Nanocomposites, methods of making same, and applications of same for multicolor surface enhanced Raman spectroscopy (SERS) detections

1. A method of making at least one nanocomposite for surface enhanced Raman spectroscopy (SERS) detection of a target of interest, comprising:

forming at least one gold nanorod;

coating a silver layer on an outer surface of the gold nanorod;

assembling a Raman reporter molecule layer on the coated silver layer, wherein the Raman reporter molecule layer comprises Raman reporter molecules that are detectable by the SERS;

coating a thiolated polyethylene glycol (PEG) layer on the assembled Raman reporter molecule layer; and

conjugating the coated thiolated PEG layer with molecules of an antibody to make the at least one nanocomposite,

wherein said forming the at least one gold nanorod comprises:

mixing a first hexadecyltrimethylammoniumbromide (CTAB) solution with a silver nitrate solution to form a first mixture;

adding a first HAuCl 4 to the first mixture to form a second mixture;

adding a first ascorbic acid to the second mixture to form a third mixture;

adding a seed solution to the third mixture to form a fourth mixture; and

centrifuging the fourth mixture to form a first precipitate, wherein the first precipitate comprises the gold nanorod; and wherein the seed solution is prepared by: mixing a second CTAB solution with a second HAuCl 4 to form a fifth mixture; and adding NaBH 4 to the fifth mixture and stirring to form the seed solution;

wherein said coating the silver layer comprises:

dispersing the gold nanorod in a third CTAB solution by sonication to form a sixth mixture;

adding a polyvinylpyrrolidone (PVP) solution and AgNO 3 to the sixth mixture and gently mixing to form a seventh mixture;

adding a second ascorbic acid to the seventh mixture to form an eighth mixture;

adding NaOH solution to the eighth mixture to form a ninth mixture, such that the pH of the ninth mixture is elevated to about pH 9, and a silver ion reduction reaction is initiated; and

centrifuging the ninth mixture to form a second precipitate, wherein the second precipitate comprises the gold nanorod coated with the silver layer.

2. The method of claim 1 , wherein the step of assembling the Raman reporter molecule layer comprises:

dispersing the gold nanorod coated with the silver layer in distilled water to form a tenth mixture;

dissolving the Raman reporter molecule comprising 4-mercaptobenzoic acid (4-MBA), p-aminothiophenol (PATP), p-nitrothiophenol (PNTP), or 4-(methylsulfanyl) thiophenol (4-MSTP), in ethanol to form a reporter solution;

adding the reporter solution to the tenth mixture and stirring to form an eleventh mixture; and

centrifuging the eleventh mixture to form a third precipitate, wherein the third precipitate comprises the gold nanorod coated with the silver layer, and assembled with the Raman report molecule layer.

3. The method of claim 2 , wherein the step of coating the thiolated PEG layer comprises:

dispersing the gold nanorod with the coated silver layer and the assembled Raman reporter layer in thiolated polyethylene glycol acid (HS-PEG-COOH) solution and vigorously stirring to form a twelfth mixture, wherein the HS-PEG-COOH solution comprises about 2 mg/ml HS-PEG and about 2 mM NaCl;

adding thiolated polyethylene glycol (HS-PEG) to the twelfth mixture and keep at about 5° C. overnight to form a thirteenth mixture; and

centrifuging the thirteenth mixture to form a fourth precipitate, wherein the fourth precipitate comprises the gold nanorod coated with the silver layer, assembled with the Raman report molecule layer, and coated with the thiolated PEG layer.

4. The method of claim 3 , wherein the step of conjugating the coated thiolated PEG layer with the molecules of the antibody comprises:

suspending the gold nanorod with the coated silver layer, the assembled Raman reporter layer, and the coated thiolated PEG layer in PBS buffer by sonicating to form a suspending mixture;

adding N-hydroxysuccinimide (NHS) and 1N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) to the suspending mixture and stirring to form a fourteenth mixture;

washing the fourteenth mixture by centrifuging twice using PBS buffer to obtain a fifth precipitate;

dispending the fifth precipitate in PBS buffer to form a fifteenth mixture;

adding molecules of the antibody to the fifteenth mixture and mixing thoroughly to form a sixteenth mixture, wherein the antibody comprises anti-EpCAM, anti-CD44, anti-IGF-1 Receptor β, anti-Keratin 18, or one or more antibodies specific to the target of interest; and

stirring the sixteenth mixture at room temperature to form the at least one nanocomposite.

5. The method of claim 1 , wherein SERS signal corresponding to the at least one nanocomposite is characterized with a predetermined color.

6. The method of claim 1 , wherein the target of interest comprises at least one tumor cell or at least one pathogen.

7. The method of claim 1 , further comprising attaching at least one molecule of interest to the at least one nanocomposite, wherein the at least one molecule of interest is a drug, a growth factor, a protein, or other biologically active molecules.

8. The method of claim 7 , further comprising attaching at least one fluorescent agent to the at least one nanocomposite.

9. A method of making at least one nanocomposite for surface enhanced Raman spectroscopy (SERS) detection of a target of interest, comprising:

forming at least one gold nanorod, comprising:

mixing a first hexadecyltrimethylammoniumbromide (CTAB) solution with a silver nitrate solution to form a first mixture;

adding a first HAuCl 4 to the first mixture to form a second mixture;

adding a first ascorbic acid to the second mixture to form a third mixture;

adding a seed solution to the third mixture to form a fourth mixture; and

centrifuging the fourth mixture to form a first precipitate, wherein the first precipitate comprises the gold nanorod;

wherein the seed solution is prepared by:

mixing a second CTAB solution with a second HAuCl 4 to form a fifth mixture; and

adding NaBH 4 to the fifth mixture and stirring to form the seed solution;

coating a silver layer on an outer surface of the gold nanorod;

assembling a Raman reporter molecule layer on the coated silver layer, wherein the Raman reporter molecule layer comprises Raman reporter molecules that are detectable by the SERS, wherein the Raman reporter molecule layer comprises p-aminothiophenol (PATP), p-nitrothiophenol (PNTP) or 4-(methylsulfanyl) thiophenol (4MSTP);

coating a thiolated polyethylene glycol (PEG) layer on the assembled Raman reporter molecule layer; and

conjugating the coated thiolated PEG layer with molecules of an antibody to make the at least one nanocomposite,

wherein said coating the silver layer comprises:

dispersing the gold nanorod in a third hexadecyltrimethylammoniumbromide (CTAB) solution by sonication to form a sixth mixture;

adding a polyvinylpyrrolidone (PVP) solution and AgNO 3 to the sixth mixture and gently mixing to form a seventh mixture;

adding a second ascorbic acid to the seventh mixture to form an eighth mixture;

adding NaOH solution to the eighth mixture to form a ninth mixture, such that the pH of the ninth mixture is elevated to about pH 9, and a silver ion reduction reaction is initiated; and

centrifuging the ninth mixture to form a second precipitate, wherein the second precipitate comprises the gold nanorod coated with the silver layer.