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[Fe-(pyrazine){Pd(CN)4}] (pyrazine = pz) thin films were fabricated using a layer-by-layer assembly approach, a method known to be tunable, versatile, and scalable, since thin films are better-suited for industrial applications. In this study, [Fe-(pz){Pd(CN)4}] powder was synthesized, and the results obtained from a vibrating sample magnetometer verified the presence of an abrupt hysteresis loop with widths of 45 K centered around 300 K, indicating good cooperativity. Super conducting quantum interference device magnetometry results indicated a slow spin transition with temperature but with evidence of hysteresis for thin film samples. X-ray absorption analysis provided further support of the spin crossover behavior but differs from the magnetometry because the spin state transition at the surface differs from the bulk of the thin film. X-ray photoelectron spectroscopy provided some insight into issues with the film deposition process and multiplex fitting was used to further support the claim that the surface of the film is different than the bulk of the film.
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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.
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Hollow block copolymer particles called polymer vesicles (polymersomes) serve as versatile containers for compartmentalization in synthetic biology and drug delivery. Recently, there has been growing interest in using polymersomes as colloidal building blocks for creating higher-order clustered structures. Most reports thus far rely on the use of DNA base-pairing interactions to "glue" polymersomes with other colloidal components. In this study, we present two alternative electrostatically driven approaches to assemble polymersomes and model colloids (micelles) into hybrid clusters. The first approach uses pH to manipulate electrostatic interactions and effectively control the clustering extent of micellar subunits on polymersomes, while the second approach relies on the hydrolysis of an acid trigger, glucono delta-lactone (GDL), to introduce temporal control over clustering. We envisage our approaches and structures reported herein will help inspire the creation of new prospects for materials science and biomedical applications.
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In an effort to reconcile the various interpretations for the cation components of the 2p3/2observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p3/2core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p3/2core levels of NiFe2O4thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles NixCo1-xFe2O4(x= 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe2O4thin film. Surface-to-bulk core level shifts are also observed in CoFe2O4and NiCo2O4thin films but not as significantly as in NiFe2O4thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles.
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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.
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Citocromos c , Nitrogênio , Magnetismo , Diamante , Fenômenos MagnéticosRESUMO
Polymersomes are polymeric analogues of liposomes with exceptional physical and chemical properties. Despite being dubbed as next-generation vesicles since their inception nearly three decades ago, polymersomes have yet to experience translation into the clinical or industrial settings. This is due to a lack of reliable methods to upscale production without compromising control over polymersome properties. Herein we report a continuous flow methodology capable of producing near-monodisperse polymersomes at scale (≥3 g/h) with the possibility of performing downstream polymersome manipulation. Unlike conventional polymersomes, our polymersomes exhibit metastability under ambient conditions, persisting for a lifetime of ca. 7 days, during which polymersome growth occurs until a dynamic equilibrium state is reached. We demonstrate how this metastable state is key to the implementation of downstream processes to manipulate polymersome size and/or shape in the same continuous stream. The methodology operates in a plug-and-play fashion and is applicable to various block copolymers.
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Long-term, real-time molecular monitoring in complex biological environments is critical for our ability to understand, prevent, diagnose, and manage human diseases. Aptamer-based electrochemical biosensors possess the promise due to their generalizability and a high degree of selectivity. Nevertheless, the operation of existing aptamer-based biosensors in vivo is limited to a few hours. Here, we report a first-generation long-term in vivo molecular monitoring platform, named aptamer-graphene microtransistors (AGMs). The AGM incorporates a layer of pyrene-(polyethylene glycol)5-alcohol and DNase inhibitor-doped polyacrylamide hydrogel coating to reduce biofouling and aptamer degradation. As a demonstration of function and generalizability, the AGM achieves the detection of biomolecules such as dopamine and serotonin in undiluted whole blood at 37 °C for 11 days. Furthermore, the AGM successfully captures optically evoked dopamine release in vivo in mice for over one week and demonstrates the capability to monitor behaviorally-induced endogenous dopamine release even after eight days of implantation in freely moving mice. The results reported in this work establish the potential for chronic aptamer-based molecular monitoring platforms, and thus serve as a new benchmark for molecular monitoring using aptamer-based technology.
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Rapid and ultrasensitive point-of-care RNA detection plays a critical role in the diagnosis and management of various infectious diseases. The gold-standard detection method of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) is ultrasensitive and accurate yet limited by the lengthy turnaround time (1-2 days). On the other hand, an antigen test offers rapid at-home detection (typically ~15 min) but suffers from low sensitivity and high false-negative rates. An ideal point-of-care diagnostic device would combine the merits of PCR-level sensitivity and rapid sample-to-result workflow comparable to antigen testing. However, the existing detection platforms typically possess superior sensitivity or rapid sample-to-result time, but not both. This paper reports a point-of-care microfluidic device that offers ultrasensitive yet rapid detection of viral RNA from clinical samples. The device consists of a microfluidic chip for precisely manipulating small volumes of samples, a miniaturized heater for viral lysis and ribonuclease inactivation, a Cas13a-electrochemical sensor for target preamplification-free and ultrasensitive RNA detection, and a smartphone-compatible potentiostat for data acquisition. As demonstrations, the devices achieve the detection of heat-inactivated SARS-CoV-2 samples with a limit of detection down to 10 aM within 25 minutes, which is comparable to the sensitivity of RT-PCR and rapidness of an antigen test. The platform also successfully distinguishes all nine positive unprocessed clinical SARS-CoV-2 nasopharyngeal swab samples from four negative samples within 25 minutes of sample-to-result time. Together, this device provides a point-of-care solution that can be deployed in diverse settings beyond laboratory environments for rapid and accurate detection of RNA from clinical samples. The device can potentially be expandable to detect other viral targets, such as human immunodeficiency virus self-testing and Zika virus, where rapid and ultrasensitive point-of-care detection is required.
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COVID-19 , Infecção por Zika virus , Zika virus , Humanos , Sistemas Automatizados de Assistência Junto ao Leito , SARS-CoV-2/genética , COVID-19/diagnóstico , Microfluídica , RNA Viral/genética , RNA Viral/análise , Zika virus/genética , Sensibilidade e EspecificidadeRESUMO
[Fe(Htrz)2(trz)](BF4) (Fe-triazole) spin crossover molecules show thermal, electrical, and optical switching between high spin (HS) and low spin (LS) states, making them promising candidates for molecular spintronics. The LS and HS transitions originate from the electronic configurations of Fe(II) and are considered to be diamagnetic and paramagnetic, respectively. The Fe(II) LS state has six paired electrons in the ground states with no interaction with the magnetic field and a diamagnetic behavior is usually observed. While the bulk magnetic properties of Fe-triazole compounds are widely studied by standard magnetometry techniques, their magnetic properties at the individual level are missing. Here we use nitrogen vacancy (NV) based magnetometry to study the magnetic properties of the Fe-triazole LS state of nanoparticle clusters and individual nanorods of size varying from 20 to 1000 nm. Scanning electron microscopy (SEM) and Raman spectroscopy are performed to determine the size of the nanoparticles/nanorods and to confirm their respective spin states. The magnetic field patterns produced by the nanoparticles/nanorods are imaged by NV magnetic microscopy as a function of applied magnetic field (up to 350 mT) and correlated with SEM and Raman. We found that in most of the nanorods the LS state is slightly paramagnetic, possibly originating from the surface oxidation and/or the greater Fe(III) presence along the nanorods' edges. NV measurements on the Fe-triazole LS state nanoparticle clusters revealed both diamagnetic and paramagnetic behavior. Our results highlight the potential of NV quantum sensors to study the magnetic properties of spin crossover molecules and molecular magnets.
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Future molecular microelectronics require the electronic conductivity of the device to be tunable without impairing the voltage control of the molecular electronic properties. This work reports the influence of an interface between a semiconducting polyaniline polymer or a polar poly-D-lysine molecular film and one of two valence tautomeric complexes, i.e., [CoIII(SQ)(Cat)(4-CN-py)2] â [CoII(SQ)2(4-CN-py)2] and [CoIII(SQ)(Cat)(3-tpp)2] â [CoII(SQ)2(3-tpp)2]. The electronic transitions and orbitals are identified using X-ray photoemission, X-ray absorption, inverse photoemission, and optical absorption spectroscopy measurements that are guided by density functional theory. Except for slightly modified binding energies and shifted orbital levels, the choice of the underlying substrate layer has little effect on the electronic structure. A prominent unoccupied ligand-to-metal charge transfer state exists in [CoIII(SQ)(Cat)(3-tpp)2] â [CoII(SQ)2(3-tpp)2] that is virtually insensitive to the interface between the polymer and tautomeric complexes in the CoII high-spin state.
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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.
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Urânio , Espectroscopia Fotoeletrônica , Urânio/química , Peptídeos , Raios X , ÍonsRESUMO
We have successfully designed a uranyl ion (U(VI)-specific peptide and used it in the fabrication of an electrochemical sensor. The 12-amino acid peptide sequence, (n) DKDGDGYIpTAAE (c), originates from calmodulin, a Ca(II)-binding protein, and contains a phosphothreonine that enhances the sequence's affinity for U(VI) over Ca(II). The sensing mechanism of this U(VI) sensor is similar to other electrochemical peptide-based sensors, which relies on the change in the flexibility of the peptide probe upon interacting with the target. The sensor was systematically characterized using alternating current voltammetry (ACV) and cyclic voltammetry. Its limit of detection was 50 nM, which is lower than the United States Environmental Protection Agency maximum contaminant level for uranium. The signal saturation time was ~40 min. In addition, it showed minimal cross-reactivity when tested against nine different metal ions, including Ca(II), Mg(II), Pb(II), Hg(II), Cu(II), Fe(II), Zn(II), Cd(II), and Cr(VI). Its reusability and ability to function in diluted aquifer and drinking water samples were further confirmed and validated. The response of the sensor fabricated with the same peptide sequence but with a nonphosphorylated threonine was also analyzed, substantiating the positive effects of threonine phosphorylation on U(VI) binding. This study places emphasis on strategic utilization of non-standard amino acids in the design of metal ion-chelating peptides, which will further diversify the types of peptide recognition elements available for metal ion sensing applications.
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Mercúrio , Treonina , Fosforilação , Íons/química , Metais , CalmodulinaRESUMO
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.
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Dopamina , Grafite , Animais , Encéfalo/metabolismo , Dopamina/metabolismo , Grafite/química , Camundongos , Norepinefrina , Oligonucleotídeos/metabolismo , Ratos , Serotonina/metabolismoRESUMO
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 doxorubicinâ¢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.
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Éteres Metílicos , Nanopartículas , Estrona/farmacologia , Humanos , Ligantes , Metacrilatos , Polietilenoglicóis , Polímeros/farmacologiaRESUMO
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.
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Albumin has consistently demonstrated its potential for enhancing the delivery of drugs and polymer-drug conjugates, binding via supramolecular forces within its multiple binding sites. Herein, we introduce saturation transfer difference (STD-NMR) as a method to identify the interactions between a polymer library and bovine serum albumin (BSA). With STD-NMR, the binding ability of polymers can be quickly screened by focusing on their individual structural features, making this technique more suitable for high throughput screening in comparison to traditional fluorescence studies.
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Polímeros , Soroalbumina Bovina , Sítios de Ligação , Espectroscopia de Ressonância Magnética/métodos , Polímeros/metabolismo , Ligação Proteica , Soroalbumina Bovina/químicaRESUMO
Global food and water safety issues have prompted the development of highly sensitive, specific, and fast analytical techniques for food and water analysis. The electrochemical aptamer-based detection platform (E-aptasensor) is one of the more promising detection techniques because of its unique combination of advantages that renders these sensors ideal for detection of a wide range of target analytes. Recent research results have further demonstrated that this technique has potential for real world analysis of food and water contaminants. This review summaries the recently developed E-aptasensors for detection of analytes related to food and water safety, including bacteria, mycotoxins, algal toxins, viruses, drugs, pesticides, and metal ions. Ten different electroanalytical techniques and one opto-electroanalytical technique commonly employed with these sensors are also described. In addition to highlighting several novel sensor designs, this review also describes the strengths, limitations, and current challenges this technology faces, and future development trend.
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Aptâmeros de Nucleotídeos/metabolismo , Técnicas Biossensoriais/métodos , Análise de Alimentos/métodos , Água/química , Animais , Eletroquímica , Humanos , Nanoestruturas/químicaRESUMO
We report the development of an electrochemical aptamer-based sensor for real time detection of tumor necrosis factor-alpha. The focus of this study is to evaluate the effects of the redox label location on the overall sensor performance, including sensor stability, detection limit, reusability, and selectivity. Three aptamer probes, each labeled with methylene blue (MB) at a specific location, were designed and employed in the fabrication of the sensors. Among the three sensors, the sensor fabricated using an aptamer with the MB label located at the distal end has a detection limit of 100â¯pM and is regenerable. The sensor fabricated using an aptamer with an internal MB modification has a detection limit of 10â¯nM and is not regenerable. Both sensors can be employed in complex biological samples such as 50% urine and 50% saliva. However, the sensor fabricated with an aptamer with the MB label located at the proximal end suffers from poor reproducibility and is highly unstable, thus limiting its application as a sensor. On the bases of these results, placing the MB label at the distal end of the aptamer probe appears to be the most advantageous for this sensor design for it does not interfere with monolayer formation and target binding.
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Aptâmeros de Nucleotídeos/metabolismo , Eletroquímica/instrumentação , Fator de Necrose Tumoral alfa/análise , Aptâmeros de Nucleotídeos/genética , Sequência de Bases , Modelos Moleculares , Oxirredução , Conformação Proteica , Fator de Necrose Tumoral alfa/química , Fator de Necrose Tumoral alfa/metabolismoRESUMO
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.
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Caderinas/química , Proteínas Imobilizadas/química , Chumbo/análise , Chumbo/urina , Peptídeos/química , Saliva/química , Sequência de Aminoácidos , Sítios de Ligação , Técnicas Biossensoriais/métodos , Cálcio/química , Carbono/química , Técnicas Eletroquímicas/métodos , Eletrodos , Ouro/química , Humanos , Azul de Metileno/químicaRESUMO
We report the design and fabrication of a "signal-on" electrochemical aptamer-based (E-AB) sensor for detection of ampicillin. The signaling of the sensor is based on target binding-induced changes in the conformation and flexibility of the methylene blue-modified aptamer probe. The sensor's response is fast; signal saturation can be reached in ~ 200s. Since all the sensor components are surface-immobilized, it is regenerable and can be reused for at least three times. It has demonstrated good specificity and is capable of differentiating between ampicillin and structurally similar antibiotics such as amoxicillin. More importantly, it is selective enough to be employed directly in complex samples, including serum, saliva, and milk. Although both alternating current voltammetry (ACV) and square wave voltammetry (SWV) are suitable sensor characterization techniques, our results show that ACV is better suited for target analysis. Even under the optimal experimental conditions, the limit of detection of the sensor obtained in ACV (1µM) is significantly lower than that obtained in SWV (30µM).