Opportunities in Melanoma Diagnosis Using Surface Enhanced Raman Scattering Biosensors

In a recent study published in Journal of Physical Chemistry C, researchers demonstrate an approach to detect tyrosinase activity (TYR), an important biomarker for melanoma diagnosis, with the help of an unprecedented surface-enhanced Raman scattering biosensor.

Study: Surface Enhanced Raman Scattering Biosensor Based on Self-Assembled Gold Nanorod Array for Fast and Sensitive Tyrosinase Detection. Image Credit: Africa Studio/Shutterstock.com

The surface-enhanced Raman scattering biosensor, fabricated on a glass chip, was developed on an array of dopamine-operated Au nanorods (Au NR) that function as capture substrates and 4-mercaptophenylboronic acid (4-MPBA) altered silver nanoparticles (Ag NPs). ) formed a surface-enhanced Raman scattering biosensor probe. Since detecting TYR activity in biological samples is essential for clinical melanoma diagnosis, the proposed approach with various advantages of sensitivity, portability, and reproducibility could be useful for melanoma diagnosis.

Tyrosinase and its Role in Melanin Synthesis

Tyrosinase, a type III dinuclear copper-containing metalloenzyme, plays an important role in melanin biosynthesis. As a result, its inhibition can prevent the development of some skin disorders. Also, this characteristic of the human enzyme of melanogenesis indicates a well-rounded catalytic enzyme activity in vivo and catalyzes the hydroxylation of L-3,4-dihydroxyphenylalanine and the oxidation of dopamine (DA) to dopaquinone (DQ). As a result, aberrant TYR expression can lead to skin conditions such as melasma, vitiligo, and the deadliest manifestation of skin cancer, melanoma.

As TYR is an important biomarker for melanoma diagnosis, various methods, including electrochemical techniques, colorimetric methods, high-performance liquid chromatography, and fluorescence, have been tried and tested to detect TYR in biological samples to date.

The inherent limitations of this technique, such as relatively low sensitivity, susceptibility to interference, and exorbitant equipment, make surface-enhanced Raman scattering biosensors a highly desirable alternative approach.

The surface-enhanced Raman scattering biosensor employs a powerful non-destructive ultrasensitive detection technique that uses molecular interactions between molecules adsorbed on the nanometallic plane and the electromagnetic field present in the resonance region.

This study developed a portable surface-enhanced Raman scattering biosensor to detect TYR activity synthesized on Au NR arrays. Effective detection of TYR activity results in a successful diagnosis of melanoma.

Au NR and its Preparation

In order to achieve significant nanorod yields, excellent uniformity, and the least amount of impurities, Au NR was prepared using more advanced methods. Initially, 0.025 mL 10 mM HAuCl₄ solution and 0.1 M CTAB having a volume of 1 mL were combined to make a seed solution. After 30 minutes of stirring, 0.8 mL NaBH . newly produced₄ at 10 mM was added to the mixture.

The resulting seed solution was left untouched at 30°C for two hours. A total of 7 g CTAB and 1.234 g NaOL were mixed in 250 mL H₂O at 50 C to produce a growth solution. 18 mL 4 mM AgNO₃ solution was added when the solution was cooled to 30°C with constant stirring.

After adding 250 mL of 1 mM HAuCl₄ and 90 minutes of stirring, the solution gradually changed from orange to colorless. After stirring for 15 minutes, 2.1 mL of 37 C HCl solution was added. The above growth solution was mixed for 30 seconds with 64 mM AA with a volume of 1.25 mL before being injected with 0.8 mL of gold ore mixture, which was then allowed to stand for 48 hours at 30 °C.

The transfer and compression at the three-phase interface driven by the Marangoni reaction formed the basis for synthesizing the Au NR array.

Successful synthesis of Ag NPs was achieved using the Lee and Meisel method, which includes reduction of AgNO₃ by citrate in the aqueous phase.

TYR Detection in Serum Samples

Serum samples were centrifuged prior to analysis at 1000 rpm for 10 min to collect the supernatant and reduce other substances that would inhibit the detection of TYR in the sample, thereby interfering with a successful diagnosis of melanoma.

A Raman spectrometer with an excitation of 785 nm, a 50X objective lens, and an exposure time of 10 seconds was then used to derive the Raman spectrum.

The TYR solution was mixed with various concentrations of inhibitor and incubated for 15 minutes at 37°C to achieve inhibition. Then, surface-enhanced Raman scattering measurements were performed on this inhibitor-treated TYR solution by introducing a surface-enhanced Raman scattering biosensor.

New Biosensor Effectively Detects TYR Activity

The experimental findings of this work revealed that recovery was in the range of 96.85-98.74% when known amounts of various concentrations of TYR were added to the serum.

The method under study was subsequently applied to screen for TYR inhibitors, and an inverse relationship was determined in which an increase in inhibitor concentrator resulted in weaker TYR activity.

These results suggest that a surface-enhanced Raman scattering biosensor can be used for quantitative analysis of TYR activity, an important biomarker for melanoma diagnosis, and screening of TYR inhibitors.

Conclusion

The advanced portable surface-enhanced Raman scattering biosensor presented in the current work is fabricated on a glass chip and is based on an Au NR array.

This novel approach to detecting TYR activity in biological samples required for preclinical melanoma diagnosis has a competitive advantage over its predecessors due to several advantages, including sensitivity, portability, and reproducibility.

This technique has a wide linear detection range that can effectively assess 0.0001 U/mL of TYR activity without complex nanofabrication. The proposed method also removes the accumulation of nanoparticles and convenient structures, making them the preferred choice for melanoma diagnosis.

Reference

Minling Li et al. (2022) Surface-Enhanced Raman Scattering Biosensor Based on Self-Assembled Gold Nanorod Arrays for Rapid and Sensitive Tyrosinase Detection. Journal of Physical Chemistry C. https://pubs.acs.org/doi/10.1021/acs.jpcc.2c03408

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