Despite recent developments in two-dimensional self-assembly, most supramolecular 2D materials are assembled by tedious methodologies, with complex surface chemistry and small sizes. We here report D/L-alternating cyclic peptides that undergo one-dimensional self-assembly into amphiphilic nanotubes, which subsequently arrange as tubular bilayers to form giant nanosheets in the mesoscale. Reversible transitions between the assembled, dispersed and aggregated states of these nanosheets can be triggered by external stimuli. The characteristic flexibility, defined chemical topology and length scale of these nanosheets set a clear distinction between this new supramolecular architecture and previously reported 2D nanostructures. The sequential 1D-to-2D self-assembly of peptides described here provides a conceptually new approach to achieve two-dimensional materials with hierarchical organisation. These giant nanosheets represent one of the largest 2D supramolecular materials ever made, with potential application as long-range molecular transporters, responsive surfaces and (bio)sensors. RESULTS Supramolecular design Cyclic peptides with an even number of amino acids and alternating D/L-chirality stack on top of one another to form hollow self-assembled cyclic peptide nanotubes

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In this work, the effect of two key structural parameters, number of arms and arm length, of star-shaped "structurally nanoengineered antimicrobial peptide polymers" (SNAPPs) on their antimicrobial activity and biocompatibility, is investigated. A library of star-shaped SNAPPs is prepared, containing varying arm numbers and arm lengths. Antimicrobial assays are then performed to assess the capacity of the SNAPPs to disrupt the membrane, inhibit the growth, and kill pathogenic bacteria. A major finding of the study is that increasing arm number and length of SNAPPs enhanced antimicrobial activity, which can be respectively attributed to the higher local concentrations of polypeptide arms and increased α-helical content. SNAPP architecture is shown to affect the bacteria membrane state and therefore mechanism of killing. Two more potent structures with up to twice the antimicrobial activity of the previously reported SNAPP are discovered in this process. Toxicities of the SNAPPs also increase with arm number and arm length, however therapeutic index calculations identified a 16-arm SNAPP and an easier to prepare 4-arm SNAPP as the best therapeutic agents. The biocompatibility of the SNAPP with the best biological activity is also evaluated in vivo, showing no markers of systemic damage in mice.

Electrochemical sensors are powerful tools widely used in industrial, environmental and medical applications. The versatility of electrochemical methods allows for the investigation of chemical composition in real time and in situ. Electrochemical detection of specific biological molecules is a powerful means for detecting disease-related markers. In the last 10 years, highly-sensitive and specific methods have been developed to detect waterborne and foodborne pathogens. In this review, we classify the different electrochemical techniques used for the qualitative and quantitative detection of pathogens. The robustness of electrochemical methods allows for accurate detection even in heterogeneous and impure samples. We present a fundamental description of the three major electrochemical sensing methods used in the detection of pathogens and the advantages and disadvantages of each of these methods. In each section, we highlight recent breakthroughs, including the utilisation of microfluidics, immunomagnetic separation and multiplexing for the detection of multiple pathogens in a single device. We also include recent studies describing new strategies for the design of future immunosensing systems and protocols. The high sensitivity and selectivity, together with the portability and the cost-effectiveness of the instrumentation, enhances the demand for further development in the electrochemical detection of microbes.