Staphylococcus aureusDetection by Fluorescent Silica Nanoparticles Modified with Metal–Dipicolylamine Complexes

Abstract

We have developed a new method for Staphylococcus aureus (S. aureus) detection, which employs fluorescent silica nanoparticles (FSiNPs) modified with metaldipicolylamine complex (M-dpa-HCC). Among the M-dpa-HCC/FSiNP complexes, Cu-dpa-HCC/FSiNP formed large aggregates with S. aureus in 10 min, which were easily observed by the naked eye. The antibacterial activity of Cu-dpa-HCC/FSiNP was also confirmed. 46 However, the culture method requires nearly five days for detection, whereas the other two methods are expensive and require expertise in handling.710 Therefore, the development of a new method for simple and rapid detection of bacteria has been actively pursued. To this end, various biosensors have been developed. 11 In particular, nanoparticle sensors are promising because their surfaces and chemical structures are easily controlled and various types of recognition sites can be introduced on the nanoparticle surface. 12,13 In addition, the nanoparticles are inexpensive, have low toxicity, and can be easily handed. 14,15 It is well known that many phosphate groups exist on the phosphatides on bacterial cell surfaces. 16 It has been reported that dipicolylamine fluorophores show diverse fluorescence responses by changing the metal species. 1719 We have developed fluorescent silica nanoparticles (FSiNPs) possessing metaldipicolylamine binding sites with coumarin fluorophore (M-dpa-HCC ( Figure 1A)), for selective phosphate recognition in water. By altering the metal species in the M-dpa-HCC/ FSiNP complexes ( Figure 1B) 25 The importance of not only simple detection of pathogenic bacteria but also high antibacterial activity for preventing infections has become widely acknowledged. 2628Herein we report an efficient method for S. aureus detection, which employs M-dpa-HCC/FSiNP complexes. Depending on the metal species in the DPA complexes, the M-dpa-HCC/ FSiNP complexes exhibited specific affinity for the anionic surface of bacteria, forming large fluorescent aggregates that were easily observed by the naked eye. The antibacterial activity of the Cu-dpa-HCC/FSiNP complex for S. aureus was also confirmed.The design of bacteria-sensitive nanoparticles was initiated with the synthesis of FSiNPs according to the Stöber method, 29 using tetraethyl orthosilicate (TEOS) and tris(2,2¤-bipyridyl)ruthenium(II) complexes (fluorescence core) as the precursor. The surface of FSiNPs was modified with 3-aminopropyltrimethoxysilane (APS) and was reacted with dpa-HCC by DMT-MM to obtain dpa-HCC/FSiNP (See Supporting Information (SI)). To evaluate the effect of dpa-HCC-coordinated metal species on bacterial recognition, the aggregation behavior of S. aureus upon the addition of M-dpa-HCC/FSiNP (M = Cu 2+ or Zn 2+ ) complexes was examined. Figure 2 shows the confocal fluorescence images of S. aureus treated with (1) metal-free dpa-HCC/FSiNP (Figures 2A2D), (2) Cu-dpa-HCC/FSiNP (Figures 2E2H), and (3) Zn-dpa-HCC/FSiNP (Figures 2I 2L). The samples were prepared by mixing S. aureus (10 8 CFU mL ¹1 ) with M-dpa-HCC/FSiNP (1 mg mL ...

Fast and Sensitive Bacteria Detection by Boronic Acid Modified Fluorescent Dendrimer

“…In the same manner as many biological challenges [ 16 , 17 ], nanoprobes with binding sites as a recognitive function represent a potential solution. For instance, nanoprobes with dipicolylamine for Staphylococcus aureus [ 18 ] or Escherichia coli [ 19 , 20 ], mannose towards E. coli [ 21 , 22 ], cationic amine groups [ 23 , 24 ] and vancomycin [ 25 ] for various species, or cell wall binding domains for corresponding bacteria [ 26 ] were developed to attempt instant and sensitive detection of bacteria. Many laboratories have focused on bacteria detection by convenient optical measurements, such as luminescence changing [ 27 , 28 ].…”

Metal and Phosphate Ion Recognition Using Dipicolylamine-modified Fluorescent Silica Nanoparticles

“…We previously reported on fluorescent silica nanoparticles (FSiNPs) modified with M (metal ion)-dpa-HCC for S. aureus detection. 24 The M-dpa-HCC/FSiNP complex efficiently formed aggregates with S. aureus. In that study, we observed interesting responses towards metal ions and phosphate anions as well.…”

Design and Function of Fluorescent Silica Nanoparticles for Bacteria Detection

“…Previously, we reported fluorescent silica nanoparticles (FSiNPs) modified with metaldipicolylamine complex (M-dpa-HCC) for Staphylococcus aureus (S. aureus) detection. 23) Among the M-dpa-HCC/FSiNP complexes, Cu-dpa-HCC/FSiNP formed large aggregates with S. aureus in 10 min, which were easily observed by the naked eye. Herein, we develop two types of fluorescent silica nanoparticles (FSiNP) and evaluate bacteria recognition function (Scheme 1).…”