Current and future technologies for monitoring cultured meat: A review

The high population growth rate, massive animal food consumption, fast economic progress, and limited food resources could lead to a food crisis in the future. There is a huge requirement for dietary proteins including cultured meat is being progressed to fulfill the need for meat-derived proteins in the diet. However, production of cultured meat requires monitoring numerous bioprocess parameters. This review presents a comprehensive overview of various widely adopted techniques (optical, spectroscopic, electrochemical, capacitive, FETs, resistive, microscopy, and ultrasound) for monitoring physical, chemical, and biological parameters that can improve the bioprocess control in cultured meat. The methods, operating principle, merits/demerits, and the main open challenges are reviewed with the aim to support the readers in advancing knowledge on novel sensing systems for cultured meat applications.

Spectroscopic characterization of the interactions between poly(2-(trimethylamino)ethyl methacrylate) chloride and the xanthene dyes, 2', 7'-difluorofluorescein and 2, 4, 5, 7-tetraiodofluorescein

Intermolecular interactions in buffered aqueous solution between the polycation, poly(2-(trimethylamino)ethyl methacrylate) chloride (pTMAEMC) and two anionic xanthene dyes, 2', 7'-difluorofluorescein (Oregon Green 488) and 2, 4, 5, 7-tetraiodofluorescein (Erythrosin B), are characterized using multiple optical spectroscopic methods. Visible absorption spectroscopy indicates the formation of ground-state pTMAEMC-dye complexes. Benesi-Hildebrand binding isotherm analysis of visible absorption spectra for pTMAEMC-dye mixtures quantifies the strength of binding interactions producing the complexes. For both Oregon Green 488 (OG) and Erythrosin B (EB) in mixtures with pTMAEMC, the concentration of the solution's sodium acetate buffer at a fixed pH alters the binding constants, K_b, suggesting that ionic strength plays a key role in determining the binding affinity of pTMAEMC for the dyes. Comparison of K_b, for the dyes indicates stronger binding of EB under all solution conditions. Steady-state fluorescence emission spectroscopy, fluorescence quenching, excited-state fluorescence lifetime measurements and fluorescence correlation spectroscopy provide complementary data for the interactions between pTMAEMC and the dyes. Mixtures of pTMAEMC with the dyes produce fluorescence enhancements and fluorescence quenching which exhibit a dependence on the buffer concentration used in the mixture. Excited-state lifetime analysis indicates that OG interacts with pTMAEMC through ground-state interactions while EB exhibits both ground-state and excited-state interactions with pTMAEMC. The spectroscopic measurements suggest that a polyelectrolyte effect for pTMAEMC due to ionic strength variation produced by the buffer concentration affects the dye binding profile of the polycation. This conclusion is supported by fluorescence correlation spectroscopy (FCS) analyses of the hydrodynamic diameter changes in pTMAEMC-OG binding in low buffer concentration (low ionic strength) solution. FCS analyses of pTMAEMC-OG mixtures also reveal diversity in the complexes formed in low ionic strength solution suggesting that other xanthene dyes will exhibit similar binding behaviors in mixtures with pTMAEMC as a function of solution ionic strength.

Nontraditional Redox Active Aliphatic Luminescent Polymer for Ratiometric pH Sensing and Sensing-Removal-Reduction of Cu(II): Strategic Optimization of Composition

Here, redox active aliphatic luminescent polymers (ALPs) are synthesized via polymerization of N,N-dimethyl-2-propenamide (DMPA) and 2-methyl-2-propenoic acid (MPA). The structures and properties of the optimum ALP3, ALP3-aggregate and Cu(I)-ALP3, ratiometric pH sensing, redox activity, aggregation enhanced emission (AEE), Stokes shift, and oxygen-donor selective coordination-reduction of Cu(II) to Cu(I) are explored via spectroscopic, microscopic, density functional theory-reduced density gradient (DFT-RDG), fluorescence quenching, adsorption isotherm-thermodynamics, and electrochemical methods. The intense blue and green fluorescence of ALP3 emerges at pH = 7.0 and 9.0, respectively, due to alteration of fluorophores from -C(═O)N(CH₃ )₂ / -C(═O)OH to -C(O^- )═N⁺ (CH₃ )₂ / -C(═O)O^- , inferred from binding energies at 401.32 eV (-C(O^- )═N⁺ (CH₃ )₂ ) and 533.08 eV (-C(═O)O^- ), significant red shifting in absorption and emission spectra, and peak at 2154 cm^-1 . The n-π* communications in ALP3-aggregate, hydrogen bondings within 2.34-2.93 Å (intramolecular) in ALP3 and within 1.66-2.89 Å (intermolecular) in ALP3-aggregate, respectively, contribute significantly in fluorescence, confirmed from NMR titration, ratiometric pH sensing, AEE, excitation dependent emission, and Stokes shift and DFT-RDG analyses. For ALP3, Stokes shift, excellent limit of detection, adsorption capacity, and redox potentials are 13561 cm^-1 /1.68 eV, 0.137 ppb, 122.93 mg g^-1 , and 0.33/-1.04 V at pH 7.0, respectively.

Revealing the Phagosomal pH Regulation and Inflammation of Macrophages after Endocytosing Polyurethane Nanoparticles by A Ratiometric pH Nanosensor

The effect of the intracellular pH of macrophages after taking up biodegradable polymer nanoparticles (NPs) on immunomodulating functions has not been explored so far. Previous studies have demonstrated that biodegradable polyurethane (PU) NPs exhibit immunosuppressive activity. Yet, the intracellular mechanism is not clearly understood. In this study, a uniquely designed pH nanosensor is employed for tracking the intracellular pH value of macrophages to reveal the intracellular journey of PU NPs and to clarify the intracellular pH effect on the corresponding inflammatory response. First, fluorescent mesoporous silica nanoparticles (FRMSNs) is used to detect the pH change in macrophages after endo/phagocytosis of PU NPs. Second, PU is coated on the external surface of FRMSNs to examine the intracellular trafficking process of PU in the macrophages. The results show that the majority of PU-coated FRMSNs remain to stay at the cytosol-early endosome/phagosome regions. The intracellular pH value and other supporting results show that the immune response of PU NPs may be correlated to their internalization journey. The retardation in the degradation process of the PU NPs may intervene with the lysosome activity and repress the immunostimulatory effect, which contributes to the low immune response of PU NPs.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and pKa values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.

Simultaneous Single-Particle Tracking and Dynamic pH Sensing Reveal Lysosome-Targetable Mesoporous Silica Nanoparticle Pathways

Nanoparticle (NP)-based targeted drug delivery is intended to transport therapeutically active molecules to specific cells and particular intracellular compartments. However, there is limited knowledge regarding the complete route of NPs in this targeting scenario. In this study, simultaneously performing motion and dynamic pH sensing using single-particle tracking (SPT) leads to an alternative method of gaining insights into the mesoporous silica nanoparticle's (MSN) journey in targeting lysosome. Two different pH-sensitive dyes and a reference dye are incorporated into mesoporous silica nanoparticles (MSNs) via co-condensation to broaden the measurable pH range (pH 4-7.5) of the nanoprobe. The phosphonate, amine, and lysosomal sorting peptides (YQRLGC) are conjugated onto the MSN's surface to study intracellular nano-biointeractions of two oppositely charged and lysosome-targetable MSNs. The brightness and stability of these MSNs allow their movement and dynamic pH evolution during their journey to be simultaneously monitored in real time. Importantly, a multidimensional analysis of MSN's movement and local pH has revealed new model intracellular dynamic states and distributions of MSNs, previously inaccessible when using single parameters alone. A key result is that YQRLGC-conjugated MSNs took an alternative route to target lysosomes apart from the traditional one, which sped up to 4 h and enhanced their targeting efficiency (up to 32%). The findings enrich our understanding of the intracellular journey of MSNs. This study offers complementary information on correlating the surface design with the full pathway of nanoparticles to achieve targeted delivery of therapeutic payload.

Activatable Formation of Emissive Excimers for Highly Selective Detection of β-Galactosidase

Small-molecular fluorescence sensors have become promising detection tools in many fields attributing to their high sensitivity, excellent temporal and spatial resolution, and low cytotoxicity. However, high concentration or aggregation-induced fluorescence quenching effect has usually hindered the development of traditional fluorescence dyes. Herein, a new fluorophore cyanovinylene dye BMZ with excimer emission property has been constructed. It shows an obvious enhanced and red-shift emission upon aggregation in aqueous solution, which overmatches the conventional pyrene with longer absorption and emission wavelengths. Using this unique optical property, a new fluorescence probe BMZ-Gal has been developed for trapping of β-galactosidase (β-Gal) activity with high selectivity, low limit of detection of 0.17 U, and rapid recognition, which is based on the β-Gal-induced formation of red-shift emitting excimer. β-Gal has a strong affinity for BMZ-Gal, which is verified through the Michaelis-Menten constants (K_m, 1.87 μM) and the hydrolysis efficiencies (K_cat/K_m, 1.78 × 10³ M^-1 s^-1). Furthermore, the assay system has been successfully used for detecting endogenous β-Gal in living ovarian cancer cells and can passively targeted to identify β-Gal in organelle level and determine its subcellular location with satisfactory accuracy. We anticipate that the new fluorophore cyanovinylene dye herein may inaugurate new opportunities for the development of excimer emission sensors.

Ionophore-based optical nanosensors incorporating hydrophobic carbon dots and a pH-sensitive quencher dye for sodium detection

Nanosensors present a biological monitoring method that is biocompatible, reversible, and nano-scale, and they offer many advantages over traditional organic indicators. Typical ionophore-based nanosensors incorporate nile-blue derivative pH indicators but suffer from photobleaching while quantum dot alternatives pose a potential toxicity risk. In order to address this challenge, sodium selective nanosensors containing carbon dots and a pH-sensitive quencher molecule were developed based on an ion-exchange theory and a decoupled recognition element from the pH indicator. Carbon dots were synthesized and integrated into nanosensors containing a pH-indicator, an analyte-binding ligand (ionophore), and a charge-balancing additive. These nanosensors are ion-selective against potassium (selectivity coefficient of 0.4) and lithium (selectivity coefficient of 0.9). Reversible nanosensor response to sodium is also demonstrated. The carbon dot nanosensors are resistant to changes in optical properties for at least 12 h and display stable selectivity to physiologically-relevant sodium (alpha = 0.5 of 200 mM NaCl) for a minimum of 6 days.

Optical pH Sensor Covering the Range from pH 0-14 Compatible with Mobile-Device Readout and Based on a Set of Rationally Designed Indicator Dyes

In this work, a family of pH-responsive fluorescent probes has been designed in a rational manner with the aid of quantum chemistry tools, covering the entire pH range from 0-14. Relying on the boron-dipyrromethene (BODIPY) core, all the probes as well as selected reference dyes display very similar spectroscopic properties with ON-OFF fluorescence switching responses, facilitating optical readout in simple devices used for detection and analysis. Embedding of the probes and reference dyes into hydrogel spots on a plastic strip yielded a test strip that reversibly indicates pH with a considerably small uncertainty of ∼0.1 pH units. These strips are not only reusable but, combined with a 3D-printed case that can be attached to a smartphone, the USB port of which drives the integrated LED used for excitation, allows for autonomous operation in on-site or in-the-field applications; the developed Android application software ("app") further simplifies operation for unskilled users.