Silver nanoparticles shaped as pentagonal nanorods killed colon cancer cells more effectively than similarly sized decahedral particles, according to a new study from researchers at Carnegie Mellon University in Qatar, a result that points to particle geometry as a decisive factor in how these materials interact with living cells.
The research, published in Frontiers in Nanotechnology, investigated the biological effects of size- and shape-controlled silver nanoparticles on HCT-116 colon carcinoma cells in culture. The team, consisting of Mekal Tbaa, Nesrine I. Affara and Nimer Murshid, synthesized two types of silver decahedral nanoparticles (AgNDs) with average diameters of 41 and 90 nanometers using photochemical methods, and silver pentagonal nanorods (AgNRs) approximately 90 nanometers in length using thermochemical synthesis.
Characterization of the particles relied on established structural tools. Ultraviolet-visible spectroscopy, transmission electron microscopy and scanning electron microscopy were used to confirm the synthesis and verify the dimensions and morphology of each nanoparticle type before any biological testing took place.
To measure cytotoxicity, the researchers exposed the cells to a range of nanoparticle concentrations and assessed viability with an MTT assay 72 hours after exposure. The results showed a clear pattern: among the decahedral particles, the smaller 41 nm AgNDs were more cytotoxic than the 90 nm AgNDs, as reflected by a lower IC50 value, demonstrating a size-dependent difference in toxicity.
The more striking finding emerged when the nanorods entered the comparison. Despite their larger length dimension of roughly 90 nanometers, the AgNRs displayed even greater cytotoxicity than either decahedral particle. This suggests that geometry, not size alone, strongly influences how nanoparticles interact with cells and how biologically active they become once they do.
Beyond the viability measurements, the team probed possible molecular mechanisms using Western blot analysis. The analysis evaluated the expression of key proteins associated with apoptotic pathways, proliferation and survival signaling cascades. This exploratory analysis showed treatment-associated differences in these proteins, including a higher relative p53 signal in cells treated with the 90 nm AgNRs.
The authors are careful to frame these molecular observations as preliminary. The Western blot findings were obtained from a single biological experiment, meaning they provide preliminary mechanistic context and require independent quantitative validation before firm conclusions can be drawn about the signaling changes underlying the toxicity differences.
Even so, the study adds to a growing appreciation that the anticancer activity of silver nanoparticles cannot be reduced to a simple dose-response relationship. Two particles with comparable dimensions but different shapes produced measurably different cytotoxic outcomes in the same cell line, and two particles of identical shape but different sizes produced a graded response tied to diameter.
The work was conducted entirely in cultured HCT-116 colon carcinoma cells, so the findings describe cellular responses in a laboratory setting rather than effects in patients or animal models. The authors note that the results emphasize the importance of precise structural development when designing nanoparticle-based therapeutic strategies, and that nanoparticle geometry should be carefully designed, taking into consideration both the size and the shape of the particles, to optimize the efficacy of such approaches.
For the field of biomedical nanotechnology, the study underscores a structure-activity relationship that could inform future work on silver-based therapeutics: as researchers seek to harness nanoparticle cytotoxicity against cancer cells, the shape of the particle may matter as much as, or more than, its size.
Subject of Research: How the size and shape of silver nanoparticles influence cytotoxicity and apoptotic signaling in HCT-116 colorectal cancer cells.
Article Title: Geometry-dependent cytotoxicity of silver nanoparticles modulates apoptotic signaling in HCT-116 colorectal cancer cells
Article References: Tbaa, M., Affara, N. I., & Murshid, N. (2026). Geometry-dependent cytotoxicity of silver nanoparticles modulates apoptotic signaling in HCT-116 colorectal cancer cells. Frontiers in Nanotechnology, 8, Article 1959898. https://doi.org/10.3389/fnano.2026.1959898
Image Credits: AI Generated
DOI: 10.3389/fnano.2026.1959898
Keywords: silver nanoparticles, nanoparticle geometry, HCT-116 cells, colorectal cancer, cytotoxicity, apoptosis, p53, decahedral nanoparticles, nanorods, structure-activity relationship, biomedical nanotechnology, Geometry-dependent
News Source: Nathaniel Bowman. (October 28, 2026). Silver Nanoparticle Shape, Not Just Size, Drives Toxicity in Colon Cancer Cells. Scienmag.
