Synthesis of nicotinamide mononucleotide from xylose via coupling engineered Escherichia coli and a biocatalytic cascade

β-Nicotinamide mononucleotide (NMN) has recently gained attention for nutritional supplement because it is an intermediate in the biosynthesis of nicotinamide adenine dinucleotide (NAD + ). In this study, we develop NMN synthesis by coupling two modules. The first module is to culture E. coli MG1655 ∆ tktA ∆ tktB ∆ ptsG to metabolize xylose to generate D -ribose in the medium. The supernatant containing D -ribose was applied in the second module which is composed of Ec RbsK- Ec PRPS- Cp NAMPT reaction to synthesize NMN, that requires additional enzymes of CHU0107 and Ec PPase to remove feedback inhibitors, ADP and pyrophosphate. The second module can be rapidly optimized by comparing NMN production determined by the cyanide assay. Finally, 10 mL optimal biocascade reaction generated NMN with good yield of 84% from 1 mM D -ribose supplied from the supernatant of E. coli MG1655 ∆ tktA ∆ tktB ∆ ptsG . Our results can further guide researchers to metabolically engineer E. coli for NMN synthesis.

Effect of morpholine and charge distribution of cyanine dyes on cell internalization and cytotoxicity

To improve the potency of Heptamethine cyanines (Hcyanines) in cancer research, we designed and synthesized two novel Hcyanines based theranostic probes, IR794-Morph and IR794-Morph-Mpip, to enhance cancer cell internalization and targeting. In acidic conditions that resemble to tumour environment, both IR794 derivatives exhibited broad NIR absorption band (704‒794 nm) and fluorescence emission (798‒828 nm) that is suitable for deep seated tumour imaging. Moreover, in vitro study revealed that IR794-Morph-Mpip exhibited better cancer targetability towards various cancer cell lines under physiological and slightly acidic conditions compared to normal cells. IR794-Morph-Mpip was fast internalized into the cancer cells within the first 5 min and mostly localized in lysosomes and mitochondria. In addition, the internalized signal was brighter when the cells were in the hypoxic environment. Furthermore, cellular uptake mechanism of both IR794 dyes, investigated via flow cytometry, revealed that endocytosis through OATPs receptors and clathrin-mediated endocytosis were the main routes. Moreover, IR794-Morph-Mpip, displayed anti-cancer activity towards all tested cancer cell types with IC₅₀ below 7 μM (at 6 h incubation), which is approximately three times lower than that of the normal cells. Therefore, increasing protonated cites in tumour environment of Hcyanines together with incorporating morpholine in the molecule can enhance structure-inherent targeting of these dyes.

Chitosan Nanoparticles-Based Ionic Gelation Method: A Promising Candidate for Plant Disease Management

By 2050, population growth and climate change will lead to increased demand for food and water. Nanoparticles (NPs), an advanced technology, can be applied to many areas of agriculture, including crop protection and growth enhancement, to build sustainable agricultural production. Ionic gelation method is a synthesis of microparticles or NPs, based on an electrostatic interaction between opposite charge types that contains at least one polymer under mechanical stirring conditions. NPs, which are commonly based on chitosan (CS), have been applied to many agricultural fields, including nanopesticides, nanofertilizers, and nanoherbicides. The CS-NP or CS-NPs-loaded active ingredients (Cu, saponin, harpin, Zn, hexaconazole, salicylic acid (SA), NPK, thiamine, silicon, and silver (Ag)) are effective in controlling plant diseases and enhancing plant growth, depending on the concentration and application method by direct and indirect mechanisms, and have attracted much attention in the last five years. Many crops have been evaluated in in vivo or in greenhouse conditions but only maize (CS-NP-loaded Cu, Zn, SA, and silicon) and soybean (CS-NP-loaded Cu) were tested for manage post flowering stalk rot, Curvularia leaf spot, and bacterial pustule disease in field condition. Since 2019, five of eight studies have been performed in field conditions that have shown interest in CS-NPs synthesized by the ionic gelation method. In this review, we summarized the current state of research and provided a forward-looking view of the use of CS-NPs in plant disease management.

Efficacy of Chitosan Nanoparticle Loaded-Salicylic Acid and -Silver on Management of Cassava Leaf Spot Disease

Leaf spot is one of the most important cassava diseases. Nanotechnology can be applied to control diseases and improve plant growth. This study was performed to prepare chitosan (CS) nanoparticle (NP)-loaded salicylic acid (SA) or silver (Ag) by the ionic gelation method, and to evaluate their effectiveness on reducing leaf spot disease and enhancing the growth of cassava plants. The CS (0.4 or 0.5%) and Pentasodium triphosphate (0.2 or 0.5%) were mixed with SA varying at 0.05, 0.1, or 0.2% or silver nitrate varying at 1, 2, or 3 mM to prepare three formulations of CS-NP-loaded SA named N1, N2, and N3 or CS-NP-loaded Ag named N4, N5, and N6. The results showed that the six formulations were not toxic to cassava leaves up to 800 ppm. The CS-NP-loaded SA (N3) and CS-NP-loaded Ag (N6) were more effective than the remaining formulations in reducing the disease severity and the disease index of leaf spot. Furthermore, N3 at 400 ppm and N6 at 200, 400, and 800 ppm could reduce disease severity (68.9–73.6% or 37.0–37.7%, depending on the time of treatment and the pathogen density) and enhance plant growth more than or equal to commercial fungicide or nano-fungicide products under net-house conditions. The study indicates the potential to use CS-NP-loaded SA or Ag as elicitors to manage cassava leaf spot disease.

Near-Infrared Fluorescent Heptamethine Cyanine Dyes for COX-2 Targeted Photodynamic Cancer Therapy

We designed and synthesized two heptamethine cyanine based theranostic probes that aimed to target COX-2 in cancer cells. One is I-IR799-CXB which I-IR799 was conjugated to COX-2 specific inhibitor, celecoxib, and another is I-IR799-IMC , where the non-selective COX inhibitor, indomethacin, was used. I-IR799 is a heptamethine cyanine derivative that can be activated by near infrared light for photodynamic therapy (PDT) purposes. I-IR799-CXB and I-IR799-IMC were tested for their cancer targeting and photodynamic efficiency towards liver hepatocellular carcinoma cells (HepG2) compared to normal liver cell, alpha mouse liver 12 cells (AML12). Interestingly, after conjugation, I-IR799-IMC exhibited superior tumour targetability and PDT efficiency than I-IR799-CXB .

Design of a surrogate for high throughput screening of fatty aldehyde reductase engineering

We designed and synthesized a fatty aldehyde surrogate containing a formyl thioester group, which can be reduced by fatty aldehyde reductase (FALR) with stoichiometric formaldehyde generation. It can be rapidly visualized and quantified using the Purpald assay. We demonstrated its successful application in the high throughput screening of FALR engineering.

Detection of hazardous mercury ion using [5]helicene-based fluorescence probe with "TurnON" sensing response for practical applications

A new fluorescence probe based on [5]helicene derivative (MT) was designed and synthesized. The chemical structure of the probe was fully characterized by NMR, mass spectrometry and X-ray crystallography. MT which is the combination of thioamide[5]helicene with Schiff base-thiophene moiety, exhibited a high selectivity to detect Hg²⁺ through irreversible desulfurization reaction with "TurnON" fluorescence response and large Stokes shift of 110 nm in aqueous methanol solution. The detection limit of MT was 1.2 ppb (6.0 × 10^-3 µM), which is lower than the limit of Hg²⁺ level in drinking water, as specified by WHO (6.0 ppb) and U.S. EPA (2.0 ppb). The Hg²⁺ detection range of the probe was 0.07-1.6 µM with good linearity. Under UV irradiation, MT possessed the capability to detect Hg²⁺ in diverse context of real samples, including drinking and sea waters, vegetable tissue and brain tumor cell. In addition, MT could be used as a paper test strip for monitoring and screening of Hg²⁺ contamination in environment.

Flavylium-Based Hypoxia-Responsive Probe for Cancer Cell Imaging

A hypoxia-responsive probe based on a flavylium dye containing an azo group (AZO-Flav) was synthesized to detect hypoxic conditions via a reductase-catalyzed reaction in cancer cells. In in vitro enzymatic investigation, the azo group of AZO-Flav was reduced by a reductase in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH) followed by fragmentation to generate a fluorescent molecule, Flav-NH2. The response of AZO-Flav to the reductase was as fast as 2 min with a limit of detection (LOD) of 0.4 μM. Moreover, AZO-Flav displayed high enzyme specificity even in the presence of high concentrations of biological interferences, such as reducing agents and biothiols. Therefore, AZO-Flav was tested to detect hypoxic and normoxic environments in cancer cells (HepG2). Compared to the normal condition, the fluorescence intensity in hypoxic conditions increased about 10-fold after 15 min. Prolonged incubation showed a 26-fold higher fluorescent intensity after 60 min. In addition, the fluorescence signal under hypoxia can be suppressed by an electron transport process inhibitor, diphenyliodonium chloride (DPIC), suggesting that reductases take part in the azo group reduction of AZO-Flav in a hypoxic environment. Therefore, this probe showed great potential application toward in vivo hypoxia detection.

Glucose conjugated aza-BODIPY for enhanced photodynamic cancer therapy

Compared with normal cells, cancer cells usually exhibit an increase in glucose uptake as part of the Warburg effect. To take advantage of this hallmark of cancer, glucose transporters could be a good candidate for cancer targeting. Herein, we report novel glycoconjugate aza-BODIPY dyes (AZB-Glc and AZB-Glc-I) that contain two glucose moieties conjugated to near-infrared dyes via the azide-alkyne cycloaddition reaction. As anticipated, a higher level of AZB-Glc uptake was observed in breast cancer cells that overexpressed glucose transporters (GLUTs), especially GLUT-1, including the triple-negative breast cancer cell line (MDA-MB-231) and human breast adenocarcinoma cell line (MCF-7), compared to that of normal cells (human fetal lung fibroblasts, HFL1). The cellular uptake of AZB-Glc was in a dose- and time-dependent manner and also depended on GLUT, as evidenced by the decreased uptake of AZB-Glc in the presence of d-glucose or a glucose metabolism suppressor, combretastatin. In addition, light triggered cell death was also investigated through photodynamic therapy (PDT), since near-infrared (NIR) light is known to penetrate deeper tissue than light of shorter wavelengths. AZB-Glc-I, the analog of AZB-Glc containing iodine for enhanced singlet oxygen production upon NIR irradiation, was used for all treatment assays. AZB-Glc-I showed significant NIR light-induced cytotoxicity in cancer cells (IC₅₀ = 1.4-1.6 μM under 1 min irradiation), which was about 20-times lower than that in normal cells (IC₅₀ = 32 μM) under the same conditions, with negligible dark toxicity (IC₅₀ > 100 μM) in all cell lines. Moreover, the singlet oxygen was detected inside the cancer cells after exposure to light in the presence of AZB-Glc-I. Therefore, our glucose conjugated systems proved to efficiently target cancer cells for enhanced photodynamic cancer therapy.

Rapid and visual detection of Cd2+ based on aza-BODIPY near infrared dye and its application in real and biological samples for environmental contamination screening

Cadmium highly toxic and hazardous, and it can adversely affect human health leading to serious disorders. Herein, a water-soluble near-infrared sensor based on aza-BODIPY (1) was developed for dual determination of Cd²⁺ in environmental and biological media. This sensor exhibited color change from colorless to green along with a fluorescence enhancement in the near-infrared (NIR) region via photoinduced electron transfer (PET) after complexation with Cd²⁺. Sensor 1 can be employed in aqueous media at physiological pH for quantitative monitoring. It shows rapid response with high sensitivity (detection limit of 2.8 ppb; linear correlation over [Cd²⁺] 1.33 - 6.67 µM) and selectivity over potentially interfering ions. NIR sensor 1 can be used to determine [Cd²⁺] in living cells and environmental samples.

ImmunoPET of the differential expression of CD146 in breast cancer

With advancement in antibody engineering, the development and characterization of new cancer-specific molecular targets are in the forefront of this PET-antibody combination "revolution". Overexpression of CD146 in different types of tumors, including breast tumor, has been associated with tumor progression and poor prognosis. Non-invasive detection of CD146 with a monoclonal antibody may provide a noninvasive diagnostic tool with high specificity and accountability.

METHODS

Herein, we have developed a CD146-specific monoclonal antibody (YY146), radiolabeled it with 52Mn and 89Zr and identified its capability in acting as a non-invasive imaging agent that specific targets CD146 in different murine breast cancer models. CD146 expression was first screened in different breast tumor cell lines through Western Blot and confirmed its binding ability to YY146 using Flow Cytometry. Serial immunoPET images were carried out after intravenous administration of 52Mn or 89Zr labeled YY146. In addition, we also performed in vivo fluorescence imaging in animals injected with YY146 conjugated with Cy5.5.

RESULTS

Western Blot results show that MDA-MB-435 cell line had greater levels of CD146 expression when compared to the other cell lines investigated. Flow cytometry confirmed binding ability of YY146. PET images revealed well correlated uptake between tumor uptake and CD146 expression levels, confirmed by biodistribution studies and fluorescence imaging.

CONCLUSION

PET imaging, for up to 7 days, of mice bearing three different breast tumors were carried out and revealed radiotracer uptake in tumors that strongly (r2 = 0.98, P < 0.01), correlated with CD146 expression levels, as confirmed by in vitro and ex vivo studies.

One-Pot Synthesis of Coumarin-Indomethacin Hybrids as COX-2 Targeting Probes for Cancer Imaging

Facile synthesis of 6- or 7-substituted coumarin-indomathacin hybrids (Coum-IDM) has been developed for specific cyclooxygenase-2 (COX-2) binding along with their intrinsic fluorescent properties. A mild and rapid condensation/dehydrative cyclization of 2-hydroxy benzaldehyde with activated indomethacin was carried out in one step under ultrasound irradiation. Coum-IDM₄ was found to be the best of this series as it presented significant binding to COX-2 and exhibited higher fluorescent intensity in cancer cells than in normal cells. Therefore, in the light of drug development tools, this new hybrid system could be a potential targeted probe for COX-2-overexpressed inflammation and cancer-cell tracking.

Characterization of NucPNP and NucV involved in the early steps of nucleocidin biosynthesis in Streptomyces calvus

Nucleocidin 1 produced by Streptomyces calvus is one of five characterized natural products containing fluorine. It was discovered in 1956, but its biosynthesis is not yet completely resolved. Recently, the biosynthetic gene cluster of 1 was identified. The nucPNP gene, which was initially annotated as orf206 and encodes a putative purine nucleoside phosphorylase, is essential for nucleocidin production. In this study, we performed in vitro assays and showed NucPNP produced adenine 3 from methylthioadenosine (MTA) 2 and adenosine 4. We also showed the downstream enzyme, NucV annotated as adenine phosphoribosyltransferase (APRT), catalyzes AMP formation from adenine 3 and 5-phospho-α-d-ribose-1-diphosphate (PRPP) 5. However, the catalytic efficiency of NucV was much slower than its homolog ScAPRT involved in the biosynthesis of canonical purine nucleoside in the same strain. These results provide new insights in nucleocidin biosynthesis and could guide future research on organofluorine formation.

A chalcone-based fluorescent responsive probe for selective detection of nitroreductase activity in bacteria

A new chalcone-based fluorescent turn-on probe (3c) responsive to nitroreductase (NTR) activity and its application toward the detection of bacteria are presented.

Near-Infrared Fluorescent pH Responsive Probe for Targeted Photodynamic Cancer Therapy

We developed a pH dependent amino heptamethine cyanine based theranostic probe (I2-IR783-Mpip) that can be activated by near infrared light. I2-IR783-Mpip, in acidic condition, exhibited an intense, broad NIR absorption band (820-950 nm) with high singlet oxygen generation upon exposure to NIR light (~850 nm). Theoretical calculations showed that the protonation of the probe in an acidic environment decreased the molecular orbital energy gaps and increased the intramolecular charge transfer efficiency. I2-IR783-Mpip exhibited good photodynamic efficiency towards liver hepatocellular carcinoma cells under physiological and slightly acidic conditions while normal human embryonic kidney cells remained alive under the same conditions. Detection of intracellular reactive oxygen species (ROS) in cells treated with I2-IR783-Mpip after NIR light exposure confirmed PDT efficiency of the probe in acidic environment. Moreover, I2-IR783-Mpip also demonstrated efficient phototoxicity under deep-seated tumour cell system. We believed this is the first PDT agent that possesses intrinsic tumour binding and selectively eradicate tumour in acidic environment under 850 nm NIR lamp.

Ultrasmall Pyropheophorbidea Nanodots for Nearinfrared Fluorescence/Photoacoustic Imaging-guided Photodynamic Therapy

Rationale: Nanoparticles (NPs) that are rapidly eliminated from the body offer great potential in clinical test. Renal excretion of small particles is preferable over other clearance pathways to minimize potential toxicity. Thus, there is a significant demand to prepare ultra-small theranostic agents with renal clearance behaviors.

Method: In this work, we report a facile method to prepare NPs with ultra-small size that show renal clearable behavior for imaging-guided photodynamic therapy (PDT). Pyropheophorbide-a (Pa), a deep red photosensitizer was functionalized with polyethylene glycol (PEG) to obtain Pa-PEG. The prepared NPs formed ultra-small nanodots in aqueous solution and showed red-shifted absorbance that enabling efficient singlet oxygen generation upon light irradiation.

Results: In vitro studies revealed good photodynamic therapy (PDT) effect of these Pa-PEG nanodots. Most of the cancer cells incubated with Pa-PEG nanodots were destroyed after being exposed to the irradiated light. Utilizing the optical properties of such Pa-PEG nanodots, in vivo photoacoustic (PA) and fluorescence (FL) imaging techniques were used to assess the optimal time for PDT treatment after intravenous (i.v.) injection of the nanodots. As monitored by the PA/FL dual-modal imaging, the nanodots could accumulate at the tumor site and reach the maximum concentration at 8 h post injection. Finally, the tumors on mice treated with Pa-PEG nanodots were effectively inhibited by PDT treatment. Moreover, Pa-PEG nanodots showed high PA/FL signals in kidneys implying these ultra-small nanodots could be excreted out of the body via renal clearance.

Conclusion: We demonstrated the excellent properties of Pa-PEG nanodots that can be an in vivo imaging-guided PDT agent with renal clearable behavior for potential future clinical translation.

Aza-BODIPY probe for selective visualization of cyclooxygenase-2 in cancer cells

AZB-IMC₂ was developed as a COX-2 specific probe that exhibited a brighter fluorescence signal in cancer cells that overexpress COX-2 compared to normal cells. Oxidative stress agent-treated inflamed cell lines inducing high COX-2 levels revealed an enhanced fluorescence signal. Inhibitory studies showed a markedly reduced fluorescence intensity in cancer cells. The results suggested that AZB-IMC₂ could be developed as a promising molecular tool for imaging guiding during surgery.

A bivalent indomethacin/Aza-BODIPY conjugate can selectively visualize the COX-2 enzyme in cancer and inflamed cells confirming its potential as a COX-2-specific biomarker in clinical applications.

Recent strategies to improve boron dipyrromethene (BODIPY) for photodynamic cancer therapy: an updated review

BODIPYs are photosensitizers activatable by light to generate highly reactive singlet oxygen (¹O₂) from molecular oxygen, leading to tissue damage in the photoirradiated region. Despite their extraordinary photophysical characteristics, they are not featured in clinical photodynamic therapy. This review discusses the recent advances in the design and/or modifications of BODIPYs since 2013, to improve their potential in photodynamic cancer therapy and related areas.

Quantum dot-NanoLuc bioluminescence resonance energy transfer enables tumor imaging and lymph node mapping in vivo

A small luciferase protein (Nluc) was conjugated to QDs as a bioluminescence resonance energy transfer (BRET) pair. The conjugate showed 76% BRET efficiency and lymph node mapping was successfully performed. The cRGD peptide was conjugated to QD-Nluc for tumor targeting. The self-illuminating QD-Nluc showed excellent energy transfer in a living system and offered an optimal tumor-to-background ratio (>85).

Aza-BODIPY based polymeric nanoparticles for cancer cell imaging

Near infrared (NIR) fluorescent dyes that are widely used for cancer imaging usually suffer from their hydrophobicity. To overcome this problem, a water-suspendable and biodegradable NIR-light-activating aza-BODIPY (AZB-NO₂) encapsulated in polymeric nanoparticles was prepared as a new class of deep-tissue imaging agent. AZB-NO₂ possesses an intense, broad NIR absorption band (600–800 nm) with a remarkably high fluorescent quantum yield. After being encapsulated with a biodegradable polycaprolactone (PCL) and a Kolliphor P188 surfactant by emulsification-solvent evaporation method, the AZB-NO₂ formed a spherical shape as observed in scanning electron micrographs (SEM) with a hydrodynamic average size of 201 nm (average PDI = 0.185). The results from transmission electron micrographs (TEM) and energy dispersive X-ray spectroscopy (EDS) elemental mapping indicated that the AZB-NO₂ homogeneously distributed in the polymeric shell. UV-visible-NIR and fluorescence spectra of the obtained nanoparticles, AZB-NO₂@PCL, revealed that the nanoparticles prepared by using 0.8 mg dye loading exhibited the highest fluorescence quantum yield. These nanoparticles were then applied for fluorescence imaging in human glioblastoma cell line (U-251). After the cells were exposed to AZB-NO₂@PCL, the materials appeared to be localized inside U-251 cells within 3 h and the fluorescence signal enhanced along with the increased incubation times. Moreover, 3D cell culture was used in this study to mimic in vivo tumor environments. The AZB-NO₂@PCL exhibited bright fluorescence from U-251 cells inside 3D Ca-alginate scaffolds after 24 h incubation. Our study successfully demonstrated that the encapsulation of hydrophobic aza-BODIPY dye could enhance the water-suspendability of the dye yielding biocompatible nanoparticles efficiently used in cancer cell imaging applications.

Encapsulation of hydrophobic aza-BODIPY dye could enhance its hydrophilicity yielding biocompatible nanoparticles which can be efficiently used in cancer cell imaging applications.

An agent for optical imaging of TrkC-expressing, breast cancer

Tropomyosin receptor kinases receptor C is expressed at high levels on the surface of tumors from metastatic breast cancer, metastatic melanoma, glioblastoma, and neuroblastoma. Previous studies have shown synthetic TrkC ligands bearing agents for photodynamic therapy could be used to completely ablate 4T1 metastatic breast tumors and suppress metastatic spread in vivo. Modification of these probes (A in the text) to make them suitable for near infrared optical imaging in vivo would require a substantial increase in molecular mass (and hence increased vulnerability to undesirable absorption, metabolism and immunogenicity effects), or significant changes to the probe design which might compromise binding to TrkC in histochemical studies and on live cells. The research featured here was undertaken to investigate if the second strategy could be achieved without compromising binding to TrkC-expressing tissues. Specifically, an "aza-BODIPY" probe was synthesized to replace a spacer fragment in the original probe A. In the event, this new probe design (1a in the text) binds TrkC⁺ breast cancer in live cell cultures, in histochemical studies and in an in vivo murine model. Probe 1a binds TrkC⁺ tissues with good contrast with respect to healthy tissues, and much more strongly than an isomeric, non-TrkC binding, probe (1b) prepared as a negative control.