Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (660 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
An acid dye used in testing for hydrochloric acid in gastric contents. It is also used histologically to test for amyloidosis.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Red, Congo.
Where it fits in the MeSH classification
- Broader topics
- Naphthalenesulfonates
Related concepts
- Amyloidosis
Research landscape
PubMed indexes 2,641 records tagged with the MeSH heading “Congo Red” (counts retrieved 2026-10-31). 652 of them (24.7%) were published from 2020 onward, and the busiest period so far is through 1999 with 780 records.
Reviews account for 94 records (3.6%) and meta-analyses for 0. Randomized controlled trials number 3 (0.1%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 780 |
| 2000-2009 | 620 |
| 2010-2019 | 589 |
| 2020 onward | 652 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 94 | 3.6% |
| Meta-analyses | 0 | 0.0% |
| Randomized controlled trials | 3 | 0.1% |
Method: PubMed query "Congo Red"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in drugs and chemicals
Studies of a chemical or drug can answer very different questions: what it is and how it behaves in cells and animals, how the body handles it, and whether it changes outcomes in people. Laboratory and animal findings often do not carry over to patients, and observational studies of exposures are confounded by who uses a substance and why. Nothing on this page is a recommendation to use, avoid, start or stop any substance or medicine; talk to a qualified clinician or pharmacist about your own situation. Check the dose, the species, the comparison group and whether a patient-relevant outcome was measured.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Congo Red and amyloids: history and relationship | 2019 | Review article Design not recorded in structured metadata | 264 | cc by PMID 30567726 · DOI · PMC6331669 |
| Congo Red Interactions with Curli-Producing E. coli and Native Curli Amyloid Fibers | 2015 | Research article Design not recorded in structured metadata | 76 | cc by PMID 26485271 · DOI · PMC4618944 |
| Recent advances in removal of Congo Red dye by adsorption using an industrial waste | 2022 | Research article Design not recorded in structured metadata | 72 | cc by PMID 35414682 · DOI · PMC9005715 |
| Phytochemical directed synthesis of flower-like ZnO nanostructures from almond peel extract for sunlight-activated congo red degradation | 2026 | Research article Design not recorded in structured metadata | 0 | cc by PMID 42060600 · DOI · PMC13132251 |
Congo Red and amyloids: history and relationship [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Staining with Congo Red (CR) is a qualitative method used for the identification of amyloids in vitro and in tissue sections.
- Closing excerpt
- Our historical review on the use of CR staining for amyloid studies may provide insight into the pitfalls and caveats related to this technique for researchers considering using this dye.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (121 words)
Staining with Congo Red (CR) is a qualitative method used for the identification of amyloids in vitro and in tissue sections. However, the drawbacks and artefacts obtained when using this dye can be found both in vitro and in vivo Analysis of scientific data from previous studies shows that CR staining alone is not sufficient for confirmation of the amyloid nature of protein aggregates in vitro or for diagnosis of amyloidosis in tissue sections. In the present paper, we describe the characteristics and limitations of other methods used for amyloid studies. Our historical review on the use of CR staining for amyloid studies may provide insight into the pitfalls and caveats related to this technique for researchers considering using this dye.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 30567726 · DOI · PMC6331669
Congo Red Interactions with Curli-Producing E. coli and Native Curli Amyloid Fibers [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Microorganisms produce functional amyloids that can be examined and manipulated in vivo and in vitro.
- Closing excerpt
- coli strains and amyloid-producing organisms.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (158 words)
Microorganisms produce functional amyloids that can be examined and manipulated in vivo and in vitro. Escherichia coli assemble extracellular adhesive amyloid fibers termed curli that mediate adhesion and promote biofilm formation. We have characterized the dye binding properties of the hallmark amyloid dye, Congo red, with curliated E. coli and with isolated curli fibers. Congo red binds to curliated whole cells, does not inhibit growth, and can be used to comparatively quantify whole-cell curliation. Using Surface Plasmon Resonance, we measured the binding and dissociation kinetics of Congo red to curli. Furthermore, we determined that the binding of Congo red to curli is pH-dependent and that histidine residues in the CsgA protein do not influence Congo red binding. Our results on E. coli strain MC4100, the most commonly employed strain for studies of E. coli amyloid biogenesis, provide a starting point from which to compare the influence of Congo red binding in other E. coli strains and amyloid-producing organisms.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 26485271 · DOI · PMC4618944
Recent advances in removal of Congo Red dye by adsorption using an industrial waste [3]
Abstract reading summary — source excerpts
- Opening excerpt
- The Congo Red dye was removed from a simulated textile wastewater solution using fly ash from a local power plant.
- Closing excerpt
- The research is a preliminary case study that highlights that fly ash posed a very good potential as a material for Congo Red dye removal.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (129 words)
The Congo Red dye was removed from a simulated textile wastewater solution using fly ash from a local power plant. The characterisation of fly ash was studied in detail by SEM, EDX, XRD, FTIR, BET surface area and TGA techniques. The influence of four parameters (contact time, initial concentration, adsorbent dose, and temperature) was analysed, the results showing that the adsorption capacity depends on these parameters. Thermodynamic and regeneration investigations as well are presented. The fit to pseudo-second-order kinetics models suggests that the removal process is a chemical adsorption. The Langmuir model fitted the experimental data, with a maximum adsorption capacity of 22.12 mg/g. The research is a preliminary case study that highlights that fly ash posed a very good potential as a material for Congo Red dye removal.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 35414682 · DOI · PMC9005715
Phytochemical directed synthesis of flower-like ZnO nanostructures from almond peel extract for sunlight-activated congo red degradation [4]
Abstract reading summary — source excerpts
- Opening excerpt
- This study reports a low-temperature green route for producing sunlight-active zinc oxide (ZnO) nanoparticles using almond peel extract as the sole complexing and stabilizing medium and evaluates their performance toward Congo red (CR) removal from water.
- Closing excerpt
- Thus, almond peel-derived ZnO offers a simple strategy to valorize an agricultural residue into a sunlight-responsive photocatalyst for treating dye-contaminated wastewater.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (252 words)
This study reports a low-temperature green route for producing sunlight-active zinc oxide (ZnO) nanoparticles using almond peel extract as the sole complexing and stabilizing medium and evaluates their performance toward Congo red (CR) removal from water. UV-visible analysis of the synthesized material shows a near UV absorption edge at 373 nm with an optical band gap energy of 3.32 eV. The photocatalyst possesses a mesoporous texture with a specific surface area of 31.89 m2/g and a mean pore diameter of 9.8 nm. FESEM reveals hierarchical flower-like assemblies composed of radially oriented ZnO rods, supported by EDS, confirming Zn and O as the dominant elements. XRD verifies phase-pure hexagonal wurtzite ZnO structures with a mean crystallite size of 39.24 nm. FTIR and XPS confirm ZnO formation and a phytochemical-derived surface overlayer containing hydroxyl, carbonyl, and aromatic functionalities, together with surface hydroxyls and chemisorbed oxygen. Photoluminescence indicates near-band-edge emission and defect-related visible bands consistent with oxygen vacancy and zinc-related trap states. Under natural sunlight (CR: 25 mg/L; catalyst dosage: 5-15 mg/100 mL; irradiation time 270 min), the material achieved 51.61 to 82.21% degradation and followed pseudo-first-order behaviour. Scavenger studies revealed that O2•- radicals are the dominant reactive species in dye degradation, with photogenerated h+ playing a secondary role and •OH contributing minimally. Also, the ZnO nanoparticles exhibited good reusability, retaining over 83.64% of their initial photocatalytic activity after four cycles under sunlight irradiation. Thus, almond peel-derived ZnO offers a simple strategy to valorize an agricultural residue into a sunlight-responsive photocatalyst for treating dye-contaminated wastewater.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42060600 · DOI · PMC13132251
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Congo red and protein aggregation in neurodegenerative diseases [5]
- Research article Optical properties of amyloid stained by Congo red: history and mechanisms [6]
- Research article Insight into amyloid structure using chemical probes [7]
- Research article Photocatalytic degradation using design of experiments: a review and example of the Congo red degradation [8]
- Research article Diseases of protein conformation: what do in vitro experiments tell us about in vivo diseases? [9]
- Research article Adsorptive amputation of hazardous azo dye Congo red from wastewater: a critical review [10]
References
- Yakupova EI, Bobyleva LG, Vikhlyantsev IM, Bobylev AG. Congo Red and amyloids: history and relationship. . 2019. PMID 30567726 · DOI · PMC6331669
- Reichhardt C, Jacobson AN, Maher MC, Uang J, McCrate OA, Eckart M, et al.. Congo Red Interactions with Curli-Producing E. coli and Native Curli Amyloid Fibers. . 2015. PMID 26485271 · DOI · PMC4618944
- Harja M, Buema G, Bucur D. Recent advances in removal of Congo Red dye by adsorption using an industrial waste. . 2022. PMID 35414682 · DOI · PMC9005715
- Sudarsan S, Van Caeneghem J, Vinayagam R, Selvaraj R. Phytochemical directed synthesis of flower-like ZnO nanostructures from almond peel extract for sunlight-activated congo red degradation. . 2026. PMID 42060600 · DOI · PMC13132251
- Frid P, Anisimov SV, Popovic N. Congo red and protein aggregation in neurodegenerative diseases. Brain Res Rev. 2007. PMID 16959325 · DOI
- Howie AJ, Brewer DB. Optical properties of amyloid stained by Congo red: history and mechanisms. Micron. 2009. PMID 19019688 · DOI
- Reinke AA, Gestwicki JE. Insight into amyloid structure using chemical probes. Chem Biol Drug Des. 2011. PMID 21457473 · DOI · PMC3097318
- Sakkas VA, Islam MA, Stalikas C, Albanis TA. Photocatalytic degradation using design of experiments: a review and example of the Congo red degradation. J Hazard Mater. 2010. PMID 19931983 · DOI
- Buxbaum JN. Diseases of protein conformation: what do in vitro experiments tell us about in vivo diseases?. Trends Biochem Sci. 2003. PMID 14607088 · DOI
- Raval NP, Shah PU, Shah NK. Adsorptive amputation of hazardous azo dye Congo red from wastewater: a critical review. Environ Sci Pollut Res Int. 2016. PMID 27255316 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.