Fabrication of nonfouling, bactericidal, and bacteria corpse release multifunctional surface through surface-initiated RAFT polymerization

Figures & data

Table 1 A summary of the various characteristics of p (DMAEMA⁺-co-MPC) copolymer brush coating

Test method	PDMS	APTES	RAFT agent	p (DMAEMA^+)	p (DMAEMA^+-co-0.10 MPC)	p (DMAEMA^+-co-0.25 MPC)	p (DMAEMA^+-co-0.50 MPC)
Static contact angle (°)	116.0±3.7	55.2±2.4	92.3±4.2	75.1±1.6	59.6±2.5	48.1±3.3	34.4±2.4
Thickness* (nm)	NA	1.8±0.3	2.5±0.4	29.4±0.6	27.4±0.6	26.4±0.7	28.6±0.6
RMS (nm)	2.78±0.26	2.06±0.32	3.42±0.41	3.16±0.31	3.32±0.27	2.88±0.47	3.48±0.35

Notes:

* Thickness measurement was done on silicon wafer. Data are presented as mean ± standard deviation. p (DMAEMA⁺-coMPC) copolymer brush coatings were synthesized by RAFT polymerization in DMAEMA⁺/MPC monomer solution in ethanol in the mass ratio of 1:0, 1:0.1, 1:0.25, and 1:0.5 and the obtained samples were named as P1-0, P1-0.1, P1-0.25 and P1-0.5, respectively.

Abbreviations: p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); PDMS, poly(dimethyl siloxane); RAFT, reversible addition–fragmentation chain transfer; NA, not available; RMS, root mean square; APTES, (3-Aminopropyl)triethoxysilane; MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 1 AFM images on various surfaces.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC). p (DMAEMA⁺-coMPC) copolymer brush coatings were synthesized by RAFT polymerization in DMAEMA⁺/MPC monomer solution in ethanol in the mass ratio of 1:0, 1:0.1, 1:0.25, and 1:0.5 and the obtained samples were named as P1-0, P1-0.1, P1-0.25 and P1-0.5, respectively.

Abbreviations: AFM, atomic force microscopy; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate; RAFT, reversible addition–fragmentation chain transfer.

Figure 2 XPS spectra collected from PDMS surface (A) wide-scan spectra, (B) PDMS surface N 1s core-level spectra, (C) PDMS surface P 2p core-level spectra. p (DMAEMA⁺)-modified PDMS (D) wide-scan spectra, (E) N 1s core-level spectra, (F) P 2p core-level spectra. p (DMAEMA⁺-co-0.25 MPC)-modified PDMS (G) wide-scan spectra, (H) N 1s core-level spectra, and (I) P 2p core-level spectra.

Abbreviations: XPS, X-ray photoelectron spectroscopy; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Table 2 Element composition (atomic%) and molecular weight of the brushes on the PDMS surface determined by XPS and GPC

Species analyzed	PDMS	p (DMAEMA^+)	p (DMAEMA^+-co-0.10 MPC)	p (DMAEMA^+-co-0.25 MPC)	p (DMAEMA^+-co-0.50 MPC)
C/O/N/P/Si (theoretical)	50.0/25.0/–/25.0	72.7/18.2/9.1/–/–	70.8/19.5/8.7/0.5/–	68.6/21.6/8.2/1.3/–	65.1/24.9/7.2/2.7/–
C/O/N/P/Si (experimental)	53.8/19.0/–/27.2	74.1/17.6/8.3/–/–	68.7/21.3/9.1/0.9/–	66.7/21.9/9.6/1.8/–	62.6/25.3/8.5/3.6/–
Mn (×10^3)	–	23.6	26.9	25.7	28.2
Mw (×10^3)	–	38.3	41.8	45.1	46.3
PDI	–	1.62	1.55	1.75	1.64

Abbreviations: PDMS, poly(dimethyl siloxane); XPS, X-ray photoelectron spectroscopy; p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacry-loyloxyethyl phosphorylcholine); GPC, gel permeation chromatography; PDI, polydispersity index; MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate; Mw, weight-average molecular weight; Mn, number-average molecular weight.

Figure 3 GPC chromatogram of p (DMAEMA⁺-co-0.25 MPC) copolymer.

Abbreviations: p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); GPC, gel permeation chromatography; MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 4 BSA adsorption.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS. The statistical significance is indicated by different letters (P<0.05).

Abbreviations: BSA, bovine serum albumin; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloy-loxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 5 Fluorescent microscopy images of live/dead staining of S. aureus adhesions.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS at 15 seconds. The green color indicates live bacteria, and the red color indicates dead bacteria, under fluorescence microscopy (the magnification is 10×). (F) Adherence of the live/dead bacteria cell density on the surfaces.

Abbreviations: S. aureus, Staphylococcus aureus; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 6 Fluorescent microscopy images of live/dead staining of S. aureus.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS at 24 hours. The green color indicates live bacteria, and the red color indicates dead bacteria, under fluorescence microscopy (the magnification is 10×). (F) Adherence of the live/dead bacteria cell density on the surfaces.

Abbreviations: S. aureus, Staphylococcus aureus; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 7 Fluorescent microscopy images of live/dead staining of S. aureus.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS at 72 hours. The green color indicates live bacteria, and the red color indicates dead bacteria, under fluorescence microscopy (the magnification is 10×). (F) Adherence of the live/dead bacteria cell density on the surfaces.

Abbreviations: S. aureus, Staphylococcus aureus; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 8 SEM images.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS after exposure to waterborne S. aureus. (F) Adherence of the bacteria cell density on the surfaces.

Abbreviations: SEM, scanning electron microscope; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); S. aureus, Staphylococcus aureus; MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 9 Changes of the viable S. aureus cells after exposure to various surfaces.

Notes: Pristine PDMS, p (DMAEMA⁺), p (DMAEMA⁺-co-0.10 MPC), p (DMAEMA⁺-co-0.25 MPC), and p (DMAEMA⁺-co-0.50 MPC)-modified PDMS for 24 hours.

Abbreviations: S. aureus, Staphylococcus aureus; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloy-loxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Figure 10 The cell viability assay of HLECs cultured on various surfaces.

Notes: (A) TCPS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), and (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS for 24 hours. The absorbance of the diluted Cell Counting Kit solution has been deducted from each data point, and the statistical significance is indicated by different letters (P<0.05).

Abbreviations: HLECs, human lens epithelial cells; TCPS, tissue culture plates; p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyl oxyethyl phosphorylcholine); PDMS, poly(dimethyl siloxane); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl metha crylate.

Figure 11 Growth and morphology of HLECs stained with FDA after 24 hours of incubation on various surfaces.

Notes: (A) Pristine PDMS, (B) p (DMAEMA⁺), (C) p (DMAEMA⁺-co-0.10 MPC), (D) p (DMAEMA⁺-co-0.25 MPC), (E) p (DMAEMA⁺-co-0.50 MPC)-modified PDMS and, (F) adherence of the HLECs density on the surfaces. The magnification is 10×.

Abbreviations: HLECs, human lens epithelial cells; FDA, fluorescein diacetate; TCPS, tissue culture plates; PDMS, poly(dimethyl siloxane); p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.

Scheme 1 Schematic illustration of the preparation of p (DMAEMA⁺-co-MPC) copolymer brushes on PDMS with nonfouling and bactericidal properties.

Abbreviations: p (DMAEMA⁺-co-MPC), (2-(dimethylamino)-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine); PDMS, poly(dimethyl siloxane); RAFT, reversible addition–fragmentation chain transfer; APTES, (3-Aminopropyl)triethoxysilane; MPC, 2-methacryloyloxyethyl phosphorylcholine; DMAEMA, 2-(dimethylamino)-ethyl methacrylate.