Howard et al. 2023 - Chitosan@DOTAGA lead and cadmium chelation

Howard and colleagues evaluated a DOTAGA-functionalized chitosan polymer as an orally administered strategy to reduce absorption and toxicity from lead and cadmium in contaminated food and water. This is mitigation and health-mechanism evidence: the source reports polymer chelation, gastrointestinal transit, and mouse exposure outcomes after contaminated feed, but it does not report consumer-product occurrence concentrations for HMTc benchmark pooling.

Key numbers

The polymer characterization reported 30 +/- 2% acetylation by NMR in the main Results section and 28% acetylated monomers in the Methods summary. The authors reported 97.7% product purity by SEC HPLC-UV and 0.338 mmol/g DOTAGA available for chelation. They calculated that 1 mg of Chitosan@DOTAGA can chelate up to 70 micrograms lead or 38 micrograms cadmium, assuming 1:1 metal:ligand chelation.

Lead and cadmium chelation characterization used 0.1 g/L Chitosan@DOTAGA with metal concentrations from 0.5 to 100 micrograms/L in the Results narrative and from 0.5 to 200 micrograms/L in the Methods preparation section. Both ranges are retained because the PDF reports both.

In the biodistribution study, mice received one oral dose of labelled Chitosan@DOTAGA at 10 mg/kg from a 10 g/L mixture solution. Table 1 reports 8.75 micrograms administered gadolinium. Detected gadolinium as percent of administered dose was concentrated in the gastrointestinal tract:

For the effectiveness study, exposed mice received rodent feed enriched with 7 mg/kg cadmium and 50 mg/kg lead for two weeks. The Chitosan@DOTAGA group received daily oral dosing of 10 mL/kg at 5 g/L polymer in 3.5 g/L NaCl; the saline group received 3.5 g/L NaCl.

Table 2 reports whole-blood metals at sacrifice:

The authors state that blood lead was lower on average in the Chitosan@DOTAGA group than in the saline-exposed group, but the saline-versus-polymer comparison was not statistically significant (p = 0.093). They also state that two Chitosan@DOTAGA-treated mice had higher cadmium values that were not statistical outliers.

Table 3 reports total histopathology scores after sacrifice:

Methods (brief)

Chitosan@DOTAGA was synthesized from chitosan extracted from Alaska snow crabs, with DOTAGA grafting performed in a water and 1,2-propanediol environment. Lead and cadmium chelation was analyzed by PerkinElmer Flexar HPLC coupled to PerkinElmer NexION 2000 ICP-MS, using a Polysep GFC-P 4000 column, 10 microliter injection volume, 0.4 mL/min flow, 0.1 M acetate buffer, and monitoring 114Cd and 208Pb.

The biodistribution study used labelled polymer in healthy female C57Bl/6 mice, with organ collection at 1, 2, 3, 4, and 24 h; Table 1 presents two mice per time point. The effectiveness study used three groups: control (14 mice), saline-treated contaminated-feed group (12 mice), and Chitosan@DOTAGA-treated contaminated-feed group (12 mice). Cadmium and lead in whole blood were measured by inductively coupled plasma optical atomic emission spectrometry after microwave mineralization in concentrated nitric acid with added hydrogen peroxide. Histopathology used blinded review of hematoxylin-eosin-stained kidney, liver, spleen, and heart samples.

Implications

Certification: Do not use this source in product-occurrence or threshold-setting concentration pools. The feed was experimentally enriched and the key outcomes are blood, organ, and histopathology endpoints in mice.

Courses: Useful mitigation evidence for explaining gastrointestinal binding strategies, the difference between exposure reduction and occurrence measurement, and why chelation studies require careful matrix routing.

App: Context-only mitigation and toxicology evidence for Pb/Cd binding approaches; not a consumer-product concentration dataset.

Wiki pages this source may touch

• remediation-evidence
• index
• lead
• cadmium
• index

Verification notes

This page was built from the PDF title/byline, abstract, Results sections, Tables 1-3, Methods, and discussion. Products and ingredients are intentionally empty because the source tests an oral polymer intervention and experimentally enriched mouse feed, not market occurrence in a consumer product.

The source is internally inconsistent on two characterization ranges: acetylation is reported as 30 +/- 2% in Results and 28% in Methods, while metal-spiking ranges are described as 0.5-100 micrograms/L in Results and 0.5-200 micrograms/L in Methods. Both discrepancies are recorded rather than harmonized.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.