Silver nanoparticles (AgNPs) are an attractive alternative to plasmonic gold nanoparticles. The relative cheapness and redox stability determine the growing interest of researchers in obtaining selective plasmonic and electrochemical (bio)sensors based on silver nanoparticles. The controlled synthesis of metal nanoparticles of a defined morphology is a nontrivial task, important for such fields as biochemistry, catalysis, biosensors and microelectronics. Cyclophanes are well known for their great receptor properties and are of particular interest in the creation of metal nanoparticles due to a variety of cyclophane 3D structures and unique redox abilities. Silver ion-based supramolecular assemblies are attractive due to the possibility of reduction by “soft” reducing agents as well as being accessible precursors for silver nanoparticles of predefined morphology, which are promising for implementation in plasmonic sensors. For this purpose, the chemistry of cyclophanes offers a whole arsenal of approaches: exocyclic ion coordination, association, stabilization of the growth centers of metal nanoparticles, as well as in reduction of silver ions. Thus, this review presents the recent advances in the synthesis and stabilization of Ag (0) nanoparticles based on self-assembly of associates with Ag (I) ions with the participation of bulk platforms of cyclophanes (resorcin[4]arenes, (thia)calix[n]arenes, pillar[n]arenes).

The determination of antibiotics in food is important due to their negative effect on human health related to antimicrobial resistance problem, renal toxicity, and allergic effects. We propose an impedimetric aptasensor for the determination of kanamycin A (KANA), which was assembled on the glassy carbon electrode by the deposition of carbon black in a chitosan matrix followed by carbodiimide binding of aminated aptamer mixed with oligolactide derivative of thiacalix[4]arene in a cone configuration. The assembling was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. In the presence of the KANA, the charge transfer resistance of the inner interface surprisingly decreased with the analyte concentration within 0.7 and 50 nM (limit of detection 0.3 nM). This was attributed to the partial shielding of the negative charge of the aptamer and of its support, a highly porous 3D structure of the surface layer caused by a macrocyclic core of the carrier. The use of electrostatic assembling in the presence of cationic polyelectrolyte decreased tenfold the detectable concentration of KANA. The aptasensor was successfully tested in the determination of KANA in spiked milk and yogurt with recoveries within 95% and 115%.

A multicyclophane with a core based on tris(2-aminoethyl)amine (TREN) linked by amide spacers to three fragments of pillar[5]arene was synthesized. The choice of the tris-amide core allowed the multicyclophane to bind to anion guests. The presence of three terminal pillar[5]arene units provides the possibility of effectively binding the colorimetric probe N-phenyl-3-(phenylimino)-3H-phenothiazin-7-amine (PhTz). It was established that the multicyclophane complexed PhTz in chloroform with a 1:1 stoichiometry (lgK_a = 5.2 ± 0.1), absorbing at 650 nm. The proposed structure of the complex was confirmed by ¹H-NMR spectroscopy: the amide group linking the pillar[5]arene to the TREN core forms a hydrogen bond with the PhTz imino-group while the pillararenes surround PhTz. It was established that the PhTz:tris-pillar[5]arene complex could be used as a colorimetric probe for fluoride, acetate, and dihydrogen phosphate anions due to the anion binding with proton donating amide groups which displaced the PhTz probe. Dye displacement resulted in a color change from blue to pink, lowering the absorption band at 650 nm and increasing that at 533 nm.

DNA sensors were assembled by consecutive deposition of thiacalix[4]arenes bearing oligolactic fragments, poly(ethylene imine), and DNA onto the glassy carbon electrode. The assembling of the layers was monitored with scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The configuration of the thiacalix[4]arene core determined self-assembling of the polymeric species to the nano/micro particles with a size of 70–350 nm. Depending on the granulation, the coatings show the accumulation of a variety of DNA quantities, charges, and internal pore volumes. These parameters were used to optimize the DNA sensors based on these coatings. Thus, doxorubicin was determined to have limits of detection of 0.01 nM (cone configuration), 0.05 nM (partial cone configuration), and 0.10 nM (1,3-alternate configuration of the macrocycle core). Substitution of native DNA with aptamer specific to aflatoxin M1 resulted in the detection of the toxin in the range of 20 to 200 ng/L (limit of detection 5 ng/L). The aptasensor was tested in spiked milk samples and showed a recovery of 80 and 85% for 20 and 50 ng/L of the aflatoxin M1, respectively.

Electrochemical enzyme biosensors are extensively utilized in clinical analysis and environmental monitoring, yet achieving effective enzyme immobilization while maintaining high activity remains a challenge. In this work, we developed a flow-through enzyme biosensor system using a 3D-printed flow-through electrochemical cell fabricated from commercially available poly (lactic acid). After modification with thiacalixarene-functionalized oligo (lactic acids) (OLAs), the material enabled efficient immobilization of uricase on the inner surface of a replaceable reactor of the cell. Swelling and hydrolytic stability of OLAs in cone, partial cone, and 1,3-alternate conformations were studied, with 1,3-alernate conformation demonstrating superior stability and enzyme immobilization performance. The use of OLAs enhanced immobilization efficiency by over 30% and protected the reactor from swelling, hydrolytic degradation, and enzyme loss. The biosensor was validated for amperometric uric acid determination, with a screen-printed carbon electrode modified with carbon black and Prussian Blue. This modification reduced the cathodic potential for uric acid detection to –0.05 V. The biosensor exhibited a linear detection range of 10 nM to 30 μM with a detection limit of 7 nM, and it performed effectively in artificial urine and synthetic blood plasma. The novel cell design, featuring easy assembly and low-cost replaceable parts, makes this biosensor a promising candidate for routine clinical analysis and other practical applications.