In this study, a chloramphenicol and aflatoxin M1 aptamer-functionalized DNA hydrogel was designed for the simultaneous detection of chloramphenicol and aflatoxin M1 for the first time. The acrydite-modified chloramphenicol aptamer sequence was used to synthesize the DNA hydrogel and for visual detection of chloramphenicol depending on the gel-to-sol transition of the target-responsive DNA hydrogel. The DNA hydrogel formulation was set as follows: 60% of each linear polyacrylamide–DNA conjugate and 40% of acrylamide and chloramphenicol aptamer/DNA strand-1 at a molar ratio of 1:1, and the lowest concentration of chloramphenicol leading to gel dissociation was 1.0 nM at 25 °C. Furthermore, the formalized aptamer-functionalized DNA hydrogel was used to detect aflatoxin M1 by measuring the recovery of the fluorescence signal that was quenched when the FAM-labeled aflatoxin M1 aptamer and BHQ1-labeled DNA strand-2 were hybridized to form a double-stranded DNA in the network of hydrogel. The detection platform was successfully applied to the detection of chloramphenicol and aflatoxin M1, both in aqueous solution and in milk. The aptamer-functionalized DNA hydrogel had detection (LOD) and quantification limits (LOQ) for aflatoxin M1 as 1.7 and 5.2 nM, respectively. Using two aptamer sequences with high affinity and specificity, the dual-sensing platform based on the DNA hydrogel achieved higher selectivity for chloramphenicol and aflatoxin M1, which demonstrated its potential as a reliable simultaneous detection platform against two different targets for monitoring food safety.

Fipronil, as a broad use insecticide, is regulated under directives and standards in many countries since it is classed as Class II moderately hazardous pesticide and Group C possible human carcinogen. In this study, amine coated iron oxide (NH 2 À Fe 3 O 4 ) is used as a new adsorbent with high adsorption capacity in the removal of fipronil from aqueous solution and eggshells.The adsorption performance was studied through batch adsorption under different concentrations of fipronil (10-200 μg/mL), different nanoparticles amount (0.1-1 mg) at different pH (4.5-6.0) and temperature (25-75 °C). Results showed that NH 2 À Fe 3 O 4 nanoparticles (0.1 mg) have excellent adsorption efficiency (97.06 %) at 25 °C, and pH 5.5. It also showed higher adsorption capacity towards fipronil sulfide, fipronil sulfone and fipronil desulfinyl with removal efficiencies of 92.82 %, 86.35 % and 76.24 % from aqueous solution and 97.62 %, 76.97 % and 62.65 % from eggshells, respectively. Fipronil adsorption process on NH 2 À Fe 3 O 4 nanoparticles showed best fitting to Langmuir adsorption isotherm indicating monolayer chemical adsorption by physicochemical interactions spontaneously on homogenous surfaces. Having higher adsorption capacity and reusability NH 2 À Fe 3 O 4 nanoparticles were shown to be effective adsorbents for removal of fipronil from aqueous solution and eggshells.

Aptamer fonksiyonlandırılmış DNA hidrojelleri yüksek özgünlük, stabilite ve esneklik gibi özellikleri nedeniyle birçok alanda kullanılmaktadır. Bu çalışma kapsamında kloramfenikole özgü aptamer dizisi fonksiyonlandırılmış DNA hidrojeli sentezi gerçekleştirilmiş ve hidrojel stabilitesi için önemli parametreler optimize edilmiştir. Sentez için 5’ uçları akridit modifiyeli kloramfenikole özgü aptamer ile ona kısmen eşlenik DNA ipliği polimer yapıya yan dal olarak katılmış ve eşlenik bölgelerin hibridizasyonu ile bir arada tutularak hidrojel sentezi gerçekleştirilmiştir. Optimize edilmiş parametreler akridit modifiyeli DNA dizilerinin konsantrasyonları, akrilamid yüzdesi, kloramfenikol aptameri ve DNA iplik 1 içeren lineer polimer çözeltilerin molar oranlarıdır. Ayrıca, reaksiyon sıcaklığı ve eşlenik bölgenin uzunluğunun jel stabilitesine etkisi değerlendirilmiştir. Sonuç olarak, DNA hidrojel stabilitesi için %60’lık lineer poliakrilamid-DNA konjugasyonundan, %40 akrilamid stok çözeltisi kullanılarak 1:1 molar oranda karıştırılan aptamer ve DNA iplik çözeltileri ile 25°C’de aptamer fonksiyonlandırılmış DNA hidrojeli sentezi tamamlanmış olmuştur. Bunlara ek olarak, aptamer dizisi ile DNA iplik arasındaki eşlenik bölgenin uzunluğunun stabiliteyi artırdığı sonucuna varılmıştır.