A sub-10-nm, folic acid-conjugated gold nanoparticle as self-therapeutic treatment of tubulointerstitial fibrosis.

Nanomedicines for treating chronic kidney disease (CKD) are on the horizon, yet their delivery to renal tubules where tubulointerstitial fibrosis occurs remains inefficient. We report a folic acid-conjugated gold nanoparticle that can transport into renal tubules and treat tubulointerstitial fibrosis in mice with unilateral ureteral obstruction. The 3-nm gold core allows for the dissection of bio-nano interactions in the fibrotic kidney, ensures the overall nanoparticle (~7 nm) to be small enough for glomerular filtration, and naturally inhibits the p38α mitogen-activated protein kinase in the absence of chemical or biological drugs. The folic acids support binding to selected tubule cells with overexpression of folate receptors and promote retention in the fibrotic kidney. Upon intravenous injection, this nanoparticle can selectively accumulate in the fibrotic kidney over the nonfibrotic contralateral kidney at ~3.6% of the injected dose. Delivery to the fibrotic kidney depends on nanoparticle size and disease stage. Notably, a single injection of this self-therapeutic nanoparticle reduces tissue degeneration, inhibits genes related to the extracellular matrix, and treats fibrosis more effectively than standard Captopril therapy. Our data underscore the importance of constructing CKD nanomedicines based on renal pathophysiology.

Generalized Optical Binding for Multiple Assemblies of Nanoparticles under Multiple Laser Beams.

Optical forces enable noncontact manipulation of micro- and nanoscale objects, offering diverse applications. When a laser beam irradiates multiple nanoparticles in a solvent, it induces the formation of an ordered array with a finite distance between particles due to optical binding, which results from the optical force exerted by scattered light. This scattered light extends beyond the irradiation area, facilitating interactions between spatially separated nanoparticle assemblies under multiple laser beams. However, the extension of optical binding in this context remains underexplored. In this study, we propose a concept of generalized optical binding between particle assemblies using two focal laser beams. Under carefully designed conditions, the scattered light between assemblies leads the particles to stable positions and impedes rotational dynamics driven by the circular polarization of the lasers. We demonstrate the fusion and reordering of two hexagonal assemblies, offering a blueprint for creating on-demand particle arrays through laser beam manipulation.

Chiroplasmonic DNA Scaffolded "Fusilli" Structures.

DNA is an ideal template for the design of nanoarchitectures with molecular-like features. Here, we present an optimized assembly strategy for the concatenation of DNA quasi-rings into long scaffolds. Ionic strength, which played a major role during self-assembly, produced the expected high quality only at 15 mM MgCl2. Atomic force microscopy (AFM) characterization showed several micrometer long tubular structures that were used as templates for the positioning of plasmonic nanoparticles (NPs) along a three-dimensional helical path using DNA tethers. As imaged by high-resolution scanning transmission electron microscopy (HR-STEM) and modeled by theoretical calculations, the NPs distributed into a "fusilli" fashion (i.e., a helical pasta shape), displaying chiroptical activity as revealed by a bisignated CD absorption, centered at the plasmon resonance wavelength. The present structures contribute to enrich the ever-developing arena of chiroplasmonic DNA-based nanomaterials and demonstrate that large assemblies are attainable for their future application to develop metamaterials.

Domain-Selective Enzymatic Cross-linking and Etching for Shape-Morphing DNA-Linked Nanoparticle Films.

The highly programmable and responsive molecular recognition properties of DNA provide unparalleled opportunities for fabricating dynamic nanostructures capable of structural transformation in response to various external stimuli. However, they typically operate in tightly controlled environments because certain conditions (ionic strength, pH, temperature, etc.) must be met for DNA duplex formation. In this study, we adopted site-specific enzymatic ligation and DNA-based layer-by-layer thin film fabrication to build shape-morphing DNA-linked nanoparticle films operational in a broad range of environments. The ligated films remained intact in unusual conditions such as pure water and high temperature causing dissociation of DNA duplexes and showed predictable and reversible shape morphing in response to various environmental changes and DNA exchange reactions. Furthermore, domain-selective ligation combined with photoinduced interlayer mixing allowed for the fabrication of unusual edge-sealed double-layered films through midlayer etching, which is difficult to realize by other methods.

Welded Gold Nanoparticle Assemblies Defined Plasmonic Coupling.

Nanoparticle assemblies with interparticle ohmic contacts are crucial for nanodevice fabrication. Despite tremendous progress in DNA-programmable nanoparticle assemblies, seamlessly welding discrete components into welded continuous three-dimensional (3D) configurations remains challenging. Here, we introduce a single-stranded DNA-encoded strategy to customize welded metal nanostructures with tunable morphologies and plasmonic properties. We demonstrate the precise welding of gold nanoparticle assemblies into continuous metal nanostructures with interparticle ohmic contacts through chemical welding in solution. We find that the welded gold nanoparticle assemblies show a consistent morphology with welded efficiency over 90%, such as the rod-like, triangular, and tetrahedral metal nanostructures. Next, we show the versatility of this strategy by welding gold nanoparticle assemblies of varied sizes and shapes. Furthermore, the experiment and simulation show that the welded gold nanoparticle assemblies exhibit defined plasmonic coupling. This single-stranded DNA encoded welding system may provide a new route for accurately building functional plasmonic nanomaterials and devices.

Kink-Controlled Gold Nanoparticles for Electrochemical Glucose Oxidation.

Enzymes in nature efficiently catalyze chiral organic molecules by elaborately tuning the geometrical arrangement of atoms in the active site. However, enantioselective oxidation of organic molecules by heterogeneous electrocatalysts is challenging because of the difficulty in controlling the asymmetric structures of the active sites on the electrodes. Here, we show that the distribution of chiral kink atoms on high-index facets can be precisely manipulated even on single gold nanoparticles; and this enabled stereoselective oxidation of hydroxyl groups on various sugar molecules. We characterized the crystallographic orientation and the density of kink atoms and investigated their specific interactions with the glucose molecule due to the geometrical structure and surface electrostatic potential.

Patterned Gold Nanoparticle Superlattice Film for Wearable Sweat Sensors.

Nanoparticle superlattices are beneficial in terms of providing strong and uniform signals in analysis owing to their closely packed uniform structures. However, nanoparticle superlattices are prone to cracking during physical activities because of stress concentrations, which hinders their detection performance and limits their analytical applications. In this work, template printing methods were used in this study to prepare a patterned gold nanoparticle (AuNP) superlattice film. By adjustment of the size of the AuNP superlattice domain below the critical size of fracture, the mechanical stability of the AuNP superlattice domain is improved. Thus, long-term sustainable high-performance signal output is achieved. The patterned AuNP superlattice film was used to construct a wearable sweat sensor based on surface-enhanced Raman scattering (SERS). The designed sensor showed promise for long-term reliable use in actual scenarios in terms of recommending water replenishment, monitoring hydration states, and tracking the intensity of activity.

Aptamer Clicked Poly(ferrocenylsilanes) at Au Nanoparticles as Platforms with Multiple Function[†].

Aptamers are widely used in biosensing due to their specific sensitivity toward many targets. Thus, gold nanoparticle (AuNP) aptasensors are subject to intense research due to the complementary properties of aptamers as sensing elements and AuNPs as transducers. We present herein a novel method for the functional coupling of thrombin-specific aptamers to AuNPs via an anionic, redox-active poly(ferrocenylsilane) (PFS) polyelectroyte. The polymer acts as a co-reductant and stabilizer for the AuNPs, provides grafting sites for the aptamer, and can be used as a redox sensing element, making the aptamer-PFS-AuNP composite (aptamer-AuNP) a promising model system for future multifunctional sensors. The aptamer-AuNPs exhibit excellent colloidal stability in high ionic strength environments owing to the combined electrosteric stabilizing effects of the aptamer and the PFS. The synthesis of each assembly element is described, and the colloidal stability and redox responsiveness are studied. As an example to illustrate applications, we present results for thrombin sensitivity and specificity using the specific aptamer.

Gold nanoparticle-powered screening of membrane protein-specific lipids from complex lipid mixtures.

Membrane proteins (MPs) are affected by binding of specific lipids. We previously developed a methodology for systematically analyzing MP-lipid interactions leveraging surface plasmon resonance (SPR). In this method, the gold sensor chip surface was modified with a self-assembled monolayer (SAM), which allowed for a larger amount of MP-immobilization. However, the laborious lipid purification step remained a bottleneck. To address this issue, a new strategy has been developed utilizing gold nanoparticles (AuNPs) instead of the gold sensor chip. AuNPs were coated with SAM, on which MP was covalently anchored. The MP-immobilized AuNPs were mixed with a lipid mixture, and the recovered lipids were quantified by LC-MS. Bacteriorhodopsin (bR) was used as an MP to demonstrate this concept. We optimized immobilization conditions and confirmed the efficient immobilization of bR by dynamic light scattering and electron micrographs. Washing conditions for pulldown experiments were optimized to efficiently remove non-specific lipids. A new binding index was introduced to qualitatively reproduce the known affinity of lipids for bR. Consequently, the low-abundant and least-studied lipid S-TeGD was identified as a candidate for bR-specific lipids. This technique can skip the laborious lipid purification process, accelerating the screening of MP-specific lipids from complex lipid mixtures.

Moringa oleifera leaves extract loaded gold nanoparticles offers a promising approach in protecting against experimental nephrotoxicity.

Cisplatin is one of the most important antitumor drugs, however; it has numerous adverse effects like nephrotoxicity which is considered one of cisplatin uses . The study was planned to evaluate the nephroprotective effect of M. oleifera leaves extract loaded gold nanoparticles (Au-NPs) against cisplatin-induced nephrotoxicity in rats. Initially, total phenolic contents (TPC) and the antioxidant activity of the M. oleifera leaves extract were evaluated and recorded 8.50 mg/g and 39.89 % respectively. After that, the dry leaves of M. oleifera were grinded into fine powder and extracted using water extraction system. Then, different volumes (0.5, 1 and 2 mL) of M. Oleifera were blended with constant volume of Au-NPs (1 mL). Both Au-NPs and M. oleifera extract loaded Au-NPs were investigated using transmission electron microscope (TEM) that illustrated the deposition of M. Oleifera onto Au-NPs. The experimental study was performed on seventy male albino rats alienated into seven groups. Group I healthy rats, group II injected with one dose of cisplatin (CisPt), groups from III to VII treated groups received CisPt then received M. Oleifera leaves extract alone and /or Au-NPs with different ratios and concentrations. After the experiment' time, serum urea and creatinine, kidney injury molecule-1 (KIM-1), advanced oxidation protein products (AOPP), monocyte chemoattractant protein-1 (MCP-1), tumor necrotic factor-α (TNF-α), and interleukin-6 (IL-6) were evaluated as markers of renal nephrotoxicity. The kidneys of rats were excised for malondialdehyde (MDA), nitric oxide (NO), and superoxide dismutase (SOD) assessments. Induction of CisPt showed a highly significant disturbance in oxidant/anti-oxidant balance and inducing inflammatory cascades supporting nephrotoxicity, while treatment with M. Oleifera leaves extract, Au-NPs, and the different concentrations of the extract loaded on Au-NPs had a crucial role in attenuating oxidative stress, enhancing antioxidant systems, and reducing inflammatory biomarkers, although the most significant results showed a powerful scavenging activity against nephrotoxicity induced by CisPt was obtained with M. Oleifera leaves extract loaded on Au-NPs with a concentration of 2:1 respectively.

Development of an electrochemical sensitive aptasensor based on a zeolite imidazolate framework-8 and gold nanoparticles for the determination of Staphylococcus aureus bacteria.

Staphylococcus aureus (S. aureus) is one of the most important pathogens that cause illness and food poisoning. In this research, using a glassy carbon electrode (GCE) modified with zeolite imidazolate framework-8 (ZIF 8) and gold nanoparticles (AuNPs), a sensitive electrochemical aptasensor has been made for the detection of the S. aureus bacteria. The morphology of the prepared AuNPs-ZIF 8 nanocomposite has been carefully characterized by means of transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS). In the manufacturing process, the S. aureus aptamer is immobilized on the AuNPs-ZIF 8 surface. Electrochemical impedance spectroscopy (EIS) method has been used for quantitative determination of S. aureus bacteria. The changes in the charge transfer resistance (Rct) of the aptamer due to the change in the concentration of bacteria are considered as the analytical signals. The proposed aptasensor has linear response in the concentration range of 1.5 × 101 to 1.5 × 107 CFU mL-1 of S. aureus bacteria. The detection limit of the method is 3.4 CFU mL-1. Using the developed aptasensor, it is possible to determine S. aureus bacteria in water and milk samples.

Development of Hollow Gold Nanoparticles for Photothermal Therapy and Their Cytotoxic Effect on a Glioma Cell Line When Combined with Copper Diethyldithiocarbamate.

Gold-based nanoparticles hold promise as functional nanomedicines, including in combination with a photothermal effect for cancer therapy in conjunction with chemotherapy. Here, we synthesized hollow gold nanoparticles (HGNPs) exhibiting efficient light absorption in the near-IR (NIR) region. Several synthesis conditions were explored and provided monodisperse HGNPs approximately 95-135 nm in diameter with a light absorbance range of approximately 600-720 nm. The HGNPs were hollow and the surface had protruding structures when prepared using high concentrations of HAuCl4. The simultaneous nucleation of a sacrificial AgCl template and Au nanoparticles may affect the resulting HGNPs. Diethyldithiocarbamate (DDTC) is metabolized from disulfiram and is a repurposed drug currently attracting attention. The chelation of DDTC with copper ion (DDTC-Cu) has been investigated for treating glioma, and here we confirmed the cytotoxic effect of DDTC-Cu towards rat C6 glioma cells in vitro. HGNPs alone were biocompatible and showed little cytotoxicity, whereas a mixture of DDTC-Cu and HGNPs was cytotoxic in a dose dependent manner. The temperature of HGNPs was increased by NIR-laser irradiation. The photothermal effect on HGNPs under NIR-laser irradiation resulted in cytotoxicity towards C6 cells and was dependent on the irradiation time. Photothermal therapy by HGNPs combined and DDTC-Cu was highly effective, suggesting that this combination approach hold promise as a future glioma therapy.

Selection and characterization of ssDNA aptamer targeting Macrobrachium rosenbergii nodavirus capsid protein: A potential capture agent in gold-nanoparticle-based aptasensor for viral protein detection.

The giant freshwater prawn holds a significant position as a valuable crustacean species cultivated in the aquaculture industry, particularly well-known and demanded among the Southeast Asian countries. Aquaculture production of this species has been impacted by Macrobrachium rosenbergii nodavirus (MrNV) infection, which particularly affects the larvae and post-larvae stages of the prawn. The infection has been recorded to cause mortality rates of up to 100% among the affected prawns. A simple, fast, and easy to deploy on-site detection or diagnostic method is crucial for early detection of MrNV to control the disease outbreak. In the present study, novel single-stranded DNA aptamers targeting the MrNV capsid protein were identified using the systematic evolution of ligands by exponential enrichment (SELEX) approach. The aptamer was then conjugated with the citrate-capped gold nanoparticles (AuNPs), and the sensitivity of this AuNP-based aptasensor for the detection of MrNV capsid protein was evaluated. Findings revealed that the aptamer candidate, APT-MrNV-CP-1 was enriched throughout the SELEX cycle 4, 9, and 12 with the sequence percentage of 1.76%, 9.09%, and 12.42%, respectively. The conjugation of APT-MrNV-CP-1 with citrate-capped AuNPs exhibited the highest sensitivity in detecting the MrNV capsid protein, where the presence of 62.5 nM of the viral capsid protein led to a significant agglomeration of the AuNPs. This study demonstrated the practicality of an AuNP-based aptasensor for disease diagnosis, particularly for detecting MrNV infection in giant freshwater prawns.

The presence of uncoated gold nanoparticle aggregates may alter the phase of phosphatidylcholine lipid as evidenced by vibrational spectroscopies.

Spherical structures built from uni- and multilamellar lipid bilayers (LUV and MLV) are nowadays considered not just as nanocarriers of various kinds of therapeutics, but also as the vehicles that, when coupled with gold (Au) nanoparticles (NPs), can also serve as a tool for imaging and discriminating healthy and diseased tissues. Since the presence of Au NPs or their aggregates may affect the properties of the drug delivery vehicle, we investigated how the shape and position of Au NP aggregates adsorbed on the surface of MLV affect the arrangement and conformation of lipid molecules. By preparing MLVs constituted from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in the presence of uncoated Au NP aggregates found i) both within liposome core and on the surface of the outer lipid bilayer, or ii) adsorbed on the outer lipid bilayer surface only, we demonstrated the maintenance of lipid bilayer integrity by microscopic techniques (cryo-TEM, and AFM). The employment of SERS and FTIR-ATR techniques enabled us not only to elucidate the lipid interaction pattern and their orientation in regards to Au NP aggregates but also unequivocally confirmed the impact of Au NP aggregates on the persistence/breaking of van der Waals interactions between hydrocarbon chains of DPPC.

Ultra-sensitive colorimetric detection of SARS-CoV-2 by novel gold nanoparticle (AuNP)-assisted loop-mediated isothermal amplification (LAMP) and freezing methods.

Loop-mediated isothermal amplification (LAMP) is a molecular diagnosis technology with the advantages of isothermal reaction conditions and high sensitivity. However, the LAMP reactions are prone to producing false-positive results and thus are usually less reliable. This study demonstrates a gold nanoparticle (AuNP)-assisted colorimetric LAMP technique for diagnosing SARS-CoV-2, which aims to overcome the false-positive results. The AuNPs were functionalized with E gene probes, specifically tailored to bind to the amplified E-gene LAMP product, using the freezing method. Varied salt concentration and AuNP/probe combinations were tested for the highest visual performance. The experiments were conducted on synthetic SARS-CoV-2 RNA (Omicron variant), as well as on clinical samples. The assay showed an exceptional sensitivity of 8.05 fg of LAMP amplicon mixture (0.537 fg/µL). The average reaction time was ~ 30 min. In conclusion, AuNP-assisted LAMP detection will not identify any potential unspecific amplification, which helps to improve the efficiency and reliability of LAMP assays in point-of-care applications. The freezing method to functionalize the AuNPs with probes simplifies the assay, which can be utilized in further diagnostic studies.

Biofuel cell-based self-powered immunosensor for detection of 17ß-estradiol by integrating the target-induced biofuel release and biogate immunoassay.

A novel biofuel cell (BFC)-based self-powered electrochemical immunosensing platform was developed by integrating the target-induced biofuel release and biogate immunoassay for ultrasensitive 17ß-estradiol (E2) detection. The carbon nanocages/gold nanoparticle composite was employed in the BFCs device as the electrode material, through which bilirubin oxidase and glucose oxidase were wired to form the biocathode and bioanode, respectively. Positively charged mesoporous silica nanoparticles (PMSN) were encapsulated with glucose molecules as biofuel and subsequently coated by the negatively charged AuNPs-labelled anti-E2 antibody (AuNPs-Ab) serving as a biogate. The biogate could be opened efficiently and the trapped glucose released once the target E2 was recognized and captured by AuNPs-Ab due to the decreased adhesion between the antigen-antibody complex and PMSN. Then, glucose oxidase oxidized the glucose to produce a large number of electrons, resulting in significantly increased open-circuit voltage (EOCV). Promisingly, the proposed BFC-based self-powered immunosensor demonstrated exceptional sensitivity for the detection of E2 in the concentration range from 1.0 pg mL-1 to 10.0 ng mL -1, with a detection limit of 0.32 pg mL-1 (S/N = 3). Furthermore, the prepared BFC-based self-powered homogeneous immunosensor showed significant potential for implementation as a viable prototype for a mobile and an on-site bioassay system in food and environmental safety applications.

Energy Transfer-Based Recognition of Membrane Cholesterol by Controlling Intradistance of Linker.

Gold nanoparticles (AuNPs) are good candidates for donor material in energy transfer systems and can easily be functionalized with various ligands on the surface with Au-S bonding. Cyclodextrin (CD) forms inclusion complexes with fluorophores due to its unique structure for host-guest interaction. In this study, we fabricated ßCD-functionalized AuNPs using different lengths of thiol ligands and recognized cholesterol to confirm the energy-transfer-based turn-on fluorescence mechanism. AuNP-ßCD conjugated with various thiol ligands and quenched the fluorescein (Fl) dye, forming ßCD-Fl inclusion complexes. As the distance between AuNPs and ßCD decreased, the quenching efficiency became higher. The quenched fluorescence was recovered when the cholesterol replaced the Fl because of the stronger binding affinity of the cholesterol with ßCD. The efficiency of cholesterol recognition was also affected by the energy transfer effect because the shorter ßCD ligand had a higher fluorescence recovery. Furthermore, we fabricated a liposome with cholesterol embedded in the lipid bilayer membrane to mimic the cholesterol coexisting with lipids in human serum. These cellular cholesterols accelerated the replacement of the Fl molecules, resulting in a fluorescence recovery higher than that of pure lipid. These discoveries are expected to give guidance towards cholesterol sensors or energy-transfer-based biosensors using AuNPs.

Label-Free Biosensor Based on Particle Plasmon Resonance Coupled with Diffraction Grating Waveguide.

Particle plasmon resonance (PPR), or localized surface plasmon resonance (LSPR), utilizes intrinsic resonance in metal nanoparticles for sensor fabrication. While diffraction grating waveguides monitor bioaffinity adsorption with out-of-plane illumination, integrating them with PPR for biomolecular detection schemes remains underexplored. This study introduces a label-free biosensing platform integrating PPR with a diffraction grating waveguide. Gold nanoparticles are immobilized on a glass slide in contact with a sample, while a UV-assisted embossed diffraction grating is positioned opposite. The setup utilizes diffraction in reflection to detect changes in the environment's refractive index, indicating biomolecular binding at the gold nanoparticle surface. The positional shift of the diffracted beam, measured with varying refractive indices of sucrose solutions, shows a sensitivity of 0.97 mm/RIU at 8 cm from a position-sensitive detector, highlighting enhanced sensitivity due to PPR-diffraction coupling near the gold nanoparticle surface. Furthermore, the sensor achieved a resolution of 3.1 × 10-4 refractive index unit and a detection limit of 4.4 pM for detection of anti-DNP. The sensitivity of the diffracted spot was confirmed using finite element method (FEM) simulations in COMSOL Multiphysics. This study presents a significant advancement in biosensing technology, offering practical solutions for sensitive, rapid, and label-free biomolecule detection.

Chrysin-functionalized gold nanoparticles and paclitaxel exhibit synergistic impact on lung cancer cell lines via regulating the AKT/PPAR-ϒ/ß-catenin pathway.

Lung cancer has become progressively widespread, posing a challenge to traditional chemotherapeutic drugs such as platinum compounds and paclitaxel (PTX) owing to growing resistance. Along with that, the chemotherapeutic drugs infer major side effects. The usage of natural compounds as chemosensitizers to boost the efficacy of these chemotherapeutic drugs and minimizing their toxicity is a plausible approach. In our investigation, we employed PTX as the standard chemotherapeutic agent and utilized chrysin-functionalized gold nanoparticles (CHR-AuNPs) to augment its cytotoxicity. Gold nanoparticles were chosen for their inherent cytotoxic properties and ability to enhance chrysin's bioavailability and solubility. Characterization of CHR-AuNP revealed spherical nanoparticles within the nano-size range (35-70 nm) with a stable negative zeta potential of -22 mV, confirmed by physicochemical analyses including UV-visible spectroscopy, Fourier transform infrared (FTIR) spectral analysis, and visual observation of the wine-red coloration. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay cytotoxicity studies demonstrated CHR-AuNP's superior efficacy compared to CHR alone, with synergistic effects observed in combination with PTX, validated by Compusyn software. Morphological changes indicative of apoptosis were more pronounced with combined treatment, corroborated by acridine orange/ethidium bromide (AO/EtBr) staining and Annexin V assays. Furthermore, the combination treatment amplified reactive oxygen species (ROS) production and destabilized mitochondrial membrane potential, while altering the expression of pro-apoptotic and anti-apoptotic proteins. Exploring the mechanistic pathways, we found that the drugs upregulated PPAR-γ expression while suppressing Akt and overexpressing PTEN, thereby impeding the Wnt/ß-catenin pathway commonly dysregulated in lung cancer. This highlights the potential of low-dose combination therapy with PTX and CHR-AuNP as a promising strategy for addressing lung cancer's challenges.

Spike Growth on Patterned Gold Nanoparticle Scaffolds.

This work reports a scaffold-templated, bottom-up synthesis of 3D anisotropic nanofeatures on periodic arrays of gold nanoparticles (AuNPs). Our method relies on substrate-bound AuNPs as large seeds with hemispherical shapes and smooth surfaces after the thermal annealing of as-fabricated particles. Spiky features were grown by immersing the patterned AuNPs into a growth solution consisting of a gold salt and Good's buffer; the number and length of spikes could be tuned by changing the solution pH and buffer concentration. Intermediate structures that informed the growth mechanism were characterized as a function of time by correlating the optical properties and spike features. Large-area (cm2) spiky AuNP arrays exhibited surface-enhanced Raman spectroscopy enhancement that was associated with increased numbers of high-aspect-ratio spikes formed on the AuNP seeds.