Duplexed DNA mediated nanogap nanoparticles for SERS-based Biosensors

다국어 초록 (Multilingual Abstract)

Gold nanoparticles (AuNPs) based plasmonic nanoparticles have been widely studied due to their excellent optical properties and their applications in catalysis, imaging, and biosensing. In particular, structures incorporating plasmonically enhanced nanogaps effectively amplify surface-enhanced Raman scattering (SERS) signals by generating localized electromagnetic field concentrations “hot spots”. These SERS enhancement effects are closely related to the size, shape, and assembly precision of the nanoparticles, highlighting the importance of precise nanostructure control.
DNA has been extensively used for nanoparticle functionalization owing to its programmability and specific binding properties. Recently, DNA modified with phosphorothioate (PS) linkages has been reported to improve binding affinity to gold nanoparticles and enhance colloidal stability.
In this study, we propose a novel assembly strategy for the precise control of nanogap formation between gold nanoparticles using double-stranded DNA (dsDNA) modified with PS groups at strategic positions. Through this approach, nanogap size and plasmonic coupling are optimized to enhance SERS signal amplification. Ultimately, this study aims to establish a highly stable and reproducible AuNP-based SERS biosensor platform, contributing to the development of highly sensitive molecular detection technologies.

국문 초록 (Abstract)

금(Au) 기반 플라즈몬 나노입자는 우수한 광학적 특성으로 인해 촉매, 이미징 및 바이오센싱 분야에서 폭넓게 연구되어 왔다. 특히 플라즈몬 증폭 나노갭을 포함하는 구조는 국소적인 전자기장 집중(hot spot)을 형성하여 표면 증강 라만 산란(SERS) 신호를 효과적으로 증폭시킨다. 이러한 SERS 증강 효과는 나노입자의 크기, 형태 및 조립 정밀도와 밀접하게 관련되어 있으며, 정밀한 나노구조 제어의 중요성을 시사한다.
DNA는 프로그램 가능성과 특이적 결합 특성으로 인해 나노입자 기능화에 널리 활용되어 왔으며, 최근에는 포스포로티오에이트(PS) 결합으로 변형된 DNA가 금 나노입자에 대한 결합력 및 콜로이드 안정성을 향상시키는 것으로 보고되고 있다.
본 연구에서는 전략적인 위치에 PS 그룹을 도입한 이중가닥 DNA(dsDNA)를 이용하여 금 나노입자 간 나노갭 형성을 정밀하게 제어하는 새로운 조립 전략을 제안한다. 본 방법을 통해 나노갭 크기와 플라즈몬 결합을 최적화하고, 그에 따른 SERS 신호 증강 효과를 향상시키고자 한다. 궁극적으로 본 연구는 높은 안정성과 재현성을 갖는 AuNP 기반 SERS 바이오센서 플랫폼을 구축하여 고감도 분자 검출 기술 개발에 기여하는 것을 목표로 한다.

목차 (Table of Contents)

• 1 ABSTRACT. 1
• 2 INTRODUCTION. 2
• 2.1 PLASMONIC NANOPARTICLES AND LOCALIZED SURFACE PLASMON RESONANCE (LSPR). 5
• 2.2 RAMAN SCATTERING. 11
• 2.3 SURFACE ENHANCED RAMAN SPECTROSCOPY (SERS). 17
• 2.4 IMPACT OF DNA AS LIGAND ON INTRA NANOGAP FORMATION. 24
• 2.5 PHOSPHOROTHIOATE (PS) MODIFICATION AS AN ALTERNATIVE FOR AUNP CONJUGATION. 28
• 3 EXPERIMENTAL SECTION 32
• 3.1 CHEMICALS AND MATERIALS. 32
• 3.2 INSTRUMENTATION. 33
• 3.3 EXPERIMENTAL SCHEME. 33
• 3.3.1 FORMATION OF DNA DOUBLE HELIX. 33
• 3.3.2 FUNCTIONALIZATION OF 40 nm AuNPs WITH PHOSPHOROTHIOATE DNA. 34
• 3.3.3 SHELL FORMATION AND THICKNESS OF AuNP:PS dsDNA CONJUGATES. 35
• 3.3.4 FUNCTIONALIZATION AND FORMATION OF AuNP:PS dsDNA:MB@Au. 36
• 4 RESULTS AND DISCUSSION. 40
• 4.1 SELECTION OF DNA SEQUENCE. 40
• 4.2 CHARACTERIZATION OF dsDNA FORMATION BY UV–Vis SPECTROSCOPY. 43
• 4.3 CONDITIONS FOR THE SYNTHESIS OF AuNP:PS dsDNA:MB@Au. 46
• 4.3.1 OPTIMIZATION OF NaCl CONCENTRATION AND INCUBATION CONDITIONS. 46
• 4.3.2 EFFECT OF AuNP:PS dsDNA RATIO ON COLLOIDAL STABILITY AND SHELL FORMATION. 51
• 4.3.3 EVALUATION OF METHYLENE BLUE (MB) CONCENTRATION FOR AuNP:PS dsDNA:MB@Au CORE–SHELL FORMATION. 56
• 4.4 DNA MEDIATED FORMATION OF AuNP:PS dsDNA:MB@Au CORE–SHELL NANOPARTICLES. 60
• 4.4.1 Ratio 1:1000 61
• 4.4.2 Ratio 1:2000 66
• 4.4.3 Ratio 1:5000 70
• 4.4.4 COMPARATIVE ANALYSIS ACROSS RATIOS. 74
• 5 CONCLUSION. 78
• 6 REFERENCES. 81