Quarternary Ammonium Salts Co

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Fluorescent Conjugated Polymers/Quarternary Ammonium Salts Co-assembly Nanoparticles: Applications in Highly Effective Antibacteria and Bioimaging Lianqi Wang, Qi Zhao, Ziqi Zhang, Zhuanning Lu, Yantao Zhao, and Yanli Tang ACS Appl. Bio Mater., Just Accepted Manuscript • DOI: 10.1021/acsabm.8b00422 • Publication Date (Web): 25 Oct 2018 Downloaded from http://pubs.acs.org on October 27, 2018

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is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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ACS Applied Bio Materials

Fluorescent

Conjugated

Ammonium

Salts

Polymers/Quarternary

Co-assembly

Nanoparticles:

Applications in Highly Effective Antibacteria and Bioimaging Lianqi Wang, Qi Zhao, Ziqi Zhang, Zhuanning Lu, Yantao Zhao, and Yanli Tang*

Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’ an 710062, P. R. China.

*E-mail: [email protected]

KEYWORDS: conjugated polymer nanoparticles, antibacteria, bioimaging, biocompatibility, quarternary ammonium salt.

ACS Paragon Plus Environment

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ABSTRACT. Bacterial resistance is one of the very severe factors that threaten human health. It is of great significance to construct a simple, highly effective, biocompatible and costefficient therapeutic route. In this paper, a new method was constructed to prepare cationic

nanoparticles,

and

the

fluorescent

conjugated

polymer

co-assembly

nanoparticles CA-CPNs was designed and synthesized based on the model conjugated polymers, PFVBT, and the model quarternary ammonium salts, cationic surfactant cetyltrimethylammonium bromide CTAB. PFVBT were designed and synthesized only by three steps. CTAB are commercially available. By reprecipitation method, the PFVBT form the core and CTAB forms a shell on the surface of CA-CPNs by hydrophobic interaction. Importantly, when incubated with bacteria, the positively charged CA-CPNs can combine with bacteria, physically destroy the bacterial membrane and kill bacteria without the requirement of light or chemical energy. When 0.80 μg/mL CA-CPNs were incubated for 30 min with Escherichia coli, over 91% bacteria were killed. Also, over 96%

Staphylococcus aureus were dead when incubated with 1.0 μg/mL CA-CPNs. In virtue of the bright red fluorescence, CA-CPNs were also successfully applied to image MCF-7 cell with good biocompatibility. Overall, a simple, cost-effective and universal method was


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provided to prepare cationic fluorescent nanoparticles that are a promising nanomaterial for biomedical applications.

INTRODUCTION

Bacterial infection is one of the major factors that threaten human health. The emergence of antibiotics has undoubtedly made a tremendous contribution to treating bacterial infections. However, with the overuse of antibiotics in recent years, bacteria have a certain resistance to conventional antibiotics, which makes them will no long be effective in the future, leading to life-threatening infectious diseases.1-5 Major effort was devoted to the development of new antibacterial agents and antibacterial methods replace antibiotics. For instance, some multi-functional polymers composite membrane, polymers hollow fiber membrane, and host-guest self-assembly materials for killing bacteria have been reported.6-8 Recently, the antimicrobial nanomaterials attracted more and more attention owing to their advantages of small size and large specific surface area that greatly enhance antibacterial activity.9-13 At present, metal nanostructure, heavy metal nanoparticles, and carbon nanomaterials present good antibacterial activity,14-20 however,


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there are drawbacks such as high biological toxicity, high cost, and environmental hazardousness.21-23 A promising alternative method for antibacteria is photodynamic therapy (PDT). PDT is dependent on the use of photosensitizers to generate reactive oxygen species (ROS) under light excitation, such as superoxide radicals, hydroxyl radicals, hydrogen peroxide, or singlet oxygen (1O2).24-29 This approach requires instruments to provide light energy. In addition, even using near-infrared (NIR) light, the tissue penetration depth is still limited as a result of light absorption and scattering by tissue. Furthermore, skin should be damaged upon exposure to NIR laser for a long time together with high power density.11 Therefore, it is of great significance to construct simple, highly effective, biocompatible and cost-efficient therapeutic routes.

Recently, conjugated polymer nanoparticles (CPNs) as a promising nanomaterial have been widely used because they have high fluorescence brightness, good biocompatibility, and modifiable properties.30-31 At present, most conjugated polymer nanoparticles were modified by amphiphilic polymers such as polyethylene glycol (PEG) and poly (styrenemaleic anhydride) (PSMA) on the surface to increase hydrophilicity and coupling sites for


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biosensing, imaging, and therapy.24,

31-36

It is reported that the effective antibacterial

performance of CPNs was realized by PDT.37-38 Quarternary ammonium salts (QAS) were commonly used as disinfectants, antiseptics, medical apparatus and instruments, and other clinical applications due to excellent antibacterial effects.18,

39

Particularly, long-

chain alkyl-QAS compounds present ultimate antibacterial activity.40 However, QAS monomers show large noxiousness toward normal cell lines, which results in the limitation in clinical application as antibacterial agent. 39

In present work, we reported a novel approach to prepare the fluorescent co-assembly conjugated polymer nanoparticles (CA-CPNs) as a highly effective, biocompatible, and convenient antibacterial agent. CA-CPNs were designed and prepared based on the model neutral fluorescent conjugated polymers, PFVBT, and the model quarternary ammonium salts, cationic surfactant cetyltrimethylammonium bromide (CTAB) (Figure 1). In this case, CA-CPNs possess the great fluorescence property and high antibacterial efficiency. Meanwhile, CA-CPNs can avoid the large cytotoxicity toward normal cell lines of CTAB monomer. In the reprecipitation process, the PFVBT forms the core by


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hydrophobic interaction, and the CTAB forms a shell on the surface of the nanoparticle. Thus the nanoparticles are positively charged, which makes them have a great affinity to bacteria. After incubating with bacteria, CA-CPNs bind to the surface of bacteria through electrostatic interactions (Figure 1). Then nanoparticles could diffuse through the cell wall and irreversibly disrupt membrane structure of bacteria, which leads to the release of the cytoplasmic constituents from cells and bacteria death.41 At low concentrations of CACPNs, the nanoparticles could kill over 91% bacteria without the requirement of light source. Furthermore, the CA-CPNs demonstrate high compatability. In addition, CACPNs can be used for bioimaging analysis owing to their bright red fluorescence.

EXPERIMENTAL SECTION

Materials and Measurements: All the organic reagents were purchased from J&K Chemical Ltd. (Beijing, China), Aladdin Industrial Corporation (Shanghai, China) or Sinopharm Chemical Reagent Co. Ltd. (Beijing, China) and were used without any further purification. The propidium iodide (PI) and bacterial medium components were bought from Sangon Biotech (Shanghai). The stains of SYTO9 and SYTO24 were obtained from


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Thermo Fisher Scientific Inc. Hoechst 33342 was obtained from Beyotime. LysoSensor Green DND-26 was purchased from Yeasen Biotech. (Shanghai). The water used in the experiment was purified by Millipore filtration system. The 1H NMR and 13C NMR spectra were measured on Bruker Ascend 400 MHz spectrometers. UV-Vis absorption spectra were taken by SHIMADZU UV-2600. The fluorescence spectra were measured on a Hitachi F-7000 spectrophotometer with a Xenon lamp. ζ potentials were measured with Malvern Nano-ZS90. Dynamic light scattering (DLS) measurements were performed on a BI-90Plus (Brookhaven Instruments Corporation) equipped with a solid-state laser operating at 659 nm. Electron spectrum of CA-CPNs and SEM images of bacterial morphology were obtained using Hitachi SU8220 field emission scanning electron microscope. TEM images of CA-CPNs were taken on JEM-2100 transmission electron microscope. Fluorescence imaging experiments of bacteria were carried out on an Olympus IX73. Confocal laser scanning microscopy images of MCF-7 cells were measured on Olympus Fluoview 1200. The Accuri C6 flow cytometer was used to study antibacterial activities. The absorbance for MTT analysis was evaluated by a microplate


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reader (Spectramax M5) at a wavelength of 490 nm. The detailed experiments about bacteria and cells were carried out according to the literature. 28, 42-43

Compound 1 and 2 were synthesized according to the literature.44-45

Synthesis of PFVBT: A mixture of Compound 2 (0.25 mmol, 96.7 mg), DMF (1.67 mL), triethylamine (0.83 mL) were added in a flask and then was degassed for 30 min. Under powerfully stirring, 4,7- dibromo-2,1,3-benzothiadiazole (0.25 mmol, 73.5 mg), Pd(OAc)2 (0.009 mmol, 2 mg), and P(o-tolyl)3 (0.049 mmol, 15 mg) were added into the solution. The reaction mixture was refluxed at 100 oC for 4 h under nitrogen. The cooled solution was extracted with CHCl3. The organic solution was washed with water and then dried over anhydrous MgSO4. The solvent was removed under vacuum and the residue was precipitated into methanol to afford PFVBT as a red solid (100mg, 77%). 1H NMR (400 MHz, CDCl3, δ): 8.08 - 8.17 (m, 1.77 H), 7.59 - 7.74 (m, 8.79 H), 2.03 - 2.10 (m, 4.00 H), 1.07 - 1.12 (m, 14.20 H), 0.75 - 0.78 (m, 7.92 H). GPC: Mn = 44810, Mw = 47827, PDI = 1.07.


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Preparation of CA-CPNs: The reprecipitation method was used to prepare CA-CPNs. In a typical preparation,100 µL PFVBT (1.0 mg/mL in THF) and 50 µL CTAB (2.0 mg/mL in H2O) were mixed in 5 mL of THF to give a homogeneous mixed solution. Then 5 mL of the mixed solution was rapidly poured into water (5 mL, 10 mL, 15 mL, respectively) under ultrasonic and ice bath. After removal of THF using a stream of nitrogen, a final nanoparticle suspension (5 mL) solution was obtained by evaporation in an oil bath at 90 oC,

followed by filtration through a 0.22 μm filter. The nanoparticles with other mass ratio

were prepared according to the similar procedure.

RESULTS AND DISCUSSION


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Figure 1. Schematic of antibacterial activity of CA-CPNs and the structure of PFVBT and CTAB.

Synthesis and Characterization of CA-CPNs. The chemical structures and synthesis of conjugated polymer PFVBT are shown in Figure 2. Compound 1 and 2 were synthesized according to the literatures.42-43 PFVBT were synthesized by compound 2 (FV) reacting with 4,7-dibromo-2,1,3-benzothiadiazole (BT), which have a weight-average molecular weight (Mw = 47827) with a polydispersity index (PDI) of 1.07. The 1H NMR spectrum of


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PFVBT was shown in Figure S1. Due to the introduction of BT units, charge transfer from FV units to BT units between intra-/inter-chain occurs. As shown in Figure 2B, PFVBT in CHCl3 exhibit the maximal absorption at 505 nm and bright red fluorescence with the maximal emission at 590 nm, which provides an important element for preparing fluorescent nanoparticles.

Figure 2. (A) Synthesis of PFVBT. Normalized absorption and emission spectra of PFVBT in CHCl3 (B) and CA-CPNs in aqueous solution (C) , respectively.


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In order to obtain functionalized conjugated polymer nanoparticles, we introduced the model quarternary ammonium salts, cationic surfactant CTAB that is commercially available and extremely cheap. CTAB will not only increase the hydrophilicity of nanoparticles but also provide effective positive charges for nanoparticles binding to bacteria or cells via electrostatic interactions. The preparation of CA-CPNs nanoparticles is outlined in Figure 3. In a typical reprecipitation method, PFVBT and CTAB were respectively dissolved in THF firstly, then they were mixed completely and rapidly poured into water under ultrasonication. The hydrophobic chain of the polymers was entwined with the hydrophobic part of CTAB to form nucleus, and the hydrophilic quaternary ammonium groups form shells on the surface. Finally, the spherical co-assembly conjugated polymer nanoparticles CA-CPNs were obtained.


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Figure 3. Schematic of preparation of CA-CPNs.

To study the effect of experimental conditions on the particle size of CA-CPNs, we prepared series of CA-CPNs under different concentrations of the CPs and CTAB, and different ratios (the organic phase to the aqueous phase). The dynamic light scattering (DLS) analysis (Figure 4A, 4B) presents that the ratio of organic phase to aqueous phase is changed from 1:1 to 1:3, the particle size gradually decreases from 93 nm to 52 nm. Figure 4C shows the size of CA-CPNs is 52 nm with a particle dispersion index (PDI) of 0.137 when concentrations of the CPs and surfactant are the same, and ratio of organic phase to aqueous phase is 1:3. However, when the ratio is 1:4, the solution becomes turbid during the preparation of nanoparticles. In addition, as the concentration ratio of PFVBT to CTAB increases from 1:1 to 1.5:1, the particle size of the nanoparticles also increases (Figure 4D). Therefore, we chose a ratio of organic phase to aqueous phase of 1:3 and the concentration ratio of PFVBT to CTAB of 1:1 for the preparation of CA-CPNs. The data of particle size obtained in different conditions were summed in Table S1 in Supporting Information. Furthermore, the photophysical properties of CA-CPNs were


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studied. As shown in Figure 2C, the absorption maximum of CA-CPNs is at 490 nm, which blue shifts approximately 15 nm compared to PFVBT in CHCl3. The blue-shift may result from a slight change in the conjugated effect of the polymers during the co-assembly process. Also, the water is a poor solvent for PFVBT, which may make some effect on the absorption of CA-CPNs. The emission maximum of CA-CPNs is at 590 nm. In addition, the absolute fluorescence quantum yield of CA-CPNs in aqueous solution is measured as 7.8%, which is advantageous for bio-imaging.


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Figure 4. Size distribution histograms of CA-CPNs prepared when the ratio of the organic phase to the aqueous phase was 1:1 (A), 1:2 (B), and 1:3 (C), respectively. CPFVBT:CCTAB = 1:1. (D) Size distribution histograms of CA-CPNs prepared with a ratio of organic phase to aqueous phase of 1:3 and CPFVBT:CCTAB = 1.5:1.


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Figure 5. (A) Transmission electron microscopy (TEM) image of CA-CPNs. The scale bar is 0.2 μm. (B) The particle size and (C) fluorescence intensity of CA-CPNs at different storing time.

The morphology of CA-CPNs was also investigated by TEM. As shown in Figure 5A, CA-CPNs display uniform and spherical morphology with a mean size of 50 nm, which is consistent with the result of DLS. The electron spectrum presented that CA-CPNs contained carbon, nitrogen, sulfur and bromine elements, which was shown in Figure S2. The ζ potential of CA-CPNs was measured as 30.2 ± 2.3 mV, which further verifies that the introduction of CTAB makes the nanoparticles containing a great deal of positive charges. Thus the strong electrostatic interaction between CA-CPNs and membrane of bacteria can occur, which provides important basic for CA-CPNs to further break bacterial membrane. In addition, the CA-CPNs demonstrate excellent colloidal stability. As shown in Figure 5B-5C, the size and fluorescence intensity of CA-CPNs did not change significantly within 10 days, and the CA-CPNs suspension remained clear without any


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precipitation after being stored in 4 oC for 1 month. Thus the stable nanoparticles with good disperse were obtained with a simple and cost-effective approach.

Figure 6. Antibacterial activity of CA-CPNs against E. coli (A) and S. aureus (B) in the dark. Antibacterial activity of CTAB against E. coli (C) and S. aureus (D) in the dark.


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Phase-contrast image (E) and fluorescence image (F) of E. coli incubated with CA-CPNs. The excitation wavelength was 530 nm. [CA-CPNs] = 1.0 μg/mL.

Antibacterial Activity of CA-CPNs. First, we studied the antibacterial activity of CACPNs against the typical Gram-negative bacteria E. coli without irradiation. As shown in Figure 6A, the red and black lines represent the antibacterial activities of CA-CPNs incubated with E. coli in the dark for 30 min and 60 min, respectively. The antibacterial activities are dependent on the concentration of CA-CPNs. The higher the concentration of CA-CPNs is, the better the antibacterial activity is. After incubation with E. coli for 30 min, 76% of cells are dead at the CA-CPNs concentration of 0.50 μg/mL. When the concentration of CA-CPNs is 0.80 μg/mL, over 91% E. coli are dead and the biocidal efficiency reaches the plateaus. We also investigated the bacterial activity of CA-CPNs against E. coli after incubation for 60 min. The result was similar to that for 30 min. The half inhibitory concentrations (IC50, 0.30 μg/mL) are the same for both 30 and 60 min. These results indicate the nanoparticles can fast combine with bacteria, destroy the bacterial membrane and kill bacteria within 30 min.


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Also, we investigated the biocidal activity of CA-CPNs against the typical Gram-positive bacteria S. aureus. As shown in Figure 6B. The trend of antibacterial activities of CACPNs against S. aureus is the same as CA-CPNs against E. coli. The antibacterial activities increase with the concentration of CA-CPNs. When 1.0 μg/mL of CA-CPNs is incubated with S. aureus in the dark for 30 min, over 96% bacteria are killed and the antibacterial efficiency reaches the plateaus. Also, the biocidal effect is almost the same after incubation for 60 min as for 30 min. The IC50 are 0.40 and 0.44 μg/mL after incubation for 30 and 60 min, respectively. These results indicated that CA-CPNs have broad-spectrum and high efficiency in killing bacteria in the dark.

In addition, a comparative study of the antibacterial efficiency of CTAB against E. coli and S. aureus at the corresponding concentrations was conducted. Figure 6C, 6D showed that CTAB with a concentration in the range of 0 μg/mL to 1.0 μg/mL has no antibacterial activity against both E. coli and S. aureus, while the antibacterial efficiency of CA-CPNs at the same concentration are over 91% for E. coli and 96% for S. aureus. As reported in literature,37 CTAB could kill bacteria in a high concentration, which can


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produce severe cell cytotoxicity at that condition. These results demonstrate that CACPNs exhibit high antibacterial activities at such low concentration and avoid using of CTAB with high concentration that can damage normal cells and contaminate environment. Furthermore, it is clearly concluded that the antibacterial activity was not derived from monomer CTAB, but was achieved by functional CA-CPNs themselves that are formed by co-assembly of PFVBT with CTAB. CA-CPNs could badly destroy the bacterial membrane by taking advantage of their relatively firm structure and abundant positive charges on the surface.

Furthermore, the antibacterial mechanism of CA-CPNs against bacteria was investigated by the followed experiments. Because CA-CPNs have positive charges and bright red fluorescence, fluorescence imaging were firstly performed after incubation of CA-CPNs with model bacteria, E. coli for 30 min. As shown in Figure 6F, the bacteria emit bright red fluorescence, indicating that nanoparticles with positive charge can bind tightly to bacteria via electrostatic interactions. Moreover, the ζ potential of E. coli was measured before and after incubation with CA-CPNs. The ζ potential of E. coli themselves is - 49.2


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± 2.4 mV. After incubating with CA-CPNs, the value remarkably increases to - 20.7 ± 4.1 mV. These results confirm our hypothesis that positively charged CA-CPNs combine with bacteria through electrostatic interactions first, and then destroy the bacterial membrane to achieve efficient antibacterial activities.

Figure 7. SEM images of E. coli incubated without (A) and with CA-CPNs (B) for 30 min. SEM images of S. aureus incubated without (C) and with CA-CPNs (D) for 30 min. Scale bars: 2.0 μm.


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In addition, to prove bacteria being damaged by physically breaking membrane, we obtained the SEM images to study the effect of CA-CPNs on the morphology of the bacteria. As shown in Figure 7A, E. coli cells alone are rod-shaped, and the surface is smooth and intact. However, after incubation with CA-CPNs for 30 min, the morphology of the bacteria changes significantly (Figure 7B). All bacteria are incomplete or even amorphous, and it can be clearly seen that there are abundant content released from damaged cells on the surface of bacteria. Similarly, S. aureus cells alone are structurally complete sphere with smooth surface (Figure 7C). After being treated with CA-CPNs for 30 min, the structure of bacteria suffers severe damage. As shown in Figure 7D, the surface of the bacteria is wrinkled and cracked. Some of the bacterial membranes stick together and fuse, and the contents of the cells flow out. These physical damages cause the death of bacteria. It should highlight that the irreversible damages on bacterial cells can occur after bacteria directly contact with CA-CPNs. Moreover, once CA-CPNs enter the bacterial cells, it is not easy to be excreted by bacteria because the surface of the nanoparticles is positively charged. CA-CPNs could further interact with ionic contents of bacteria via electrostatic interactions. Therefore, bacteria hardly produce drug resistance.


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Compared with traditional antibiotics, CA-CPNs demonstrate promising antibacterial performance. Although photodynamic therapy for antibacterial treatment has received widespread attention due to high efficiency, it requires light or chemical energy to provide energy, which makes it complicated when used. It is noted that CA-CPNs can achieve broad-spectrum and high-efficiency biocide without the requirement of light or other energy, which provides a simple and prospective application in antibacteria.

Table 1. Comparison of antibacterial activity of several different antibacterial materials Materials

Light wavelengt

Dose

Type of bacteria and

Ref.

h (λ)

of materials

disinfection efficiency

PBF nanoparticles

White light

20 μM

E. coli (90%, 40 min)

38

NaYF4:Yb,Tm/PFVCN

980 nm

10 μM

E. coli (90%, 30 min)

12

PBFBT-NP

White light

0.8 μM

E. coli (100%, 60 min)

42

ZnO-Au hybrid

sunlight

0.1 mg/mL

E. coli (90%, 10 min),

15

S. aureus (95%, 10

nanostructures

min) MoS2/H2O2

808 nm

100 μg/mL

E. coli (97%, 10 min),

11

S. aureus (100%, 10 min) C60-GQDs

Dark

200 μg/mL

S. aureus (95%, 3 h)

46

Carbon nanotubes

Dark

200 μg/mL

E. coli (80%, 24 h)

47

Au-APA NPs

Dark

2.5 μg/mL

E. coli (100%, 24 h)

10

AgNPs/OCNT

Dark

10 μg/mL

E. coli, S.

48

aureus (100%, 2 h) CA-CPNs

Dark

0.8

E. coli (91%, 30 min),

This

μg/mL(1.5

S. Aureus (96%, 30

work

μM), 1

min)


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μg/mL (1.9 μM)

Finally, the antibacterial activities of different nanoparticle materials are compared with CA-CPNs. As shown in Table 1, it can be seen that the CA-CPNs can achieve highly efficient and broad-spectrum antibacterial effect in the dark, while other antibacterial materials could obtain satisfactory antibacterial effect under light irradiation with high concentration and/or longer time. These results demonstrate that CA-CPNs can efficiently kill bacteria at very low dosage in an easy and fast way, which is superior to that of most nanoparticles based on photodynamic therapy or without irradiation.

Figure 8. Confocal fluorescence microscopy images of MCF-7 treated with 1.0 μg/mL of CA-CPNs for 18 h. The fluorescence imaging of Hoechst 33342 (fluorescent stains for


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labeling DNA), LysoSensor Green DND-26 (lysosome dye), and CA-CPNs were collected at 425-475 nm (λex: 405 nm), 500-550 nm (λex: 488 nm), and 560-675 nm (λex: 488 nm), respectively. Scale bar: 40 μm.

Cell Imaging and Biocompatibility of CA-CPNs. In virtue of bright red fluorescence of CACPNs, it can be used for cell imaging. Because cells have negative charges on the surface, the positively charged CA-CPNs can combine with cells through electrostatic interactions and hydrophobic interactions, and then enter cells by endocytosis for bioimaging. CA-CPNs at a concentration of 1.0 μg/mL were used for fluorescence imaging. After the CA-CPNs were incubated with the model cell, MCF-7 cells for 18 h, fluorescence images were measured on a confocal laser scanning microscope. As shown in Figure 8, the bright red fluorescence in the cells from the CA-CPNs channel can be clearly observed. Furthermore, the red fluorescence area completely overlap with the blue (Hoechst, nucleus dye) and green fluorescence area (LysoSensor Green, lysosome dye), which indicates that CA-CPNs can enter both the lysosome and the nucleus through the nuclear pores for fluorescence imaging. Furthermore, the traditional MTT assay was used


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to study the biocompatibility of CA-CPNs. Figure S3 shows the cytotoxicity of at different concentrations (0.5-10 μg/mL) of CA-CPNs incubated with MCF-7 cells in the dark for 48 h. Even if the concentration of CA-CPNs is increased to 1.5 μg/mL (At a concentration of 1.0 μg/mL for CA-CPNs, two kinds of typical bacteria were over 91% dead), the viability of MCF-7 is greater than 92%. However, when the concentration was higher than 1.5 μg/mL, the cell viability of MCF-7 gradually decreased. The results indicate that CA-CPNs have low cell cytotoxicity while they have highly effective antibacterial activity at low concentration.

CONCLUSIONS

In summary, a new approach for the preparation of cationic nanoparticles was constructed and a multifunctional fluorescent nanomaterial CA-CPNs with great performance has been successfully synthesized based on the neutral PFVBT and cationic surfactant CTAB. The CA-CPNs are obtained handily and cost-effectively. Especially, CACPNs overcome the disadvantage of low antibacterial activity of most of conjugated polymers and nanoparticles in the dark, and exhibit efficient and broad-spectrum biocidal


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activities at the low concentration. Moreover, the cytotoxicity of CA-CPNs is very low. Taking advantage of the excellent fluorescence properties of CA-CPNs, they can be used as an excellent bioimaging agent. In brief, there are several advantages: (1) Easy, costeffective and universal preparation. (2) Fast, broad-spectrum and highly efficient antibacterial performance. (3) Good biocompatibility. (4) Convenient use without requirement of light source. This work provides a new way to prepare nanoparticles that is potential for in vitro and in vivo antibacterial treatments and bioimaging.

ASSOCIATED CONTENT

Supporting Information

The Supporting Information is available free of charge on the ACS Publications website.

Figure S1, Figure S2, Figure S3, and Table S1 (PDF)

AUTHOR INFORMATION Corresponding Author * Email:[email protected].


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ORCID

Yanli Tang: 0000-0002-9979-6808

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT

This work was supported by the National Natural Science Foundation of China (No. 21675106), Natural Science Basic Research Plan in Shaanxi Province of China (No. 2017JM2019), the 111 Project (No. B14041), the Program for Changjiang Scholars and Innovative Research Team in University (No. 14R33).

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