Smart polymer-based calcium-ion self-regulated nanochannels by mimicking the biological Ca2+-induced Ca2+ release process

In nature, ion channels play key roles in controlling ion transport between cells and their surroundings. Calcium ion (Ca 2+ )-induced Ca 2+ release (CICR), a critical control mechanism for Ca 2+ channels, occurs due to a Ca 2+ concentration gradient working in synergy with ryanodine receptors, which are famously known as “calcium sparks”. Inspired by this self-regulated biological process, a smart Ca 2+ concentration-modulated nanochannel system was developed by integrating a poly{ N -isopropylacrylamide- co -acrylamide-[4-(trifluoromethyl) phenyl]-2-thiourea 0.2 - co -acrylamide-DDDEEKC 0.2 } (denoted as PNI- co -CF 3 -PT 0.2 - co -DDDEEKC 0.2 ) three-component copolymer onto the nanochannels of a porous anodic alumina (PAA) membrane. In this smart polymer design, the DDDEEKC hepta-peptide unit has an extraordinary binding affinity with Ca 2+ through coordination bonds, while CF 3 -PT functions as a hydrogen bond mediation unit, facilitating the remarkable conformational transition of the PNI main chain in response to Ca 2+ -specific adsorption. Due to these futures, the dynamic gating behaviors of the modified nanochannels could be precisely manipulated by the Ca 2+ concentration. In addition, the sensitive Ca 2+ response, as low as 10 pM with a high specificity toward Ca 2+ capable of discriminating Ca 2+ from other potential interference metal ions (e.g., K + , Cu 2+ , Mg 2+ , Zn 2+ , Fe 3+ , and Al 3+ ), remarkable morphological change in the nanochannel and satisfactory reversibility indicate the great potential of Ca 2+ -responsive polymers for the fabrication of biodevices and artificial nanochannels. Nanochannels: smart polymer mimics calcium-sensitive membrane protein A calcium-responsive polymer that mimics the function of pore-forming membrane proteins found in muscle cells offers a new platform for biotechnology and regenerative medicine. Inspired by the types of calcium channels that regulate muscle contraction, a team led by Guangyan Qing from the Dalian Institute of Chemical Physics, China, created a three-component smart material. It includes a seven amino acid peptide that recognizes calcium ions, a chemical that mediates conformational changes, and a flexible polymer that opens and closes the nanochannel in response to changes in calcium levels. The researchers showed that the material changed shape controllably and reversibly in response to minute changes in calcium concentrations. They propose the smart polymer could have many applica