A NIR luminescent copolymer based on platinum porphyrin as high permeable dissolved oxygen sensor for microbioreactors

The Challenges of O2 Detection in Biological Fluids: Classical Methods and Translation to Clinical Applications

Dissolved oxygen (DO) is deeply involved in preserving the life of cellular tissues and human beings due to its key role in cellular metabolism: its alterations may reflect important pathophysiological conditions. DO levels are measured to identify pathological conditions, explain pathophysiological mechanisms, and monitor the efficacy of therapeutic approaches. This is particularly relevant when the measurements are performed in vivo but also in contexts where a variety of biological and synthetic media are used, such as ex vivo organ perfusion. A reliable measurement of medium oxygenation ensures a high-quality process. It is crucial to provide a high-accuracy, real-time method for DO quantification, which could be robust towards different medium compositions and temperatures. In fact, biological fluids and synthetic clinical fluids represent a challenging environment where DO interacts with various compounds and can change continuously and dynamically, and further precaution is needed to obtain reliable results. This study aims to present and discuss the main oxygen detection and quantification methods, focusing on the technical needs for their translation to clinical practice. Firstly, we resumed all the main methodologies and advancements concerning dissolved oxygen determination. After identifying the main groups of all the available techniques for DO sensing based on their mechanisms and applicability, we focused on transferring the most promising approaches to a clinical in vivo/ex vivo setting.

Colorimetric and ratiometric fluorescent response for anthrax bio-indicator: A combination of rare earth MOF and rhodamine-derived dye

Bacillus anthracis spores have a unique biomarker of calcium dipicolinate (CaDPA). In this work, we reported a composite nanostructure for the optical sensing of DPA, with Eu (III)-doped metal-organic framework (MOF) as supporting lattice, a rhodamine-derived dye as sensing probe, respectively. By means of XRD, IR, TGA and photophysical analysis, this composite structure was carefully discussed. It was found that rhodamine absorption and emission were enhanced by DPA, while Eu emission was quenched by DPA. As a consequence, two sensing skills were observed from this composite structure, which are colorimetric sensing based on absorption spectra and ratiometric fluorescent sensing based on emission spectra. Linear sensing response was observed for both sensing channels with a warning signal at DPA concentration higher than 140 μM. Good selectivity was confirmed with a low LOD value of 0.52 μM. The sensing mechanism was revealed as the combination of emission turn-on effect triggered by DPA-released protons and emission turn-off effect originated from electron-transfer from EuBTC to DPA. This composite structure showed its advantage of naked eye detection and two sensing skills with linear response.

Review of Dissolved Oxygen Detection Technology: From Laboratory Analysis to Online Intelligent Detection

Dissolved oxygen is an important index to evaluate water quality, and its concentration is of great significance in industrial production, environmental monitoring, aquaculture, food production, and other fields. As its change is a continuous dynamic process, the dissolved oxygen concentration needs to be accurately measured in real time. In this paper, the principles, main applications, advantages, and disadvantages of iodometric titration, electrochemical detection, and optical detection, which are commonly used dissolved oxygen detection methods, are systematically analyzed and summarized. The detection mechanisms and materials of electrochemical and optical detection methods are examined and reviewed. Because external environmental factors readily cause interferences in dissolved oxygen detection, the traditional detection methods cannot adequately meet the accuracy, real-time, stability, and other measurement requirements; thus, it is urgent to use intelligent methods to make up for these deficiencies. This paper studies the application of intelligent technology in intelligent signal transfer processing, digital signal processing, and the real-time dynamic adaptive compensation and correction of dissolved oxygen sensors. The combined application of optical detection technology, new fluorescence-sensitive materials, and intelligent technology is the focus of future research on dissolved oxygen sensors.

Rapid prototyping of a novel and flexible paper based oxygen sensing patch via additive inkjet printing process

A novel and flexible oxygen sensing patch was successfully developed for wearable, industrial, food packaging, pharmaceutical and biomedical applications using a cost-efficient and rapid prototypable additive inkjet print manufacturing process. An oxygen sensitive ink was formulated by dissolving ruthenium dye and ethyl cellulose polymer in ethanol in a 1 : 1 : 98 (w/w/w) ratio. The patch was fabricated by depositing the oxygen sensitive ink on a flexible parchment paper substrate using an inkjet printing process. A maximum absorbance from 430 nm to 480 nm and a fluorescence of 600 nm was observed for the oxygen sensitive ink. The capability of the oxygen sensitive patch was investigated by measuring the fluorescence quenching lifetime of the printed dye for varying oxygen concentration levels. A fluorescence lifetime decay (τ) from ≈4 μs to ≈1.9 μs was calculated for the printed oxygen sensor patch, for oxygen concentrations varying from ≈5 mg L⁻¹ to ≈25 mg L⁻¹. A sensitivity of 0.11 μs mg L⁻¹ and a correlation coefficient of 0.9315 was measured for the printed patches. The results demonstrated the feasibility of employing an inkjet printing process for the rapid prototyping of flexible and moisture resistant oxygen sensitive patches which facilitates a non-invasive method for monitoring oxygen and its concentration levels.

A paper-based low cost and rapid prototypable flexible oxygen sensing patch was developed for the first time using a cost-efficient additive inkjet print manufacturing process for wearable, food packaging, pharmaceutical and biomedical applications.

Integration and application of optical chemical sensors in microbioreactors

The quantification of key variables such as oxygen, pH, carbon dioxide, glucose, and temperature provides essential information for biological and biotechnological applications and their development. Microfluidic devices offer an opportunity to accelerate research and development in these areas due to their small scale, and the fine control over the microenvironment, provided that these key variables can be measured. Optical sensors are well-suited for this task. They offer non-invasive and non-destructive monitoring of the mentioned variables, and the establishment of time-course profiles without the need for sampling from the microfluidic devices. They can also be implemented in larger systems, facilitating cross-scale comparison of analytical data. This tutorial review presents an overview of the optical sensors and their technology, with a view to support current and potential new users in microfluidics and biotechnology in the implementation of such sensors. It introduces the benefits and challenges of sensor integration, including, their application for microbioreactors. Sensor formats, integration methods, device bonding options, and monitoring options are explained. Luminescent sensors for oxygen, pH, carbon dioxide, glucose and temperature are showcased. Areas where further development is needed are highlighted with the intent to guide future development efforts towards analytes for which reliable, stable, or easily integrated detection methods are not yet available.

Influence of polymer composition on the sensitivity towards nitrite and nitric oxide of colorimetric disposable test strips

The influence of polymer composition on the sensitivity towards nitrite (NO₂^-) and nitric oxide (NO) of a series of 19 polymeric hydrogel films has been studied. The polymers, based on the hydrophilic monomer 2-hydroxyethylmethacrylate (HEMA), are able to encapsulate the colorimetric indicator 1,2-diaminoanthraquinone (DAQ) and to respond to NO₂^- and NO by visual changes. In the case of nitrite, the calculated limits of detection (LOD) for two of the polymeric sensors (10 μM) are very close to the sensitivity estimated for free DAQ in solution (LOD 5 μM), but with the advantage of a solid supported sensor with the format of a disposable test-strip made with affordable starting chemicals. The results are interpreted taking into account the nature and proportions of monomers and cross-linkers used for the synthesis of polymers. Key factors for obtaining sensitive materials are the hydrophilic character of the film along with the utilization of low levels of cross-linker and the use of an acidic monomer, like acrylic acid, as a building block.

High-performance dissolved oxygen sensors based on platinum(ii) porphyrin embedded in polystyrene beads

A ratiometric dissolved oxygen sensor synthesized via a swelling method exhibits high sensitivity, good reversibility and photo-stability.

Achieving near-infrared emission in platinum(ii) complexes by using an extended donor–acceptor-type ligand

Three D–A-type mononuclear and dinuclear platinum(ii) complexes, (TPA-BTPy)Pt(pic), (TPA-BTPy-Fl)Pt(pic) and [Fl(TPA-BTPy)₂]Pt₂(pic)₂, were designed and obtained.

Small molecular neutral microcrystalline iridium(III) complexes as promising molecular oxygen sensors

Small molecular neutral Ir(III) complexes have been demonstrated to be promising self-inclusive microcrystalline thin-film oxygen sensors with relatively high sensitivity (Ksv = 6.41), good stability, and linear Stern-Volmer behavior (R(2) = 0.9979).

In vivo and in situ tracking cancer chemotherapy by highly photostable NIR fluorescent theranostic prodrug

In vivo monitoring of the biodistribution and activation of prodrugs is urgently required. Near infrared (NIR) fluorescence-active fluorophores with excellent photostability are preferable for tracking drug release in vivo. Herein, we describe a NIR prodrug DCM-S-CPT and its polyethylene glycol-polylactic acid (PEG-PLA) loaded nanoparticles as a potent cancer therapy. We have conjugated a dicyanomethylene-4H-pyran derivative as the NIR fluorophore with camptothecin (CPT) as the anticancer drug using a disulfide linker. In vitro experiments verify that the high intracellular glutathione (GSH) concentrations in tumor cells cause cleavage of the disulfide linker, resulting in concomitantly the active drug CPT release and significant NIR fluorescence turn-on with large Stokes shift (200 nm). The NIR fluorescence of DCM-S-CPT at 665 nm with fast response to GSH can act as a direct off-on signal reporter for the GSH-activatable prodrug. Particularly, DCM-S-CPT possesses much better photostability than ICG, which is highly desirable for in situ fluorescence-tracking of cancer chemotherapy. DCM-S-CPT has been successfully utilized for in vivo and in situ tracking of drug release and cancer therapeutic efficacy in living animals by NIR fluorescence. DCM-S-CPT exhibits excellent tumor-activatable performance when intravenously injected into tumor-bearing nude mice, as well as specific cancer therapy with few side effects. DCM-S-CPT loaded in PEG-PLA nanoparticles shows even higher antitumor activity than free CPT, and is also retained longer in the plasma. The tumor-targeting ability and the specific drug release in tumors make DCM-S-CPT as a promising prodrug, providing significant advances toward deeper understanding and exploration of theranostic drug-delivery systems.

Detection and identification of Cu2+ and Hg2+ based on the cross-reactive fluorescence responses of a dansyl-functionalized film in different solvents

A dansyl-functionalized fluorescent film sensor was specially designed and prepared by assembling dansyl on a glass plate surface via a long flexible spacer containing oligo(oxyethylene) and amine units. The chemical attachment of dansyl moieties on the surface was verified by contact angle, XPS, and fluorescence measurements. Solvent effect examination revealed that the polarity-sensitivity was retained for the surface-confined dansyl moieties. Fluorescence quenching studies in water declared that the dansyl-functionalized SAM possesses a higher sensitivity towards Hg(2+) and Cu(2+) than the other tested divalent metal ions including Zn(2+), Cd(2+), Co(2+), and Pb(2+). Further measurements of the fluorescence responses of the film towards Cu(2+) and Hg(2+) in three solvents including water, acetonitrile, and THF evidenced that the present film exhibits cross-reactive responses to these two metal ions. The combined signals from the three solvents provide a recognition pattern for both metal ions at a certain concentration and realize the identification between Hg(2+) and Cu(2+). Moreover, using principle component analysis, this method can be extended to identify metal ions that are hard to detect by the film sensor in water such as Co(2+) and Ni(2+).

A naked-eye and ratiometric near-infrared probe for palladium via modulation of a π-conjugated system of cyanines

The modulation of π-conjugated electrons in cyanine dyes can result in a ratiometric fluorescence change with a large Stokes shift (270 nm), especially for realizing palladium detection in aqueous samples using indicator paper and in living cells by ratiometric mode.