Switchable Nanozyme Activity of Porphyrins Intercalated in Layered Gadolinium Hydroxide

In this study, organo-inorganic nanohybrids LHGd-MTSPP with enzyme-like activity were prepared by in situ intercalation of anionic 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin and its complexes with Zn(II) and Pd(II) (MTSPP, M = 2H, Zn(II) and Pd(II)) into gadolinium layered hydroxide (LHGd). The combination of powder XRD, CHNS analysis, FT-IR, EDX, and TG confirmed the layered structure of the reaction products. The basal interplanar distances in LHGd-MTSPP samples were 22.3-22.6 Å, corresponding to the size of an intercalated tetrapyrrole molecule. According to SEM data, LHGd-MTSPP hybrids consisted of individual lamellar nanoparticles 20-50 nm in thickness. The enzyme-like activity of individual constituents, LHGd-Cl and sulfoporphyrins TSPP, ZnTSPP and PdTSPP, and hybrid LHGd-MTSPP materials, was studied by chemiluminescence analysis using the ABAP/luminol system in phosphate buffer solution. All the individual porphyrins exhibited dose-dependent antioxidant properties with respect to alkylperoxyl radicals at pH 7.4. The intercalation of free base TSPP porphyrin into the LHGd preserved the radical scavenging properties of the product. Conversely, in LHGd-MTSPP samples containing Zn(II) and Pd(II) complexes, the antioxidant properties of the porphyrins changed to dose-dependent prooxidant activity. Thus, an efficient approach to the design and synthesis of advanced LHGd-MTSPP materials with switchable enzyme-like activity was developed.

Synthesis of Mg-Fe-Cl hydrotalcite-like nanoplatelets as an oral phosphate binder: evaluations of phosphorus intercalation activity and cellular cytotoxicity

The patients with end-stage of renal disease (ESRD) need to take oral phosphate binder. Traditional phosphate binders may leave the disadvantage of aluminum intoxication or cardiac calcification. Herein, Mg-Fe-Cl hydrotalcite-like nanoplatelet (HTln) is for the first time characterized as potential oral phosphate binder, with respect to its phosphorus uptake capacity in cow milk and cellular cytotoxicity. A novel method was developed for synthesizing the Mg-Fe-Cl HTln powder in different Mg²⁺: Fe³⁺ ratios where the optimization was 2.8:1. Addition of 0.5 g Mg-Fe-Cl HTln in cow milk could reduce its phosphorus content by 40% in 30 min and by 65% in 90 min. In low pH environment, the Mg-Fe-Cl HTln could exhibit relatively high performance for uptaking phosphorus. During a 90 min reaction of the HTln in milk, no phosphorus restoration occurred. In-vitro cytotoxicity assay of Mg-Fe-Cl HTln revealed no potential cellular cytotoxicity. The cells that were cultured in the HTln extract-containing media were even more viable than cells that were cultured in extract-free media (blank control). The Mg-Fe-Cl HTln extract led to hundred ppm of Mg ion and some ppm of Fe ion in the media, should be a positive effect on the good cell viability.

Modes of tetra(4-pyridyl)porphyrinatomanganese(III) ion intercalation inside natural clays

BACKGROUND

Metalloporphyrin ions, with planar shape, have been known to intercalate horizontally and diagonally between montmorillonite layers. Perpendicular intercalation inside montmorillonite has not been reported earlier. This work aims at achieving perpendicular intercalation inside montmorillonite in natural clays. Possible intercalation inside other forms of natural clay will also be investigated.

METHODS

Natural clays were purified and characterized. The naked clay powder was then refluxed with tetra(4-pyridyl)porphyrinatomanganese(III) ion (MnTPyP(+)) solution in methanol with continuous stirring for different times. Electronic absorption spectra, atomic absorption spectra, Fourier Transform infrared spectra, scanning electron microscopy and X-ray diffraction were all used in clay characterization and in intercalation study.

RESULTS

The natural clay involved different phases, namely montmorillonite, biotite, kaolinite, illite and traces of quartz. Montmorillonite clay allowed horizontal, diagonal and perpendicular intercalation of the metalloporphyrin ions. Biotite allowed only horizontal intercalation. The mode of intercalation was deduced by monitoring the clay inter-planar distance value change. Intercalation occurred inside both micro- and nano-size clay powders to different extents. The nano-powder (average size ~50 nm) showed uptake values up to 3.8 mg MnTPyP/g solid, whereas the micro-size powder (average size ~316 nm) exhibited lower uptake (2.4 mg MnTPyP/g solid). Non-expandable clay phases did not allow any intercalation. The intercalated MnTPyP(+) ions showed promising future supported catalyst applications.

CONCLUSIONS

Depending on their phase, natural clays hosted metalloporphyrin ions. Montmorillonite can allow all three possible intercalation geometries, horizontal, diagonal and for the first time perpendicular. Biotite allows horizontal intercalation only. Non-expandable clays allow no intercalation. Graphical abstractMetalloporphyrin complexes can be intercalated into montmorillonite in horizontal, perpendicular and diagonal geometries.

Highly active and selective catalysts for olefin hydrosilylation reactions using metalloporphyrins intercalated in natural clays

Mechanisms showing how the metalloporphyrin ions selectively catalyze olefin hydrosilylation reactions and the solvent-like behavior associated with the clay supported metalloporphyrin catalyst.