An aptasensor strip-based colorimetric determination method for kanamycin using cellulose acetate nanofibers decorated DNA-gold nanoparticle bioconjugates.

The preparation of portable colorimetric biosensor strips is described by combining aptamer-immobilized electrospun nanofiber membranes (A-NFMs) with signal probes (DNA-conjugated gold nanoparticles (AuNPs)) for determination of kanamycin (KMC) as a model analyte. The A-NFMs were decorated with complementary single-stranded DNA (cDNA) of KMC aptamer-conjugated AuNPs (cDNA@Au) to get the colorimetric biosensor strips. The constructed biosensor strips showed a significant absorbance decreasing band at 510 nm which induce a visual color change from pink to white when exposed to KMC, with a low detection limit of 2.5 nM (at S/N = 3). The effect is due to disassembling of cDNA@Au from NFMs in the presence of KMC because the aptamer has a higher affinity to KMC than its complementary DNA, which resulted in replacing cDNA@Au with KMC. Satisfactory performance was observed in real sample (drinking water and milk) analysis with a recovery of 98.9-102.2%. The constructed colorimetric biosensor test strips hold great application promise for food safety control. Graphical abstract Schematic representation of biosensor strips for kanamycin detection prepared with the cDNA@Au immobilized aptamer-based cellulose acetate nanofibers.

Aminated polyacrylonitrile nanofibers with immobilized gold-silver core-shell nanoparticles for use in a colorimetric test strip for copper(II).

The authors describe colorimetric test strips by using electrospun nanofiber membranes (NFMs) carrying gold/silver core/shell nanoparticles (Au/Ag NPs). The Au/Ag NPs were immobilized on aminated porous polyacrylonitrile NFMs to obtain test strips with a tortuous porous structure and a large surface area (38.6 m2 g-1). The color of the resultant NFMs, measured at a wavelength of 420 nm, is red-shifted when exposed to copper ions (Cu2+) with a color change from yellow to pink to colorless. The effect is due to leaching Au/Ag NPs from the NFMs in the presence of ammonium chloride, thiosulfate and Cu2+ upon which soluble thiosulfate complexes of Ag+, Au3+ and Cu2+ are formed. The effect can be readily seen with bare eyes. Under optimized conditions, this method has a low limit of detection (50 nM at S/N = 3), a fast assay time (3 min), good specificity, and excellent reversibility. The colorimetric test strip was successfully applied to the analysis of Cu2+ in drinking water sample. Graphical abstract Schematic of the preparation of test strips for Cu2+ by immobilizing Au/Ag core-shell nanoparticles on aminated polyacrylonitrile nanofibers.

Evaluation of polypropylene melt blown nonwoven as the interceptor for oil.

The present study aims to evaluate PolyPropylene meltblown nonwoven sorbents as interceptor barrier for oils (motor oil - soybean oil). Experiments carried out in oil-water bath under both static and dynamic conditions. Among tested sorbents, sorbent P3 with porosity 85.93% show high sorption capacity. In which it achieves the highest absorption values 13.13 and 11.91 g/g for motor oil and soybean oil, respectively. Followed by sorbent P2 with porosity 88.30% and sorbent P1 with porosity 91.46%. Besides, results show that sorbent P1 registered the highest oil retention rate followed by sorbent P2 and sorbent P3, respectively. The SEM observation indicates that pore size and porosity play a significant role in deciding oil sorption and retention. At static condition, oil interception performance was evaluated. oil begins to break through the interceptor barrier in sorbent P3 at 29 min for motor oil with intercepting efficiency 98.00% and at 22 min for soybean oil with intercepting efficiency 96.57%. As the thickness of the interceptor barrier increases the time for initial leakage prolonged. After oil leakage, steady oil spillage took place. The typical oil leaking rate was divided into three phases in which oils leaks sharply increased rate, decrease rate and finally gently. Under dynamic conditions, quickly oil leakage happens compared to a static condition. With water flow rate 166 ml/s, the initial oil leakage for sorbent P3 shortens at 16 min for motor oil and 7 min for soybean oil, with Interception efficiencies at 93.42% and 90.00%, respectively.

Fast-Response and Reusable Oxytetracycline Colorimetric Strips Based on Nickel (II) Ions Immobilized Carboxymethylcellulose/Polyacrylonitrile Nanofibrous Membranes.

Driven by economic interests, the abuse of antibiotics has become a significant concern for humans worldwide. As one of the most commonly used antibiotics, oxytetracycline (OTC) residue in animal-derived foods occurs occasionally, which has caused danger to humanity. However, there is still no simple and efficient solution to detect OTC residue. Here, an easily-operated colorimetric strategy for OTC detection was developed based on nickel ions (Ni2+) immobilized carboxymethylcellulose/polyacrylonitrile nanofibrous membranes (Ni@CMC/PAN NFMs). Owing to numerous O- and N-containing groups OTC has a strong tendency to complex with Ni2+ on the strips, inducing a color change from light green to yellow visible to the naked eye. The NFMs structural features, CMC functionalization process, and Ni2+ immobilization amount was carefully regulated to assure OTC detection whilst maintaining the inherent characteristics of NFMs. With the benefits of the large specific surface area (SSA) and small pore size of NFMs, the strips not only exhibited a rapid response (2 min), and low detection limit (5 nM) but also performed with good reversibility and selectivity concerning OTC detection over other antibiotics. The successful development of such enchanting nanofibrous materials may provide a new comprehension into the design and improvement of colorimetric strips.