阅读说明：本技术 一种高灵敏和双选择性的ctc检测spr传感器及其制备方法 (High-sensitivity and double-selectivity CTC detection SPR sensor and preparation method thereof ) 是由 陈红霞 于 2019-11-05 设计创作，主要内容包括：本发明公开了一种检测CTC的SPR生物传感系统,包括SPR生物传感器、细胞膜功能化的纳米颗粒和叶酸修饰的纳米颗粒,SPR生物传感器包括表面修饰有JUP抗体的免疫芯片,细胞膜功能化的纳米颗粒含有JUP蛋白和叶酸受体,细胞膜功能化的纳米颗粒通过抗原-抗体的相互作用与免疫芯片结合,叶酸修饰的纳米颗粒通过叶酸-叶酸受体的相互作用与细胞膜功能化的纳米颗粒结合。本发明利用细胞膜功能化的金纳米颗粒与叶酸修饰的金纳米颗粒实现双选择性的结合CTC,改善了单一的抗原抗体特异性识别所出现的假阳性问题,检测成本低,操作方便。(The invention discloses an SPR (surface plasmon resonance) biosensing system for detecting CTC (CTC), which comprises an SPR biosensor, cell membrane functionalized nanoparticles and folic acid modified nanoparticles, wherein the SPR biosensor comprises an immune chip with a surface modified with a JUP antibody, the cell membrane functionalized nanoparticles contain JUP protein and folic acid receptors, the cell membrane functionalized nanoparticles are combined with the immune chip through the interaction of an antigen-antibody, and the folic acid modified nanoparticles are combined with the cell membrane functionalized nanoparticles through the interaction of the folic acid-folic acid receptors. The invention realizes the double-selective combination of CTC by utilizing the gold nanoparticles with functionalized cell membranes and the gold nanoparticles modified by folic acid, improves the false positive problem caused by single antigen-antibody specificity identification, and has low detection cost and convenient operation.)

1. An SPR biosensor system for detecting CTC, which is characterized by comprising an SPR biosensor, cell membrane functionalized nanoparticles and folic acid modified nanoparticles,

wherein the content of the first and second substances,

the SPR biosensor comprises an immune chip with a surface modified with a JUP antibody,

the cell membrane functionalized nano-particle contains JUP protein and folate receptor,

the cell membrane functionalized nanoparticles are bound to the immuno chip through antigen-antibody interaction, and the folate-modified nanoparticles are bound to the cell membrane functionalized nanoparticles through folate-folate receptor interaction.

2. The SPR biosensing system of claim 1, wherein the nanoparticles are gold nanoparticles, magnetic nanoparticles or nano-quantum dots.

3. The SPR biosensing system of claim 1, wherein the cell membrane functionalized nanoparticles have a particle size of 40-65nm and the folate-modified nanoparticles have a particle size of 15-30 nm.

4. A SPR sensing method for CTC detection is characterized by comprising the following steps: adding 80-100 mu L of 10-10 mu L of immune chip with surface modified with JUP antibody⁵Cell membrane functionalized nanoparticles per mL cell membrane and 100-120 μ L5-8 μ M folic acid modified nanoparticles, with 30-45min as incubation time, were tested for CTC using SPR instrument at room temperature.

5. The CTC detection SPR sensing method of claim 4, wherein the biochip having the surface modified with the JUP antibody is prepared by:

(1) immersing the chip in a protein connecting agent for reaction for 8-12 hours, after the reaction is finished, putting the chip in a methanol solution for washing for 1 hour, after washing, slightly cleaning the chip by ultrapure water and drying the water on the surface of the chip by nitrogen,

(2) the chip with the protein connecting agent is installed on an SPR instrument, then 100 mu L of 0.905 mu g/mL JUP antibody is added to the surface of the chip, after incubation for 2 hours, the surface of the chip is washed by buffer solution to elute unconnected JUP antibody, in order to avoid nonspecific adsorption on the surface of the chip, the chip is reacted with 0.01mg/mL BSA solution for half an hour, and finally the immune chip with the surface modified with JUP antibody is obtained.

6. The CTC detection SPR sensing method of claim 4, wherein the cell membrane functionalized nanoparticles are prepared by:

(a) obtaining cell membrane fragments: centrifuging the digested cancer cells or whole blood at 1000rpm for 5 minutes, redissolving the resulting pellet in an equal volume of PBS buffer, then sonicating the solution using an ultrasonic cleaning instrument at 42kw for 5 minutes, after sonication, centrifuging the solution at 700g for 10 minutes to obtain a supernatant, redissolving the supernatant in an equal volume of PBS buffer, then centrifuging at 14,000g for 30 minutes, the resulting supernatant being the desired cell membrane fragments,

(b) mixing the supernatant obtained in the step (a) with a pre-prepared nanoparticle solution, wherein the volume ratio of the two solutions is 1: 1, sequentially passing through polycarbonate membranes of 400nm, 200nm and 100nm on a high-pressure extruder, and finally obtaining the cell membrane functionalized nano-particles.

7. The CTC detection SPR sensing method of claim 6, wherein the nanoparticles are gold nanoparticles, magnetic nanoparticles, or nano quantum dots.

8. The CTC detection SPR sensing method of claim 6, wherein the cell membrane functionalized nanoparticles have a particle size of 40-65 nm.

9. The CTC detection SPR sensing method of claim 4, wherein the method of preparing the folate-modified nanoparticle comprises the steps of:

(i) by using 0.1M Na₂HPO₄Preparing a folic acid solution: 50mM NaOH was added to adjust the pH to 7, and 0.1M Na was added₂HPO₄Until the solution is clear, a folic acid solution with a concentration of about 1mM is produced,

(ii) functionalization of nanoparticles by using 1mM newly synthesized folic acid solution: adding 1mM folic acid solution to 5mL of the pre-synthesized nanoparticle solution to obtain 12. mu.M folic acid solution dissolved in 5mL of the nanoparticle solution, stirring in the dark for 20 minutes, centrifuging at 12,000g for 20 minutes to obtain a wine red precipitate, and re-dissolving the wine red precipitate in an equal volume of PBS buffer to finally obtain the folic acid modified nanoparticles.

10. The CTC detection SPR sensing method of claim 9, wherein the nanoparticles are gold nanoparticles, magnetic nanoparticles or nano quantum dots and the particle size of the folate-modified nanoparticles is 15-30 nm.

Technical Field

The invention relates to the field of circulating tumor cell detection, in particular to a gold nano SPR sensor based on cell membrane functionalization and a preparation method thereof.

Background

Circulating Tumor Cells (CTCs) are a class of cells released into the blood system from neoplastic lesions and play a key role in the spread of metastatic cancer. CTCs may reflect the risk of tumor metastasis progression and may facilitate accurate treatment by detecting CTCs in the blood. Thus, detection of CTCs is very important for cancer. Currently, CTCs are enriched and detected primarily based on their biological or physical properties, such as specific proteins on the cell surface, cell size, and charged nature of the cell. Commonly used methods for detection of CTCs include immunomagnetic bead methods and microfluidic technologies. Furthermore, CellSearch, invented by Veridex, is the only commercial product approved by the FDA and CFDA for CTC detection. The principle of the CellSearch assay is to enrich cells over-expressing epithelial cell adhesion molecule (EpCAM) with antibody-coated magnetic beads and detect cells in a whole blood sample by separation by an external magnetic field. However, immunomagnetic bead or microfluidic technologies are both EpCAM-based CTC assay methods, but they fail to detect EpCAM-low expressing cancers. In addition, these methods typically require long pretreatment times, expensive instruments, and high costs, which hamper their clinical application. Due to the limitations of previous assays, there is a need to develop simple, rapid and sensitive assays to detect CTCs.

The Surface Plasmon Resonance (SPR) technology is a leading technology for sensitively detecting the interaction between a ligand on a chip and a target biomolecule, applies the SPR principle to detect the interaction between the ligand on a biosensor chip and an analyte, and is widely applied to various fields. When the light is totally reflected on the surfaces of the prism and the metal film, evanescent waves are formed and enter the light-phobic medium, and certain plasma waves exist in the medium (assumed as a metal medium). Resonance may occur when the two waves meet. When the evanescent wave resonates with the surface plasmon wave, the detected reflected light intensity is greatly reduced. Energy is transferred from photons to surface plasmons, and most of the energy of incident light is absorbed by the surface plasmon waves, causing the energy of reflected light to be drastically reduced. A minimum peak is seen from the reflected light intensity response curve, the corresponding wavelength of the incident light is the resonance wavelength, and the corresponding incident angle theta is the SPR angle. The electrons absorb the light energy, so that the reflected light intensity is greatly reduced at an angle, wherein the angle at which the reflected light completely disappears is the SPR angle. The SPR angle changes with the refractive index of the chip surface, which is proportional to the mass of molecules bound to the gold surface. Thus, specific signals of the interaction between biomolecules can be obtained by dynamic changes of the SPR angle during the biological reaction process. The technology has the advantages of convenient and fast detection process, high sensitivity, wide application range and real-time dynamic detection, becomes an established tool in the research of the interaction of biomolecules, and is used for quickly and sensitively detecting chemical and biological analytes.

In recent years, more and more research has focused on the use of nanoparticles in cancer, particularly for the detection of cancer cells. Gold nanoparticles (AuNPs) have the advantages of large surface area, simple preparation process, stable structure, good biocompatibility, simple surface functionalization and the like, and are widely applied to various biological applications, such as drug delivery, imaging, catalysis, biosensors and the like. At present, common molecules that bind to AuNPs mainly include DNA, RNA, proteins and drugs. Cell membrane coating has received considerable attention due to its wide source, low cost, long cycle time and good biocompatibility. The cells used to extract the membrane mainly include red blood cells, platelets and cancer cells. Cancer cells can provide targets and increase the uptake rate of nanoparticles to cancer cell membrane functionalized AuNPs (M-AuNPs). Sonication can break the entire cell membrane into pieces and disperse specific marker proteins on the cell membrane surface into each piece of membrane. This phenomenon increases the number of targets detected, thereby amplifying the signal. In addition, AuNPs encapsulated in cell membrane fragments can have an amplifying effect on the signal. Therefore, M-AuNPs can be applied to sensitive detection of CTC.

Plakoglobin (JUP), also known as gamma-catenin, is an important component of desmosomes, the main function of which is cell adhesion. Studies by KolligsFT have shown that human overexpression of JUP in normal cells promotes the migration of CTCs, leading to tumor metastasis. Therefore, cancer cell surface overexpressed JUP has been used as a marker protein in sensitive detection of CTCs.

Accordingly, those skilled in the art have been devoted to developing a SPR sensor for detecting M-AuNPs through CTCs with high sensitivity and high specificity.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the technical problem to be solved by the present invention is to improve the sensitivity and specificity of detecting CTCs and to improve the false positive problem arising from the specific recognition by a single antigen antibody during the detection of CTCs.

In order to achieve the above object, the present invention provides an SPR biosensor system for detecting CTCs, which comprises an SPR biosensor, cell membrane functionalized nanoparticles and folate-modified nanoparticles, wherein the SPR biosensor comprises an immunocip modified with a JUP antibody on the surface, the cell membrane functionalized nanoparticles comprise a JUP protein and a folate receptor, the cell membrane functionalized nanoparticles are combined with the immunocip through antigen-antibody interaction, and the folate-modified nanoparticles are combined with the cell membrane functionalized nanoparticles through folate-folate receptor interaction.

Further, the nano-particles are gold nano-particles, magnetic nano-particles or nano quantum dots. Preferably gold nanoparticles.

Furthermore, the particle size of the cell membrane functionalized nano-particles is 40-65nm, and the particle size of the folic acid modified nano-particles is 15-30 nm.

The invention relates to a CTC detection SPR sensing method, which is characterized in that 80-100 mu L of 10-10 mu L of an immune chip with a surface modified with a JUP antibody is added⁵Cell membrane functionalized nanoparticles per mL, 100-120 mu L of 5-8 mu M folic acid modified nanoparticles are added, incubation time is 30-45min, and detection of CTC is performed by using an SPR instrument at room temperature. A further linear equation is: y-62.2 +292x, linear correlation coefficient 0.9722, limit of detection 1 cell/mL.

Further, the immuno chip with the surface modified with the JUP antibody is prepared according to the following method:

(1) immersing the chip in a protein connecting agent for reaction overnight, placing the chip in a methanol solution for washing for one hour after the reaction is finished, slightly cleaning the chip by ultrapure water after washing, and drying the water on the surface of the chip by nitrogen,

(2) the chip with the protein connecting agent is installed on an SPR instrument, then 100 mu L of 0.905 mu g/mL JUP antibody is added on the surface of the chip, after incubation for 2 hours, the surface of the chip is washed by buffer solution to elute unconnected JUP antibody, in order to avoid nonspecific adsorption on the surface of the chip, the chip is reacted with 0.01mg/mL BSA solution for half an hour, and finally the immune chip with the surface modified with JUP antibody is obtained.

Further, the cell membrane functionalized nanoparticles are prepared by the following method:

(a) obtaining cell membrane fragments: centrifuging the digested cancer cells or whole blood at 1000rpm for 5 minutes, redissolving the resulting pellet in an equal volume of PBS buffer, then sonicating the solution using an ultrasonic cleaning instrument at 42kw for 5 minutes, after sonication, centrifuging the solution at 700g for 10 minutes to obtain a supernatant, redissolving the supernatant in an equal volume of PBS buffer, then centrifuging at 14,000g for 30 minutes to obtain a supernatant that is the desired cell membrane fragments,

(b) mixing the supernatant obtained in the step (a) with a pre-prepared nanoparticle solution, wherein the volume ratio of the two solutions is 1: 1, sequentially passing through polycarbonate membranes of 400nm, 200nm and 100nm on a high-pressure extruder, and finally obtaining the cell membrane functionalized nano-particles.

Further, the nano-particles are gold nano-particles, magnetic nano-particles or nano quantum dots.

Further, the particle size of the cell membrane functionalized nano-particles is 40-65 nm.

Further, the preparation method of the folic acid modified nano-particles comprises the following steps:

(i) by using 0.1M Na₂HPO₄Preparing a folic acid solution: 50mM NaOH was added to adjust the pH to 7, and 0.1M Na was added₂HPO₄Until the solution is clear, a folic acid solution with a concentration of about 1mM is produced,

(ii) functionalization of nanoparticles by using 1mM newly synthesized folic acid solution: adding 1mM folic acid solution to 5mL of the pre-synthesized nanoparticle solution to obtain 12. mu.M folic acid solution dissolved in 5mL of the nanoparticle solution, stirring in the dark for 20 minutes, centrifuging at 12,000g for 20 minutes to obtain a wine red precipitate, and re-dissolving the wine red precipitate in an equal volume of PBS buffer to finally obtain the folic acid modified nanoparticles.

Furthermore, the nano-particles are gold nano-particles, magnetic nano-particles or nano quantum dots, and the particle size of the folic acid modified nano-particles is 15-30 nm.

Technical effects

Compared with the prior art, the method can detect the trace target CTC by using a sensitive SPR technology, the used SPR has extremely low detection limit and can detect as low as 1 cell, and the method realizes sensitive detection of the CTC by using a triple means of cell membrane fragments, gold nanoparticles wrapped in cell membranes and folic acid modified gold nanoparticles to achieve a signal amplification effect, so that the SPR angle is obviously increased.

The invention realizes the double-selective combination of CTC by utilizing the gold nanoparticles with functionalized cell membranes and the gold nanoparticles modified by folic acid, improves the false positive problem caused by single antigen-antibody specificity identification, and has low detection cost and convenient operation.

The method is simple and convenient to operate, low in cost and high in specificity and sensitivity.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a TEM image of M-AuNPs of the present invention;

FIG. 2 is a UV spectrum of AuNPs, M-AuNPs and FA-AuNPs according to the present invention;

FIG. 3 is a graph of the particle sizes of AuNPs, M-AuNPs and FA-AuNPs according to the present invention;

FIG. 4 is Zeta potential diagrams of AuNPs, M-AuNPs and FA-AuNPs according to the present invention;

FIG. 5 is a graph of the linear correlation between different cell concentrations and changes in SPR angle of the present invention.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

The gold nanoparticles wrapped by the cell membrane can be replaced by other nanoparticles including magnetic nanoparticles and nano quantum dots so as to realize different detection purposes.

The principle of the invention is as follows: an artificial CTC sample was simulated by overexpressing the spiked human breast cancer cell line MCF-7 with JUP. Prolinker is a calixarene derivative containing-SH, which can be bound to the chip surface by gold-sulfhydryl bonds, and its calixarene cavity can be used to anchor the JUP antibody to the chip surface. Cell membrane-wrapped gold nanoparticles (M-AuNPs) were obtained by compressing cell membrane fragments with AuNPs. In the presence of cancer cells, membrane surface overexpressed JUP proteins and folate receptors can be coated onto AuNPs. M-AuNPs specifically interact with JUP antibodies and folate-functionalized AuNPs (FA-AuNPs). Because the JUP antibody exists on the chip and the M-AuNPs contain JUP, the M-AuNPs can be combined with the surface of the chip through the specific interaction of the antigen and the antibody, the refractive index on the SPR chip can be changed, and the angle change of the SPR is utilized to sensitively detect the CTC. Thus, this M-AuNPs-based strategy can be implemented by dual recognition and multiple signal amplification approaches to achieve efficient and sensitive detection of CTCs. The nano particles wrapped by the cancer cell membrane are used as a means for amplifying SPR signals, and the method provides a new platform for realizing sensitive detection of CTC.

The SPR measurement method for detecting CTC by utilizing the specificity of M-AuNPs and FA-AuNPs comprises the following steps:

(a) the synthesis steps of the M-AuNPs are as follows: to obtain cell membrane debris, the digested cancer cells or whole blood were centrifuged at 1000rpm for 5 minutes, the resulting pellet was reconstituted in an equal volume of PBS buffer, and the solution was then sonicated using an ultrasonic cleaning instrument at 42kw for 5 minutes. After sonication, the solution was centrifuged at 700g for 10 minutes. The supernatant was reconstituted in an equal volume of PBS buffer and then centrifuged at 14,000g for 30 minutes, the resulting supernatant being the desired cell membrane fraction. Mixing the obtained cell membrane fragments with the prepared AuNPs, and sequentially passing through polycarbonate membranes of 400nm, 200nm and 100nm on a high-pressure extruder to obtain cell membrane-coated gold nanoparticles (M-AuNPs). The control group was AuNPs. The results are shown in FIGS. 1-4, and the resulting M-AuNPs were characterized by Dynamic Light Scattering (DLS), Zeta potential and Transmission Electron Microscopy (TEM). The particle size, potential and ultraviolet absorption of the gold nanoparticles before and after cell membrane functionalization are changed, and successful modification of cell membranes is proved.

(b) The synthesis steps of the gold nanoparticles modified by folic acid are as follows: the synthesis procedure of folate modified gold nanoparticles was the same as the reference. First, by using 0.1M Na₂HPO₄A Folic Acid (FA) solution was prepared, 50mM NaOH was added to adjust the pH to 7, and 0.1M Na was added₂HPO₄Until the solution cleared, a solution of FA at a concentration of about 1mM was produced. Next, AuNPs were functionalized by using a 1mM newly synthesized FA solution. A1 mM FA solution was added to 5mL of presynthesized AuNPs to obtain a 12. mu.M FA solution dissolved in 5mL of AuNPs, and stirred in the dark for 20 minutes. After centrifugation at 12,000g for 20 minutes, a wine-red precipitate was obtained and redissolved in an equal volume of PBS buffer. As shown in FIGS. 2-4, the UV absorption peak, particle size and potential of FA-AuNPs were changed compared with AuNPs, thus proving the successful synthesis of FA-AuNPs. Among these, references are: zhao, s.s., Bichelberger, m.a., Colin, d.y., Robitaille, r., Pelletier, j.n.,&Masson,J.F.(2012).Monitoring methotrexate in clinical samples from cancerpatients during chemotherapy with a LSPR-based competitive sensor.Analyst,137(20),4742-4750.

(c) detecting CTC by SPR: the SPR chip is purchased from the market, and the chip type is autolabSPRchip. Firstly, preparing 0.1mM of a Prolinker solution, placing the chip in the Prolinker solution for reaction overnight, placing the chip in a methanol solution for washing for one hour after the reaction is finished, slightly cleaning the chip with ultrapure water after washing, and drying the water on the surface of the chip with nitrogen. Thereafter, the chip with the linker attached thereto was mounted on the SPR instrument. Then, 100. mu.L of 0.905. mu.g/mL JUP antibody was added to the surface of the chip to which the Prolinker was attached. After 2 hours of incubation, the chip surface was washed with buffer to elute the unbound antibody. To avoid non-specific adsorption on the chip surface, the chip was reacted with 0.01mg/mL BSA solution for half an hour. Then, 100. mu.L of 10 was added⁵cells/mL of M-AuNPs. The JUP protein is contained on the surface of the cell membrane and can be specifically recognized by the JUP antibody on the surface of the chip, so that the cell membrane is combined on the surface of the chip. Meanwhile, because FA receptors are over-expressed on the surface of the cancer cell membrane,adding 100 mu L of 6 mu M FA-AuNPs, allowing FA to specifically recognize with FA receptor, binding FA-AuNPs to the surface of the chip, and further amplifying the signal.

Wherein, the adopted CTC cell concentrations are respectively as follows: 10⁵cell/mL, 10⁴cell/mL, 10³cell/mL, 10²cell/mL, 10¹cells/mL

And (3) testing conditions are as follows: SPR measurements at different concentrations of CTCs were performed at room temperature using an SPR meter with 30min as incubation time. As shown in FIG. 2, the change of SPR angle caused by the increase of the concentration of CTC is larger, and the cell concentration and the change of SPR angle show better linear correlation. The linear equation is: y is-62.2 +292x, the linear correlation coefficient is 0.9722, the detection limit is 1 cell/mL, and the detection requirement is met.

The embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made according to the purpose of the invention, and all changes, modifications, substitutions, combinations or simplifications made according to the technical solutions of the present invention shall be equivalent substitution ways, so long as the invention is consistent with the purpose of the present invention, and all the changes belong to the protection scope of the present invention.