Nitrogen-Vacancy Magnetic Relaxometry of Nanoclustered Cytochrome C Proteins.

Nitrogen-vacancy (NV) magnetometry offers an alternative tool to detect paramagnetic centers in cells with a favorable combination of magnetic sensitivity and spatial resolution. Here, we employ NV magnetic relaxometry to detect cytochrome C (Cyt-C) nanoclusters. Cyt-C is a water-soluble protein that plays a vital role in the electron transport chain of mitochondria. Under ambient conditions, the heme group in Cyt-C remains in the Fe3+ state, which is paramagnetic. We vary the concentration of Cyt-C from 6 to 54 µM and observe a reduction of the NV spin-lattice relaxation time (T1) from 1.2 ms to 150 µs, which is attributed to the spin noise originating from the Fe3+ spins. NV T1 imaging of Cyt-C drop-casted on a nanostructured diamond chip allows us to detect the relaxation rates from the adsorbed Fe3+ within Cyt-C.

Streamlined Formation and Manipulation of Charged Polymersomes.

Charged polymersomes are attractive for advanced material applications due to their versatile encapsulation capabilities and charge-induced functionality. Although desirable, the pH-sensitivity of charged block copolymers adds complexity to its self-assembly process, making it challenging to produce charged polymersomes in a reliable manner. In this work, a flow approach to control and strike a delicate balance between solvent composition and pH for self-assembly is used. This allows for the identification of a phase window to reliably produce of charged polymersomes. The utility of this approach to streamline downstream processes, such as morphological transformation or in-line purification is further demonstrated. As proof-of-concept, it is shown that the processed polymersomes can be used for surface modifications facilitated by charge complexation.

Multiplexed Monitoring of Neurochemicals via Electrografting-Enabled Site-Selective Functionalization of Aptamers on Field-Effect Transistors.

Neurochemical corelease has received much attention in understanding brain activity and cognition. Despite many attempts, the multiplexed monitoring of coreleased neurochemicals with spatiotemporal precision and minimal crosstalk using existing methods remains challenging. Here, we report a soft neural probe for multiplexed neurochemical monitoring via the electrografting-assisted site-selective functionalization of aptamers on graphene field-effect transistors (G-FETs). The neural probes possess excellent flexibility, ultralight mass (28 mg), and a nearly cellular-scale dimension of 50 µm × 50 µm for each G-FET. As a demonstration, we show that G-FETs with electrochemically grafted molecular linkers (-COOH or -NH2) and specific aptamers can be used to monitor serotonin and dopamine with high sensitivity (limit of detection: 10 pM) and selectivity (dopamine sensor >22-fold over norepinephrine; serotonin sensor >17-fold over dopamine). In addition, we demonstrate the feasibility of the simultaneous monitoring of dopamine and serotonin in a single neural probe with minimal crosstalk and interferences in phosphate-buffered saline, artificial cerebrospinal fluid, and harvested mouse brain tissues. The stability studies show that multiplexed neural probes maintain the capability for simultaneously monitoring dopamine and serotonin with minimal crosstalk after incubating in rat cerebrospinal fluid for 96 h, although a reduced sensor response at high concentrations is observed. Ex vivo studies in harvested mice brains suggest potential applications in monitoring the evoked release of dopamine and serotonin. The developed multiplexed detection methodology can also be adapted for monitoring other neurochemicals, such as metabolites and neuropeptides, by simply replacing the aptamers functionalized on the G-FETs.

Development of an Albumin-Polymer Bioconjugate via Covalent Conjugation and Supramolecular Interactions.

Preexisting serum albumin-polymer bioconjugates have been formed either through covalent conjugation or supramolecular interactions. However, the viability of producing a bioconjugate where both covalent conjugation and supramolecular interactions have been adopted is yet to be explored. In this work, the noncovalent interaction of two polymers bearing fatty acid-based end-functionalities were compared and the superior binder was carried forward for testing with serum albumin that possessed a polymer conjugated to its Cys34 residue. The studies demonstrated that an albumin-polymer bioconjugate equipped with polymers via both covalent and supramolecular interactions can be successfully achieved.

Controlling the Biological Behaviors of Polymer-Coated Upconverting Nanoparticles by Adjusting the Linker Length of Estrone Ligands.

The estrone ligand is used for modifying nanoparticle surfaces to improve their targeting effect on cancer cell lines. However, to date, there is no common agreement on the ideal linker length to be used for the optimum targeting performance. In this study, we aimed to investigate the impact of poly(poly ethylene glycol methyl ether methacrylate) (PPEGMEMA) linker length on the cellular uptake behavior of polymer-coated upconverting nanoparticles (UCNPs). Different triblock terpolymers, poly(poly (ethylene glycol) methyl ether methacrylate)-block-polymethacrylic acid-block-polyethylene glycol methacrylate phosphate (PPEGMEMAx-b-PMAAy-b-PEGMP3: x = 7, 15, 33, and 80; y = 16, 20, 18, and 18), were synthesized with different polymer linker chain lengths between the surface and the targeting ligand by reversible addition-fragmentation chain transfer polymerization. The estrone ligand was attached to the polymer via specific terminal conjugation. The cellular association of polymer-coated UCNPs with linker chain lengths was evaluated in MCF-7 cells by flow cytometry. Our results showed that the bioactivity of ligand modification is dependent on the length of the polymer linker. The shortest polymer PPEGMEMA7-b-PMAA16-b-PEGMP3 with estrone at the end of the polymer chain was found to have the best cellular association behavior in the estrogen receptor (ER)α-positive expression cell line MCF-7. Additionally, the anticancer drug doxorubicin•HCl was encapsulated in the nanocarrier to evaluate the 2D and 3D cytotoxicity. The results showed that estrone modification could efficiently improve the cellular uptake in ERα-positive expression cell lines and in 3D spheroid models.

Evidence for surface effects on the intermolecular interactions in Fe(II) spin crossover coordination polymers.

From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), it is evident that the spin state transition behavior of Fe(II) spin crossover coordination polymer crystallites at the surface differs from the bulk. A comparison of four different coordination polymers reveals that the observed surface properties may differ from bulk for a variety of reasons. There are Fe(II) spin crossover coordination polymers with either almost complete switching of the spin state at the surface or no switching at all. Oxidation, differences in surface packing, and changes in coordination could all contribute to making the surface very different from the bulk. Some Fe(II) spin crossover coordination polymers may be sufficiently photoactive so that X-ray spectroscopies cannot discern the spin state transition.

Coordination Chemistry of Uranyl Ions with Surface-Immobilized Peptides: An XPS Study.

The coordination chemistry of uranyl ions with surface immobilized peptides was studied using X-ray photoemission spectroscopy (XPS). All the peptides in the study were modified using a six-carbon alkanethiol as a linker on a gold substrate with methylene blue as the redox label. The X-ray photoemission spectra reveal that each modified peptide interacts differently with the uranyl ion. For all the modified peptides, the XPS spectra were taken in both the absence and presence of the uranium, and their comparison reveals that the interaction depends on the chemical group present in the peptides. The XPS results show that, among all the modified peptides in the current study, the (arginine)9 (R9) modified peptide showed the largest response to uranium. In the order of response to uranium, the second largest response was shown by the modified (arginine)6 (R6) peptide followed by the modified (lysine)6 (K6) peptide. Other modified peptides, (alanine)6 (A6), (glutamic acid)6 (E6) and (serine)6 (S6), did not show any response to uranium.

Evolution of an Electronic Health Record Based-Human Immunodeficiency Virus (HIV) Screening Program in an Urban Emergency Department for Diagnosing Acute and Chronic HIV Infection.

BACKGROUND: Since 2006, Centers for Disease Control and Prevention guidelines recommend routine opt-out human immunodeficiency virus (HIV) testing among sexually active 13- to 64-year-olds. Earlier diagnosis and treatment of HIV infection reduces morbidity and mortality and can limit transmission to others. OBJECTIVE: Our aim was to increase HIV testing, diagnosis, and linkage to care in the emergency department (ED). METHODS: Beginning May 4, 2015, we utilized our electronic health record (EHR) to enhance HIV testing in patients seen in the Rush University Medical Center emergency department in Chicago, IL, who were 13-64 years of age, did not have HIV listed on their problem list, and did not have an HIV antigen/antibody (Ag/Ab) test in the EHR within the past rolling 12-month period. Strategies included use of a "Best Practice Advisory" and later auto-order screening linked to a complete blood count order. RESULTS: Our baseline HIV test rate was 2.5% of the target population by age (average of 93 tests per month). From May 4, 2015 to January 31, 2019, 137,749 patients of 240,091 ED visits met our test criteria and 23,588 (17.1% of the target population) HIV Ag/Ab tests were performed, resulting in 164 positive tests. We identified 18 acute seroconverters, 51 new chronically infected persons, and 95 known infected, many of who had not disclosed their status. Our positive test rate was 0.70%, which dropped to 0.29% if only newly diagnosed individuals were counted. CONCLUSIONS: EHR enhancements in a large urban ED identifies both newly diagnosed acute and chronically HIV-infected persons. Identification of previously diagnosed patients offers an opportunity to relink them to care.

Application of Calcium-Binding Motif of E-Cadherin for Electrochemical Detection of Pb(II).

We report, for the first time, the use of a 13-amino-acid peptide sequence derived from the calcium-binding site of E-cadherin in the fabrication of an electrochemical peptide-based (E-PB) Pb(II) sensor. The sensing mechanism is analogous to that of previously developed E-PB sensors. Binding of Pb(II) rigidifies the surface-immobilized and methylene blue (MB)-modified peptide probe, thereby limiting the accessibility of the tethered MB to the electrode surface. This change in probe flexibility results in a reduction in the MB current that is dependent on the target concentration. The sensor behaves as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry, but it can behave as a "signal-on" sensor in differential pulse voltammetry when a longer pulse width is employed. It is capable of specific detection of Pb(II) and is selective enough to be employed in realistically complex samples such as diluted tap water, saliva, and urine samples. The detection is fast; signal saturation can be achieved in <60 s. The sensor can also be fabricated on gold-plated screen-printed carbon electrodes, electrode substrates that are ideal for cost-effective analysis of Pb(II) in real-world settings.

Tunable Signal-Off and Signal-On Electrochemical Cisplatin Sensor.

We report the first electrochemical cisplatin sensor fabricated with a thiolated and methylene blue (MB)-modified oligo-adenine (A)-guanine (G) DNA probe. Depending on the probe coverage, the sensor can behave as a signal-off or signal-on sensor. For the high-coverage sensor, formation of intrastrand Pt(II)-AG adducts rigidifies the oligo-AG probe, resulting in a concentration-dependent decrease in the MB signal. For the low-coverage sensor, the increase in probe-to-probe spacing enables binding of cisplatin via the intrastrand GNG motif (N = A), generating a bend in the probe which results in an increase in the MB current. Although both high-coverage signal-off and low-coverage signal-on sensors are capable of detecting cisplatin, the signal-on sensing mechanism is better suited for real time analysis of cisplatin. The low-coverage sensor has a lower limit of detection, wider optimal AC frequency range, and faster response time. It has high specificity for cisplatin and potentially other Pt(II) drugs and does not cross-react with satraplatin, a Pt(IV) prodrug. It is also selective enough to be employed directly in 50% saliva and 50% urine. This detection strategy may offer a new approach for sensitive and real time analysis of cisplatin in clinical samples.