Gold nanoparticles have quietly become one of the most versatile tools in modern bionanotechnology, and a new open-access review in Discover Metals pulls together why. The article, published on 16 June 2026, systematically surveys how these particles are made, what makes them optically and thermally special, and where they are heading in biomedical imaging, photothermal therapy and targeted drug delivery. Its central argument is that the future of gold nanomedicine depends less on any single breakthrough than on matching the right synthesis route to the right application, with purity, scalability and clinical translation as the deciding criteria.
The physical property that underpins nearly everything gold nanoparticles can do is localized surface plasmon resonance, or LSPR. Free conduction electrons on the particle surface oscillate coherently when struck by light of a matching frequency, producing exceptionally strong optical signals. That collective oscillation gives gold nanoparticles their striking colors, but in medicine it does something more useful: it allows the particles to act as contrast agents across multiple imaging modalities, including computed tomography, photoacoustic imaging, fluorescence, magnetic resonance imaging and X-ray scatter imaging. Because gold has a high atomic number, it attenuates X-rays efficiently, making it attractive for CT contrast, while the plasmon resonance itself drives photoacoustic and optical signals.
The same plasmonic physics has a thermal consequence. When the oscillating electrons relax, they dissipate the absorbed photon energy as localized Joule heating rather than re-emitting it all as light. Under near-infrared irradiation, this converts gold nanoparticles into tiny heat sources, a principle known as plasmonic photothermal therapy. The review emphasizes that the temperature rise depends strongly on particle geometry: nanorods can raise suspension temperatures by roughly 45 to 55 degrees Celsius under irradiation, compared with about 25 degrees for spherical particles of comparable material. Near-infrared light in the 700 to 900 nanometer window penetrates tissue best, so rod-shaped and shell-shaped particles tuned to absorb there are the preferred designs for ablating malignant tissue with controlled irradiation.
Shape control is therefore not cosmetic. The review organizes gold nanoparticles into one-dimensional structures such as nanorods, nanowires, nanotubes and nanobelts; two-dimensional nanoplates including squares, stars, pentagons, truncated triangles and hexagons; and three-dimensional architectures such as nanodumbbells, nanoshells, nanostars, nanotadpoles and branched dendrites. These non-spherical and hollow forms shift plasmon absorption into the visible and near-infrared regions, with absorption profiles sensitive to exact shape. Transmission electron microscopy images in the review show the diversity of achievable morphologies, from quasi-spheres to ultrathin nanowires, each with distinct optical behavior.
On the manufacturing side, the review divides synthesis into two broad philosophies. Top-down methods break bulk gold into nanoscale pieces, using grinding, lithography, laser ablation, sputtering or thermal decomposition. Bottom-up methods assemble atoms into nanostructures, typically through colloidal chemistry or biological routes. The classical chemical canon is well represented: the Turkevich method of 1951 uses trisodium citrate as both reducer and stabilizer with a gold chloride precursor, later refined by Frens in 1973 to tune particle sizes between 15 and 150 nanometers; the Brust-Schiffrin approach of 1994 transfers gold ions into an organic phase with a phase-transfer catalyst and reduces them with sodium borohydride in the presence of thiol ligands; and seeded-growth techniques build nanorods from small gold seeds with the help of cationic surfactants that adsorb preferentially onto particular crystal facets.
The review’s strongest enthusiasm, however, is reserved for pulsed laser ablation in liquids, or PLAL. In this top-down technique, a focused nanosecond or femtosecond pulsed laser strikes a gold target submerged in liquid. The laser fluence exceeds the ablation threshold, generating a plasma plume whose expansion is confined by the surrounding liquid; cavitation bubble dynamics and subsequent Ostwald ripening produce ligand-free colloidal nanoparticles, typically in the 5 to 50 nanometer range. Because no chemical reducing agents or surfactant stabilizers are involved, the resulting particles carry clean surfaces free of contamination, which the review identifies as a key advantage for purity, yield and biocompatibility over chemical routes. Those pristine surfaces also make PLAL-made particles ideal platforms for later functionalization with biocompatible polymers. Documented uses include labels for immunochromatographic assays and laser-assisted colloids that enhance surface-enhanced Raman scattering for in vivo bio-imaging.
At the opposite end of the sustainability spectrum sits green biosynthesis. Traditional chemical synthesis often relies on toxic solvents and generates harmful by-products, so researchers have turned to plants, bacteria, yeast and fungi as biological reducing and capping agents. Microbial routes can proceed intracellularly, with enzymes converting transported metal ions inside the cell, or extracellularly, where organisms secrete enzymes such as nitrate reductase and hydrogenase to do the reduction outside. Extracellular synthesis is considered especially attractive because it skips the cell-disruption steps, such as ultrasound or detergent treatment, that intracellular methods require. Fungi are singled out as particularly effective bio-inspired factories because they secrete large quantities of extracellular enzymes, including NADPH-dependent sulfite reductases, hydrolases, cellulases, proteases and amylases, that can reduce gold ions.
Plant and fruit extracts offer an even simpler entry point, requiring no cell culture at all. The review catalogs recent examples: willow leaf extract yielding spherical particles of 50 to 63 nanometers with antifungal and muscle-relaxant properties; Simarouba glauca extract producing spherical and triangular particles whose size shrinks as extract concentration rises, with antimicrobial activity against Staphylococcus aureus; Hygrophila spinosa giving roughly 68-nanometer spheres with antioxidant activity and cytotoxicity against breast and ovarian cancer cell lines; Chinese quince fruit extract producing 20 to 40 nanometer spheres active against S. aureus, E. coli and MCF-7 breast cancer cells; and even fruit waste such as grape peel, yielding 20 to 80 nanometer particles cytotoxic to A431 skin cancer cells, and mango seed extract producing round, triangular and irregular particles active against HeLa and MCF-7 lines. The review notes these biofunctionalized particles, generally in the 10 to 80 nanometer range, carry inherent stability from their biomolecular coatings, though the reported activities are in vitro observations rather than clinical results.
Between synthesis and therapy lies the targeting problem. Passive targeting exploits the enhanced permeability and retention effect, in which leaky tumor vasculature lets nanoparticles of roughly 20 to 100 nanometers accumulate in tumors, achieving on the order of 1 to 5 percent of the injected dose per gram of tumor without any ligand, but with substantial heterogeneity across patients and tumor types. Active targeting adds ligands such as RGD peptides, antibodies like anti-EGFR, or aptamers that bind overexpressed receptors such as integrins or HER2, shifting particle distribution from the extracellular space into cells through receptor-mediated endocytosis. The review is candid that the gains are often marginal, on the order of a 10 to 20 percent improvement in total uptake, because binding-site barriers limit how much extra payload actually gets in. Hybrid imaging platforms attempt to compensate by combining modalities on a single particle: gold’s high atomic number for CT, plasmon resonance for photoacoustic imaging, and doped gadolinium or iron shells for MRI relaxivity boosts, with reported trimodal CT-photoacoustic-photothermal nanocage designs delivering two- to five-fold contrast gains.
The review closes with a sober assessment of what stands between the laboratory and the clinic. Photothermal therapy with rods and nanoshells can exceed 50 percent conversion efficiency and heat tissue to 50 to 70 degrees Celsius, working independently of oxygen to depths of about 5 centimeters, whereas photodynamic therapy depends on photosensitizers, generates reactive oxygen species, is limited by tumor hypoxia and penetrates only about 1 to 2 centimeters. Yet persistent obstacles remain: reproducibility of synthesis, low and variable tumor accumulation, and the slow pace of clinical translation. The authors’ roadmap calls for scaled-up femtosecond PLAL production, biohybrid nanoparticle architectures, multimodal platforms that integrate photothermal therapy with real-time photoacoustic feedback, and GMP-compliant manufacturing protocols. As a review, the article synthesizes existing literature rather than presenting new experimental data, but its integrated framing of synthesis, morphology and application offers a clear map of where gold nanomedicine is, and is not yet, ready to go.
Subject of Research: Synthesis methods, plasmonic properties and biomedical applications of gold nanoparticles
Article Title: Review of gold nanoparticles: synthesis, properties and applications
Article References: Rahman, M. A., Vishala, D., Hasnain, S. M. M., Paramasivam, P., & Ayanie, A. G. (2026). Review of gold nanoparticles: synthesis, properties and applications. Discover Metals, 59(1), Article 4. https://doi.org/10.1007/s13404-026-00370-8
Image Credits: AI Generated
DOI: 10.1007/s13404-026-00370-8
Keywords: gold nanoparticles, plasmon resonance, pulsed laser ablation in liquids, green synthesis, photothermal therapy, drug delivery, molecular imaging, nanorods, tumor targeting, theranostics, nanomedicine, Review
News Source: Nathaniel Bowman. (October 28, 2026). Gold nanoparticles under the laser: a review maps the road from clean synthesis to cancer theranostics. Scienmag.
