HCl buffer containing dopamine (DA) refers to Tris-HCl buffer with a DA concentration of 2-5 mg / mL.

[0028] Furthermore, the photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating provided by the present invention is characterized in that: the method of loading / coating / attaching the hydrogel matrix to the surface of the catheter is as follows: immersing the catheter in the hydrogel matrix for 10-30 min, allowing the hydrogel matrix to be uniformly deposited on the surface, and then curing it under 365 nm ultraviolet light for 30 min-1 h to obtain the final PVC-BP-PDA-SBMA / Ag coated catheter.

[0029] Furthermore, the present invention also suggests the application of this catheter as an antibacterial catheter and as an antithrombotic catheter.

[0030] The function and effect of this embodiment:

[0031] In the design of this invention, the surface photoinitiated grafting effect is improved by coating the conduit surface with benzophenone (BP), so that the hydrogel layer formed by SBMA can be more firmly attached to the PVC surface.

[0032] In this invention, the self-polymerization property of dopamine (PDA) under oxygen-rich and weakly alkaline conditions forms a highly adhesive interfacial layer on the catheter substrate surface, thereby improving the interfacial stability between the hydrogel coating and the substrate. MBA acts as a crosslinking agent to initiate the self-polymerization of SBMA monomers under ultraviolet light irradiation, forming a three-dimensional crosslinked network and embedding Ag NPs within the hydrogel matrix. Thus, a bifunctional hydrogel coating possessing both antibacterial activity and antithrombotic adhesion properties is obtained.

[0033] In this invention, thanks to the broad-spectrum antibacterial properties of Ag NPs, the pSBMA-A coating achieves an antibacterial efficiency of up to 99% against Escherichia coli and Staphylococcus aureus. Simultaneously, the high hydrophilicity of SBMA effectively reduces thrombus adhesion, and the coating exhibits good biocompatibility. Therefore, this strategy provides a surface-functionalized solution for preventing catheter-related infections and thrombotic complications. Attached Figure Description

[0034] Figure 1 A schematic diagram of the construction of the hydrogel catheter in this embodiment;

[0035] Among them, (a) the PVC substrate is pretreated with benzophenone (BP) and dopamine (DA) in sequence to promote the formation of a hydrogel coating on the catheter surface; (b) a cross-linking network is formed with sulfobetaine methacrylate (SBMA) and MBA, and Ag NPs are uniformly dispersed in the hydrogel, thereby achieving the dual effects of antibacterial and antifouling.

[0036] Figure 2 Characterization of Ag NPs

[0037] Among them, (a) UV-Vis absorption spectrum of Ag NPs solution; (b) TEM image of Ag NPs; (c) histogram of Ag NPs particle size distribution and fitting curve of normal distribution; (d) high-resolution TEM (HRTEM) image of Ag NPs; (e) lattice fringe intensity profile and fitting curve of sine function; (f) photographs of Ag NPs solution stored at room temperature under ambient light for 1–30 days.

[0038] Figure 3 Characterization of hydrogel coating structure

[0039] Among them, (a–d) are SEM images of blank PVC, pBDA, pSBMA and pSBMA-A coating; (e–h) are cross-sectional morphologies of the corresponding samples; and (i–l) are elemental surface distribution diagrams of the pSBMA-A coating.

[0040] Figure 4 FTIR and Raman spectra of blank PVC, pBDA, pSBMA and pSBMA-A coating

[0041] (a) is FTIR, and (b) is Raman spectrum.

[0042] Figure 5 XPS and full-spectrum scanning structures of .pSBMA-A

[0043] Among them, (a) XPS full spectrum; (b) C 1s; (c) N 1s; (d) O 1s; (e) S 2p; (f) Ag 3d.

[0044] Figure 6 Antibacterial effect test results

[0045] (a) Colony diagrams of *E. coli* and *S. aureus* on PVC, pBDA, pSBMA, and pSBMA-A surfaces; (b) CFU statistics of *E. coli* and *S. aureus* on different materials. Data are expressed as mean ± standard deviation (n=3). Statistical analysis was performed using two-way ANOVA and Tukey multiple comparisons. **p<0.01, ***p<0.001.

[0046] Figure 7 Antibacterial stability results

[0047] The study included (a) the plate culture results of *E. coli* and *S. aureus* after immersion in artificial urine for 3 days using PVC, pSBMA, and pSBMA-A hydrogel coatings; and (b) the statistical analysis of CFU results. Data are expressed as mean ± standard deviation (n=3). Statistical analysis was performed using two-way ANOVA with Tukey multiple comparisons. *p<0.05, **p<0.01, ***p<0.001.

[0048] Figure 8 Hydrophilicity experiment

[0049] The data include: (a) morphology images of deionized water droplets on the convex and concave surfaces of PVC, PDA, pBDA, pSBMA, and pSBMA-A samples; (b) statistical results of the helix weight (H / W) of water droplets on the convex surfaces of different materials; and (c) statistical results of the helix weight (H / W) of water droplets on the concave surfaces of different materials. Data are expressed as mean ± standard deviation (n=3). Statistical analysis was performed using one-way ANOVA and Tukey multiple comparisons. ns indicates no significant difference; **p<0.01, ***p<0.001.

[0050] Figure 9 In vitro antithrombotic adhesion assay

[0051] The study included (a) SEM images of thrombus formation on the surfaces of PVC, pBDA, pSBMA, and pSBMA-A catheters and corresponding regions; and (b) analysis of thrombus adhesion quality on the surfaces of different catheter samples. Data are expressed as mean ± standard deviation (n=3). Statistical analysis was performed using one-way ANOVA and Tukey multiple comparisons. ns indicates no significant difference; *p<0.05, **p<0.01.

[0052] Figure 10 Cytotoxicity and hemolysis assays

[0053] The data include (a) cell viability after co-culturing different samples (positive control, PVC, pBDA, pSBMA, and pSBMA-A) with cells; (b) OD value at 450 nm; (c) hemolysis rate of different samples (the inset shows the hemolysis results of the positive control, negative control, and each catheter sample; the green dashed line represents the non-hemolysis threshold of 2%); and (d) OD value at 545 nm. Data are expressed as mean ± standard deviation (n=3). Statistical analysis was performed using one-way ANOVA and Tukey multiple comparisons. ns indicates no significant difference; **p<0.01, ***p<0.001. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Example 1. Preparation of hydrogel catheters

[0056] like Figure 1As shown, the outer surface of the tube is coated with benzophenone (BP) and polydopamine (PDA) in sequence. Then, by integrating SBMA, silver nanoparticles (Ag NPs) and MBA, a thin and strong coating is deposited on the surface of the PVC conduit pretreated with BP and PDA using a photoinitiation method.

[0057] 1.1. Experimental Materials

[0058] Polyvinyl chloride (PVC) pipe (approximately 5.3 mm outer diameter) was purchased from Cofoe Medical Technology Co., Ltd. (Hunan, China). Dopamine hydrochloride (98%), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA, 97%), N,N′-methylenebisacrylamide (MBA, 99%), Irgacure 2959 (I-2959, 99%), Tris, 99%, benzophenone (BP, 99%), tannic acid (95%), trisodium citrate dihydrate (99%), and calcium chloride (96%) were purchased from Aladdin Reagent Co., Ltd. (Shanghai, China). 2.5% glutaraldehyde fixative was purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China). Silver nitrate (AgNO3, 0.1 M) solution was purchased from Guangzhou Hewei Pharmaceutical Technology Co., Ltd. (Guangzhou, China). Sodium citrate anticoagulated rabbit blood was purchased from Nanjing Senbeijia Biotechnology Co., Ltd. (Nanjing, China). Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923) were provided by Shanghai Chest Hospital (Shanghai, China). Premium fetal bovine serum (FBS, New Zealand source) was purchased from HyClone (USA). Dulbecco modified Eagle medium (DMEM) was purchased from Shanghai Yuli Biotechnology Co., Ltd. (Shanghai, China). Cell counting kit-8 (CCK-8) was purchased from Shanghai Shenger Biotechnology Co., Ltd. (Shanghai, China). Ultrapure water was prepared using the Milli-Q system (Millipore, USA). All chemicals and reagents were used as is without further purification.

[0059] 1.2. Experimental Methods

[0060] 1.2.1. Preparation of silver nanoparticle precursors

[0061] Silver nanoparticles (Ag NPs) were prepared using the citrate reduction method of AgNO3 in aqueous solution (Lee–Meisel method): 100 mL of an aqueous solution containing sodium citrate (5 mM) and tannic acid (0.025 mM) was added to a three-necked round-bottom flask equipped with a reflux condenser and heated. When the solution boiled vigorously, 2.5 mL of silver nitrate solution (10 mM) was slowly added dropwise. The system immediately turned yellow, and the reaction was continued with heating and stirring for 20 min, followed by cooling to room temperature. The final colloidal Ag NPs solution was obtained with a final silver concentration of 0.25 mM. This concentration is clinically preferred, as higher concentrations of Ag have been found to cause cytotoxicity in some experimental cases.

[0062] 1.2.2. Preparation of Silver-Loaded Zwitterionic Hydrogel Precursor Solution

[0063] S1. Under light-protected conditions, add sulfobetaine methacrylate (SBMA), MBA (0.05 g) and photoinitiator (e.g., I-2959) to deionized water and stir continuously at room temperature until completely dissolved.

[0064] S2. Add the Ag NPs precursor colloidal solution prepared in 1.2.1, and stir for another 30-60 min. Sonicate the resulting mixture for 5-10 min to ensure uniform dispersion of Ag NPs.

[0065] In step S1, the mass ratio of SBMA to MBA is 10-100:1, preferably 40-80:1. In some experiments, it was found that when the crosslinking agent is insufficient, it will lead to insufficient crosslinking and failure to form a gel, while excessive crosslinking agent will lead to an overly brittle gel.

[0066] The amount of photoinitiator used is 0.1-0.5 wt% of the total material.

[0067] In a preferred embodiment, the amount of SBMA is preferably 10 wt% of the total material (including Ag NPs in S2), MBA is 0.05 g, photoinitiator is 0.05 g, and deionized water is 40 mL.

[0068] Compared with crosslinking agents such as PEGDA (polyethylene glycol diacrylate) and Genipin, experiments show that MBA has strong compatibility with zwitterionic monomer SBMA free radical copolymerization and is more effective in both thermal and photoinitiation.

[0069] In step S2, the amount of Ag NPs precursor colloid used is 0.0015-0.01 mmol / 40 mL of the S1 reaction system, preferably with a final Ag NPs concentration of 0.01-0.08 mM. The amount of Ag NPs used is mainly limited by antibacterial properties and cytotoxicity. Too much Ag NPs may result in better antibacterial properties but also excessive cytotoxicity, while too little Ag NPs may avoid toxicity issues but result in poor antibacterial properties. In a preferred embodiment, the final concentration of Ag NPs is 0.05 mM.

[0070] 1.2.3. Preparation of Silver-Loaded Hydrogel Coating

[0071] S1. Clean and dry the PVC conduit; for example, rinse it three times each with alcohol and deionized water, and dry it in an oven at a temperature not exceeding 60 °C.

[0072] S2. Immerse the cleaned catheter in BP solution for 5-30 minutes;

[0073] S3. Add to Tris-HCl buffer containing dopamine (DA) and stir overnight at room temperature (6-18h).

[0074] S4. Dry in an oven at no higher than 60 °C for 10-25 min to obtain a pretreated conduit with a PVC-BP-PDA coating;

[0075] S5. Immerse the pretreated conduit in the zwitterionic hydrogel precursor solution containing Ag NPs prepared in 1.2.2 for 10-30 min to allow the precursor solution to be uniformly deposited on the surface.

[0076] S6. Curing under 365 nm ultraviolet light for 30 min-1 h yields the final PVC-BP-PDA-SBMA / Ag coated conduit.

[0077] In S2, BP solution generally refers to an alcoholic solution of BP with a concentration of 5-20 wt%.

[0078] In a preferred experimental example, the concentration of the BP ethanol solution was 10 wt%;

[0079] In other experimental cases, it was found that hydrogels could also initiate polymerization on the surface when the catheter was not coated with BP as the first coating. However, the subsequent coating structure was more inclined to physical adsorption. This bonding method made it easy for the active ingredient to detach locally under immersion and friction, which also limited the sustained release effect of the active ingredient.

[0080] In S3, Tris-HCl buffer containing dopamine (DA) generally refers to Tris-HCl buffer with a DA concentration of 2-5 mg / mL (pH 8.5, 10 mM).

[0081] The purpose of this step is to form PDA. The presence of PDA allows a large number of catechol / amine functional groups to extend onto the surface of the duct, which further makes the hydrogel more likely to "grab" the surface and reduces the risk of delamination. Its core function is to transform the originally inert, hydrophobic PVC surface into a more adhesive interface with reactive groups, thereby improving the stability and uniformity of the subsequent hydrogel coating. This is because, in some experimental cases, it was found that using BP alone without PDA resulted in insufficient adhesion of the subsequent hydrogel layer, and the coating surface was prone to problems such as discontinuous coverage and uneven thickness.

[0082] In other test cases, it was found that not using BP or PDA resulted in very low or trace amounts of stable coating.

[0083] 1.2.4. Preparation of comparative materials

[0084] Comparative material 1. PVC-BP-PDA-SBMA coating (pSBMA) without Ag NPs was prepared using the same steps.

[0085] Comparative material 2. PVC conduits pretreated with BP and PDA were immersed in Ag NPs solution (0.05 mM) for 3 h to obtain pBDA coating.

[0086] Example 2. Physicochemical characterization of hydrogel catheters

[0087] 2.1. Experimental Methods: The UV-Vis absorption spectra of the silver nanoparticle precursor solution were determined using a UV-Vis spectrophotometer (Hitachi U-3900, Japan). The particle size distribution and average particle size of Ag NPs were analyzed using transmission electron microscopy (TEM, JEOL JEM-F200, Japan). The surface morphology and coating thickness of the samples were observed using scanning electron microscopy (SEM, Quanta 450, FEI, USA), and elemental distribution was analyzed by energy dispersive spectroscopy (EDS). The surface chemical composition of the samples was determined using X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha, USA); the chemical structure of the coating was characterized by Fourier transform infrared spectroscopy (FTIR, Thermo Fisher Scientific Nicolet iS20, USA).

[0088] 2.2. Experimental Results:

[0089] 2.2.1. Characterization of Ag NPs

[0090] like Figure 2As shown in Figure a, a single surface plasmon resonance peak appears at 404 nm based on the UV-Vis absorption spectrum of the Ag NPs solution. The typical dipole resonance peak of approximately spherical silver nanoparticles is usually located around 400 nm, indicating that the prepared Ag NPs are predominantly spherical.

[0091] like Figure 2 TEM results showed that the synthesized Ag NPs had a uniform spherical structure.

[0092] like Figure 2 The particle size distribution, represented by c, shows that the product in this embodiment conforms to a log-normal distribution, with an average particle size of 15.99 ± 0.11 nm. The particles are mainly concentrated in a narrow distribution range of 10–25 nm. Frequency distribution and cumulative distribution results indicate that D10, D50, and D90 are 11.89 nm, 14.97 nm, and 18.12 nm, respectively, with D50 being very close to the average particle size. Beyond D90, the cumulative distribution curve tends to flatten and increase slowly, and can be well fitted by the Boltzmann distribution function, indicating that larger particles account for a small proportion and have little impact on the overall average particle size.

[0093] like Figure 2 The high-resolution TEM (HRTEM) image of d shows clear lattice fringes with a plane spacing of approximately 0.2074 nm, corresponding to the (200) plane of face-centered cubic silver.

[0094] like Figure 2 The intensity profile of the lattice fringes in e exhibits regular sinusoidal periodic oscillations, reflecting the stable periodic arrangement of the crystal atomic layers, indicating that the synthesized Ag NPs have good crystallinity.

[0095] like Figure 2 f shows photographs of Ag NPs solutions stored at room temperature and under ambient light for 1–30 days. The solution color showed no obvious change, indicating that the prepared Ag NPs solution has good long-term stability.

[0096] 2.2.2. Hydrogel Coating Structure

[0097] like Figure 3 As shown in Figure a, SEM observation of the coating surface morphology revealed that the untreated PVC surface was smooth and flat; while... Figure 3 The pBDA coating in b exhibits a rough, granular morphology, which is likely due to the deposition and polymerization of dopamine (DA) on the surface. After UV curing, a hydrogel coating forms on the PVC surface. Figure 3 As can be seen from c and 3d, compared with pBDA, the surfaces of pSBMA and pSBMA-A coatings are smoother and more uniform. The SBMA coating effectively masks the DA particle features, indicating that the hydrogel coating was successfully constructed.

[0098] like Figure 3 The cross-sectional morphology of eh further reveals the coating thickness and structure, with a coating thickness of approximately 2 μm.

[0099] like Figure 3 The elemental distribution results of i–l show that the elements are uniformly distributed in the pSBMA-A coating: the C signal comes from the PVC substrate, SBMA, MBA, and dopamine; the N signal comes from SBMA, MBA, and dopamine; the S signal comes from the sulfonic acid group (-SO3-) of sulfobetaine; and the Ag signal comes from Ag NPs in the hydrogel network. These results not only confirm the successful deposition of the hydrogel coating on the PVC surface but also demonstrate that the Ag NPs are uniformly dispersed in the hydrogel network.

[0100] like Figure 4 The FTIR results of a showed that the pBDA, pSBMA, and pSBMA-A samples were at 3435 cm⁻¹. -1 Strong and broad absorption peaks were observed at all locations, corresponding to the O–H stretching vibration and N–H bending vibration of dopamine (DA). Furthermore, the pSBMA and pSBMA-A coatings showed strong absorption peaks at 1038 cm⁻¹. -1 With 1197 cm -1 The presence of two characteristic absorption peaks at the point corresponds to the symmetric and antisymmetric stretching vibrations of the sulfonic acid group (-SO3-), respectively, proving that the SBMA monomer was successfully grafted onto the substrate surface and formed a hydrogel coating.

[0101] like Figure 4 The Raman spectrum of b shows that with the introduction of the hydrogel coating, the PVC substrate at 3070 cm⁻¹ -1 The C–H stretching vibrations at 1387 cm⁻¹ gradually weakened or even disappeared; meanwhile, the pBDA, pSBMA, and pSBMA-A samples showed a decrease in C–H stretching vibrations at 1387 cm⁻¹. -1 With 1588 cm -1 The peaks at that location correspond to the D and G bands of dopamine. Raman results further confirm the successful introduction of the PDA interface layer and the construction of the hydrogel coating on the substrate.

[0102] like Figure 5 As shown, XPS further confirmed the successful grafting of the pSBMA-A hydrogel coating onto the substrate surface. Characteristic peaks of Ag 3d and S 2p appeared in the full-spectrum scan, corresponding to the Ag NPs embedded in the hydrogel network and the S element in SBMA, respectively. In the high-resolution N 1s spectrum, the peak at 402.31 eV was attributed to quaternary ammonium N from sulfobetaine. + Simultaneously, peaks related to NH and NH2 groups formed during the self-polymerization of PDA on the substrate surface can also be observed. The high-resolution S 2p spectrum shows a pair of spin-orbit splitting peaks with a binding energy difference of 1.16 eV, corresponding to SO3 2p... 3 / 2(167.51 eV) and SO3 2p 1 / 2 (168.77 eV), providing strong evidence for the successful grafting of SBMA. Furthermore, XPS detected a weak Ag signal (<0.1 at.%), and the Ag 3d spectrum in the high-resolution Ag 3d spectrum showed... 5 / 2 With Ag 3d 3 / 2 The binding energy difference of the peaks is 6 eV, indicating the presence of metallic Ag NPs in the coating.

[0103] Example 3. In vitro antibacterial experiment

[0104] 3.1. Antibacterial effect

[0105] 3.1.1. Experimental Methods: The antibacterial effect was evaluated using a standardized bacterial adhesion assay. Before testing, all samples were cut into 10 mm lengths and sterilized by irradiation with 254 nm UV light for 30 min in a biosafety cabinet. Bacteria were collected by centrifugation (5000 rpm, 5 min) and resuspended in PBS. A suspension of *Escherichia coli* (ATCC 25922) and *Staphylococcus aureus* (ATCC 25923) was prepared to a final volume of 10 μL. 6 CFU·mL -1 The sterilized tubing was immersed in a sterile bacterial suspension and incubated at 37 °C for 18 h. After incubation, the sample was transferred to a sterile centrifuge tube containing 2 mL PBS and sonicated for 15 min to detach the adhering bacteria. The resulting bacterial suspension was serially diluted 10-fold, and 100 μL of the diluted solution was spread onto an agar plate. After incubation at 37 °C for 18 h, the bacterial load was quantified by colony counting. The calculation of CFU / cm² is given by formula (1).

[0106] (1)

[0107] Where N is the number of colonies on the plate; DF is the dilution factor (the reciprocal of the dilution); V wash V is the volume of the elution buffer. plate A represents the coating volume; A represents the surface area of ​​the catheter segment.

[0108] 3.1.2. Experimental Results

[0109] During the use of medical catheters, bacteria typically adhere to the substrate surface first through van der Waals forces and specific interactions, then colonize the surface and eventually cause infection. To evaluate the antibacterial properties of pBDA, pSBMA, and pSBMA-A hydrogel coatings, this study selected representative Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli as model bacteria.

[0110] The results are as follows Figure 6As shown in figure a, the pBDA coating exhibited only limited antibacterial activity, and a large number of colonies could still be observed on the plate. Quantitative analysis of colony-forming units (CFU) ( Figure 6 b) shows that the average CFU of E. coli and S. aureus on the pBDA surface are 1.70 × 10⁻⁶. 4 CFU / cm² and 1.43×10 4 The CFU / cm² value corresponds to an antibacterial rate of approximately 40%. In contrast, the pSBMA coating, due to its hydrophilicity from zwitterions, significantly reduces bacterial adhesion, lowering the average CFU of E. coli and S. aureus to 8.29 × 10³ CFU / cm² and 6.46 × 10³ CFU / cm², respectively, thus increasing the antibacterial efficiency to approximately 70%. Notably, the pSBMA-A coating performed best: the average CFU of E. coli and S. aureus were only 0.24 × 10² CFU / cm² and 0.48 × 10² CFU / cm², respectively, achieving an antibacterial efficiency of approximately 99% against both bacteria.

[0111] 3.2. In vitro antibacterial stability

[0112] 3.2.1. Experimental Method: The samples were immersed in artificial urine (mainly composed of magnesium chloride, sodium chloride, sodium sulfate, potassium chloride, phosphate, ammonium chloride, urea, etc.) for 3 days. After immersion, the samples were removed, dried at room temperature, and then subjected to in vitro antibacterial testing again according to the above method.

[0113] 3.2.2. Experimental Results

[0114] After immersing the pSBMA and pSBMA-A hydrogel coatings in artificial urine for 3 days, their antibacterial properties were reassessed using E. coli (Gram-negative) and S. aureus (Gram-positive). Results are as follows... Figure 7 As shown in Figure a, only a small number of colonies were observed on the surface of the pSBMA-A coating, while the number of colonies on the surface of the pSBMA coating was significantly greater, indicating that the pSBMA-A coating can still maintain strong antibacterial activity in complex simulated physiological environments.

[0115] right Figure 7 Quantitative analysis of the data showed that the colony count on the pSBMA-A coating surface after immersion was significantly lower than that on the pSBMA coating. Specifically, the average CFU of E. coli and S. aureus on the pSBMA-A surface were 1.11 × 10⁻⁶. 4 CFU / cm² and 1.77×10 4The CFU / cm² value corresponds to an antibacterial efficiency of approximately 80%; while the average CFU of E. coli and S. aureus on the pSBMA surface are 4.17 × 10³ CFU / cm² and 4.79 × 10³ CFU / cm², respectively, with an antibacterial efficiency of approximately 50%. These results indicate that the pSBMA-A hydrogel coating maintains stable antibacterial properties even after immersion in artificial urine for 3 days. This may be attributed to the cross-linked network structure formed within the pSBMA-A coating: this structure not only ensures the uniform distribution of Ag NPs in the sulfobetaine network but also effectively delays their loss in artificial urine, thus maintaining high antibacterial activity after immersion.

[0116] Example 4. Hydrophilicity Test

[0117] Traditional water droplet methods typically require a completely flat substrate, making it difficult to reflect the impact of bending stress on the surface hydrophilicity of medical catheters during actual use. To better reflect application scenarios, this study employs a more practical characterization method: with a constant droplet volume, hydrophilicity is characterized by the ratio of the vertical distance from the highest point of the droplet to the sample surface to its spread width on the surface (H / W). The smaller this ratio, the more fully the droplet spreads, and the better the hydrophilicity of the coating.

[0118] 4.1. Experimental Methods: The hydrophilicity of the sample surface was analyzed using a contact angle meter (OCA20, Dataphysics, Germany). Each sample was measured three times at different locations, with 3 μL of deionized water added each time. The hydrophilicity of the inner and outer surfaces of the samples was evaluated based on formula (2).

[0119] (2)

[0120] The vertical distance from the highest point of the water droplet to the sample surface is defined as H. s The linear width of a water droplet spreading on a sample surface is defined as W. i .

[0121] 4.2. Experimental Results

[0122] like Figure 8 As shown in Figure a, due to the different degrees of bending stress on the inner and outer surfaces of the conduit, the degree of water droplet spreading on their surfaces varies. Compared with PVC, PDA, and pBDA samples, the pSBMA and pSBMA-A hydrogel coatings make water droplets spread significantly more easily on the outer surface; on the inner surface, the pSBMA and pSBMA-A coatings can almost completely flatten the water droplets.

[0123] like Figure 8As shown in b–c, statistical analysis of the H / W ratio of water droplets on convex and concave surfaces reveals that the introduction of the hydrogel coating gradually decreases both the droplet height and the H / W ratio: the H / W ratio on the convex surface decreases from 0.70±0.13 to 0.18±0.02, and on the concave surface from 0.52±0.02 to 0.08±0.01, indicating a significant improvement in the hydrophilicity of the duct surface. This is mainly attributed to the zwitterionic structure of sulfobetaine: the quaternary ammonium cation and sulfonate anion can interact strongly with water molecules through electrostatic interactions and hydrogen bonds, forming a stable hydration layer on the surface, thereby enhancing the hydrophilicity of the coating.

[0124] Example 5. In vitro antithrombotic adhesion experiment

[0125] 5.1. Experimental Methods: Each sample was cut into 30 mm lengths and rinsed three times each with distilled water and sterile saline. The initial mass Wi of the catheter was recorded before circulation. 50 mL of fresh rabbit blood containing an anticoagulant was mixed with 5 mL of CaCl2 solution (0.2 mol / L) to induce thrombus formation. The sample was fixed to the inner wall of a silicone tube (6.4 mm inner diameter, 60 mm length). A polypropylene straight connector (4.8 mm to 6.4 mm) was used to connect the short silicone tube to the long silicone tube (4.8 mm inner diameter, 400 mm length) to construct a closed blood circulation system. The blood flow rate was adjusted to 0.1 L / min using a peristaltic pump, and circulation was stopped after 1.5 h. After the cycle was completed, the sample was removed, gently rinsed with PBS, photographed and weighed (Ws); then fixed with 2.5% glutaraldehyde fixative (4 °C, 12 h), and dehydrated with ethanol / water gradient solutions (25%, 50%, 75%, 95% and 100%, 15 min per step). Finally, the surface morphology was observed by SEM.

[0126] 5.2. Experimental Results

[0127] In the in vitro blood circulation experiment, the sample photograph after circulation is as follows: Figure 9 As shown in Figure a, both blank PVC and pBDA-coated catheters showed significant blood clot deposition on their surfaces; in contrast, pSBMA and pSBMA-A hydrogel-coated catheters showed significantly reduced blood clot deposition. Figure 9 SEM image analysis of the area shown in Figure a revealed a large accumulation of red blood cells on the surfaces of blank PVC and pBDA, while the number of red blood cells on the surfaces of pSBMA and pSBMA-A was significantly reduced, resulting in a smoother and denser surface with almost no visible red blood cell aggregation. This further demonstrates the excellent antifouling properties of the pSBMA and pSBMA-A hydrogel coatings. Compared to blank PVC and pBDA, the pSBMA and pSBMA-A coatings showed a significant reduction in thrombus adhesion after blood circulation: Figure 9As shown in b, the thrombus adhesion mass decreased from 52.40±15.74 mg to 12.03±0.47 mg (a reduction of approximately 77%). This indicates that the hydrophobic surface of PVC easily promotes coagulation and leads to thrombus adhesion, while the high hydrophilicity brought by SBMA grafting significantly enhances the material's antifouling properties. This is because the sulfobetaine group has excellent hydrophilicity and hydration ability, which can form a hydration layer on the material surface, thereby effectively inhibiting the adhesion and aggregation of thrombi on the catheter surface.

[0128] Example 6. Hemolysis and Cytotoxicity Experiment

[0129] 6.1. Hemolysis Assay Experimental Method: Biocompatibility is a key requirement for the application of biomedical materials in the human body. First, cut the sample into 10 mm lengths. Take 2 mL of fresh anticoagulated blood, centrifuge at 2500 rpm for 10 min at 4 °C, discard the supernatant, and retain the red blood cell pellet. Add an equal volume of PBS to the pellet, gently resuspend by pipetting, and centrifuge again at 2500 rpm for 10 min at 4 °C, discarding the supernatant. Repeat washing 3 times until the supernatant is clear and transparent. Dilute the washed concentrated red blood cells with PBS to prepare a 2.5% (v / v) red blood cell suspension. Place the sample in 1 mL of PBS containing the 2.5% red blood cell suspension and incubate at 37 °C for 1 h. Use 1% Triton X-100 as a positive control and PBS as a negative control. After incubation, centrifuge at 2500 rpm for 10 min at room temperature (or 4 °C), take 200 μL of supernatant and add it to a 96-well plate, measure the absorbance at 545 nm using an ELISA reader, and calculate the hemolysis rate according to formula (3).

[0130] hemolysis ratio (%) = × 100% (3)

[0131] Among them, A sample A represents the absorbance of the sample group. negative Absorbance of the negative control, A positive The absorbance is for the positive control.

[0132] 6.2. Cytotoxicity Assay: The compatibility of samples with L-929 cells was assessed using the CCK-8 assay. First, samples were cut into 10 mm lengths and sterilized by UV irradiation for 30 min. Cells were cultured in complete medium (89% high-glucose DMEM, 10% fetal bovine serum, 1% penicillin-streptomycin) and seeded in 96-well plates (4 × 10³ cells / well). Simultaneously, PVC, pBDA, pSBMA, and pSBMA-A samples were immersed in 1 mL of complete medium and incubated at 37 °C, 5% CO2 for 24 h to obtain sample extracts. 5% DMSO was used as a positive control, and blank complete medium was used as a negative control. After cell attachment, the medium in the wells was aspirated, and 100 μL of sample extract was added to each well for further incubation for 24 h. Subsequently, the extract was discarded, and 100 μL of medium containing 10% CCK-8 was added, and the cells were incubated at 37 °C, 5% CO2 for 1 h. Measure the absorbance at 450 nm and calculate the cell viability according to formula (4).

[0133] Cell viability (%) = × 100% (4)

[0134] Among them, A sample The absorbance of the sample (including sample extract, complete culture medium, cells, and CCK-8 solution); A blank Absorbance of the blank control (including complete culture medium and CCK-8 solution); A negative Absorbance for negative controls (including complete culture medium, cells, and CCK-8 solution).

[0135] 6.3. Experimental Results

[0136] Figure 10 The cell viability of blank PVC catheters and hydrogel-coated catheters (pBDA, pSBMA, and pSBMA-A) is presented. CCK-8 results showed that, compared to the positive control, the cell viability of pSBMA and pSBMA-A hydrogel-coated catheters after co-culturing with cells for 24 h was higher than 80%. Based on ISO 10993-5:2009, the prepared pSBMA-A hydrogel-coated catheter can be considered a non-cytotoxic material.

[0137] Figure 10 b represents the optical density (OD) value at 450 nm. There was no significant difference between the blank PVC, pBDA, pSBMA, and pSBMA-A samples and the negative control.

[0138] Figure 10c shows the hemolysis rate of blank PVC catheters and pBDA, pSBMA, and pSBMA-A coated catheters to human erythrocytes (HRBCs). The hemolysis rates of blank PVC, pBDA, pSBMA, and pSBMA-A were 0.26±0.15%, 0.35±0.15%, 0.39±0.11%, and 0.47±0.10%, respectively. All samples had a hemolysis rate below 2% (ASTM F756-17, 2025), therefore they can be considered non-hemolytic.

[0139] Figure 10 d represents the OD value at 545 nm. The absorbance of the blank PVC and all coated catheters was below 0.1, showing a significant difference compared to the positive control. Overall, the hemolysis and cytotoxicity results together indicate that the pSBMA-A hydrogel coating is suitable for biomedical applications.

[0140] Explanation of the above experiment:

[0141] Unless otherwise specified, all data are expressed as mean ± standard deviation (n=3). One-way ANOVA was used for multiple group comparisons; two-way ANOVA was used for experiments involving two independent variables. Tukey's test was used for post-hoc multiple comparisons. p < 0.05 was considered statistically significant. ns indicates no significant difference; *p < 0.05, **p < 0.01, ***p < 0.001.

[0142] Summary of the comparison results:

[0143] The comparative experimental results above suggest that the excellent antibacterial properties of the pSBMA-A hydrogel coating may stem from the efficient loading and uniform dispersion of silver nanoparticles (Ag NPs) within the three-dimensional hydrogel network. Compared to the AgNPs@CS / SCS system (particle size approximately 90±9 nm) reported by Mengni Fan et al., the Ag NPs introduced in this study have a smaller particle size (15.99 ± 0.11 nm). Under the confinement effect of the hydrogel network, the small-sized Ag NPs can be highly dispersed, thereby significantly improving the effective antibacterial utilization rate of silver, achieving strong antibacterial activity while reducing the potential cytotoxicity of silver. The PDA layer can serve as a universal adhesion interface for Ag NP loading and can impart certain antibacterial properties; however, its antibacterial effect is highly dependent on the loading method of Ag NPs and the Ag... + Effective release. At the same time, the pBDA coating lacks inherent anti-adhesion ability, and bacteria can still initially adhere to and colonize its surface, thereby weakening the actual antibacterial efficiency of Ag NPs.

[0144] In contrast, the pSBMA hydrogel network rich in zwitterionic groups can form a dense and stable hydration layer on the material surface, significantly reducing bacterial adhesion and thus exhibiting a better antibacterial effect. This mechanism is primarily based on "anti-adhesion," effectively reducing the number of initially attached bacteria in plate experiments. However, its antibacterial effect is mainly passive, originating from inhibiting bacterial attachment and colonization rather than directly killing bacteria. In the pSBMA-A coating, a synergistic effect is formed between the zwitterionic hydrogel network and Ag NPs: on the one hand, the cross-linked hydrogel network provides physical fixation for Ag NPs, inhibiting their aggregation and ensuring uniform distribution; on the other hand, the weak interaction between the zwitterionic groups and the Ag NP surface further improves their dispersion stability and promotes Ag... + The structure not only enhances the antibacterial efficiency and durability of Ag NPs but also allows for a reduction in silver loading, thereby effectively mitigating potential biotoxicity. Therefore, the pSBMA-A coating combines anti-adhesion properties with silver-mediated active bactericidal activity, achieving nearly 99% antibacterial efficiency against E. coli and S. aureus at relatively low silver content, significantly outperforming either PDA or pSBMA coatings alone.

[0145] The function and effect of this embodiment:

[0146] In this embodiment, an SBMA crosslinked zwitterionic hydrogel network was constructed in situ on the catheter surface via photoinitiated free radical polymerization, and small-sized Ag NPs (15.99 ± 0.11 nm) were introduced during the polymerization process. A PDA adhesion layer improved the coating stability, and the Ag NPs were uniformly embedded in the hydrogel, forming a composite coating with both anti-adhesion and active antibacterial functions. This coating formed a uniform and continuous structure (approximately 2 μm thick) on the PVC surface, and both zwitterionic groups and silver elements were successfully introduced and stably loaded.

[0147] The pSBMA-A coating of this embodiment exhibits an antibacterial rate of nearly 99% against E. coli and S. aureus, and maintains high antibacterial activity even after immersion in artificial urine, demonstrating good antibacterial stability. Simultaneously, the coating significantly reduces thrombus adhesion and erythrocyte aggregation, improving antithrombotic performance by approximately 77%, demonstrating excellent anti-protein adsorption and antithrombotic capabilities. Furthermore, the coating exhibits a low hemolysis rate (minimum approximately 0.47 ± 0.10%) and good cell compatibility.

[0148] In this embodiment, the pSBMA-A coating is formed by photopolymerization of SBMA monomers to create a three-dimensional cross-linked zwitterionic hydrogel network, introducing small-sized Ag NPs (15.99 ± 0.11 nm) during the polymerization process. The cross-linked network physically confines the Ag NPs, ensuring uniform dispersion and preventing aggregation, thereby maximizing antibacterial activity and reducing potential cytotoxicity even with low silver content. The dense zwitterionic groups on the surface form a stable hydration layer, resisting non-specific bacterial adhesion and initial colonization; simultaneously, the network enables Ag… + The continuous release of Ag can effectively kill residual bacteria while avoiding instantaneous high concentrations. + The coating's superior antibacterial properties stem from a synergistic mechanism: the zwitterionic hydrogel provides an anti-adhesion interface and stabilizes Ag NPs, while the small-sized Ag NPs enable efficient utilization and controlled release, thus achieving nearly 99% antibacterial efficiency against E. coli and S. aureus with good biocompatibility.

Claims

1. A catheter with a photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating, characterized in that: Includes a hydrogel matrix that is loaded / coated / attached to the surface of the conduit; The hydrogel matrix is ​​formed by using MBA as a crosslinking agent to initiate the self-polymerization of SBMA monomers under ultraviolet light irradiation, forming a three-dimensional crosslinked network while embedding Ag NPs within the hydrogel matrix.

2. The catheter with a photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 1, characterized in that: The method for preparing the hydrogel matrix is ​​as follows: S1. Under light-protected conditions, stir SBMA, MBA and photoinitiator continuously at room temperature until completely dissolved; S2. Add Ag NPs precursor colloidal solution, stir for 30-60 min, and then disperse to obtain the target hydrogel matrix.

3. The catheter with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 2, characterized in that: The mass ratio of SBMA to MBA is 10-100:1; The amount of the photoinitiator is 0.1-0.5 wt% of the total material. The concentration of Ag NPs was 0.01-0.08 mM.

4. The catheter with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 1, characterized in that: The surface of the catheter is also pretreated with PDA.

5. The catheter with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 1, characterized in that: The surface of the catheter is also pretreated with BP.

6. The catheter with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 1, characterized in that: The pretreatment method for the catheter is as follows: S1. Clean and dry the PVC conduit; S2. Immerse the cleaned catheter in BP solution for 5-30 minutes; S3. Add to Tris-HCl buffer containing dopamine and stir overnight at room temperature; S4. Dry in an oven at a temperature not exceeding 60°C for 10-25 min to obtain a pretreated conduit with a PVC-BP-PDA coating.

7. The catheter with a photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 6, characterized in that: The concentration of the BP solution is 5-20 wt%; Tris-HCl buffer containing dopamine (DA) refers to Tris-HCl buffer with a DA concentration of 2-5 mg / mL.

8. The catheter with a photoinitiated in-situ self-polymerized silver zwitterionic hydrogel coating as described in claim 1, characterized in that: The method for loading / coating / attaching the hydrogel matrix to the surface of the conduit is as follows: immerse the conduit in the hydrogel matrix for 10-30 min, allow the hydrogel matrix to be uniformly deposited on the surface, and then cure it under 365 nm ultraviolet light for 30 min-1 h to obtain the final PVC-BP-PDA-SBMA / Ag coated conduit.

9. The application of the photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating of the catheter as described in any one of claims 1-8 in antibacterial catheters.

10. The application of the photo-initiated in-situ self-polymerized silver zwitterionic hydrogel coating of the catheter as described in any one of claims 1-8 in antithrombotic catheters.

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