KR20170007653A

KR20170007653A - Method for Detecting Dopamine

Info

Publication number: KR20170007653A
Application number: KR1020150098506A
Authority: KR
Inventors: 김종성; 조비
Original assignee: 가천대학교 산학협력단
Priority date: 2015-07-10
Filing date: 2015-07-10
Publication date: 2017-01-19
Also published as: KR101764005B1

Abstract

The present invention relates to a dopamine detection method. More particularly, the present invention relates to a method of preparing a dopamine-containing solution, comprising: (i) contacting a core / shell quantum dot with a dopamine-containing solution using a crosslinking agent; (ii) detecting fluorescence extinction of the quantum dot after oxidizing dopamine bound to the quantum dot; And (iii) determining the concentration of the dopamine by comparing the fluorescence quenching and the reference fluorescence quenching.

Description

Method for Detecting Dopamine < RTI ID = 0.0 >

In recent years, the easy, and low cost, few studies have been carried out for the production of more various types of biosensors have the advantages of generating the exact signal (APF Turner, Chem. Soc. Rev. 42, 3184 (2013)).

Dopamine (DA) (3,4-dihydroxyphenylethylamine) is one of the most important catechol neurotransmitters. In 1958, Swedish scientist Arivd Carlsson first reported that dopamine is present in high concentrations in the striatum, about 70% of the total brain, and that dopamine is a neurotransmitter in the brain.

The important role of dopamine in hormone, kidney, myocardial and central nervous system functions is well known. Some serious diseases such as Parkinson's disease and epilepsy are associated with dopamine deficiency. Since dopamine concentration is a major marker for biological research and clinical diagnosis, there is a need to produce selective, sensitive and rapid dopamine detection materials.

However, the concentration of dopamine in vivo is very low. For example, the dopamine concentration in the extracellular fluid of the central nervous system is less than 100 nM. Moreover, the dopamine concentration varies widely from 1.0 x 10 ^-7 M to 1.0 x 10 ^-3 M depending on time and location.

The quantum dot is a fluorescent semiconductor nanoparticle having a confined exciton confined in all three directions. Compared with organic fluorescent dyes, quantum dots have promising optical properties and attractive electrochemical properties such as high quantum yield, narrow emission peak, strong signal intensity, and adjustable photoluminescence, It is collecting. Specifically, significant advances have been made in applying quantum dots to biological probes. Due to the small size of the functionalized quantum dot, significant fluorescent quenching by rapid electron energy transfer (EET) to the target molecule surface occurs.

Methods have been developed for direct measurement of dopamine, including flow-injection analysis, spectrophotometry, high performance liquid chromatography (HPLC), transistor-based sensing, and electrochemical detection. The emergence of nanotechnology has led to the development of new dopamine detection methods using nanomaterials. For example, Ganguly et al. Produced a dopamine sensor based on silver nanoparticles (M. Ganguly, C. Mondal, J. Jana, A. Pal, and T. Pal, Langmuir 30, 4120 (2014) was produced dopamine sensor of the carbon nanotube-based (RE Sabzi, K. Rezapour and N. Samad, J. Serb Chem Soc 75, 537 (2010)...), Zhao et quantum dots of dopamine-enhanced chemiluminescence detection (QD-enhanced chemiluminescence detection) (Y. Zhao, S. Zhao, J. Huang, and F. Ye, Talanta 85, 2650 (2011)). However, these prior art techniques use two-step detection based on surface modification of nanomaterials.

In the present invention, a method for detecting an in situ dopamine using a carboxyl CdSe / ZnS quantum dot is disclosed. Dopamine is conjugated to the quantum dots using a crosslinking agent such as 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and sulfo-N-hydroxysuccinimide. Detect dopamine in situ through fluorescence quenching of the quantum dots by dopamine.

It is an object of the present invention to provide a method of preparing a dopamine-containing solution, comprising: (i) contacting a core / shell quantum dot with a dopamine-containing solution using a crosslinking agent; (ii) detecting fluorescence extinction of the quantum dot after oxidizing dopamine bound to the quantum dot; And (iii) obtaining the concentration of the dopamine by comparing the fluorescence extinction degree and the reference fluorescence extinction coefficient.

That is, the present invention provides a simple and easy method for detecting the concentration of dopamine present in a trace amount in a sample through fluorescence quenching of a quantum dot.

The above-described object of the present invention is achieved by a process for preparing a dopamine-containing solution comprising: (i) contacting a core / shell quantum dot with a dopamine-containing solution using a crosslinking agent; (ii) detecting fluorescence extinction of the quantum dot after oxidizing dopamine bound to the quantum dot; And (iii) obtaining the concentration of the dopamine in comparison with the fluorescence extinction and the reference fluorescence extinction.

As used herein, "fluorescence quenching" means any process that reduces the fluorescence intensity of a substance. A variety of molecular interactions result in the fluorescence quenching. Such molecular interactions include excited-state reactions, molecular rearrangements, energy transfer, ground-state complex formation, and collisional quenching.

In this specification, "electronic energy transfer (EET)" is a mechanism for describing energy transfer between two photosensitive molecules (chromophore). Donor chromophore, initially in an electronically excited state, can transfer energy to a dipole-dipole coupling through a non-radioactive dipole-dipole coupling. Since the efficiency of this energy transfer is inversely proportional to the sixth power of the distance between donor and acceptor, EET is very sensitive to intermolecular distance.

In the process of the present invention, the crosslinking agent may be a mixture of N- (3-Dimethylaminopropyl) -N-ethylcarbodiimide (EDC) and sulfo-N-hydroxysuccinimide (sulfo-NHS).

In this specification, the quantum dot preferably uses a quantum dot having a core / shell structure. The quantum dots are so large in surface area to volume ratio that most of the constituent atoms are exposed on the surface, leaving the atoms or molecular orbits in a completely unbonded form, which can act as a defect site for quenching the fluorescence of the quantum dots. For this reason, a shell of another semiconductor having a wider band gap is grown on the surface of the core to obtain an electromagnetic insulating effect. Moreover, the shell serves to stabilize and enhance the fluorescence emitted by the excited core, preferably passivating the core with a higher band gap than the core, so that the excitation of the quantum dots is confined to the core, Not only protects against oxidation, but also prevents Cd / Se from leaching into the surrounding solution. According to the present invention, preferably, quantum dots of a CdSe / ZnS core / shell structure can be used.

According to the present invention, the size of the core quantum dot may preferably be about 5 nm to about 12 nm. When the diameter is too small or too large, it is difficult to realize the light emission characteristics due to the decrease in stability or it may be difficult to emit light in the desired wavelength range. For example, quantum dots with a core of 3 nm CdSe emit 520 nm light while quantum dots with a core of 5.5 nm CdSe emit 630 nm light, and the emission width is affected by the size distribution.

In the method of the present invention, the core quantum dots include a group II-VI compound, such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, Temple of such HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe including three won small compound, or HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe of Lt; / RTI > GaN, GaN, GaN, GaSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, InN, InS, InSb, , AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, or GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb &Lt; / RTI > SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or SnPbSSe, SnPbSeTe, or SnPbSeTe , SnPbSTe, and the like; Group IV compounds may be selected from single elements such as Si and Ge or these element compounds such as SiC and SiGe.

In addition, the shell portion may be made of any one of ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaAs, GaSb, HgO, HgS, HgSe, HgTe, InAs, InSb, AlAs, AlN, AlP, or AlSb. The thickness of the shell portion may be between 8 nm and 10 nm.

In one embodiment of the present invention, the core / shell quantum dot is a CdSe / ZnS core / shell quantum dot. According to one embodiment of the present invention, a carboxyl group may be introduced on the shell surface of the quantum dot to facilitate bonding with dopamine. The solution containing the CdSe / ZnS core / shell quantum dot is contacted with a substance containing dopamine. At this time, the CdSe / ZnS core / shell quantum dots and dopamine are bonded to each other using EDC and sulfo-NHS as a crosslinking agent to bond the quantum dots to the dopamine. The pH of the binding process between the quantum dot and the dopamine may be 1-13.

After the quantum dot and dopamine are conjugated, dopamine is easily oxidized by oxygen or an electron donor. After the dopamine oxide, o-oxide of dopamine (dopamine oxide) from the quantum dot-a by electron extractor nongi energy transfer to (o -quinone group) the fluorescence intensity of the quantum dots is a quencher. At this time, the fluorescence extinction degree of the quantum dot depends on the dopamine concentration. Thus, the amount of dopamine can be measured by measuring the fluorescence quenching of such dopamine-conjugated quantum dots.

The principle of fluorescence quenching is shown in Fig. First, dopamine is conjugated to the surface of the quantum dots and the dopamine is oxidized to dopamine- o -quinone in an alkaline solution. And the fluorescence intensity of the quantum dots is extinguished by electron transfer from the quantum dots to the o -quinone group of the dopamine oxide. When the dopamine concentration is different, the fluorescence quenching is different. Based on this fluorescence quenching, dopamine can be detected.

More specifically, the fluorescence extinction degree is determined for a pH of 1-13 using a sample for which the concentration of dopamine is known. A reference fluorescence extinction graph is created using the fluorescence extinction data (see FIG. 3H). Thereafter, the pH value is adjusted (for example, pH 9) for an unknown sample of which the dopamine concentration is not known, and then the fluorescence quenching degree for the unknown sample is measured. Finally, the concentration of the unknown sample can be determined by interpolating the pH and fluorescence extinction value of the unknown sample in the reference fluorescence extinction graph (FIG. 3h).

According to the method of the present invention, dopamine can be detected in situ on a nanoscale using a quantum dot-based biosensor. The method of the present invention is very simple and has a very low detection limit, so it can be applied to direct detection of dopamine in vivo.

1 shows the structure of dopamine-coupled quantum dots and the photoluminescence quenching through electron energy transfer.
2 (a) to 2 (g) show the photoluminescence intensity spectra of dopamine-bonded quantum dots with increasing pH in an aqueous solution (a) pH = 1; b = (D) pH = 7; (e) pH = 9; (f) pH = 11; (g) pH = 13) As shown in FIG.
Figures 3 (a) -3 (g) illustrate the dopamine concentration at various external pH conditions (a) 1 nM; (b) 10 nM; (c) 100 nM; (d) 1 μM; (e) 10 μM; FIG. 3 (h) shows the photoluminescence (fluorescence) extinction of quantum dots as a function of pH at the emission peak, and FIG. 3 give.
FIG. 4 is a photoluminescence emission spectrum of the dopamine-conjugated quantum dot one day after dopamine concentration of 10 μM.
5 is a photoluminescence spectrum (pH 9) of a dopamine-bonded quantum dot after the addition of an extra quantum dot.

The present invention can be all accomplished by the following description. The following description should be understood to describe preferred embodiments of the present invention, but the present invention is not necessarily limited thereto.

Example

The CdSe / ZnS carboxyl quantum dots (CdSe / ZnS carboxyl QD) were conjugated with dopamine using the EDC / sulfo-NHS bridging method. The photoluminescence intensity (PL intensity) of the quantum dot was measured in various dopamine concentrations and various pH solutions.

First, 5 μL of a carboxyl CdSe / ZnS quantum dot (QD605-Carboxyl, Invitrogen) and 10 μM EDC (1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride) were dissolved in 100 μL of phosphate buffered saline . After 5 minutes, the mixture was dissolved in 5 mL of deionized water. 5 μM of sulfo-NHS (sulfo-N-hydroxysuccinimide) was added together while changing the dopamine concentration from 1 nM to 1 mM in a 10-fold average interval. The experiment was carried out with the pH of the solution gradually changing from 1 to 13. Fluorescence extinction was investigated using a cubic cell-using spectrofluorometer.

As shown in Fig. 1, dopamine molecules were bonded to the surface of CdSe / ZnS quantum dots. Dopamine is easily oxidized, not only by oxygen, but also by electron donors, especially in alkaline solutions. Due to electron energy transfer, the emission PL intensity of the dopamine-conjugated quantum dot (DA @ QD) is easily quenched. Furthermore, under high alkalinity, DA @ QD fluorescence was strongly quenched as shown in FIG. The photoluminescence intensity before dopamine implantation was normalized based on the intensity of the quantum dot. All experiments (7 total) were carried out with definite pH values.

Figure 2 shows that the fluorescence quenching of the quantum dots is dependent on dopamine concentration. Generally, the photoluminescence intensity of the quantum dot decreases with increasing dopamine concentration. However, as shown in Figure 2 (f), the photoluminescence intensity at 100 μM dopamine was greater than the photoluminescence intensity at 1 mM dopamine, which would be due to the oxidation of dopamine. At pH 13, the highest oxidation of dopamine resulted in more fluorescence emission. Figure 2f also shows that the photoluminescence intensity was more strongly quenched in an alkaline solution in which more dopamine was oxidized and the transfer of excited electrons from the quantum dot was increased and, in turn, stronger fluorescence quenching took place. However, when the pH was greater than 9, fluorescence from oxidized dopamine exceeded fluorescence extinction via electron energy transfer (EET), especially at high dopamine concentrations. Figure 2 (h) shows the normalized degree of fluorescence quenching of the quantum dots as a function of dopamine concentration at the emission peak. At the same dopamine concentration, DA @ QD showed the highest fluorescence extinction at pH 9. That is, the photoluminescence signal for dopamine was more sensitive at pH 9. Figure 3 shows the photoluminescence spectra of the quantum dots as a function of pH under a constant dopamine concentration ((a) 1 nM; (b) 10 nM; (c) 100 nM; (d) 1 uM; (f) 100 [mu] M; and (g) 1 mM). In solutions with various pH values I was set to the photoluminescence intensity of the quantum dot and IQ to the photoluminescence intensity of DA @ QD. Therefore, the fluorescence quenching is defined as (1 - IQ / I). Figure 3 (h) shows the intensity of fluorescence quenching as a function of pH at the emission peak. Under high pH conditions, higher amounts of dopamine were conjugated to the quantum dots. The highest fluorescence extinction of the QDs was about 90% and occurred at 1 mM of dopamine at pH 9. However, the photoluminescence emission peak of DA @ QD was not observed due to the photoluminescence emission of the larger oxidized dopamine at high concentration. pH 9 seemed to be the most suitable condition for detecting dopamine in the range between high concentration (1 mM) and low concentration (1 nM).

4 shows the photoluminescence emission spectrum of DA @ QD after one night. Under acidic conditions, dopamine was not oxidized. At pH 1, a pronounced emission peak belonging to DA @ QD was observed at 605 nm. However, at pH 7 to pH 13, a significant emission peak due to oxidized dopamine appeared at about 480 nm. It is considered that the photoluminescence intensity is quenched by electron energy transfer between DA @ QD and fluorescent dopamine oxide complex.

Experiments were also conducted to demonstrate this assumption. Extra quantum dots were added to the DA @ QD mixture and the photoluminescence spectra were measured after 1 minute and 1 day. The photoluminescence spectrum of this complex is shown in Figure 5 (pH 9). The emission spectrum of DA @ QD, shown in red, showed one peak at 480 nm, which signifies oxidation of dopamine, and another peak at 605 nm by the quantum dot. After the addition of extra quantum dots, the peak at 605 nm immediately improved and the peak at 480 nm remained unchanged, indicating that dopamine was not oxidized. However, after 24 hours, the peak at 605 nm was completely extinguished and the peak at 480 nm improved, which may be due to increased dopamine oxidation by the extra quantum dot. These results show that fluorescence quenching allows DA @ QD to be used as a sensing medium for the detection of pH, oxygen and other oxidizing agents.

It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

(i) contacting a core / shell quantum dot with a dopamine-containing solution using a crosslinking agent;
(ii) detecting fluorescence extinction of the quantum dot after oxidizing dopamine bound to the quantum dot; And
(iii) determining the concentration of the dopamine in comparison with the fluorescence quenching and the reference fluorescence quenching.

The dopamine detection method according to claim 1, wherein the cross-linking agent is 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and sulfo-N-hydroxysuccinimide.

The dopamine detection method according to claim 1, wherein the pH of step (i) is 1-13.

The dopamine detection method according to claim 1, wherein a carboxyl group is present on the surface of the quantum dot.