Nanoparticles made with orange-peel extract showed activity against selected bacterial and Candida isolates, including multidrug-resistant bacteria, and appeared more selective for two cancer cell lines than for a normal breast-cell line in laboratory assays. The finding is a laboratory signal, not a treatment result: the study generated no animal or clinical efficacy evidence.
From patient samples to plant-made particles
The study reported 64 clinical specimens collected from breast cancer patients between 2024 and 2025, including abscess samples, wound swabs, urine and vaginal swabs. Collection required written informed consent and institutional review-board approval. It also reported 64 recovered microbial isolates: 26 E. coli, 17 K. pneumoniae, 12 S. aureus, 3 B. subtilis and 6 C. albicans. The paper does not establish a one-to-one link between the specimen and isolate totals, and it did not report the number of patients.
To define the bacterial resistance profile, 58 purified bacterial isolates were tested against 15 antibiotics. Multidrug resistance meant non-susceptibility to at least one agent in three or more antimicrobial classes. The antimicrobial screening also compared the nanoparticles with orange-peel extract, heat-inactivated extract, zinc nitrate, standard antimicrobial disks and untreated sterile disks.
The particles were made by combining an aqueous 1 mM zinc nitrate hexahydrate solution with orange-peel extract, setting the mixture to pH 8.5, then incubating it in the dark at 37 °C with shaking at 200 rpm for 24 hours. Characterization reported a 368-nanometre absorption peak, a mean hydrodynamic size of 32.45 nanometres, low polydispersity of 0.186 and a zeta potential of minus 36.4 millivolts. The particles were described as highly crystalline hexagonal wurtzite nanostructures. These summary values were reported without confidence intervals or replicate variability.
The antimicrobial picture was uneven
On agar plates, the ZnONP inhibition zones, the clear areas around a test sample where growth is blocked, ranged from 18.0 ± 1.0 to 24.0 ± 1.4 millimetres. E. coli had the largest zone and C. albicans the smallest. That is a measure of activity in a plate assay, not a clinical response.
The concentration tests gave a more mixed result. MIC, the lowest concentration reported to stop growth, ranged from 120 to 512 micrograms per millilitre. MBC and MFC, the reported concentrations for killing bacteria and fungi, ranged from 240 to 1,024 micrograms per millilitre. E. coli was most susceptible by these measures and C. albicans least susceptible. Ciprofloxacin had lower bacterial MICs, 25 to 50 micrograms per millilitre, and no reported antifungal activity. The paper also said the stated MIC assay range did not match the reported values.
Time-kill tests showed concentration- and time-dependent patterns. At four times the MIC, E. coli and B. subtilis reached the assay's limit of detection within 8 to 12 hours, while C. albicans remained incompletely killed after 24 hours at MIC. In biofilm tests at three-quarters of the MIC, the reported ZnONP inhibition values ranged from 55.2 ± 1.8% to 68.3 ± 1.7%. The corresponding ciprofloxacin values were 78.6 ± 1.6% to 89.1 ± 1.4%, with treatment differences reported at p < 0.05. A biofilm is a surface-attached microbial community, so this result describes a different assay behavior from simply stopping growth.
Cancer-cell signals appeared in culture
Another set of tests measured radical-scavenging activity, a chemical indicator of antioxidant behavior, using DPPH and ABTS assays. The ZnONP IC₅₀ was approximately 38 to 40 micrograms per millilitre. Ascorbic acid measured about 27 to 28, orange-peel extract about 60 to 62, and zinc nitrate more than 100. Because lower IC₅₀ values indicate greater potency in this assay, the nanoparticles fell between the reference compound and the two other test materials. The result does not measure a clinical antioxidant benefit.
In cancer-cell tests, IC₅₀ means the concentration corresponding to a 50% reduction in measured viability. The reported values were 58.98 micrograms per millilitre for MCF-7 and 87.93 for HepG2, compared with more than 250 for normal MCF-10A cells. Reported selectivity indices were greater than 4.24 for MCF-7 and greater than 2.84 for HepG2. The gap is notable within the cell model, but it is not a clinical therapeutic-window estimate.
Confocal imaging found concentration-dependent intracellular fluorescence across 6.25 to 50 micrograms per millilitre. MCF-7 showed the strongest signal, followed by HepG2, while MCF-10A was weaker; the reported comparison at 50 micrograms per millilitre had p < 0.001. Fluorescence is a surrogate for internalization in these cultures and does not establish tumor targeting in a living body.
The researchers also measured BAX and BCL2, genes associated with apoptosis, or programmed cell death. Relative to untreated controls, BAX was approximately 3.4-fold and BCL2 0.4-fold in MCF-7. In MDA-MB-231, the corresponding values were 2.9-fold and 0.3-fold, with p < 0.0001. The pattern is consistent with an apoptosis-related response, but gene-expression changes alone do not establish the complete mitochondrial pathway.
What the experiments cannot tell us
Taken together, the study is evidence of activity in controlled laboratory systems using selected clinical isolates and human cell lines. It does not show that the nanoparticles treat infection or cancer in humans, establish tumor targeting in a living body, or provide animal data on efficacy, biodistribution, pharmacokinetics or systemic safety. The paper's next questions are whether the results hold in animal models and whether the preparation can be reproduced after standardizing orange-peel composition and synthesis conditions. Those steps would be needed before a clinical interpretation.
Paper data and sources
Original title: Combating multidrug-resistant pathogens, breast cancer (MCF-7) and hepatocellular carcinoma (HepG2) using biofabricated zinc oxide nanoparticles.
Authors: Gamal M El-Sherbiny, Dina M Elkhashab, M E Shehata, Amira Salah El-Din Youssef
Journal/Repository: Scientific reports
Status: Peer-reviewed
First online: 2026-08-20
DOI: 10.1038/s41598-026-66940-0
Original paper · Full text