Optical Fiber-Mediated Immunosensor with a Tunable Detection Range for Multiplexed Analysis of Veterinary Drug Residues.

We describe herein a newly developed chemiluminescent optical fiber immunosensor (OFIS) with a tunable detection range for multiplexed analysis of veterinary drug residues with vastly different concentrations in milk samples. The optical fiber probe is used as a carrier of biorecognition element as well as a transducer, enabling a low-cost compact design, which makes this system suitable for cost-effective on-site detection of the target analytes. Importantly, the synergy between modulation of the length of the optical fiber sensing region and the number of fibers allows performing multiplexed immunoassays in an easily controllable manner over a tunable detection range from pg/mL to µg/mL analyte concentrations. By combining the optical fiber sensor with a nanocomplex signal amplification system, a highly sensitive chemiluminescent OFIS system is demonstrated for the multiplexed assaying of veterinary drug residues in milk samples with linear ranges of 10-(2 × 104) pg/mL for chloramphenicol, 0.5-500 ng/mL for sulfadiazine, and 0.1-300 µg/mL for neomycin. This controllable strategy, based on modulation of the fiber probe, provides a versatile platform for multiplexed quantitative detection of both low-abundance and high-abundance targets, which shows great potential for on-site testing in food safety.

Utilizing three monoclonal antibodies in the development of an immunochromatographic assay for simultaneous detection of sulfamethazine, sulfadiazine, and sulfaquinoxaline residues in egg and chicken muscle.

A rapid and sensitive immunochromatographic assay (ICA) based on competitive format was developed and validated for simultaneous detection of sulfamethazine (SM(2)), sulfadiazine (SDZ), and sulfaquinoxaline (SQX) in chicken breast muscle and egg samples. For this purpose, three monoclonal antibodies raised against those three sulfonamides were conjugated to colloidal gold particles and applied to the conjugate pads of the test strip. The competitors of the sulfonamides (SM(2)/SDZ/SQX-bovine serum albumin conjugates) were immobilized onto a nitrocellulose membrane at three detection zones to form T(1), T(2), and T(3), respectively. With this method, the cutoff values for the three test lines were achieved at 80 µg/kg, which is lower than the maximum residue levels (MRLs) established for sulfonamides. The recoveries in negative samples spiked at concentrations of 10, 50, and 100 µg/kg ranged from 75% to 82% for egg samples and from 78% to 81% for chicken samples. The method was compared with the HPLC method by testing 180 eggs and chicken breast samples from local markets, and an agreement rate of 99.7% was obtained between the two methods.

[Preparation of monoclonal antibody against sulfadiazine and development of an ELISA kit].

AIM: To prepare monoclonal antibody (mAb) against sulfadiazine (SD) and develop an ELISA kit for rapidly detecting residual SD in different kinds of samples. METHODS: BALB/c mice were immunized with the conjugate of SD and BSA, and then anti-SD mAb was prepared by hybridoma technique. The purified ascitic mAb and HRP-labeled SD were used to establish a competitive ELISA for detection of SD in samples. RESULTS: 5 hybridoma cell lines secreting anti-SD mAbs 1A1, 1B8, 1E4, 2C1 and 3D9 were obtained. 1A1, 1B8 and 1E4 belonged to IgG1, while 2C1 and 3D9 belonged to IgG2. The I50 and theoretical minimum detectable amount of the kit was 9.3 microg/L and 0.6 microg/L, respectively. The recovery rates of the kit for SD in different kinds of samples were higher than 60%. The cross-reaction rate of the kit for other sulfanilamide drugs was lower than 3%. CONCLUSION: 5 mAbs against SD have been prepared successfully and possess high titer and specificity. The development of an ELISA kit for rapidly detecting SD can meet the needs of detection of SD in different samples.

Sulphadiazine desensitization in patients with AIDS and cerebral toxoplasmosis.

The objectives of this study were to evaluate the efficacy of a sulphadiazine desensitization protocol to treat patients with AIDS and cerebral toxoplasmosis (CT) and known sulphonamide allergy, to ensure that an adequate dose of sulphadiazine (2-4 g/day) was achieved rapidly (within 4-5 days), and to assess the effect of concurrent corticosteroid (CS) administration on the success rate of the regimen. Sixteen patients with CT and a past history or current manifestations of sulphonamide allergy were desensitized to sulphadiazine from October 1988 to December 1989. The protocol employed the oral administration of gradually increasing increments of sulphadiazine 3-hourly over 5 days. Success was defined as tolerance of 2-4 g oral sulphadiazine per day for at least 7 days until death or the present time without any allergic reactions. Our success rated overall was 10 out of 16 patients (62%). Seven patients achieved a final dose of 4 g/day and three a dose of 2 g/day. Concurrent CS administration did not appear to affect the outcome in the small number of patients studied. Our sulphadiazine regimen rapidly, successfully and safely desensitized patients with CT and sulphonamide allergy, allowing the optimal first-line treatment to continue. The aetiology of allergy in HIV-infected patients and the mechanisms by which desensitization works are unknown.

Sulfadiazine-induced allergy in six Doberman pinschers.

Treatment with sulfadiazine-trimethoprim caused serious, but reversible, allergic drug reactions in 6 Doberman Pinschers 10 to 21 days after the first drug exposure and/or within 1 hour to 10 days after reexposure. Nonseptic polyarthritis was found in all dogs. Glomerulonephropathy, focal retinitis, polymyositis, skin rash, fever, anemia, leukopenia, and thrombocytopenia were found in some dogs. These clinical abnormalities were typical of an immune-mediated vasculitis and mimicked other immune-mediated disorders. In a drug challenge study, 1 dog was given sulfadiazine and trimethoprim separately. Administration of trimethoprim alone did not result in any abnormalities; however, exposure to sulfadiazine caused recurrence of the polyarthritis, glomerulonephropathy, and focal retinitis within 5 days, suggesting that sulfadiazine likely was the offending agent in all cases. In addition, during the sulfadiazine reexposure, marked complement activation was documented at the time clinical signs were apparent, supporting the suggestion that sulfadiazine caused an immune complex disease (type-III hypersensitivity reaction). Since all dogs were of the same breed, a genetic predisposition of some Doberman Pinschers to react adversely to sulfadiazine was suspected.

Lymphocyte transformation test in drug-induced toxic epidermal necrolysis.

Lymphocyte transformation tests (LTT) to drugs remain widely used in drug reactions, despite controversies about their real usefulness. We tested the lymphocytes of 12 patients recovering from a drug-induced Toxic epidermal necrolysis (TEN). There was no difference between the amounts of thymidine incorporated when patients' lymphocytes were cultivated with culprit or innocent drugs. In both situations the lymphocytes from patients reacted like the lymphocytes from controls cultivated with the same panel of drugs. These negative results do not exclude that a hypersensitivity reaction may play a role in the physiopathology of TEN. Anyhow, they clearly indicate that testing lymphocyte transformation to drugs has no practical value in the diagnosis of TEN.