pH Sensitivity Research Articles

Low-temperature Deposited Highly Sensitive Integrated All-Solid Electrodes for Electrochemical pH Detection

This article describes the process of fabricating an integrated all-solid electrode (IASE) by integrating thin films of titanium dioxide (TiO<i>2</i>) and silver/silver chloride (Ag/AgCl) onto an indium tin oxide (ITO) substrate. The fabrication of a pH sensing electrode (SE) involved utilizing a spin-coated thin film composed of TiO<i>2</i>. Thermally produced thin films of Ag/AgCl were used to develop solid reference electrodes (RE). The present work examined the impact of the drying process on the pH sensitivity and linearity of the low-temperature deposited IASE. The drying procedure was carried out within a temperature range from room temperature to 100°C. The investigation involved the examination of crystallinity, surface morphology, and thin film composition through the utilization of field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX) methods. In addition, a comparison was made between the pH sensing performance of the IASE and a commercially available Ag/AgCl RE. The findings of this research demonstrate that the IASE sample, which underwent a drying process at a temperature of 100°C, exhibited remarkable sensitivity and linearity values of 66.7 mV/pH and 0.9827, separately, when compared to the commercially available RE.

Laponite-Enabled Freeform Manufacturing of Tough Hydrogels with Colorimetric pH Sensitivity

Laponite-Enabled Freeform Manufacturing of Tough Hydrogels with Colorimetric pH Sensitivity

Machine learning-assisted identification of potential cancer inhibitors: Multifunctional biomineralized CaCO3-polyethyleneimine nanoparticle carriers and their application in lung cancer therapy

Cancer, as a prevalent phenomenon among malignant tumors, has a late-stage diagnosis rate approaching half, significantly limiting treatment efficacy and imposing substantial physiological and psychological burdens on patients. Therefore, developing innovative therapeutic platforms that simultaneously optimize diagnostic accuracy, enhance therapeutic efficacy, and minimize side effects is a critical scientific challenge in the field of precision cancer medicine. In this study, we employed a simple and efficient one-pot synthesis method combined with polyethyleneimine (PEI)-mediated biomineralization technology to successfully prepare calcium carbonate-polyethyleneimine (CaCO3-PEI) composite nanoparticles. These nanoparticles exhibit high pH sensitivity and can rapidly degrade under the mildly acidic conditions that mimic the tumor microenvironment, providing potential for targeted tumor therapy. Subsequently, we encapsulated compound 1, which has potential for lung cancer treatment, within the CaCO3-PEI nanoparticles, successfully constructing the CaCO3-PEI@1 composite system. Structural analysis of this composite system was conducted through characterization techniques. In vitro cell experiments demonstrated that the CaCO3-PEI@1 composite system exhibited significant anticancer effects by effectively inhibiting cancer cell proliferation through the regulation of apoptosis-related protein Bax expression. This provides new insights and experimental evidence for the development of cancer treatment strategies. Based on the experiment and molecular docking identified activity against lung cancer, the compound 1 was used as the initiator for the machine learning model, and up to 10,000 episodes were generated, after thorough examination, it was found about two-thirds of the generated episodes were entirely different from each other, which demonstrated that the machine learning model was a powerful tool for designing of potential inhibitors against lung cancer.

Nano-pesticide delivery system based on UiO-66 with pH sensitivity for precise control of Spodoptera frugiperda.

Metal-organic frameworks have the advantages of easy synthesis, high loading capacity and good biocompatibility, making them essential materials for constructing pesticide nano-delivery systems. In this study, a pH-responsive nano-controlled-release formulation Chl@UiO-66 was prepared using UiO-66 as the nano-scale carrier for adsorbing chlorantraniliprole (Chl). The appearance, pesticide loading, release behaviour, insecticidal activity, long-term control efficacy and safety of Chl@UiO-66 for non-target organisms were extensively evaluated. The results showed that the prepared Chl@UiO-66 was a regular octahedron with a uniform particle size of 230 nm and pesticide loading of 15.62%. The release of pesticides under alkaline conditions was superior to that under acidic and neutral conditions, which showed pH-responsive performance. Chl@UiO-66 had an excellent ability to protect pesticides from ultraviolet degradation. Compared with chlorantraniliprole suspension concentrate, Chl@UiO-66 had a better control effect against Spodoptera frugiperda and long-term control efficacy. The prepared nano-controlled-release formulation had low toxicity to zebrafish, earthworms and human BEAS-2B cells. Chl@UiO-66 is a new pesticide formulation with high efficacy and low toxicity that provides a smart controlled-release solution. © 2024 Society of Chemical Industry.

Carbon Dots Prepared by One-step Sintering Method and their Application for pH Detection

Introduction: In recent years carbon dots (CDs) have attracted researchers due to their unique physicochemical and fluorescent (FL) features, which can be applied in many fields such as battery materials, fluorescence sensing, display, biological imaging and photocatalysis. Method: We prepared CDs by using a facile one-step sintering method. The fluorescent properties and the application of pH detection were measured and analyzed. Results: The results show that CDs emit bright purplish-blue light centred at 425 nm excited by 355 nm UV light. FL intensity shows a linear relationship with pH values at 1~4 and 7~11, respectively. The reasonable mechanism of the tested effective pH sensitivity is discussed. Conclusion: Our study shows that the CDs prepared by the one-step sintering method have great potential to be used as pH sensors for physiochemical measurements.

A Highly CO2-Sensitive Wood-Based Smart Tag for Strawberry Freshness Monitoring.

Smart tags are used for monitoring the freshness of foods. However, they often lack significant color changes, and their accuracy needs to be improved. In this study, a poplar veneer with a natural pore structure was selected as a matrix to prepare a smart tag with high pH sensitivity for tracking the freshness of strawberries. The delignified veneer was modified using 2,3-epoxypropyltrimethylammonium chloride (EPTAC) to be given positive charges to adsorb bromothymol blue (BTB) through electrostatic interactions. The adsorption capacity of the veneer reached 7.0 mg/g at 50 °C for 4 h, and the veneer showed an obvious blue color. The smart tags exhibited distinct color changes at different pHs and showed quick color changes in response to acetic acid. As the freshness of strawberries decreased, the color of the smart tags changed from blue to yellow-green, which indicated that the accuracy was high. In this study, an effective method was fabricated to prepare a highly sensitive tag, promoting popular application to ensure food quality.

Smart Accumulating Dual-Targeting Lipid Envelopes Equipping Oncolytic Adenovirus for Enhancing Cancer Gene Therapeutic Efficacy.

Systemic delivery of oncolytic adenovirus (oAd) for cancer gene therapy must overcome several limitations such as rapid clearance from the blood, nonspecific accumulation in the liver, and insufficient delivery to the tumor tissues. In the present report, a tumor microenvironment-triggered artificial lipid envelope composed of a pH-responsive sulfamethazine-based polymer (PUSSM)-conjugated phospholipid (DOPE-HZ-PUSSM) and another lipid decorated with epidermal growth factor receptor (EGFR) targeting peptide (GE11) (GE11-DOPE) was utilized to encapsulate replication-incompetent Ad (dAd) or oAd coexpressing short-hairpin RNA (shRNA) against Wnt5 (shWnt5) and decorin (dAd/LP-GE-PS or oAd/LP-GE-PS, respectively). In vitro studies demonstrated that dAd/LP-GE-PS transduced breast cancer cells in a pH-responsive and EGFR-specific manner, showing a higher level of transduction than naked Ad under a mildly acidic pH of 6.0 in EGFR-positive cell lines. In vivo biodistribution analyses revealed that systemic administration of oAd/LP-GE-PS leads to a significantly higher level of intratumoral virion accumulation compared to naked oAd, oAd encapsulated in a liposome without PUSSM or EGFR targeting peptide moiety (oAd/LP), or oAd encapsulated in a liposome with EGFR targeting peptide alone (oAd/LP-GE) in an EGFR overexpressing MDA-MB-468 breast tumor xenograft model, showing that both pH sensitivity and EGFR targeting ability were integral to effective systemic delivery of oAd. Further, systemic administration of all liposomal oAd formulations (oAd/LP, oAd/LP-GE, and oAd/LP-GE-PS) showed significantly attenuated hepatic accumulation of the virus compared to naked oAd. Collectively, our findings demonstrated that pH-sensitive and EGFR-targeted liposomal systemic delivery of oAd can be a promising strategy to address the conventional limitations of oAd to effectively treat EGFR-positive cancer in a safe manner.

Microcrystalline cellulose and itaconic acid pH sensitive semi interpenetrating network hydrogel for oral insulin delivery

Diabetes mellitus is one of the important causes of death worldwide. Generally, a subcutaneous route is used for insulin administration, but has showed low patient compliance. Extensive research has been conducted to identify molecules capable of delivering insulin orally, for this hydrogel based on microcrystalline cellulose and itaconic acid have been produced and explored. Free radical polymerization as a technique was employed for manufacturing the hydrogels using potassium persulphate as initiator and N, N′-methylene bisacrylamide (NNMBA) as a crosslinker. These pH- sensitive exhibited a swelling capacity of up to 20.38 g/g in distilled water and also revealed stronger swelling in glucose solutions than saline solutions. The pH sensitivity of the hydrogels was confirmed by studying the swelling in different pH solutions. Alkaline solutions showed higher swelling than acidic solutions. SEM established the porous nature, and the structure was examined by FTIR analysis. Thermal degradation was examined using TGA. In vitro release study was done by Bradford assay at 595 nm. The result was further confirmed by in-vivo investigations on male Wistar adult rats and hence is an excellent vehicle for oral insulin administration.

Complexes of polymeric acids and short polyamines as binary stimulus-sensitive systems

Stimulus-sensitive polymers are of great interest due to their unusual properties in solution and diverse applications. Copolymers with different groups (hydrophilic, hydrophobic and ionizable) are typical stimulus-sensitive polymers, and varying the copolymer composition allows the pH and thermal sensitivity to be adjusted for a particular application. We found that complexes of polymeric acids with short methylated polyamines having trimethylene insertions between amine groups exhibit stimulus-sensitive properties in aqueous media at moderate pH and temperature. The position of the lower critical temperature of the solution depends on the ratio of polyacid to polyamine and on the pH. The complex of poly(acrylic acid) and pentaamine was found to be electrosensitive: exposure to an electric field with reversible polarity (8 Hz) led to precipitation of the polymer. These binary stimulus-sensitive compositions consist of two simple substances and are a promising alternative to copolymer-based systems, since the adjustment of properties does not require the synthesis of new substances and expensive toxicological studies in the case of biomedical applications.

Targeted delivery of quercetin using gelatin/starch/Fe3O4 nanocarrier to suppress the growth of liver cancer HepG2 cells

To suppress HepG2 liver cancer cells, a nanocarrier (NC) consisting of Fe3O4, Gelatin (G), and Starch (S) was synthesized and characterized for targeted delivery of Quercetin (QC) drug. The spectra obtained from X-ray diffraction (XRD) and Fourier transform infrared (FTIR) demonstrated that the nanoparticles (NP) in the NC are well-interconnected to each other and have formed a regular structure. Also, field emission scanning electron microscopy (FE-SEM) indicates a smooth and homogeneous surface of the synthesized NC. The results of the vibrating sample magnetometer (VSM) also corroborated the correctness of the synthesis of Fe3O4 NPs and Gelatin/Starch/Fe3O4@Quercetin NC (G/S/Fe3O4@QC) because the magnetic properties of Fe3O4 decreased with the addition of G/S@QC. Stability and particle size were determined by zeta potential and Dynamic light scattering (DLS). The percentage of drug loading and encapsulation efficiency of QC in the NC was 46.25 % and 87 %, respectively. QC profile release in acidic and natural environments showed controlled release and pH sensitivity of the NC. Cytotoxicity of L929 and HepG2 treated cells with the G/S/Fe3O4@QC was investigated by MTT staining, which agreed with the flow cytometry result. The results of Flowcytometry and MTT showed 43.5 % apoptosis and 42 % cytotoxicity in treated HepG2 cells by G/S/Fe3O4@QC, while it was not toxic to L929 normal cells. According to the results, G/S/Fe3O4@QC is a suitable NC for the targeted delivery of QC as a drug against HepG2 cancer cells.

Optimized Drop-Casted Polyaniline Thin Films for High-Sensitivity Electrochemical and Optical pH Sensors

Conducting polymers used in chemical sensors are attractive because of their ability to confer reversible properties controlled by the doping/de-doping process. Polyaniline (PANI) is one of the most prominent materials used due to its ease of synthesis, tailored properties, and higher stability. Here, PANI thin films deposited by the drop-casting method on fluorine-doped tin oxide (FTO) substrates were used in electrochemical and optical sensors for pH measurement. The response of the devices was correlated with the deposition parameters; namely, the volume of deposition solution dropped on the substrate and the concentration of the solution, which was determined by the weight ratio of polymer to solvent. The characterisation of the samples aimed to determine the structure–property relationship of the films and showed that the chemical properties, oxidation states, and protonation level are similar for all samples, as concluded from the cyclic voltammetry and UV–VIS spectroscopic analysis. The sensing performance of the PANI film is correlated with its relative physical properties, thickness, and surface roughness. The highest electrochemical sensitivity obtained was 127.3 ± 6.2 mV/pH, twice the Nernst limit—the highest pH sensitivity reported to our knowledge—from the thicker and rougher sample. The highest optical sensitivity, 0.45 ± 0.05 1/pH, was obtained from a less rough sample, which is desirable as it reduces light scattering and sample oxidation. The results presented demonstrate the importance of understanding the structure–property relationship of materials for optimised sensors and their potential applications where high-sensitivity pH measurement is required.

An "All-in-One" Strategy to Reconstruct Temporomandibular Joint Osteoarthritic Microenvironment Using γ-Fe2O3@TA@ALN Nanoparticles.

Current clinical strategies for the treatment of temporomandibular joint osteoarthritis (TMJOA) primarily target cartilage biology, overlooking the synergetic effect of various cells and inorganic components in shaping the arthritic microenvironment, thereby impeding the effectiveness of existing therapeutic options for TMJOA. Here, γ-Fe2O3@TA@ALN magnetic nanoparticles (γ-Fe2O3@TA@ALN MNPs) composed of γ-Fe2O3, tannic acid (TA), and alendronate sodium (ALN) are engineered to reconstruct the osteoarthritic microenvironment and mitigate TMJOA progression. γ-Fe2O3@TA@ALN MNPs can promote chondrocytes' proliferation, facilitate chondrogenesis and anisotropic organization, enhance lubrication and reduce cartilage wear, and encourage cell movement. Magnetic-responsive γ-Fe2O3@TA@ALN MNPs also exhibit pH sensitivity, which undergoes decomposition within acidic environment to release ALN on demand. Under a 0.2 T static magnetic field, γ-Fe2O3@TA@ALN MNPs accelerate the synthesis of cartilage-specific proteins, and suppress catabolic-related genes expression and reactive oxygen species generation, affording additional protection to TMJ cartilage. In TMJOA mouse models, articular injection of γ-Fe2O3@TA@ALN MNPs effectively alleviates cartilage degeneration and subchondral bone loss in short and long terms, offering promising avenues for the development of therapeutic interventions for TMJOA.

A Fluorogenic Chemogenetic pH Sensor for Imaging Protein Exocytosis.

Fluorescent protein-based pH biosensors enable the tracking of pH changes during protein trafficking and, in particular, exocytosis. The recent development of chemogenetic reporters combining synthetic fluorophores with self-labeling protein tags offers a versatile alternative to fluorescent proteins that combines the diversity of chemical probes and indicators with the selectivity of the genetic encoding. However, this hybrid protein labeling strategy does not avoid common drawbacks of organic fluorophores such as the risk of off-target signal due to unbound molecules. Here, we describe a novel fluorogenic and chemogenetic pH sensor based on a cell-permeable molecular pH indicator called pHluo-Halo-1, whose fluorescence can be locally activated in cells by reaction with HaloTag, ensuring excellent signal selectivity in wash-free imaging experiments. pHluo-Halo-1 was selected out of a series of four fluorogenic molecular rotor structures based on protein chromophore analogues. It displays good pH sensitivity with a pKa of 6.3 well-suited to monitor pH variations during exocytosis and an excellent labeling selectivity in cells. It was applied to follow the secretion of CD63-HaloTag fusion proteins using TIRF microscopy. We anticipate that this strategy based on the combination of a tunable and chemically accessible fluorogenic probe with a well-established protein tag will open new possibilities for the development of versatile alternatives to fluorescent proteins for elucidating the dynamics and regulatory mechanisms of proteins in living cells.

TGF-β1 and FOXM1 siRNA co-loaded nanoparticles by disulfide crosslinked PEG-PDMAEMA for the treatment of triple-negative breast cancer and its bone metastases in vitro

Introduction Triple-negative breast cancer (TNBC) is characterized by higher malignancy and mortality and is prone to distant metastasis, among which bone is the most common site. It’s urgent to explore new strategies for the treatment of TNBC and its bone metastases. Methods A tumor environment responsive vector, poly-(dimethylaminoethyl methacrylate)-SS-poly(ethylene glycol)-SS-poly-(dimethylaminoethyl methacrylate) (PDMAEMA-SS-PEG-SS-PDMAEMA), was constructed to co-delivery transforming growth factor-β1 (TGF-β1) siRNA and forkhead box M1 (FOXM1) siRNA in MDA-MB-231 cells. The preparation, characterization, in vitro release, stability, and transfection efficiency of nanoparticles were measured. Cell viability, migration, and invasion of MDA-MB-231 cells were determined. Cell chemotactic migration and cell heterogeneity adhesion of MDA-MB-231 cells to the human osteoblast-like cell line MG-63 were determined. Results PDMAEMA-SS-PEG-SS-PDMAEMA self-assembled with siRNA at N/P of 15:1 into nanoparticles with a particle size of 122 nm. In vitro release exhibited redox and pH sensitivity, and the nanoparticles protected siRNA from degradation by RNase and serum protein, remaining stable at 4 °C with similar transfection efficiency with lipo2000. Nanoparticles co-loaded with TGF-β1 siRNA and FOXM1 siRNA inhibited the cell viability, migration and invasion of MDA-MB-231 cells, as well as chemotactic migration and heterogeneous adhesion of MDA-MB-231 cells to MG-63 cells, showing a synergetic effect. After gene silencing on TGF-β1 and FOXM1, the epithelial to mesenchymal transition (EMT) related molecules vimentin mRNA expression decreased while E-cadherin increased. Conclusions PDMAEMA-SS-PEG-SS-PDMAEMA was suitable for TGF-β1 siRNA and FOXM1 siRNA delivery, exhibiting a synergetic inhibition effect on TNBC and its bone metastases, which might be related to its synergetic inhibition on EMT.

Folic acid-conjugated bovine serum albumin-coated selenium-ZIF-8 core/shell nanoparticles for dual target-specific drug delivery in breast cancer.

Methotrexate (MTX), a frequently used chemotherapeutic agent, has limited water solubility, leading to rapid clearance even in local injections. In the present study, we developed folic acid-conjugated BSA-stabilized selenium-ZIF-8 core/shell nanoparticles for targeted delivery of MTX to combat breast cancer. FT-IR, XRD, SEM, TEM, and elemental mapping analysis confirmed the successful formation of FA-BSA@MTX@Se@ZIF-8. The developed nano-DDS had a mean diameter, polydispersity index, and zeta potential of 254.8nm, 0.17, and - 16.5 mV, respectively. The release behavior of MTX from the nanocarriers was pH-dependent, where the cumulative release percentage at pH 5.4 was higher than at pH 7.4. BSA significantly improved the blood compatibility of nanoparticles so that after modifying their surface with BSA, the percentage of hemolysis decreased from 12.67 to 5.12%. The loading of methotrexate in BSA@Se@ZIF-8 nanoparticles reduced its IC50 on 4T1 cells from 40.29µg/mL to 16.54µg/mL, and by conjugating folic acid on the surface, this value even decreased to 12.27µg/mL. In vivo evaluation of the inhibitory effect in tumor-bearing mice showed that FA-BSA@MTX@Se@ZIF-8 caused a 2.8-fold reduction in tumor volume compared to the free MTX, which is due to the anticancer effect of selenium nanoparticles, the pH sensitivity of ZIF-8, and the presence of folic acid on the surface as a targeting agent. More importantly, histological studies and animal body weight monitoring confirmed that developed nano-DDS does not have significant organ toxicity. Taking together, the incorporation of chemotherapeutics in folic acid-conjugated BSA-stabilized selenium-ZIF-8 nanoparticles may hold a significant impact in the field of future tumor management.

Optimizing the synthesis conditions of CaAl‐layered double hydroxide and poly (3‐hydroxybutyrate)/CaAl‐LDH nanocomposite for potential use in antibacterial drug delivery

AbstractCalcium aluminum layered double hydroxide (CaAl‐LDH) has gained significance for drug delivery applications due to its multiple advantages, including high drug‐loading capacity, pH sensitivity, biocompatibility, high acceptable intake values of metal ions, and its ability to provide sustained release of the intercalated drug. In this study, pristine CaAl‐LDH was synthesized by co‐precipitation method at different pH values (9 and 10) and aging times (16 and 24 h) to obtain LDH with higher d‐spacing, which is beneficial for achieving a high drug loading efficiency. Ofloxacin (OFX), an antibiotic drug, was loaded into CaAl‐LDH via regeneration (CaAl‐LDH‐OFX(RG)) and co‐precipitation (CaAl‐LDH‐OFX(CPT)) methods, and achieved drug loading of 28.3% and 36.5%, respectively. The release behavior of OFX from CaAl‐LDH‐OFX(RG) and CaAl‐LDH‐OFX(CPT) formulations was examined in simulated conditions representing the gastrointestinal tract. CaAl‐LDH‐OFX(RG) showed less initial burst release of OFX compared to CaAl‐LDH‐OFX(CPT) in acidic as well as neutral pH conditions. In order to overcome the degradation of the drug before reaching the target site, CaAl‐LDH‐OFX(RG) was reinforced at 1, 3, and 5 wt% in poly (3‐hydroxybutyrate) (PHB) matrix by sonication‐assisted solution casting method. The PHB‐based nanocomposites were characterized by XRD, FESEM, TGA, and FTIR analyses. FESEM characterization of PHB‐based films loaded with 3 wt% of CaAl‐LDH‐OFX(RG) revealed compact morphology without any aggregate formation. Moreover, PHB/3CaAl‐LDH‐OFX(RG) films demonstrated sustained release of OFX at pH 1.2 (95.60% in 96 h), pH 6.8 (78% in 113 h), and pH 7.4 (40.90% in 107 h). The promising potential of PHB‐based formulations for antibacterial drug delivery systems was confirmed by their significant antibacterial activity against Escherichia coli and Staphylococcus aureus.Highlights pH and aging time influence the structural characteristics of pristine CaAl‐LDH. Ofloxacin loaded CaAl‐LDH prepared by co‐precipitation and regeneration methods. Sustained release of ofloxacin from poly (3‐hydroxybutyrate)‐based formulation. Poly (3‐hydroxybutyrate)‐based formulations exhibit excellent antibacterial activity.

Preparation and characterization of intelligent packaging labels based on pea starch, κ-carrageenan and black raspberry extract for monitoring freshness of pork

Intelligent biodegradable packaging has gained significant attention recently due to its great potential for food freshness monitoring. In this study, we developed intelligent labels using pea starch (PS), κ-carrageenan (KC) and black raspberry extract (BRE) and evaluated their physicochemical properties and effectiveness in pork freshness monitoring. Incorporation of KC significantly decreased tensile strength (TS) (33.43 to 19.84 MPa) and increased elongation at break (EAB) (6.26 to 7.41 %) and water vapor permeability (WVP) (2.11 to 2.48 × 10−9 g m−1 s−1 Pa−1) of PS label. Incorporation of BRE significantly decreased WVP (2.48 to 1.96 × 10−9 g m−1 s−1 Pa−1) and increased TS (19.84 to 29.68 MPa) and EAB (7.41 to 11.09 %) of PS-KC label. PS-KC-BRE labels showed increased light barrier performance, thermal stability, antioxidant activity, pH and ammonia sensitivities, and significant visible color change as pH indicators. Findings suggest PS-KC-BRE labels can be used as intelligent packaging in food industry.

Development and investigation of a polysaccharide ternary nanocomposite based on basil seed gum/graphene oxide/anthocyanin for intelligent food packaging

A new pH-sensitive intelligent packaging system was developed composed of extracted and purified basil seed gum (BG) containing aqueous malva sylvestris extract (MS) and varying amounts of synthesized graphene oxide (GO). In the following, the characteristics of prepared films including spectroscopic, physio-mechanical, thermogravimetry, fracture-surface morphology, anthocyanin release, and pH and TVB-N sensitivity, were investigated. Our results revealed that the addition of 0.5 wt % MS into the BG matrix induced pH sensitivity to the film and resulted in a visible color change from pH 2.0 to 14.0; however, it reduced the thermal and physio-mechanical properties. In this regard, the effective presence of the optimum concentration of GO (0.25 wt%) in enhancing the mechanical and thermal properties of the BG-MS films was shown. Moreover, inspecting the release kinetics demonstrated a controllable release for BG-MS-GO film compared to the BG-MS film in 48 h. Furthermore, the total volatile basic nitrogen (TVB-N) content and pH value were shown to be highly correlated with the color changes of the freshness indicator film during the storage of salmon fillets at 25 °C for 36 h. Therefore, it was shown that BG-MS-GO film can be used as a highly effective freshness/spoilage indicator of proteinic products.

Glycoconjugate coumarins exploiting metabolism-enhanced fluorescence and preferential uptake: New optical tools for tumor cell staining

The possibility to visually discriminate cells based on their metabolism and capability to uptake exogenous molecules is an important topic with exciting fallback on translational and precision medicine. To this end, probes that combine several complementary features are necessary. The ideal probe is selectively uptaken and activated in tumor cells compared with control ones and is not fluorescent in the extracellular medium. Fluorogenic compounds that combine enzyme-activated pH sensitivity and good cell uptake can be an ideal solution, provided that the sensed enzymes are dysregulated in tumor cells. Here, we present synthesis and in vitro evaluation of a new class of glyco-coumarin based probes that merge all these features. These probes show uptake ratio in tumor vs. control cells up to 3:1, with a cell to background ratio upon administration of the probe up to 5:1. These features make this new family of fluorogenic targeted probes a promising tool in life science.

A pH-Responsive Protein Assembly through Clustering of a Charge-Tunable Single Amino Acid Repeat.

Specific targeting of tumor cells is a key to achieving high therapeutic efficacy while minimizing off-target side effects. As a general approach to targeting diverse tumor cells, considerable attention has been paid to the tumor microenvironment, particularly its slightly acidic pH (6.5-6.8). However, existing pH-sensitive nanomaterials, based on organic polymers and proteins, often lack sufficient pH sensitivity and specificity. Here, we demonstrate a strategy to construct a pH-responsive protein assembly through clustering of a single amino acid repeat as a charge-tunable moiety. As a proof of concept, a histidine peptide with varying lengths was displayed on the surface of a ferritin assembly composed of 24 subunits by genetic fusion to a subunit. The resulting self-assembled ferritin particles, termed "pHerricle (pH-responsive ferritin particle)", were shown to exhibit a specific binding to tumor cells in response to pH changes through cooperative effects of histidine peptides. Increasing the histidine peptide length from 0 to 12 residues increased the pHerricle's cell-binding capacity by 21-fold and allowed modulation of the targetable pH range. General applicability as a tumor cell-targeting platform was shown by specific delivery of a cytotoxic cargo by the pHerricle into tumor cells of various origins in a pH-dependent manner.