In vitro and in vivo studies on bacteria and encrustation resistance of heparin/poly-L-lysine-Cu nanoparticles coating mediated by PDA for ureteral stent application

Abstract

Ureteral stents are commonly utilized as a medical device to aid the flow of urine. However, biofilm formation and encrustation complications have been clinical problems. To overcome this challenge, heparin/poly-L-lysine-copper (Hep/PLL-Cu) nanoparticle was immobilized on a dopamine-coated polyurethane surface (PU/NPs). The stability and structural properties of the nanoparticles were characterized by Zeta potential, poly dispersion index, transmission electron microscopy, atom force microscopy and contact angle. The surface composition, antibacterial potency, encrustation resistance rate and biocompatibility of PU/NPs were investigated by scanning electron microscope, X-ray photoelectron spectroscopy, antibacterial assay and MTS assay, respectively. In addition, the anti-encrustation property was studied by implanting coated NPs stents in the rat bladder for 7 days. It was shown that the size and distribution of Hep/PLL-Cu nanoparticles were uniform. PU/NPs could inhibit Proteus mirabilis proliferation and biofilm formation, and exhibit no cytotoxicity. Less encrustation (Ca and Mg salt) was deposited both in vitro and in vivo on samples, demonstrating that the NPs coating could be a potential surface modification method of ureteral material for clinical use.

Keywords: biofilm; encrustation; nanoparticles; ureteral stents.

Graphical Abstract

Figure 1.

Schematic drawing of the preparation and immobilization process of NPs on PU/PDA.

Figure 2.

TEM images of prepared nanoparticle.

Figure 3.

SEM images for (a) PU, (b) PU/PDA, (c) NPs.

Figure 4.

(a–c) 3D dimensional AFM images for PU, PU/PDA and NPs; (d) surface roughness of samples, data were presented as mean and standard deviation (n = 3, **P < 0.01, ***P < 0.001).

Figure 5.

(a) XPS wide scan of spectra; (b) PU high-resolution spectra of N1s; (c) PU/PDA high-resolution spectra of N1s; (d) NPs high-resolution spectra of N1s; (e) S2p high-resolution spectra; and (f) high-resolution spectra of Cu2p.

Figure 6.

Water contact angles and droplet images of water.

Figure 7.

Cumulative releases of heparin and Cu ions from NPs immobilized surface (n = 3).

Figure 8.

Cells proliferation rates of different samples cultured for 1, 3 and 5 days. Data were presented as mean and standard deviation (n = 3, △P ≥ 0.05).

Figure 9.

Bacterial colonies counts in the AU solution after incubating with different samples for 24 h, (a) PU, (b) PU/PDA, (c) NPs, (d) antibacterial rates of different samples in AU solution. Data were presented as mean and standard deviation (n = 3, *P < 0.05).

Figure 10.

(a) Merge fluorescent images indicating live and dead bacteria on samples after 24 h coculture, (b) proportion of live and dead bacteria.

Figure 11.

SEM micrographs of different samples immersed in AU solution for 2, 4 and 6 weeks.

Figure 12.

(a) Encrustation weight, Ca (b) and Mg (c) contents of different samples after immersions in AU solution for 2, 4 and 6 weeks, *P ≤ 0.05, △P ≥ 0.05.

Figure 13.

Encrustations of the ureteral stents after 7 days implantation, (a) photo of implanted PU stent, (b) SEM image of implanted PU stent, (c) SEM micrograph of encrustation, (d) EDS spectra at encrustation site, (e) photo of implanted nanoparticles stent, (f) SEM image of implanted nanoparticles stent, Ca (g) and Mg (h) deposition amounts on nanoparticles and PU ureteral stent after 7 days of implantation (n = 3, *P < 0.05).

Figure 14.

Mechanism of Hep/PLL-Cu (NPs) stent, (a) PU stent, (b) release of Cu ions from the NPs killing majority of the urease-producing bacteria on NPs, (c) release of ${\text{SO}}_3^{ -}$ group from heparin molecule blocks the crystal growth sites hereby reducing the formation of urine crystals.