Comparative study of gold nanoparticle synthesis routes using sodium citrate and tannic acid: Evaluation of biomedical applicationsAbstract
Gold nanoparticles (AuNPs) exhibit remarkable optical, electrical, and biological properties, making them highly desirable for biomedical applications. This study compared two distinct AuNPS synthesis routes: the Turkevich method, employing sodium citrate as a reducing agent, and a green synthesis method using tannic acid. UV-Vis spectroscopy and FTIR confirmed successful synthesis, revealing spherical, monodisperse AuNPs. Sodium citrate-synthesized AuNPs exhibited an average diameter of 19.40 ± 2.34 nm and demonstrated lower cytotoxicity, with cell viability of approximately 85.89%, suggesting suitability for drug delivery. In contrast, tannic acid-synthesized AuNPs had an average diameter of 9.56 ± 2.66 nm and reduced cell viability to approximately 40.56%, making them potential candidates for targeted anticancer therapies. Antibacterial assays revealed no significant activity for either type of AuNPs against tested bacteria, consistent with studies indicating that higher concentrations or larger particle sizes may be necessary for antibacterial effects. These findings emphasize the importance of tailoring AuNPs properties based on their intended biomedical use, with implications for enhancing sustainability and functionalization approaches.
Key words
Gold nanoparticles; green synthesis; cytotoxicity; biomedical applications
INTRODUCTION
Gold nanoparticles (AuNPs) have gained prominence in research because their unique chemical and physical properties, primarily determined by surface atoms, interact with ligands similarly to corresponding metal complexes (Toma et al. 2010). AuNPs possess optical and electrical properties, high stability, good biocompatibility, and antimicrobial activity, making them applicable as catalysts, biosensors, and biological markers in drug delivery and cancer treatment (Coura et al. 2017). Studies indicate that AuNPs are among the most biologically viable options for radiotherapy due to their lower toxicity compared with other metals (Dos Santos & Nicolucci 2018).
AuNPs are used in various applications, such as immobilizing thiolated DNA probes on electrodes, because they retain biological activity and electrical conductivity (Dos Santos et al. 2020). They are also used in plasmonic sensors, where the distance between gold nanoparticles influences the sensors’ response (Santos et al. 2017). Localized surface plasmon resonance in AuNPs is also an important property and is explored in solar cells (Ghobashy et al. 2024, Santos et al. 2016).
Therefore, AuNPs play a key role in the biomedical field, mainly because of their unique properties and versatility. These nanoparticles have been widely used in this area due to their superior biocompatibility, unique physicochemical properties, and ease of functionalization (Wang et al. 2022). Their large surface-to-volume ratio, stability, excellent biocompatibility, low toxicity, and functionality make them highly attractive for biomedical applications (Pedziwiatr-Werbicka et al. 2018).
Researchers can incorporate these nanoparticles into larger structures, such as polymeric nanoparticles or liposomes, to enhance diagnostic applications, improve drug delivery, and add imaging labels (Dykman et al. 2025, Mieszawska et al. 2013). Functionalization of gold nanoparticles enables targeted delivery to various cell types, bioimaging, gene delivery, drug delivery, and other therapeutic and diagnostic applications (Alex & Tiwari 2015). Studies have demonstrated that AuNPs can increase the sensitivity and specificity of certain clinical diagnostics (Li et al. 2023).
Gold nanoparticles play a fundamental role in the biomedical field, offering a wide range of therapeutic and diagnostic applications due to their unique properties and functionalization capabilities. Gold nanoparticles have been produced using chemical reducers that can be natural, resulting in nanostructures with predominantly spherical morphology and diameters ranging from 10 nm to 40 nm (Da Silva & Rodriguez 2019). These nanostructures have interesting properties for chemical and biological applications, being widely used in various research areas due to their unique characteristics and versatility (Ghoreishi & Mortazavi-Derazkola 2025).
The synthesis route using tannic acid differs from the Turkevich route in the reducing and stabilizing agents used. In the Turkevich route, sodium citrate is a reducing and stabilizing agent in synthesizing gold nanoparticles, allowing precise particle size control in 10 to 150 nm (Xia et al. 2010). On the other hand, the synthesis route using tannic acid as a reducing agent leads to the formation of nanoparticles (Gangula et al. 2011).
The Turkevich route is known for its simplicity and efficiency in producing controlled-sized gold nanoparticles. It is widely used because of its environmentally friendly procedure and flexibility in adjusting particle size. However, the synthesis route using tannic acid may offer specific advantages, such as the ability to use plant extracts as sources of reducing agents, making the process more sustainable and eco-friendlier, thus known as the green route (Anzola et al. 2025, Gangula et al. 2011, Milaneze et al. 2016).
A comparative study was conducted between two gold nanoparticle synthesis routes: one using sodium citrate as a reducing agent, known as the Turkevich route, and the other using tannic acid as a reducing agent. Although tannic acid is a main active component in plant extracts commonly used in green synthesis, we used commercially available tannic acid in this study. The study aims to evaluate which approach offers better properties and applicability for the proposed biomedical investigations, particularly regarding the efficacy, stability, and safety of the resulting nanoparticles. The nanoparticles from each method will be analyzed for size, morphology, and toxicity to identify the most suitable synthesis strategy for biological applications.
MATERIALS AND METHODS
Material
The materials used in this study, including those for gold nanoparticle (AuNP) synthesis and cytotoxicity tests, were high-purity reagents. For the synthesis of AuNPs, chloroauric acid (HAuCl4) (Sigma Aldrich/16903-35-8) was used as the gold precursor, along with tannic acid (Synth/A2012.01.AF) and sodium citrate (Sigma Aldrich/6132-04-3), which acted as reducing agents in the different synthesis routes. To clean the glassware, aqua regia was prepared from hydrochloric acid (Sigma Aldrich/7647-01-0) and nitric acid (Sigma Aldrich/7697-37-2) in a 3:1 ratio. All procedures used distilled and deionized water to ensure purity and avoid sample contamination. A lung epithelial cell line (MRC-5) was used to evaluate and compare the viability of the AuNPs. The cell line belongs to the cell bank of the (RPT11H) Biotechnological Compounds Bioassay Platform - ILMD/FIOCRUZ.
Methods
Synthesis of AuNPs – Turkevich Method
Solutions of 35 µL of commercial HAuCl4 (30 % w/w in dilute HCl, 1.4 mol·L-1) in 100 mL of distilled water and 2 g of sodium citrate in 25 mL of distilled water were prepared. The chloroauric acid solution was transferred to a round-bottom flask and heated to 90°C. After reaching this temperature, 5 mL of the sodium citrate solution was added. The system was refluxed for 30 minutes.
Synthesis of AuNPs – Using Tannic Acid
A solution was prepared by diluting 35 µL of commercial HAuCl₄ (30% w/w in dilute HCl, 1.4 mol·L-1) in 100 mL of distilled and deionized water. The solution was stirred in a round-bottom flask until a homogeneous mixture formed. The mixture was then heated to 50°C, and a tannic acid solution (7 × 10-4 mol·L-1) was added dropwise. The system was maintained under reflux for 30 minutes.
Characterizations
UV-Vis spectrophotometer
UV–Vis characterization of the AuNPs was performed using a UV–Vis spectrophotometer (Evolution 220 – Thermo Scientific, equipped with a double beam and a fiber optic probe). Quartz cuvettes with a 1 cm optical path were used. The measurements were carried out in aqueous solution, using distilled water as the reference. Prior to analysis, the colloids were diluted by mixing 200 µL of the colloidal suspension with distilled water to a final volume of 2 mL.
Chemical characterization by FTIR spectroscopy
The Fourier transform infrared (FTIR) spectra were obtained using a Thermo Scientific Nicolet iS20, with 128 scans. The spectra were collected between 4000 and 650 cm−1, with a resolution of 8 cm−1.
Transmission Electron Microscope
The TEM images were obtained using the Jeol JEM-1400 Flash Transmission Electron Microscope (TEM) series, operated at a voltage of 120 kV. Following Farias et al. (2024), diameter measurements were obtained using ImageJ image-processing software, recording 100 nanoparticle diameters.
Antimicrobial Susceptibility Test (AST)
The bacterial strains used in this study belong to the Biotechnological Bioassays Platform (RPT11H) of the Leônidas and Maria Deane Institute (ILMD) – Oswaldo Cruz Foundation (FIOCRUZ), Manaus-AM, Brazil. Table I describes the Gram-negative bacteria used in the assay.
The AuNPs solutions synthesized with sodium citrate and tannic acid were designated A and B, respectively. A volume of 50 µL from each solution (A and B) was applied to the agar surface. The bacterial strains were initially cultured in 3 mL of Brain Heart Infusion (BHI) broth (HIMEDIA) and subsequently diluted in culture medium to match the 0.5 McFarland standard (1.5 × 108 CFU/mL). All experiments were conducted in triplicate to ensure reproducibility.
Antibacterial activity was determined using the agar diffusion method, as described by Grove and Randall (Grove & Randall 1955), with modifications according to Bastos et al. (2022). Müller-Hinton agar (MHA) (HIMEDIA) was used for the tests. After sterilization, 15 mL of MHA medium was distributed into sterile 90 x 15 mm Petri dishes. The plates were left at room temperature until solidified. The streaking process began immediately after preparing the inoculum. A sterile swab was inserted into each tube containing a different inoculum. After this procedure, the target microorganisms were seeded over the entire surface of the plate in three directions, rotating the plate approximately 60° to ensure uniform inoculum distribution. Next, add 50 µL of A and B solutions dropwise to the surface until the medium absorbs them. Afterward, place membranes approximately 10 to 15 mm in diameter on the MHA surface. The plates were incubated at 37°C for 24 hours. After incubation, the inhibition zones were measured.
In Vitro Cell Viability and Cytotoxicity Assay
A human normal lung epithelial cell line (MRC-5) was used to evaluate and compare AuNP viability. Cells were cultured in Dulbecco’s Modified Eagle Medium (DMEM), supplemented with 10% inactivated fetal bovine serum. Cells were plated at 0.5 × 104 cells/well in 96-well plates and treated with 100 µL of AuNPs. The plates were incubated at 37°C in 5% CO2 for 48 and 72 hours. After incubation, add 10 µL of Alamar Blue® (Sigma-Aldrich, Brazil) (0.4%) to each well, then incubate for three periods (1, 2, and 3 hours). Readings were performed on a microplate reader (GloMax® Explorer) at an emission wavelength of 580-640 nm and an excitation wavelength of 520 nm. Cell growth served as the positive control, and doxorubicin, tested at the same concentrations, served as the death control. A fluorescence control was performed at the same concentrations (AuNP + medium). The percentage of cell viability was calculated relative to the cell control, and the cytotoxic concentration for 50% (CC50) was determined by nonlinear regression analysis using GraphPad Prism 8.0.1.
RESULTS AND DISCUSSION
Synthesis of AuNPs and UV-Vis Analysis
Both synthesis routes for gold nanoparticles, using sodium citrate and tannic acid as reducing agents, efficiently produced the nanoparticles. The resulting solutions (see Figure 1a) exhibited colors consistent with those reported in the literature, indicating the successful formation of AuNPs. Spherical AuNPs are typically observed in a range of colors, including brown, orange, red, purple, and blue (Subara & Jaswir 2018). Particle aggregation influences solution color, and specific wavelength absorption in colloidal AuNPs produces vibrant colors due to surface plasmon resonance (SPR).
a) Illustration of the AuNPs solutions, and b) UV-Vis spectra collected for AuNPs synthesized with sodium citrate and tannic acid.
The UV-Vis spectra (Figure 1b) of the AuNPs synthesized via both routes exhibited a characteristic peak in the specific region between 520 and 550 nm (Alex & Tiwari 2015). This absorbance peak is consistent with the literature and indicates the SPR phenomenon, confirming successful AuNP formation. However, since the absorption of AuNPs depends on the particle size (Khan et al. 2020), in this experiment, the spherical AuNPs synthesized with sodium citrate registered an absorbance peak at a higher wavelength (around 533 nm), while the AuNPs synthesized with tannic acid were approximately at 529 nm.
Transmission Electron Microscopy - TEM
In Figure 2a, the TEM micrograph of AuNPs synthesized via the Turkevich method reveals a spherical and monodisperse morphology with minimal aggregation. Figure 2b presents the statistical analysis of particle diameters, indicating an average size of 19.8 nm with a standard deviation of 2.34 nm. The recorded minimum and maximum diameters were 14.1 nm and 23.3 nm, respectively. This synthesis method is known for its simplicity, speed, and reproducibility, yielding highly stable spherical nanoparticles with small size dispersion (10–25 nm range) and excellent potential for functionalization with various organic ligands (Zan & Zan 2022).
AuNPs obtained with sodium citrate: a) TEM image and b) Statistical analysis of the diameter AuNPs obtained with tannic acid: c) TEM image and d) Statistical analysis of the diameter.
Regarding the AuNPs synthesized using Tannic Acid, it is observed that the AuNPs also exhibit a spherical and monodisperse morphology (Figure 2c). However, the particle size is smaller than the AuNPs synthesized with sodium citrate. Similar characteristics were reported by Khan et al. (2020), who conducted a study on green synthesis using plant extracts to reduce metal ions. According to the statistical analysis of the diameter of the AuNPs synthesized with tannic acid (Figure 2d), the particles have an average diameter of 9.56 nm and a standard deviation of 2.66 nm. The maximum and minimum diameters recorded were 5.08 nm and 18.28 nm, respectively.
FTIR of AuNPs Solution
Figure 3 presents the FTIR spectra of AuNP solutions obtained by both routes. In the spectrum of AuNPs synthesized with sodium citrate, a broad absorption band at 3443 cm-1 indicates the presence of the hydroxyl functional group (-OH), derived from the aqueous solvent used in synthesis (Milli-Q water). The peak at approximately 1736 cm-1 is characteristic of the carbonyl group (-C=O), while the signal at 1420 cm-1 corresponds to the bending of -OH in carboxylic acids, such as β-ketoglutaric acid, a byproduct of the reaction between sodium citrate and chloroauric acid (Moraes Segundo et al. 2021).
FTIR spectra of AuNPs solutions synthesized using a) sodium citrate and b) tannic acid as reducing agents.
In the FTIR spectrum of AuNPs synthesized with tannic acid, the presence of phenol, carboxylic acid, and carbonyl groups can be observed, originating from tannic acid itself, which plays a role in reducing AuNPs. Absorption bands at 3370 cm-1, attributed to -OH stretching, at 1670 cm-1, representing the carbonyl group (C=O), and at 1431 cm-1, associated with -OH bending in carboxylic acids, confirm the presence of aromatic compounds and phenol-derived structures (Zan & Zan 2022). This spectroscopic analysis validates the expected chemical functionality for both synthesis routes. Hydroxyl and carboxyl groups in the sodium citrate synthesized AuNPs are consistent with compounds typically formed in carboxylate reactions. In contrast, the tannic acid synthesized AuNPs display functional groups associated with aromatic and phenolic structures. These findings confirm successful AuNP reduction and stabilization through their respective synthesis methods while highlighting distinct surface properties that may be leveraged for diverse biomedical applications.
Antimicrobial Susceptibility Test (AST)
The criterion for determining antimicrobial activity was an inhibition zone of 5 millimeters or greater (Al-Hebshi et al. 2006, Ostrosky et al. 2008). Table II describes the evaluation criteria for antimicrobial activity using the agar diffusion method.
The AuNPs solutions synthesized with sodium citrate and tannic acid were identified as substances A and B, respectively. Evaluation showed that both substances had no antibacterial activity against the tested bacteria (Escherichia coli, Shigella, and Pseudomonas aeruginosa) (Figure 4). For sodium citrate-synthesized AuNPs, with an average diameter of 19.8 nm, and tannic acid-synthesized AuNPs, with an average diameter of 9.56 nm, the concentrations used were 2,5 μg/mL for both solutions. These results align with Chatterjee et al. (2011), who studied the effects of AuNPs on E. coli growth using various concentrations (25 μg/mL, 50 μg/mL, 75 μg/mL, and 100 μg/mL) of gold nanoparticles. No significant differences in bacterial growth curves were observed, suggesting that AuNPs at these concentrations do not exhibit notable toxicity for bacterial systems.
Antimicrobial assay of AuNPs in bacterial cultures: a) Escherichia coli (EAEC), b) Escherichia coli (EIEC), c) Shigella flexneri, and d) Pseudomonas aeruginosa.
Similarly, Hernández-Sierra et al. (2008) found that 80 nm AuNPs showed antibacterial activity against S. aureus only at very high concentrations, requiring 197 μg/mL to observe this effect. These findings suggest that, at lower or moderate concentrations, AuNPs may not show toxic effects on bacteria, supporting the idea that their antibacterial activity is linked to concentration and possibly size. The lack of antibacterial activity observed in the AuNPs from this study, with sizes and concentrations differing from those reported in the literature, can be attributed to their biocompatibility and low toxicity. These characteristics make AuNPs promising for biomedical applications, such as drug delivery systems, though they may not be effective at lower concentrations for directly combating pathogens.
In vitro cell viability and cytotoxicity assay
The AuNPs solutions synthesized with sodium citrate and tannic acid were tested on the mrc5 cell line, and the results are presented in Figure 5a), which displays the viability and cytotoxicity compared to the control of viable cells (100%).
Evaluation of the viability and cytotoxicity of AuNPs synthesized with Sodium Citrate and Tannic Acid.
The analysis revealed that both nanoparticle solutions reduced cell viability compared to the viable cell control (100%). Specifically, AuNPs synthesized with sodium citrate reduced cell viability to approximately 40.56%, while AuNPs synthesized with tannic acid maintained significantly higher viability, around 85.89%.
Gold nanoparticles synthesized with tannic acid are not classified as cytotoxic, since the literature establishes that a substance is considered cytotoxic only when cell viability falls below 50% (Corrêa 2022). In the present study, cell viability remained above this threshold, reinforcing the low-toxicity profile and biocompatibility of these nanoparticles, making them promising for biomedical applications that require cellular safety.
In contrast, sodium citrate synthesized gold nanoparticles exhibited higher cytotoxicity. Although undesirable in some contexts, this behavior can be therapeutically advantageous in anticancer strategies, where a controlled level of toxicity promotes selective tumor-cell death. Therefore, despite their cytotoxicity, citrate-stabilized nanoparticles may suit applications that require more aggressive action against malignant cells.
The higher cytotoxicity observed in AuNPs produced via the Turkevich route may relate to both residual citrate and average particle diameter. Nanoparticle size and the high surface-area-to-volume ratio strongly influence their reactivity and interaction with the biological environment, potentially intensifying toxic effects (Dorić et al. 2017, Zhang et al. 2008).
Recent research shows that AuNPs of approximately 10 nm exhibit cytotoxicity around 55%, whereas 20 nm particles exhibit lower toxicity, around 40%. In this study, citrate-synthesized AuNPs had an average size of 19.8 nm but showed higher-than-expected cytotoxicity (approximately 60%), suggesting additional influences such as residual stabilizer. In contrast, AuNPs synthesized with tannic acid exhibited lower cytotoxicity despite their smaller average diameter (9.58 nm) (Wang et al. 2022, Bastos et al. 2022).
CONCLUSIONS
In this study, AuNPs were synthesized using two routes: the Turkevich route with sodium citrate and the tannic acid route. Both synthesis methods effectively produced AuNPs, as confirmed by UV-Vis and FTIR analyses, which verified nanoparticle formation and the functional groups present in each solution. The synthesized nanoparticles exhibited spherical and monodisperse morphology. Cell viability assays indicated that AuNPs synthesized with sodium citrate showed no significant cytotoxicity, making them suitable for biomedical applications, such as drug delivery systems. In contrast, AuNPs synthesized with tannic acid showed higher cytotoxicity and demonstrated potential for use in anticancer therapies. Furthermore, the two AuNPs types showed no antibacterial activity at the tested concentrations, aligning with previous studies that suggest higher concentrations or larger nanoparticle sizes are necessary for an antibacterial effect. Thus, we conclude that the choice of synthesis route should consider the specific application, with Turkevich route AuNPs being ideal for drug delivery systems. In contrast, AuNPs synthesized with tannic acid may be better suited for anticancer therapies.
Acknowledgements
We thank Universidade Federal do Amazonas (UFAM), Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
Data availability
References
-
ALEX S & TIWARI A. 2015. Functionalized gold nanoparticles: Synthesis, properties and applications - a review. J Nanosci Nanotechnol 15: 1869-1894. DOI 10.1166/jnn.2015.9718.
» https://doi.org/10.1166/jnn.2015.9718 -
AL-HEBSHI N, AL-HARONI M & SKAUG N. 2006. In vitro antimicrobial and resistance-modifying activities of aqueous crude khat extracts against oral microorganisms. Arch Oral Biol 51: 183-188. DOI 10.1016/j.archoralbio.2005.08.001.
» https://doi.org/10.1016/j.archoralbio.2005.08.001 -
ANZOLA CEA, FARIAS TLS, JÚNIOR MDV, GANDARILLA A, BRITO WR & PAULA MS. 2025. Síntese e caracterização de nanopartículas de prata e ouro: uma abordagem verde. Observ Econ Latinoam 23: e11294. DOI 10.55905/oelv23n9-004.
» https://doi.org/10.55905/oelv23n9-004 -
BASTOS IS ET AL. 2022. Silver tungstate microcrystals and their performance over several clinical multidrug resistant microorganisms. Colloids Surf A Physicochem Eng Asp 647: 129132. DOI 10.1016/j.colsurfa.2022.129132.
» https://doi.org/10.1016/j.colsurfa.2022.129132 -
DORIĆ A, MULAOMEROVIĆ D, FOJNICA A, ALISPAHIĆ B, HALILOVIĆ S & OMANOVIĆ-MIKLIČANIN E. 2017. Development of the method for quantification of amino acid adsorbed on nanoparticle surface. In: Badnjevic A (Ed), CMBEBIH 2017. IFMBE Proceedings, vol 62, p. 171-172. Springer, Singapore. https://doi.org/10.1007/978-981-10-4166-2_27.
» https://doi.org/10.1007/978-981-10-4166-2_27 -
CHATTERJEE S, BANDYOPADHYAY A & SARKAR K. 2011. Effect of iron oxide and gold nanoparticles on bacterial growth leading towards biological application. J Nanobiotechnology 9: 34. DOI 10.1186/1477-3155-9-34.
» https://doi.org/10.1186/1477-3155-9-34 -
CORRÊA DOG. 2022. CITOTOXICIDADE DE NOVAS LIGAS A BASE DE TITÂNIO VISANDO APLICAÇÕES BIOMÉDICAS. Universidade Estadual Paulista. https://repositorio.unesp.br/server/api/core/bitstreams/969af3a3-7881-4d83-8bc7-7c67c5fcc654/content (Unpublished).
» https://repositorio.unesp.br/server/api/core/bitstreams/969af3a3-7881-4d83-8bc7-7c67c5fcc654/content -
COURA MF, ARROYOS G & FREM RCG. 2017. Síntese de nanopartículas de ouro utilizando redutores químicos naturais. Blucher Chem Eng Proc 1: 1497-1502. DOI 10.5151/chemeng-cobeqic2017-267.
» https://doi.org/10.5151/chemeng-cobeqic2017-267 -
DA SILVA PHC & RODRIGUEZ AFR. 2019. Síntese e caracterização de nanopartículas de ouro coloidal com o látex como um agente redutor. Nativa 7: 268-272. DOI 10.31413/nativa.v7i3.6544.
» https://doi.org/10.31413/nativa.v7i3.6544 -
DOS SANTOS GS, DE MELO FL, DE ANDRADE CAS & DE OLIVEIRA MDL. 2020. Desenvolvimento de plataformas nanoestruturadas para a biodetecção de Shistosoma mansoni / Development of nanostructured platforms for the biodetection of Shistosoma mansoni. Braz J Dev 6: 91158-91163. DOI 10.34117/bjdv6n11-503.
» https://doi.org/10.34117/bjdv6n11-503 -
DOS SANTOS VF & NICOLUCCI P. 2018. Fator de aumento de dose em radioterapia com nanopartículas: estudo por simulação de Monte Carlo. Rev Bras Fis Med 11: 2. DOI 10.29384/rbfm.2017.v11.n3.p2.
» https://doi.org/10.29384/rbfm.2017.v11.n3.p2 -
DYKMAN L, KHLEBTSOV B & KHLEBTSOV N. 2025. Drug delivery using gold nanoparticles. Adv Drug Deliv Rev 216: 115481. DOI 10.1016/j.addr.2024.115481.
» https://doi.org/10.1016/j.addr.2024.115481 -
FARIAS T ET AL. 2024. Electrospun poly(ɛ-caprolactone) membranes modified with heparin and essential fatty acids for biomedical applications. J Appl Polym Sci 141: e55853. DOI 10.1002/app.55853.
» https://doi.org/10.1002/app.55853 -
GANGULA A, PODILA R, M R, KARANAM L, JANARDHANA C & RAO AM. 2011. Catalytic reduction of 4-nitrophenol using biogenic gold and silver nanoparticles derived from Breynia rhamnoides. Langmuir 27: 15268-15274. DOI 10.1021/la2034559.
» https://doi.org/10.1021/la2034559 -
GHOBASHY MM, ALKHURSANI SA, ALQAHTANI HA, EL-DAMHOUGY TK & MADANI M. 2024. Gold nanoparticles in microelectronics advancements and biomedical applications. Mater Sci Eng B 301: 117191. DOI 10.1016/j.mseb.2024.117191.
» https://doi.org/10.1016/j.mseb.2024.117191 -
GHOREISHI SM & MORTAZAVI-DERAZKOLA S. 2025. Eco-friendly synthesis of gold nanoparticles via tangerine peel extract: Unveiling their multifaceted biological and catalytic potentials. Heliyon 11: e40104. DOI 10.1016/j.heliyon.2024.e40104.
» https://doi.org/10.1016/j.heliyon.2024.e40104 - GROVE DC & RANDALL WA. 1955. Assay methods of antibiotics: a laboratory manual. New York: Medical Encyclopedia, 238 p.
-
HERNÁNDEZ-SIERRA JF, RUIZ F, CRUZ PENA DC, MARTÍNEZ-GUTIÉRREZ F, MARTÍNEZ AE, DE JESÚS POZOS GUILLÉN A, TAPIA-PÉREZ H & MARTÍNEZ CASTAÑÓN G. 2008. The antimicrobial sensitivity of Streptococcus mutans to nanoparticles of silver, zinc oxide, and gold. Nanomedicine 4: 237-240. DOI 10.1016/j.nano.2008.04.005.
» https://doi.org/10.1016/j.nano.2008.04.005 -
KHAN SA, SHAHID S & LEE CS. 2020. Green synthesis of gold and silver nanoparticles using leaf extract of Clerodendrum inerme; characterization, antimicrobial, and antioxidant activities. Biomolecules 10: 835. DOI 10.3390/biom10060835.
» https://doi.org/10.3390/biom10060835 -
LI Y, YANG J & HE X. 2023. Characterizing polyproline II conformational change of collagen superhelix unit on adsorption on gold surface. Nanoscale Adv 5: 5322-5331. DOI 10.1039/d3na00185g.
» https://doi.org/10.1039/d3na00185g -
MIESZAWSKA AJ, MULDER WJM, FAYAD ZA & CORMODE DP. 2013. Multifunctional gold nanoparticles for diagnosis and therapy of disease. Mol Pharm 10: 831-847. DOI 10.1021/mp3005885.
» https://doi.org/10.1021/mp3005885 -
MILANEZE BA ET AL. 2016. Facile synthesis of monodisperse gold nanocrystals using Virola oleifera. Nanoscale Res Lett 11: 465. DOI 10.1186/s11671-016-1683-3.
» https://doi.org/10.1186/s11671-016-1683-3 -
MORAES SEGUNDO JDP, MORAES MOS, BRITO WR, SEGALA K, GARCIA-BASABE Y, ROCCO MLM & D’ÁVILA MA. 2021. Synthesis of gallic acid imprinted polymer and incorporation in poly(caprolactone) mat via electrospinning. Express Polym Lett 15: 654-665. DOI 10.3144/EXPRESSPOLYMLETT.2021.55.
» https://doi.org/10.3144/EXPRESSPOLYMLETT.2021.55 -
OSTROSKY EA, MIZUMOTO MK, LIMA MEL, KANEKO TM, NISHIKAWA SO & FREITAS BR. 2008. Métodos para avaliação da atividade antimicrobiana e determinação da Concentração Mínima Inibitória (CMI) de plantas medicinais. Rev Bras Farmacogn 18: 301-307. DOI 10.1590/S0102-695X2008000200026.
» https://doi.org/10.1590/S0102-695X2008000200026 -
PEDZIWIATR-WERBICKA E ET AL. 2018. Dendronization of gold nanoparticles decreases their effect on human alpha-1-microglobulin. Int J Biol Macromol 108: 936-941. DOI 10.1016/j.ijbiomac.2017.11.004.
» https://doi.org/10.1016/j.ijbiomac.2017.11.004 -
SANTOS JFL, SANTOS MJL, THESING A, TAVARES F, GRIEP J & RODRIGUES MRF. 2016. Ressonância de plasmon de superfície localizado e aplicação em biossensores e células solares. Quim Nova 39: 1098-1111. DOI 10.21577/0100-4042.20160126.
» https://doi.org/10.21577/0100-4042.20160126 - SANTOS R, COSTA K, COSTA J & CRUZ A. 2017. Análise do efeito da distância entre nanopartículas de ouro na resposta de sensores plasmônicos. In: XXXV Simpósio Brasileiro de Telecomunicações e Processamento de Sinais, São Pedro, SP, Brazil, p. 3-6. DOI 10.14209/sbrt.2017.119.
-
SUBARA D & JASWIR I. 2018. Gold nanoparticles: Synthesis and application for Halal authentication in meat and meat products. Int J Adv Sci Eng Inf Technol 8: 1633-1641. DOI 10.18517/ijaseit.8.4-2.7055.
» https://doi.org/10.18517/ijaseit.8.4-2.7055 -
TOMA HE, ZAMARION VM, TOMA SH & ARAKI K. 2010. The coordination chemistry at gold nanoparticles. J Braz Chem Soc 21: 1158-1176. DOI 10.1590/S0103-50532010000700003.
» https://doi.org/10.1590/S0103-50532010000700003 -
WANG P, ZHANG J, LU Y, GUO Z, JIANG Q & SUN J. 2022. DNA-mediated assembly of a gold-nanoparticle film with controllable sonic behavior detected by novel electric-induced ultrasound. Biomater Sci 10: 6190-6200. DOI 10.1039/d2bm00778a.
» https://doi.org/10.1039/d2bm00778a -
XIA H, BAI S, HARTMANN J & WANG D. 2010. Synthesis of monodisperse quasi-spherical gold nanoparticles in water via silver(I)-assisted citrate reduction. Langmuir 26: 3585-3589. DOI 10.1021/la902987w.
» https://doi.org/10.1021/la902987w -
ZAN RA & ZAN ASHS. 2022. Nanopartículas metálicas de ouro (AU) e prata (AG) associadas a substâncias naturais, uma proposta de síntese biogênica pouco explorada / Metallic nanoparticles of gold (AU) and silver (AG) associated with natural substances, a proposal for a little explored biogenic synthesis. Braz J Dev 8: 38637-38658. DOI 10.34117/bjdv8n5-385.
» https://doi.org/10.34117/bjdv8n5-385 -
ZHANG L, GU FX, CHAN JM, WANG AZ, LANGER RS & FAROKHZAD OC. 2008. Nanoparticles in medicine: Therapeutic applications and developments. Clin Pharmacol Ther 83(5): 761-769. https://doi.org/10.1038/sj.clpt.6100400.
» https://doi.org/10.1038/sj.clpt.6100400
