As drug delivery, therapy, and medical imaging are becoming increasingly cell-specific, there is a critical need for high fidelity and high-throughput screening methods for cell surface interactions. Cell membrane-mimicking surfaces, i.e., supported lipid bilayers (SLBs), are currently not sufficiently robust to meet this need. Here we describe a method of forming fluidic and air-stable SLBs through tethered and dispersed cholesterol groups incorporated into the bottom leaflet. Achieving air stability allows us to easily fabricate SLB microarrays from direct robotic spotting of vesicle solutions. We demonstrate their application as cell membrane-mimicking microarrays by reconstituting peripheral as well as integral membrane components that can be recognized by their respective targets. These demonstrations establish the viability of the fluidic and air-stable SLB platform for generating content microarrays in high throughput studies, e.g., the screening of drugs and nanomedicine targeting cell surface receptors.

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We herein report the construction of peroxidase (POD)-mimicking catalysts based on the strategy of peptide assembly and molecular imprinting. Upon the co-assembly of Fmoc-FFH and hemin, we firstly fabricated the...

Synthesis of giant unimolecular dendrimers is challenging due, in part, to difficulties encountered at higher generations, in both convergent and divergent protocols because of the multistep construction/purification process. Herein, we report a hybrid synthetic procedure in which the core is constructed last. This quantitative assembly generated a metallodendrimer that is supercharged (120+), large (11.3 nm diameter), and its core was previously established. The series of complexes has been unequivocally characterized by NMR, ESI-IM-MS, and TEM techniques.

Under chaotropic conditions, DNA released from lysed cells causes the aggregation of paramagnetic beads in a rotating magnetic field in a manner that is independent of the presence of other cellular components. The extent of aggregation correlates with the mass of DNA in a quantitative manner (Leslie, D. C. et al., J. Am. Chem. Soc. 2012, 134, 5689-96), and from this, the number of DNA-containing cells in the sample can be enumerated. Microbial growth testing is demonstrated by monitoring bead aggregation with E. coli in the presence of ampicillin. Without the need for fluorescent labeling or Coulter counting, the white blood cell count can be defined directly from a microliter of crude whole blood. Specificity is brought to the process by coupling bead-based immunocapture with DNA-bead aggregation allowing for the enumeration of CD4+ T cells from human blood samples. The results of DNA-induced bead aggregation had a 95% correlation with those generated by flow cytometry. With the process requiring only inexpensive, widely available benchtop laboratory hardware, a digital camera, and a simple algorithm, this provided a highly accessible alternative to more expensive cell-counting techniques.

Intracellular pH (pHi) is a crucial parameter in cell biology; thus, a series of pH probes have been developed to determine pHi changes in living cells. However, more sensitive and non-perturbing ratiometric pH probes are needed for accurate pHi measurements. While the fluorescence of circular permutated YFP (cpYFP) is hypersensitive to pH changes due to its intrinsic properties, the single excitation peak of this protein restricts its capacity of becoming a rational type of pH sensor. Herein, we collected several cpYFP-based probes with dual excitation peaks and constructed their corresponding loss-of-function mutants to screen for a potential competent pH probe. The most sensitive probe was named NocPer. NocPer consists of cpYFP inserted into inactive-mutated GAF and AAA + , which are two regulatory domains of E. coli NorR, a nitric oxide (NO)-specific transcription factor. Fluorescence emission of NocPer peaks at 517 nm while exhibiting dual excitation peaks at 420 and 495 nm, which can be used for ratiometric imaging. This new pH sensor has a large ratio response dynamic (pH range of 7.0–11.0), which covers the physiological pH range (pH 7.0–8.0), and exhibits an approximately 3-fold higher fluorescent signal in response to a pH increase from 7.0 to 8.0 than that of pHluorin. Using NocPer, we discovered a new biological phenomenon in which NO exposure decreases the E. coli pHi, which led to the hypothesis that pathogens decrease their own pHi during infection. Further, we elucidated that the NO-induced inhibition of cytochrome c oxidase in the respiratory chain is responsible for the decline in pHi, which might represent a protective strategy of E. coli under NO stress conditions. Our results demonstrated that NocPer is a ratiometric pH probe with high sensitivity for the physiological pH range.

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