Injectable bioactive poly(propylene fumarate) and polycaprolactone based click chemistry bone cement for spinal fusion in rabbits

Degenerative spinal pathology is a widespread medical issue, and spine fusion surgeries are frequently performed. In this study, we fabricated an injectable bioactive click chemistry polymer cement for use in spinal fusion and bone regrowth. Taking advantages of the bioorthogonal click reaction, this cement can be crosslinked by itself eliminating the addition of a toxic initiator or catalyst, nor any external energy sources like UV light or heat. Furthermore, nano-hydroxyapatite (nHA) and microspheres carrying recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human vascular endothelial growth factor (rhVEGF) were used to make the cement bioactive for vascular induction and osteointegration. After implantation into a rabbit posterolateral spinal fusion (PLF) model, the cement showed excellent induction of new bone formation and bridging bone, achieving results comparable to autograft control. This is largely due to the osteogenic properties of nano-hydroxyapatite (nHA) and the released rhBMP-2 and rhVEGF growth factors. Since the availability of autograft sources is limited in clinical settings, this injectable bioactive click chemistry cement may be a promising alternative for spine fusion applications in addressing various spinal conditions.

Immobilization of fumarase from thermophilic eukaryotic red alga Cyanidioschyzon merolae on ceramic carrier

Fumarase is an enzyme catalyzing reversible reaction between fumarate and L-malate in the citric acid cycle. Fumarase is used in the industrial production of L-malate, and its immobilization is required for reuse of the fumarases to reduce the cost. Accordingly, understanding the properties of immobilized fumarase is crucial, and several groups report on the storage stability and kinetic parameters of immobilized fumarase. Here we have immobilized fumarase from the thermophilic red alga Cyanidioschyzon merolae (CmFUM) on ceramic beads and investigated its biochemical and physical properties. CmFUM demonstrated sufficient stability and reusability for industry use after immobilization. Notably, the thermostability was dramatically enhanced through immobilization. The Km value and kcat of immobilized CmFUM for fumarate were 1.7 mM and 22.7 s-1 respectively. The Km value for fumarate was lower than that of other reported immobilized fumarases, indicating a high substrate affinity of immobilized CmFUM. Furthermore, the enhanced stability resulting from immobilization partially compensated for the decrease in activity. The high affinity towards fumarate and good thermostability of immobilized CmFUM revealed in this study are advantageous traits for improving enzyme-mediated isomer-specific L-malate production.

Fingerprinting of physical manufacturing properties of different acids for effervescent systems

The study aimed to fingerprint the physical manufacturing properties of five commonly used acid sources in effervescent systems for designing the formulation and process of such systems. The hygroscopicity, texture properties, rheological torque, compressibility, tabletability, etc., were investigated to inspect 'powder direct compression (DC)' and 'wet granulation and compression' properties of citric (CA), tartaric (TA), malic (MA), fumaric (FA), and adipic acid (AA). The DC ability was evaluated by the SeDeM expert system. The results indicated that all acid powders failed to meet flowability requirements for DC, and plastic deformation dominated during compression. Furthermore, CA exhibited strong hygroscopicity and punch sticking, while MA demonstrated the best tabletability. TA had a large wet granulation space and was relatively the most suitable for DC. AA was extremely hygroscopic, and its flowability improved significantly as particle size increased. Finally, FA displayed the lowest hygroscopicity and ejection force as well as great compressibility and wet granulation space, and did not exhibit punch sticking, while the granule fragments dissolved slowly during disintegration. Generally speaking, the formulation or granulation affected the tabletability, indicating that pairing with other acids or suitable fillers could potentially improve its disadvantages. These multidimensional assessments effectively reduce the pre-exploration and enhance the efficiency of the development of effervescent systems.

Biodegradable poly(caprolactone fumarate) 3D printed scaffolds for segmental bone defects within the Masquelet technique

Segmental bone defects, often clinically treated with nondegradable poly(methylmethacrylate) (PMMA) in multistage surgeries, present a significant clinical challenge. Our study investigated the efficacy of 3D printed biodegradable polycaprolactone fumarate (PCLF)/PCL spacers in a one-stage surgical intervention for these defects, focusing on early bone regeneration influenced by spacer porosities. We compared nonporous PCLF/PCL and PMMA spacers, conventionally molded into cylinders, with porous PCLF/PCL spacers, 3D printed to structurally mimic segmental defects in rat femurs for a 4-week implantation study. Histological analysis, including tissue staining and immunohistochemistry with bone-specific antibodies, was conducted for histomorphometry evaluation. The PCLF/PCL spacers demonstrated compressive properties within 6 ± 0.5 MPa (strength) and 140 ± 15 MPa (modulus). Both porous PCLF/PCL and Nonporous PMMA formed collagen-rich membranes (PCLF/PCL: 92% ± 1.3%, PMMA: 86% ± 1.5%) similar to those induced in the Masquelet technique, indicating PCLF/PCL's potential for one-stage healing. Immunohistochemistry confirmed biomarkers for tissue regeneration, underscoring PCLF/PCL's regenerative capabilities. This research highlights PCLF/PCL scaffolds' ability to induce membrane formation in critical-sized segmental bone defects, supporting their use in one-stage surgery. Both solid and porous PCLF/PCL spacers showed adequate compressive properties, with the porous variants exhibiting BMP-2 expression and woven bone formation, akin to clinical standard PMMA. Notably, the early ossification of the membrane into the pores of porous scaffolds suggests potential for bone interlocking and regeneration, potentially eliminating the need for a second surgery required for PMMA spacers. The biocompatibility and biodegradability of PCLF/PCL make them promising alternatives for treating critical bone defects, especially in vulnerable patient groups.

Effect of the Addition of Inorganic Fillers on the Properties of Degradable Polymeric Blends for Bone Tissue Engineering

Bone tissue exhibits self-healing properties; however, not all defects can be repaired without surgical intervention. Bone tissue engineering offers artificial scaffolds, which can act as a temporary matrix for bone regeneration. The aim of this study was to manufacture scaffolds made of poly(lactic acid), poly(ε-caprolactone), poly(propylene fumarate), and poly(ethylene glycol) modified with bioglass, beta tricalcium phosphate (TCP), and/or wollastonite (W) particles. The scaffolds were fabricated using a gel-casting method and observed with optical and scanning electron microscopes. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), wettability, and degradation tests were conducted. The highest content of TCP without W in the composition caused the highest hydrophilicity (water contact angle of 61.9 ± 6.3°), the fastest degradation rate (7% mass loss within 28 days), moderate ability to precipitate CaP after incubation in PBS, and no cytotoxicity for L929 cells. The highest content of W without TCP caused the highest hydrophobicity (water contact angle of 83.4 ± 1.7°), the lowest thermal stability, slower degradation (3% mass loss within 28 days), and did not evoke CaP precipitation. Moreover, some signs of cytotoxicity on day 1 were observed. The samples with both TCP and W showed moderate properties and the best cytocompatibility on day 4. Interestingly, they were covered with typical cauliflower-like hydroxyapatite deposits after incubation in phosphate-buffered saline (PBS), which might be a sign of their excellent bioactivity.

Enhanced Solubility and Polarization of 13C-Fumarate with Meglumine Allows for In Vivo Detection of Gluconeogenic Metabolism in Kidneys

Hyperpolarized 13C-labeled fumarate probes tissue necrosis via the production of 13C-malate. Despite its promises in detecting tumor necrosis and kidney injuries, its clinical translation has been limited, primarily due to the low solubility in conventional glassing solvents. In this study, we introduce a new formulation of fumarate for dissolution dynamic nuclear polarization (DNP) by using meglumine as a counterion, a nonmetabolizable derivative of sorbitol. We have found that meglumine fumarate vitrifies by itself with enhanced water solubility (4.8 M), which is expected to overcome the solubility-restricted maximum concentration of hyperpolarized fumarate after dissolution. The achievable liquid-state polarization level of meglumine-fumarate is more than doubled (29.4 ± 1.3%) as compared to conventional dimethyl sulfoxide (DMSO)-mixed fumarate (13.5 ± 2.4%). In vivo comparison of DMSO- and meglumine-prepared 50-mM hyperpolarized [1,4-13C2]fumarate shows that the signal sensitivity in rat kidneys increases by 10-fold. As a result, [1,4-13C2]aspartate and [13C]bicarbonate in addition to [1,4-13C2]malate can be detected in healthy rat kidneys in vivo using hyperpolarized meglumine [1,4-13C2]fumarate. In particular, the appearance of [13C]bicarbonate indicates that hyperpolarized meglumine [1,4-13C2]fumarate can be used to investigate phosphoenolpyruvate carboxykinase, a key regulatory enzyme in gluconeogenesis.

[Identification of the binding proteins of organic acid metabolites by matrix thermal shift assay]

Organic acid metabolites exhibit acidic properties. These metabolites serve as intermediates in major carbon metabolic pathways and are involved in several biochemical pathways, including the tricarboxylic acid (TCA) cycle and glycolysis. They also regulate cellular activity and play crucial roles in epigenetics, tumorigenesis, and cellular signal transduction. Knowledge of the binding proteins of organic acid metabolites is crucial for understanding their biological functions. However, identifying the binding proteins of these metabolites has long been a challenging task owing to the transient and weak nature of their interactions. Moreover, traditional methods are unsuitable for the structural modification of the ligands of organic acid metabolites because these metabolites have simple and similar structures. Even minor structural modifications can significantly affect protein interactions. Thermal proteome profiling (TPP) provides a promising avenue for identifying binding proteins without the need for structural modifications. This approach has been successfully applied to the identification of the binding proteins of several metabolites. In this study, we investigated the binding proteins of two TCA cycle intermediates, i.e., succinate and fumarate, and lactate, an end-product of glycolysis, using the matrix thermal shift assay (mTSA) technique. This technique involves combining single-temperature (52 ℃) TPP and dose-response curve analysis to identify ligand-binding proteins with high levels of confidence and determine the binding affinity between ligands and proteins. To this end, HeLa cells were lysed, followed by protein desalting to remove endogenous metabolites from the cell lysates. The desalted cell lysates were treated with fumarate or succinate at final concentrations of 0.004, 0.04, 0.4, and 2 mmol/L in the experimental groups or 2 mmol/L sodium chloride in the control group. Considering that the cellular concentration of lactate can be as high as 2-30 mmol/L, we then applied lactate at final concentrations of 0.2, 1, 5, 10, and 25 mmol/L in the experimental groups or 25 mmol/L sodium chloride in the control group. Using high-sensitivity mass spectrometry coupled with data-independent acquisition (DIA) quantification, we quantified 5870, 5744, and 5816 proteins in succinate, fumarate, and lactate mTSA experiments, respectively. By setting stringent cut-off values (i.e., significance of changes in protein thermal stability (p-value)<0.001 and quality of the dose-response curve fitting (square of Pearson's correlation coefficient, R2)>0.95), multiple binding proteins for these organic acid metabolites from background proteins were confidently determined. Several known binding proteins were identified, notably fumarate hydratase (FH) as a binding protein for fumarate, and α-ketoglutarate-dependent dioxygenase (FTO) as a binding protein for both fumarate and succinate. Additionally, the affinity data for the interactions between these metabolites and their binding proteins were obtained, which closely matched those reported in the literature. Interestingly, ornithine aminotransferase (OAT), which is involved in amino acid biosynthesis, and 3-mercaptopyruvate sulfurtransferase (MPST), which acts as an antioxidant in cells, were identified as lactate-binding proteins. Subsequently, an orthogonal assay technique developed in our laboratory, the solvent-induced precipitation (SIP) technique, was used to validate the mTSA results. SIP identified OAT as the top target candidate, validating the mTSA-based finding that OAT is a novel lactate-binding protein. Although MPST was not identified as a lactate-binding protein by SIP, statistical analysis of MPST in the mTSA experiments with 10 or 25 mmol/L lactate revealed that MPST is a lactate-binding protein with a high level of confidence. Peptide-level empirical Bayes t-tests combined with Fisher's exact test also supported the conclusion that MPST is a lactate-binding protein. Lactate is structurally similar to pyruvate, the known binding protein of MPST. Therefore, assuming that lactate could potentially occupy the binding site of pyruvate on MPST. Overall, the novel binding proteins identified for lactate suggest their potential involvement in amino acid synthesis and redox balance regulation.

Integrative Salt Selection and Formulation Optimization: Perspectives of Disproportionation and Microenvironmental pH Modulation

We report a novel utilization of a pH modifier as a disproportionation retardant in a tablet formulation. The drug molecule of interest has significant bioavailability challenges that require solubility enhancement. In addition to limited salt/cocrystal options, disproportionation of the potential salt(s) was identified as a substantial risk. Using a combination of Raman spectroscopy with chemometrics and quantitative X-ray diffraction in specially designed stress testing, we investigated the disproportionation phenomena. The learnings and insight drawn from crystallography drove the selection of the maleate form as the target API. Inspired by the fumarate form's unique stability and solubility characteristics, we used fumaric acid as the microenvironmental pH modulator. Proof-of-concept experiments with high-risk (HCl) and moderate-risk (maleate) scenarios confirmed the synergistic advantage of fumaric acid, which interacts with the freebase released by disproportionation to form a more soluble species. The resultant hemifumarate helps maintain the solubility at an elevated level. This work demonstrates an innovative technique to mediate the solubility drop during the "parachute" phase of drug absorption using compendial excipients, and this approach can potentially serve as an effective risk-mitigating strategy for salt disproportionation.

Extrusion 3D-printing and characterization of poly(caprolactone fumarate) for bone regeneration applications

Polycaprolactone fumarate (PCLF) is a cross-linkable PCL derivative extensively considered for tissue engineering applications. Although injection molding has been widely used to develop PCLF scaffolds, platforms developed using such technique lack precise control on architecture, design, and porosity required to ensure adequate cellular and tissue responses. In particular, the scaffolds should provide a suitable surface for cell attachment and proliferation, and facilitate cell-cell communication and nutrient flow. 3D printing technologies have led to new architype for biomaterial development with micro-architecture mimicking native tissue. Here, we developed a method for 3D printing of PCLF structures using the extrusion printing technique. The crosslinking property of PCLF enabled the unique post-processing of 3D printed scaffolds resulting in highly porous and flexible PCLF scaffolds with compressive properties imitating natural features of cancellous bone. Generated scaffolds supported excellent attachment and proliferation of mesenchymal stem cells (MSC). The high porosity of PCLF scaffolds facilitated vascularized membrane formation demonstrable with the stringency of the ex ovo chicken chorioallantoic membrane (CAM) implantation. Furthermore, upon implantation to rat calvarium defects, PCLF scaffolds enabled an exceptional new bone formation with a bone mineral density of newly formed bone mirroring native bone tissue. These studies suggest that the 3D-printed highly porous PCLF scaffolds may serve as a suitable biomaterial platform to significantly expand the utility of the PCLF biomaterial for bone tissue engineering applications.

Rapid Colorimetric and Fluorometric Discrimination of Maleic Acid vs. Fumaric Acid and Detection of Maleic Acid in Food Additives

An anthracene thiazole based Schiff base L was synthesized and employed for fluorescence switch-on detection of maleic acid in aqueous DMSO. The non-fluorescent L (10-5 M) showed an instantaneous and selective fluorescence enhancement at 506 nm upon interaction with maleic acid (10-5 M). Other potential carboxylic acids (10-5 M), such as malic acid, citric acid, acetic acid, cinnamic acid, tartaric acid, succinic acid, fumaric acid, oxalic acid and malonic acid failed to alter the chromo-fluorogenic properties of L. Probe L can be employed to detect maleic acid down to 2.74 × 10-6 M. The probe L showed good linearity from 2.97 to 6.87 µM. Analytical utility of L was examined by detecting maleic acid in various food additives and drosophila larvae.

Organic-inorganic composite of polypropylene fumarate and nanohydroxyapatite as carrier of antibiotics for the treatment of bone infections

Current treatment approaches in clinics to treat the infectious lesions have partial success thus demanding the need for development of advanced treatment modalities. In this study we fabricated an organic-inorganic composite of polypropylene fumarate (PPF) and nanohydroxyapatite (nHAP) by photo-crosslinking as a carrier of two clinically used antibiotics, ciprofloxacin (CIP) and rifampicin (RFP) for the treatment of bone infections. Carboxy terminal-PPF was first synthesized by cis-trans isomerization of maleic anhydride which was then photo-crosslinked using diethylfumarate (DEF) as crosslinker and bis-acylphosphine oxide (BAPO) as photo-initiator under UV lights (P). A composite of PPF and nHAP was fabricated by incorporating 40 % of nHAP in the polymeric matrix of PPF (PH) which was then characterized for different physicochemical parameters. CIP was added along with nHAP to fabricated CIPloaded composite scaffolds (PHC) which was then coated with RFP to synthesize RFP coated CIP-loaded scaffolds (PHCR). It was observed that there was a temporal separation in the in vitro release of two antibiotics after coating PHC with RFP with 80.48 ± 0.40 % release of CIP from PHC and 62.43 ± 0.21 % release of CIP from PHCR for a period of 60 days. Moreover, in vitro protein adsorption was also found to be maximum in PHCR (154.95 ± 0.07 μg/mL) as observed in PHC (75.42 ± 0.06 μg/mL), PH (24.47 ± 0.08 μg/mL) and P alone (4.47 ± 0.02 μg/mL). The scaffolds were also evaluated using in vivo infection model to assess their capacity in reducing the bacterial burden at the infection site. The outcome of this study suggests that RFP coated CIP-loaded PPF composite scaffolds could reduce bacterial burden and simultaneously augment bone healing during infection related fractures.

Solubility-driven optimization of benzothiopyranone salts leading to a preclinical candidate with improved pharmacokinetic properties and activity against Mycobacterium tuberculosis

Solubility-driven optimization of the salts of nitro benzothiopyranone 1, which targets DprE1, led to an antimycobacterial preclinical candidate 2. Five pharmaceutically acceptable salts, including the maleate (2), fumarate (3), citrate (4, 5), and l-malate (6) of compound 1, were prepared via the salt formation reaction and evaluated for their physicochemical and pharmacokinetic properties. Compared with 1, all the target salts exhibited greatly increased aqueous solubility and improved oral bioavailability in mice. Maleate salt 2, which displayed higher chemical stability and lower log P, showed substantially improved bioavailability in rats and a much better in vivo effect compared with free base 1 at the same dose. The X-ray crystal structure of 2 revealed that the exposed hydrophilic piperazine-maleate moiety in the crystal structure cell may be critical in increasing the solubility of 2. Thus, this maleate salt 2 overcame the poor druggability of benzothiopyranone derivatives and was identified as a promising preclinical candidate for treating tuberculosis.

Deuterium MRSI of tumor cell death in vivo following oral delivery of 2 H-labeled fumarate

PURPOSE

There is an unmet clinical need for direct and sensitive methods to detect cell death in vivo, especially with regard to monitoring tumor treatment response. We have shown previously that tumor cell death can be detected in vivo from 2 H MRS and MRSI measurements of increased [2,3-2 H2 ]malate production following intravenous injection of [2,3-2 H2 ]fumarate. We show here that cell death can be detected with similar sensitivity following oral administration of the 2 H-labeled fumarate.

METHODS

Mice with subcutaneously implanted EL4 tumors were fasted for 1 h before administration (200 μl) of [2,3-2 H2 ]fumarate (2 g/kg bodyweight) via oral gavage without anesthesia. The animals were then anesthetized, and after 30 min, tumor conversion of [2,3-2 H2 ]fumarate to [2,3-2 H2 ]malate was assessed from a series of 13 2 H spectra acquired over a period of 65 min. The 2 H spectra and 2 H spectroscopic images were acquired using a surface coil before and at 48 h after treatment with a chemotherapeutic drug (etoposide, 67 mg/kg).

RESULTS

The malate/fumarate signal ratio increased from 0.022 ± 0.03 before drug treatment to 0.12 ± 0.04 following treatment (p = 0.023, n = 4). Labeled malate was undetectable in spectroscopic images acquired before treatment and increased in the tumor area following treatment. The increase in the malate/fumarate signal ratio was similar to that observed previously following intravenous administration of labeled fumarate.

CONCLUSION

Orally administered [2,3-2 H2 ]fumarate can be used to detect tumor cell death noninvasively following treatment with a sensitivity that is similar to that obtained with intravenous administration.

Direct Production of a Hyperpolarized Metabolite on a Microfluidic Chip

Microfluidic systems hold great potential for the study of live microscopic cultures of cells, tissue samples, and small organisms. Integration of hyperpolarization would enable quantitative studies of metabolism in such volume limited systems by high-resolution NMR spectroscopy. We demonstrate, for the first time, the integrated generation and detection of a hyperpolarized metabolite on a microfluidic chip. The metabolite [1-13C]fumarate is produced in a nuclear hyperpolarized form by (i) introducing para-enriched hydrogen into the solution by diffusion through a polymer membrane, (ii) reaction with a substrate in the presence of a ruthenium-based catalyst, and (iii) conversion of the singlet-polarized reaction product into a magnetized form by the application of a radiofrequency pulse sequence, all on the same microfluidic chip. The microfluidic device delivers a continuous flow of hyperpolarized material at the 2.5 μL/min scale, with a polarization level of 4%. We demonstrate two methods for mitigating singlet-triplet mixing effects which otherwise reduce the achieved polarization level.

Direct Extraction of Fumaric Acid from Rhizopus oryzae Suspensions-Interfacial Mass Transfer

Experimental studies on the reactive extraction of fumaric acid with Amberlite LA-2 from Rhizopus oryzae suspensions using three solvents with different dielectric constants varying from 9.08 to 1.90 (dichloromethane, n-butyl acetate, and n-heptane, respectively) underlined the particular behavior of the extraction system in the presence of fungal biomass. The interfacial mass flow of the reaction product was found to be significantly affected by the biomass, due mainly to its adsorption onto the phase separation interface, this leading to the appearance of a physical barrier against the solute's transfer. However, the magnitude of the adsorption phenomenon was found to depend on Rhizopus oryzae's affinity for the solvent phase, which increased significantly from dichloromethane to n-heptane. The negative influence of the biomass on the interfacial mass transfer can be partially counteracted by adding 1-octanol into the organic phase, improving the solvent's ability to solve the fumaric acid-Amberlite LA-2 complex and simplifying the reactive extraction mechanism, effects that were found to be more important for low-polar solvents. Consequently, for the same mixing intensity, the maximum amplification factor was reached for n-heptane, its value being almost 5-6 times higher than that obtained for dichloromethane and over 2 times higher than that obtained with n-butyl acetate.

Black phosphorus incorporation modulates nanocomposite hydrogel properties and subsequent MC3T3 cell attachment, proliferation, and differentiation

A promising strategy that emerged in tissue engineering is to incorporate two-dimensional (2D) materials into polymer scaffolds, producing materials with desirable mechanical properties and surface chemistries, which also display broad biocompatibility. Black phosphorus (BP) is a 2D material that has sparked recent scientific interest due to its unique structure and electrochemical characteristics. In this study, BP nanosheets (BPNSs) were incorporated into a cross-linkable oligo[poly(ethylene glycol) fumarate] (OPF) hydrogel to produce a new nanocomposite for bone regeneration. BPNSs exhibited a controllable degradation rate coupled with the release of phosphate in vitro. MTS assay results together with live/dead images confirmed that the introduction of BPNSs into OPF hydrogels enhanced MC3T3-E1 cell proliferation. Moreover, the morphology parameters indicated better attachments of cells in the BPNSs containing group. Immunofluorescence images as well as intercellular ALP and OCN activities showed that adding a certain amount of BPNSs to OPF hydrogel could greatly improve differentiation of pre-osteoblasts on the hydrogel. Additionally, embedding black phosphorous into a neutral polymer network helped to control its cytotoxicity, with optimal cell growth observed at BP concentrations as high as 500 ppm. These results reinforced that the supplementation of OPF with BPNSs can increase the osteogenic capacity of polymer scaffolds for use in bone tissue engineering.

Hyperpolarized 13 C Magnetic Resonance Imaging of Fumarate Metabolism by Parahydrogen-induced Polarization: A Proof-of-Concept in vivo Study

Hyperpolarized [1-13 C]fumarate is a promising magnetic resonance imaging (MRI) biomarker for cellular necrosis, which plays an important role in various disease and cancerous pathological processes. To demonstrate the feasibility of MRI of [1-13 C]fumarate metabolism using parahydrogen-induced polarization (PHIP), a low-cost alternative to dissolution dynamic nuclear polarization (dDNP), a cost-effective and high-yield synthetic pathway of hydrogenation precursor [1-13 C]acetylenedicarboxylate (ADC) was developed. The trans-selectivity of the hydrogenation reaction of ADC using a ruthenium-based catalyst was elucidated employing density functional theory (DFT) simulations. A simple PHIP set-up was used to generate hyperpolarized [1-13 C]fumarate at sufficient 13 C polarization for ex vivo detection of hyperpolarized 13 C malate metabolized from fumarate in murine liver tissue homogenates, and in vivo 13 C MR spectroscopy and imaging in a murine model of acetaminophen-induced hepatitis.

Development of a naftopidil-chitosan-based fumaric acid solid dispersion to improve the dissolution rate and stability of naftopidil

Naftopidil (NAF), an α₁-adrenoceptor antagonist, is administered as a treatment for benign prostatic hyperplasia; however, according to the Biopharmaceutical Classification System (BCS IV), it is a poorly-soluble drug that exhibits poor permeability. We aimed to increase the dissolution (%) of NAF by adding chitosan to a polymer-free formulation. Compared to the formulation prepared using Flivas®, at 60 min, the solid dispersion (SD) formulation containing NAF, fumaric acid, chitosan, and US2® in a 1:1:2:1 weight ratio improved the dissolution (%) of NAF in distilled water, pH 1.2 media, pH 4.0 and pH 6.8 buffers by 27.2-, 1.2-, 1.1- and 6.5-fold, respectively. The physicochemical properties of the SD1 formulation were also found to be altered, including its thermal properties, crystal intensity, and chemical interaction. As a result, the hydrogen bonding that occurs between NAF and fumaric acid was identified as a major factor in the increase in NAF dissolution (%). Further, chitosan was observed to contribute to the stability of NAF and SD1, which was assessed over a 3-month period. To our knowledge, this is the first study to employ a polymer-free system to improve the solubilization of NAF.

Choline Hydrogen Dicarboxylate Ionic Liquids by X-ray Scattering, Vibrational Spectroscopy and Molecular Dynamics: H-Fumarate and H-Maleate and Their Conformations

We explore the structure of two ionic liquids based on the choline cation and the monoanion of the maleic acid. We consider two isomers of the anion (H-maleate, the cis-isomer and H-fumarate, the trans-isomer) having different physical chemical properties. H-maleate assumes a closed structure and forms a strong intramolecular hydrogen bond whereas H-fumarate has an open structure. X-ray diffraction, infrared and Raman spectroscopy and molecular dynamics have been used to provide a reliable picture of the interactions which characterize the structure of the fluids. All calculations indicate that the choline cation prefers to connect mainly to the carboxylate group through OH⋯O interactions in both the compounds and orient the charged head N(CH3)3+ toward the negative portion of the anion. However, the different structure of the two anions affects the distribution of the ionic components in the fluid. The trans conformation of H-fumarate allows further interactions between anions through COOH and CO2- groups whereas intramolecular hydrogen bonding in H-maleate prevents this association. Our theoretical findings have been validated by comparing them with experimental X-ray data and infrared and Raman spectra.

Coupled Electrochemical and Microbial Catalysis for the Production of Polymer Bricks

Power-to-X technologies have the potential to pave the way towards a future resource-secure bioeconomy as they enable the exploitation of renewable resources and CO2 . Herein, the coupled electrocatalytic and microbial catalysis of the C5 -polymer precursors mesaconate and 2S-methylsuccinate from CO2 and electric energy by in situ coupling electrochemical and microbial catalysis at 1 L-scale was developed. In the first phase, 6.1±2.5 mm formate was produced by electrochemical CO2 reduction. In the second phase, formate served as the substrate for microbial catalysis by an engineered strain of Methylobacterium extorquens AM-1 producing 7±2 μm and 10±5 μm of mesaconate and 2S-methylsuccinate, respectively. The proof of concept showed an overall conversion efficiency of 0.2 % being 0.4 % of the theoretical maximum.

Terahertz spectroscopic characterizations and DFT calculations of carbamazepine cocrystals with nicotinamide, saccharin and fumaric acid

Carbamazepine cocrystals with nicotinamide, saccharin and fumaric acid were synthesized and characterized by time-domain terahertz spectroscopy. Lattice vibrations of cocrystals with their individual constituents were investigated by means of the dispersion-corrected density functional theory with and without cell parameter constraints. The simulated THz spectra successfully reproduce the features of all the crystals in their experimental spectra. A better agreement between experimental and theoretical THz spectra is achieved when the cell parameter constraints are applied in geometry optimization. Some intensive modes of neat carbamazepine and cocrystals were discussed in terms of the motions of hydrogen bonds. The effect of lattice vibration on these cocrystallizations was further examined to gain insights into the thermodynamics. It is found that lattice vibration is favorable for all these cocrystal formations.

Phosphate functionalization and enzymatic calcium mineralization synergistically enhance oligo[poly(ethylene glycol) fumarate] hydrogel osteoconductivity for bone tissue engineering

A current approach in bone tissue engineering is the implantation of polymeric scaffolds that promote osteoblast attachment and growth as well as biomineralization. One promising polymer is oligo[poly(ethylene glycol) fumarate] (OPF), a polyethylene glycol-based material that is biocompatible, injectable, and biodegradable, but in its native form does not support robust bone cell attachment or growth. To address this issue, this study evaluated the osteoconductivity of bis[02-(methacryloyloxy)ethyl] phosphate (BP) functionalized OPF hydrogels (OPF-BP) using MC3T3-E1 pre-osteoblast cells, both before and after enzymatic mineralization with a calcium solution. The inclusion of negatively charged functional groups allowed for the tailored uptake and release of calcium, while also altering the mechanical properties and surface topography of the hydrogel surface. In cell culture, OPF-BP hydrogels with 20 and 30% (w/w) BP optimized osteoblast attachment, proliferation, and differentiation after a 21-day in vitro period. In addition, the OPF-BP30 treatment, when mineralized with calcium, exhibited a 128% increase in osteocalcin expression when compared with the non-mineralized treatment. These findings suggest that phosphate functionalization and enzymatic calcium mineralization can act synergistically to enhance the osteoconductivity of OPF hydrogels, making this processed material an attractive candidate for bone tissue engineering applications.

Fumaric acid incorporated Ag/agar-agar hybrid hydrogel: A multifunctional avenue to tackle wound healing

Wound and its treatment is one of the major health concerns throughout the globe. Various extrinsic and intrinsic factors can influence the dynamics of healing mechanism. One such extrinsic factor is moist environment in wound healing. The advantages of optimum hydration in wound healing are enhanced autolytic debridement, angiogenesis and accelerated cell proliferation and collagen formation. But hydrated wounds often end up with patient's uncomfortability, associated infection, and tissue lipid peroxidation. Healing process prefers antimicrobial, anti-inflammatory and optimum moist microenvironment. Here, we have synthesized fumaric acid incorporated agar-silver hydrogel (AA-Ag-FA); characterized by UV-Visible spectroscopy, FTIR spectroscopy and TEM. The surface morphology is evaluated through SEM. The size of the silver nanoparticles (Ag NPs) was found to be 10-15 nm. The hydrogel shows potential antibacterial effect against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa which are predominantly responsible for wound infection. The gel shows reasonable antioxidant property evaluated through 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Topical application of the gel on the wound site heals the wound at much faster rate even compared to standard (Mega heal, Composition: Colloidal silver 32 ppm hydrogel) gel. Histological analysis reveals better tissue proliferation (i.e. epithelialization), more granulation tissue formation, neovascularisation, fibroblast and mature collagen bundles. The lipid peroxidation of wound tissue estimated through malondialdehyde (MDA) assay was found to be reasonably less when treated with AA-Ag-FA hydrogel compared to standard (Mega heal). Cytotoxicity of the samples tested through MTT assay and live-dead cell staining shows its nontoxic biocompatibility nature. In our hydrogel scaffold, the bio-degradable agar-agar provides the moist environment; the Ag NPs inside the gel acts as bactericidal agent and fumaric acid facilities the antioxidant and angiogenesis path implicitly.

Injectable Catalyst-Free Poly(Propylene Fumarate) System Cross-Linked by Strain Promoted Alkyne-Azide Cycloaddition Click Chemistry for Spine Defect Filling

A new PPF-BCN/hyPCL32-N3 injectable system that can be cross-linked by catalyst-free, strain promoted alkyne-azide cycloaddition (SPAAC) click chemistry was developed for tissue engineering applications. The system consisted of two components: PPF-BCN, poly(propylene fumarate) (PPF) functionalized with (1R,8S,9s)-bicyclo[6.1.0]non-4-yn-9-ylmethanol (BCN-OH), and hyPCL32-N3, a hyper-branched 32-arm poly(ε-caprolactone) (PCL) dendrimer functionalized with azide as the cross-linker core. Fast SPAAC click reaction allowed the desired gelation of the system without using any toxic initiator or catalyst. Compared to the conventional injectable formulation, e.g., poly(methyl methacrylate) (PMMA), our PPF-BCN/hyPCL32-N3 (abbreviated as PFCL-Click) injectable system showed enhanced biocompatibility and low heat generation during cross-linking. After reaction, the cross-linked PFCL-Click scaffolds supported excellent proliferation and differentiation of preosteoblast cells on the surface. The PFCL-Click system can be successfully injected into vertebral bodies of rabbit spine and can be monitored by X-ray imaging after incorporating zirconium dioxide (ZrO2) powder. With these unique advantages, this injectable system has promising potential for bone defect repair and other tissue engineering and regenerative medicine applications.

Structural Study of Monomethyl Fumarate-Bound Human GAPDH

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a core enzyme of the aerobic glycolytic pathway with versatile functions and is associated with cancer development. Recently, Kornberg et al . published the detailed correlation between GAPDH and di- or monomethyl fumarate (DMF or MMF), which are well-known GAPDH antagonists in the immune system. As an extension, herein, we report the crystal structure of MMF-bound human GAPDH at 2.29 Å. The MMF molecule is covalently linked to the catalytic Cys152 of human GAPDH, and inhibits the catalytic activity of the residue and dramatically reduces the enzymatic activity of GAPDH. Structural comparisons between NAD+bound GAPDH and MMF-bound GAPDH revealed that the covalently linked MMF can block the binding of the NAD+ cosubstrate due to steric hindrance of the nicotinamide portion of the NAD+ molecule, illuminating the specific mechanism by which MMF inhibits GAPDH. Our data provide insights into GAPDH antagonist development for GAPDH-mediated disease treatment.