76 research outputs found
Surface plasmon resonance assay for label-free and selective detection of hiv-1 p24 protein
The early detection of the human immunodeficiency virus (HIV) is of paramount importance to achieve efficient therapeutic treatment and limit the disease spreading. In this perspective, the assessment of biosensing assay for the HIV-1 p24 capsid protein plays a pivotal role in the timely and selective detection of HIV infections. In this study, multi-parameter-SPR has been used to develop a reliable and label-free detection method for HIV-1 p24 protein. Remarkably, both physical and chemical immobilization of mouse monoclonal antibodies against HIV-1 p24 on the SPR gold detecting surface have been characterized for the first time. The two immobilization techniques returned a capturing antibody surface coverage as high as (7.5 ± 0.3) × 1011 molecule/cm2 and (2.4 ± 0.6) × 1011 molecule/cm2, respectively. However, the covalent binding of the capturing antibodies through a mixed self-assembled monolayer (SAM) of alkanethiols led to a doubling of the p24 binding signal. Moreover, from the modeling of the dose-response curve, an equilibrium dissociation constant KD of 5.30 × 10−9 M was computed for the assay performed on the SAM modified surface compared to a much larger KD of 7.46 × 10−5 M extracted for the physisorbed antibodies. The chemically modified system was also characterized in terms of sensitivity and selectivity, reaching a limit of detection of (4.1 ± 0.5) nM and an unprecedented selectivity ratio of 0.02
Doping-induced carrier profiles in organic semiconductors determined from capacitive extraction-current transients
A method to determine the doping induced charge carrier profiles in lightly and moderately doped organic semiconductor thin films is presented. The theory of the method of Charge Extraction by
a Linearly Increasing Voltage technique in the doping-induced capacitive regime (doping-CELIV) is extended to the case with non-uniform doping profiles and the analytical description is verified with drift-diffusion simulations. The method is demonstrated experimentally on evaporated organic small- molecule thin films with a controlled doping profile, and solution-processed thin films where the non- uniform doping profile is unintentional, probably induced during the deposition process, and a priori unknown. Furthermore, the method offers a possibility of directly probing charge-density distributions at interfaces between highly doped and lightly doped or undoped layers
A large-area organic transistor with 3D-printed sensing gate for noninvasive single-molecule detection of pancreatic mucinous cyst markers
Early diagnosis in a premalignant (or pre-invasive) state represents the only chance for cure in neoplastic diseases such as pancreatic-biliary cancer, which are otherwise detected at later stages and can only be treated using palliative approaches, with no hope for a cure. Screening methods for the purpose of secondary prevention are not yet available for these cancers. Current diagnostic methods mostly rely on imaging techniques and conventional cytopathology, but they do not display adequate sensitivity to allow valid early diagnosis. Next-generation sequencing can be used to detect DNA markers down to the physical limit; however, this assay requires labeling and is time-consuming. The additional determination of a protein marker that is a predictor of aggressive behavior is a promising innovative approach, which holds the potential to improve diagnostic accuracy. Moreover, the possibility to detect biomarkers in blood serum offers the advantage of a noninvasive diagnosis. In this study, both the DNA and protein markers of pancreatic mucinous cysts were analyzed in human blood serum down to the single-molecule limit using the SiMoT (single-molecule assay with a large transistor) platform. The SiMoT device proposed herein, which exploits an inkjet-printed organic semiconductor on plastic foil, comprises an innovative 3D-printed sensing gate module, consisting of a truncated cone that protrudes from a plastic substrate and is compatible with standard ELISA wells. This 3D gate concept adds tremendous control over the biosensing system stability, along with minimal consumption of the capturing molecules and body fluid samples. The 3D sensing gate modules were extensively characterized from both a material and electrical perspective, successfully proving their suitability as detection interfaces for biosensing applications. KRAS and MUC1 target molecules were successfully analyzed in diluted human blood serum with the 3D sensing gate functionalized with b-KRAS and anti-MUC1, achieving a limit of detection of 10 zM and 40 zM, respectively. These limits of detection correspond to (1 ± 1) KRAS and (2 ± 1) MUC1 molecules in the 100 μL serum sample volume. This study provides a promising application of the 3D SiMoT platform, potentially facilitating the timely, noninvasive, and reliable identification of pancreatic cancer precursor cysts
Ultrafast Dynamics of Localized and Delocalized Polaron Transitions in P3HT/PCBM Blend Materials: The Effects of PCBM Concentration
Nowadays, organic solar cells have the interest of engineers for manufacturing flexible and low cost devices. The considerable progress of this nanotechnology area presents the possibility of investigating new effects from a fundamental science point of view. In this letter we highlight the influence of the concentration of fullerene molecules on the ultrafast transport properties of charged electrons and polarons in P3HT/PCBM blended materials which are crucial for the development of organic solar cells. Especially, we report on the femtosecond dynamics of localized (P2at 1.45 eV) and delocalized (DP2at 1.76 eV) polaron states of P3HT matrix with the addition of fullerene molecules as well as the free-electron relaxation dynamics of PCBM-related states. Our study shows that as PCBM concentration increases, the amplified exciton dissociation at bulk heterojunctions leads to increased polaron lifetimes. However, the increase in PCBM concentration can be directly related to the localization of polarons, creating thus two competing trends within the material. Our methodology shows that the effect of changes in structure and/or composition can be monitored at the fundamental level toward optimization of device efficiency
Electron correlation effects in electron-hole recombination in organic light-emitting diodes
We develop a general theory of electron--hole recombination in organic light
emitting diodes that leads to formation of emissive singlet excitons and
nonemissive triplet excitons. We briefly review other existing theories and
show how our approach is substantively different from these theories. Using an
exact time-dependent approach to the interchain/intermolecular charge-transfer
within a long-range interacting model we find that, (i) the relative yield of
the singlet exciton in polymers is considerably larger than the 25% predicted
from statistical considerations, (ii) the singlet exciton yield increases with
chain length in oligomers, and, (iii) in small molecules containing nitrogen
heteroatoms, the relative yield of the singlet exciton is considerably smaller
and may be even close to 25%. The above results are independent of whether or
not the bond-charge repulsion, X_perp, is included in the interchain part of
the Hamiltonian for the two-chain system. The larger (smaller) yield of the
singlet (triplet) exciton in carbon-based long-chain polymers is a consequence
of both its ionic (covalent) nature and smaller (larger) binding energy. In
nitrogen containing monomers, wavefunctions are closer to the noninteracting
limit, and this decreases (increases) the relative yield of the singlet
(triplet) exciton. Our results are in qualitative agreement with
electroluminescence experiments involving both molecular and polymeric light
emitters. The time-dependent approach developed here for describing
intermolecular charge-transfer processes is completely general and may be
applied to many other such processes.Comment: 19 pages, 11 figure
A Single-Molecule Bioelectronic Portable Array for Early Diagnosis of Pancreatic Cancer Precursors
A cohort of 47 patients is screened for pancreatic cancer precursors with a portable 96-well bioelectronic sensing-array for single-molecule assay in cysts fluid and blood plasma, deployable at point-of-care (POC). Pancreatic cancer precursors are mucinous cysts diagnosed with a sensitivity of at most 80% by state-of-the-art cytopathological molecular analyses (e.g., KRASmut DNA). Adding the simultaneous assay of proteins related to malignant transformation (e.g., MUC1 and CD55) is deemed essential to enhance diagnostic accuracy. The bioelectronic array proposed here, based on single-molecule-with-a-large-transistor (SiMoT) technology, can assay both nucleic acids and proteins at the single-molecule limit-of-identification (LOI) (1% of false-positives and false-negatives). It comprises an enzyme-linked immunosorbent assay (ELISA)-like 8 × 12-array organic-electronics disposable cartridge with an electrolyte-gated organic transistor sensor array, and a reusable reader, integrating a custom Si-IC chip, operating via software installed on a USB-connected smart device. The cartridge is complemented by a 3D-printed sensing gate cover plate. KRASmut, MUC1, and CD55 biomarkers either in plasma or cysts-fluid from 5 to 6 patients at a time, are multiplexed at single-molecule LOI in 1.5 h. The pancreatic cancer precursors are classified via a machine-learning analysis resulting in at least 96% diagnostic-sensitivity and 100% diagnostic-specificity. This preliminary study opens the way to POC liquid-biopsy-based early diagnosis of pancreatic-cancer precursors in plasma
Ultrafast Charge Photogeneration Dynamics in Ground-State Charge-Transfer Complexes Based on Conjugated Polymers
Charge transport and recombination in bulk heterojunction solar cells studied by the photoinducted charge extraction by linearly increasing voltage technique
Charge carriermobility and recombination in a bulk heterojunctionsolar cell based on the mixture of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C61 (PCBM) has been studied using the novel technique of photoinduced charge carrier extraction in a linearly increasing voltage (Photo-CELIV). In this technique, charge carriers are photogenerated by a short laser flash, and extracted under a reverse bias voltage ramp after an adjustable delay time (tdel). The Photo-CELIV mobility at room temperature is found to be μ = 2 × 10−4 cm2 V−1 s−1, which is almost independent on charge carrier density, but slightly dependent on tdel. Furthermore, determination of charge carrier lifetime and demonstration of an electric field dependent mobility is presented
Bimolecular recombination coefficient as a sensitive testing parameter for low-mobility solar-cell materials
Bimolecular charge carrier recombination has been clarified in bulk-heterojunction solar cells based on a blend of regioregular poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]- methanofullerene using the time-of-flight method. We show how bimolecular recombination influences the charge carrier transport, how it limits the efficiency of low-mobility solar cells, and how to estimate the bimolecular recombination coefficient. We found that bimolecular recombination in these efficient photovoltaic materials is orders of magnitude slower as compared to Langevin recombination expected for low-mobility materials. This effect is inherent to the nanomorphology of the bicontinuous interpenetrating network creating separate pathways for electrons and holes, and paves the way for the fabrication of bulk-heterojunction solar cells where bimolecular recombination is not the limiting factor
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