Organoid Technology and the COVID Pandemic

COVID-19 is caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and has emerged as a devastating pandemic. SARS-CoV-2 not only causes respiratory illness but also leads to impairment of multi-organ function. Scientists are racing to evaluate a range of experimental therapeutics to target COVID-19 systemically. The World Health Organization (WHO) and the Center for Disease Control and Prevention (CDC) are accelerating global research priorities to mobilize innovation towards diagnostics, treatments, and vaccines against COVID-19. In this scenario, information about appropriate organ-specific physiologically relevant models is critical to generate knowledge about the pathophysiology and therapeutic targeting of COVID-19. Human and animal organoids are providing a unique platform, demonstrating their applicability for experimental virology. This review provides a brief analysis of the available organoid models used to study and device strategies to combat COVID-19

Phosphatase models: Synthesis, structure and catalytic activity of zinc complexes derived from a phenolic Mannich-base ligand

A series of dinuclear [Zn2(L1)2X2] (1\u20133) and mononuclear [Zn(HL2)X2] complexes (4\u20136), (X = Cl, Br, I) were synthesised from two Mannich-base compartmental ligands, namely [bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL1) and 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL2), respectively. They were characterised by routine physicochemical techniques (CHN, UV, IR, ESI-MS and NMR) and complex 2\u20135 was further structurally characterised by single crystal X-ray analysis where the Zn. . .Zn bond-distance is 3.10\u20133.12 \uc5. All the quintessential complexes exhibit excellent phosphatase activity and the experimental first order rate constant values (kcat) for the hydrolysis of 4-nitrophenyl phosphate ester (PNPP) reaction in methanol are in the range from 1.05 to 214 s1 at 25 C evaluated by monitoring spectrophotometrically the gradual release of p-n nitrophenolate (kmax = 427 nm, e = 18500 M1 cm1). The coordinated X halides affect the phosphatase activity in the order Br > Cl > I (in dinuclear complexes) and Cl > Br > I (in mononuclear) and the trend in the two cases has been well recognised to be due to a different rate determining step. Moreover the influence of chloro atom in para-position of the phenol ring and the role of solvent have been rationalised by comparing the kinetic parameters with those obtained for the corresponding methyl analogues having reasonably close structural resemblance as reported by Sanyal et al. (2014)

Influence of the coordination environment of zinc(II) complexes of designed mannich ligands on phosphatase activity: A combined experimental and theoretical study

A mononucleating (HL1) and a dinucleating (HL2) \u201cendoff\u201d compartmental ligand have been designed and synthesized by controlled Mannich reaction using p-cresol and bis(2-methoxyethyl)amine, and their formation has been rationalized. Six complexes have been prepared on treating HL1 and HL2 with ZnIIX2 (X = Cl 12, Br 12, I 12) with the aim to investigate their hydrolytic activity on phosphoester bond cleavage. Interestingly, the mononucleating ligand was observed to yield dinuclear complexes, [Zn2(L1)2X2] (1 123), while the potential dinucleating ligand generated mononuclear complexes, [Zn(HL2)X2] (4 126). Four (1 124), out of six complexes studied, were characterized by single-crystal X-ray diffraction (XRD): the Zn ion exhibits trigonal bipyramidal and tetrahedral coordination spheres in the di- and mononuclear complex, respectively. The hydrolytic kinetics, followed spectrophotometrically with 4-nitrophenylphosphate (4-NPP) in buffered dimethylformamide (DMF) (97.5% DMF, v/v) because of solubility reasons, under excess substrate conditions (substrate:complex = 20:1), indicated that the complexes enormously accelerate the rate of phosphomonoester hydrolysis with first order rate constants (kcat) in the range 2 1210 s 121 at 25 \ub0C. In each case kinetic data analyses have been run by Michaelis 12Menten treatment. The efficacy in the order of conversion of substrate to product (pnitrophenolate ion) follows the trend 1 > 2 > 3 > 4 > 5 > 6, and the ratio of kcat of an analogous dinuclear to mononuclear complex is 432. An electrospray ionization-mass spectrometry (ESI-MS) study has revealed the dissociation of the centrosymmetric dinuclear complex to two mononuclear species instead of a syn-cooperative catalysis. Density functional theory (DFT) calculations have been performed to rationalize our proposed mechanistic pathway for phosphatase activity. The comparative analysis concludes the following facts under experimental conditions: (1) the halide bound to the active site affects the overall rate in the order: Cl 12 > Br 12 > I 12 regardless of nuclearity; (2) dinuclear complexes prevail over the mononuclear ones

A series of mononuclear nickel(II) complexes of Schiff-base ligands having N,N,O- and N,N,N-donor sites: Syntheses, crystal structures, solid state thermal property and catecholase-like activity

Four new mononuclear nickel(II) complexes, namely [NiL1(H2O)3](NO3)2 (1), [NiL2(H2O)3](NO3)2 (2), [NiL3(H2O)3](NO3)2 (3) and [NiL4(ClBz)(H2O)] 1.25(H2O) (4) have been synthesized via Schiff-base formation by condensation between 2-benzoylpyridine and N-(2-aminoethyl)pyrrolidine for L1, salicylaldehyde and N-(2-aminoethyl)piperazine (L2), 5-chlorosalicylaldehyde and N-(2-aminoethyl)piperazine (L3), and 5-chlorosalicylaldehyde and N-(2-aminoethyl)morpholine (L4). These complexes are comprehensively characterized via routine physicochemical techniques as well as by single crystal X-ray structural analyses. Despite all the nickel complexes are mononuclear, the catecholase activity shows prominent variation depending on the coordination environment around the metal center. Complexes 2 and 3 derived from same amine bear an extra positive charge on the ligand system facilitating the substrate\u2013catalyst interaction to promote the oxidation of 3,5-DTBC to 3,5-DTBQ. On the contrary complexes 1 and 4 remain inert in nature, although 1 shows structural similarities in terms of coordination environment with nickel substituted catechol oxidase

Nuclearity dependent solvent contribution to the catechol oxidase activity of novel copper(II) complexes derived from Mannich-base ligand platforms: synthesis, crystal structure and mechanism

A set of tetra-and dinuclear copper(II) complexes, Cu-4(L-1)(mu-O)(OAc)(4)] (1), Cu-2(L-2)(2)](ClO4)(2) (2), Cu-2(L-2)(2)(OAc)(2)] (3), Cu-2(L-2)(2)(Br)(2)] (4) and Cu-2(L-2)(2)(Cl)(2)] (5), were synthesized from two Mannich-base ligands HL1 and HL2, where HL1 = 2,6-bisbis(2-methoxyethyl)aminomethyl]-4-methylphenol and HL2 = 2-bis(2-methoxyethyl)aminomethyl]-4-methylphenol. The catalytic efficiency of the complexes for catecholase activity was systematically evaluated by spectrophotometry using 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) in pure dry acetonitrile (MeCN) and water-MeCN solvent mixtures (10%, 25%, 40% and 50% water). In spite of remarkable rate enhancements by the tetranuclear species in MeCN (k(cat) = 0.0218 s(-1)), complex 1 follows a reverse trend in the solvent dependent kinetic study compared to complexes 2-5 with a minimum at 25% water (k(cat) = 0.0118 s(-1)) under similar experimental conditions. Theoretical modeling involving the reactions of complexes 1, 3 and 5 provides the counterintuitive rationalization of the apparently dramatic behaviour of these novel catechol models on addition of water to the MeCN solution. More importantly, it vindicates the combination of the contradictory parameters like alcoholysis and hydrolysis as the governing factors for k(cat) extrema in catalytic pathways. Thus, the reactivity and mechanism of Mannich-base metallocatalysts across water-induced oxidation of catechols is predictable through their nuclearity

Catecholase activity of Mannich-based dinuclear CuII complexes with theoretical modeling: New insight into the solvent role in the catalytic cycle

Four new dinuclear CuII complexes were synthesised from two Mannich-base ligands namely 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL1) and 2-[bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL2): [Cu2(L1)(OH)](ClO4)2CH3OH (1), [Cu2(L2)2](ClO4)2H2O (2), [Cu2(L2)2(NO3)2] (3) and [Cu2(L2)2(OAc)2] H2O (4) and well characterised. X-ray diffraction analysis of the complexes reveals a Cu Cu distance of 2.9183(13), 2.9604(6), 3.0278(4) and 3.0569(11) \uc5, respectively. In 1 the metal coordination geometry is intermediate between trigonal bipyramidal (TBP) and square pyramidal (SP) (t = 0.488), in 2 the geometry is TBP (0.828 and 0.639) and in 3 and 4 is SP (t = 0.188 and 0.083, respectively). Spectrophotometric investigations to evaluate the catecholase activity of complexes against 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) in three different solvents (acetonitrile, methanol and DMSO) under completely aerobic conditions reveal that complexes 1\u20134 are able to oxidise 3,5-DTBC in all the solvents, while TCC can be oxidised only in acetonitrile (kcat = 0.0002\u20130.02 s1). Intensive DFT calculations prove an ionic pathway for 1\u20133 while a unique neutral catalytic cycle for 4

Relation between the catalytic efficiency of the synthetic analogues of catechol oxidase with their electrochemical property in the Free State and substrate-bound state

A library of 15 dicopper complexes as synthetic analogues of catechol oxidase has been synthesized with the aim to determine the relationship between the electrochemical behavior of the dicopper(II) species in the absence as well as in the presence of 3,5-di-tert-butylcatechol (3,5-DTBC) as model substrate and the catalytic activity, kcat, in DMSO medium. The complexes have been characterized by routine physicochemical techniques as well as by X-ray single-crystal structure analysis in some cases. Fifteen \u201cend-off\u201d compartmental ligands have been designed as 1 + 2 Schiff-base condensation product of 2,6-diformyl-4-R-phenol (R = Me, tBu, and Cl) and five different amines, N-(2-aminoethyl)- piperazine, N-(2-aminoethyl)pyrrolidine, N-(2-aminoethyl)- morpholine, N-(3-aminopropyl)morpholine, and N-(2-aminoethyl)piperidin

Influence of the Coordination Environment of Zinc(II) Complexes of Designed Mannich Ligands on Phosphatase Activity: A Combined Experimental and Theoretical Study

A mononucleating (HL¹) and a dinucleating (HL²) “end-off” compartmental ligand have been designed and synthesized by controlled Mannich reaction using <i>p</i>-cresol and bis­(2-methoxyethyl)­amine, and their formation has been rationalized. Six complexes have been prepared on treating HL¹ and HL² with Zn^IIX₂ (X = Cl^–, Br^–, I^–) with the aim to investigate their hydrolytic activity on phosphoester bond cleavage. Interestingly, the mononucleating ligand was observed to yield dinuclear complexes, [Zn₂(L¹)₂X₂] (<b>1</b>–<b>3</b>), while the potential dinucleating ligand generated mononuclear complexes, [Zn­(HL²)­X₂] (<b>4</b>–<b>6</b>). Four (<b>1</b>–<b>4</b>), out of six complexes studied, were characterized by single-crystal X-ray diffraction (XRD): the Zn ion exhibits trigonal bipyramidal and tetrahedral coordination spheres in the di- and mononuclear complex, respectively. The hydrolytic kinetics, followed spectrophotometrically with 4-nitrophenylphosphate (4-NPP) in buffered dimethylformamide (DMF) (97.5% DMF, v/v) because of solubility reasons, under excess substrate conditions (substrate:complex = 20:1), indicated that the complexes enormously accelerate the rate of phosphomonoester hydrolysis with first order rate constants (<i>k</i>_cat) in the range 2–10 s^–1 at 25 °C. In each case kinetic data analyses have been run by Michaelis–Menten treatment. The efficacy in the order of conversion of substrate to product (<i>p</i>-nitrophenolate ion) follows the trend <b>1</b> > <b>2</b> > <b>3</b> > <b>4</b> > <b>5</b> > <b>6</b>, and the ratio of <i>k</i>_cat of an analogous dinuclear to mononuclear complex is ≃2. An electrospray ionization-mass spectrometry (ESI-MS) study has revealed the dissociation of the centrosymmetric dinuclear complex to two mononuclear species instead of a syn-cooperative catalysis. Density functional theory (DFT) calculations have been performed to rationalize our proposed mechanistic pathway for phosphatase activity. The comparative analysis concludes the following facts under experimental conditions: (1) the halide bound to the active site affects the overall rate in the order: Cl^– > Br^– > I^– regardless of nuclearity; (2) dinuclear complexes prevail over the mononuclear ones

Role of ligand backbone of tridentate Schiff-base on complex nuclearity and bio-relevant catalytic activities of zinc(II) complexes: Experimental and theoretical investigations

Reaction of ZnII-acetate with two N, N, O-donor Schiff-base ligands, HL1 {4-Chloro-2-[(2-morpholin-4-ylethylimino)- methyl]-phenol} and HL2 {4-Chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phenol}, which are formed in situ via condensation of 5-chlorosalicylaldehyde and N-(2-aminoethyl/propyl)morpholine, produce one tri- and one mononuclear species, Zn3L1(OAc)4 (1) and ZnL2(OAc) (2). The hypothetical ZnL1(OAc) and Zn3L2(OAc)4 are energetically unfavorable by 9.2 and 5.1 kcal/mol, in compare with their respective real counterparts 1 and 2 evidenced from DFT calculations. Both 1 and 2 catalyze the hydrolytic cleavage of phosphoester bond of (4-nitrophenyl) phosphate where 1 shows higher activity than that of 2. The proposed mechanistic pathways of phosphatase activity of 1 and 2 and the higher efficiency of the latter have been rationalized by DFT study. DNA cleavage activities have been investigated using supercoiled pET28a plasmid DNA where both the complexes show dose dependent DNA cleavage activity with varying degree. Complex 1 shows excellent breakage activity even at a concentration of 20 lM. However, in both cases hydroxyl radical pathway is most probably operative in DNA cleavage activity

Influence of the Coordination Environment of Zinc(II) Complexes of Designed Mannich Ligands on Phosphatase Activity: A Combined Experimental and Theoretical Study

A mononucleating (HL¹) and a dinucleating (HL²) “end-off” compartmental ligand have been designed and synthesized by controlled Mannich reaction using <i>p</i>-cresol and bis­(2-methoxyethyl)­amine, and their formation has been rationalized. Six complexes have been prepared on treating HL¹ and HL² with Zn^IIX₂ (X = Cl^–, Br^–, I^–) with the aim to investigate their hydrolytic activity on phosphoester bond cleavage. Interestingly, the mononucleating ligand was observed to yield dinuclear complexes, [Zn₂(L¹)₂X₂] (<b>1</b>–<b>3</b>), while the potential dinucleating ligand generated mononuclear complexes, [Zn­(HL²)­X₂] (<b>4</b>–<b>6</b>). Four (<b>1</b>–<b>4</b>), out of six complexes studied, were characterized by single-crystal X-ray diffraction (XRD): the Zn ion exhibits trigonal bipyramidal and tetrahedral coordination spheres in the di- and mononuclear complex, respectively. The hydrolytic kinetics, followed spectrophotometrically with 4-nitrophenylphosphate (4-NPP) in buffered dimethylformamide (DMF) (97.5% DMF, v/v) because of solubility reasons, under excess substrate conditions (substrate:complex = 20:1), indicated that the complexes enormously accelerate the rate of phosphomonoester hydrolysis with first order rate constants (<i>k</i>_cat) in the range 2–10 s^–1 at 25 °C. In each case kinetic data analyses have been run by Michaelis–Menten treatment. The efficacy in the order of conversion of substrate to product (<i>p</i>-nitrophenolate ion) follows the trend <b>1</b> > <b>2</b> > <b>3</b> > <b>4</b> > <b>5</b> > <b>6</b>, and the ratio of <i>k</i>_cat of an analogous dinuclear to mononuclear complex is ≃2. An electrospray ionization-mass spectrometry (ESI-MS) study has revealed the dissociation of the centrosymmetric dinuclear complex to two mononuclear species instead of a syn-cooperative catalysis. Density functional theory (DFT) calculations have been performed to rationalize our proposed mechanistic pathway for phosphatase activity. The comparative analysis concludes the following facts under experimental conditions: (1) the halide bound to the active site affects the overall rate in the order: Cl^– > Br^– > I^– regardless of nuclearity; (2) dinuclear complexes prevail over the mononuclear ones