Development of quantitative immunochromatographic kit and visual screening immunoassay strip for cadmium.

Cadmium is a highly toxic heavy metal for humans. In 2006, the Codex Alimentarius Commission set the international standard value of Cd contained in polished rice at 0.4 mg kg(-1), thus requiring the monitoring of Cd in food. We developed two types of Cd immunochromatographic kit by using anti-(Cd-EDTA) antibody. One is the quantitative Cd immunochromatographic device which can precisely measure Cd concentrations. The other is the Cd screening strip that enables visible evaluation of Cd exceeding 0.003 mg L(-1). Compared with conventional instrumental analysis methods, the immunoassay kits provide rapid, simple, and inexpensive on-site methods. For these kits, we also developed an efficient pretreatment method that can be easily administrated on-site. In this method, brown rice samples are coarsely crushed by a hand-held grinder then mixed with an enzyme solution, and Cd is extracted with HCl. The extracted solution is then purified by a newly developed Cd-selective ion exchange column. Cd concentrations measured by the quantitative Cd immunochromatographic devices correlated well with those obtained by ICP-OES (r (2) = 0.96). The Cd screening strips performed well in tests; pretreated purification solution which gave Cd concentrations exceeding 0.4 mg kg(-1) according to the Cd immunochromatographic devices gave corresponding results with the Cd screening strips with no false positives or false negatives. These results indicate that the two immunochromatographic kits are useful for on-site measurement of Cd concentrations and screening of Cd present in brown rice.

Interlaboratory study of immunochromatography for the rapid determination of cadmium concentrations in cereals and soybeans.

Cadmium (Cd) is one of the most toxic heavy metals to humans. To prevent the distribution of Cd-contaminated food, a simple and quick on-site test for measuring Cd concentrations in agricultural products is needed. Recently, an immunochromatography kit developed for determining Cd in rice was reported to be useful for determining Cd in many other crops. We conducted an interlaboratory study to evaluate the kit for determining Cd in cereals (wheat and rice) and soybeans. Ten test materials were used, and 12 test samples including two sets of blind duplicates were distributed to 12 laboratories in Japan. The Cd recoveries (relative to certified values or values determined by inductively coupled plasma-MS) from all test materials were 84.6-125.1%. Repeatability RSD values of the test materials ranged from 8.8 to 14.8%. Reproducibility RSD values ranged from 13.4 to 27.6%, averaging 21.3%. The Horwitz ratio ranged from 0.61 to 1.36. The reproducibility was within the range of ELISA results for measuring toxins and allergens in food. Our results indicated that the kit was an inexpensive, reliable tool for quick and easy on-site determination of Cd in cereals and soybeans.

Immunochromatography for the rapid determination of cadmium concentrations in wheat grain and eggplant.

BACKGROUND: A simple and quick on-site test for trace levels of cadmium (Cd) in food is needed because of the human toxicity of this heavy metal. We developed an immunochromatography kit which uses the antigen-antibody complex reaction between the Cd-ethylenediaminetetraacetic acid (Cd-EDTA) complex and an anti-Cd-EDTA antibody. We previously reported the successful use of this kit to determine Cd concentrations in brown rice with respect to the international standard: 0.4 mg kg⁻¹. Here, we measured, using this immunochromatography kit, Cd concentrations in crops with lower international standards than rice. RESULTS: Cadmium extracted with 0.1 mol L⁻¹ HCl from wheat grain and fresh eggplant was purified sufficiently using an ion-exchange column treatment. Appropriate HCl extraction rates and dilution rates for the column eluate were selected; Cd concentrations in wheat grain and fresh eggplant were determined successfully by immunochromatography with respect to the international standards of 0.2 mg kg⁻¹ and 0.05 mg kg⁻¹ fresh weight, respectively. CONCLUSION: Approximate Cd concentrations in wheat grain and fresh eggplant can be monitored easily and quickly by this method at locations where facilities for acid digestion and precision analysis are not available.

Biodegradation and bioabsorption innovation of the functionally graded bovine bone-originated apatite with blood permeability.

Bioabsorbable and functionally graded apatite (fg-HAp) ceramics were designed using bovine bone by the calcination and partial dissolution-precipitation methods. The fg-HAp ceramics that were developed had gradual distributions of the degree of crystallinity and the grain size of single-phase hydroxyapatite from the surface layer of the pore wall to the bulk structure region. Calcination at 1073 K gave a specific surface area of 30 m2 x g-1 and porosities of 60-80%. The pore structure of the fg-HAp was classified into two regions: a macro-pore region (100-600 microm) originating from spongy bone and a micro-pore region (10-160 nm) related to body fluid permeation and blood permeability. By implantation in subcutaneous tissue of rat, it was confirmed that body fluid permeated the bulk region of the fg-HAp ceramics through the micro-pores. The volumetric populations occupied by body fluid were 60% at 4 weeks and 68% at 8 weeks in the ceramics explants, indicating drastic bioabsorption, although the body fluid was found to be immunopositive for an albumin as the main serum protein in blood. On the fg-HAp ceramics developed here, the bioabsorption rate could be controlled by careful selection of the calcination temperature. These ceramics can be applied as new biomimetic ceramics exhibiting surface and bulk degradations and cellular absorption by giant cells.