Hydrophobic and hydrophilic drug loading capacity of micro diatom frustule from diatomite

The aim of this work was to strengthen the evidence of using micro diatom frustule as a promising candidate for drug loading materials for both hydrophobic and hydrophilic drug models. The morphological, surface elemental composition of diatomite powder, a raw source of micro diatom frustules and purified diatomite to collect micro diatom frustule were investigated. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) confirmed again the porous silica structure of micro diatom structure as well as validated a necessity of raw diatomite purification before using. UV- vis was used to measure drug loading content of untreated and treated surface of micro diatom frustule with maximum loading for hydrophobic and hydrophilic drugs after 24 hours were at 5.48 ± 0.42% and 5.70 ± 0.34, respectively. Moreover, we also proved that the ability of drug adsorption on materials surface by the reduction of specific surface area and pore size of micro diatom frustule after loading using a (Brunauer–Emmett–Teller) BET method. Besides, the hydrophobic loading capacity of materials was affected by surface modification. Based on the results, micro diatom frustule showed a potential for a drug delivery system.

Diatom Frustule Array for Flow-Through Enhancement of Fluorescent Signal in a Microfluidic Chip

Diatom frustules are a type of natural biomaterials that feature regular shape and intricate hierarchical micro/nano structures. They have shown excellent performance in biosensing, yet few studies have been performed on flow-through detection. In this study, diatom frustules were patterned into step-through holes and bonded with silicon substrate to form an open-ended filtration array. Then they were fixed into a microfluidic chip with a smartphone-based POCT. Human IgG and FITC-labeled goat–anti-human IgG were adopted to investigate the adsorption enhancement when analyte flowed through diatom frustules. The results indicated up to 16-fold enhancement of fluorescent signal sensitivity for the flow-through mode compared with flow-over mode, at a low concentration of 10.0 μg/mL. Moreover, the maximum flow rate reached 2.0 μL/s, which resulted in a significant decrease in the testing time in POCT. The adsorption simulation results of diatom array embedded in the microchannel shows good agreement with experimental results, which further proves the filtration enrichment effect of the diatom array. The methods put forward in this study may open a new window for the application of diatom frustules in biosensing platforms.

Insight into diatom frustule structures using various imaging techniques

The diatom shell is an example of complex siliceous structure which is a suitable model to demonstrate the process of digging into the third dimension using modern visualization techniques. This paper demonstrates importance of a comprehensive multi-length scale approach to the bio-structures/materials with the usage of state-of-the-art imaging techniques. Imaging of diatoms applying visible light, electron and X-ray microscopy provide a deeper insight into the morphology of their frustules.

Study on the Hemostasis Characteristics of Biomaterial Frustules Obtained from Diatom Navicula australoshetlandica sp.

Diatoms, known as photosynthetic unicellular algae, can produce natural biosilica frustules that exhibit great biocompatibility, superhydrophilicity, and superhemophilicity. In our study, the diatom Navicula australoshetlandica sp. was isolated from aquaculture wastewater and pretreated to obtain frustules so as to explore their hemostasis characteristics. A special “porous web” (6–8 nm) substructure in the ordered nanopores (165–350 nm) of boat-shaped diatom frustule was observed in Navicula australoshetlandica sp. using SEM and TEM analysis. Moreover, X-ray, N2 adsorption–desorption isotherms, and BET analysis showed that the diatom frustule is a mesoporous material with a surface area of 401.45 m2 g−1 amorphous silica. FTIR analysis showed that Navicula australoshetlandica sp. frustules possessed abundant OH functional groups. A low hemolysis ratio was observed for 1–5 mg mL−1 diatom frustules that did not exceed 1.55 ± 0.06%, which indicates favorable hemocompatibility. The diatom frustules exhibited the shortest clotting time (134.99 ± 7.00 s) with a hemostasis material/blood (mg/μL) ratio of 1:100, which is 1.83 times (112.32 s) shorter than that of chitosan. The activated partial thromboplastin time (aPTT) of diatom frustule was also 44.53 s shorter than the control. Our results demonstrate the potential of Navicula australoshetlandica sp. diatom frustules to be used as medical hemostasis material.

Bacillariophyta of the Yavorivsky National Park, Broadleaf Forest Zone of Ukraine, including Сaloneis albus-columba, sp. nov.

Diatoms (Bacillariophyta) are one of the major biological components in all kinds of aquatic ecosystems both in freshwater and marine ones. The nature reserve fund of Ukraine includes 52 national parks, in the vast majority of which Bacillariophyta have not been studied. This investigation presents first data on the diatoms in Yavorivsky National Park located in Lviv region. The material consists of the epiphytic samples of microalgae that were collected from different substrates in aquatic ecosystems of the Yavorivsky National Park in 2014. In the hydrotopes of the park 180 diatom species from 56 genera were found, among them Achnanthidium catenatum (Bily & Marvan) Lange-Bertalot, Cymbopleura apiculata Krammer, Fallacia sublucidula (Hustedt) D. G. Mann in Round, Crawford & Mann, Gomphonema lagenula Kützing, G. supersedens Reichardt, G. pseudopusillum Reichardt, Paraplaconeis minor (Grunow) Lange-Bertalot, Placoneis constans (Hustedt) E. J. Cox, Psammothidium bioretii (Germain) Bukhtiyarova & Round, P. vernadskyi Bukhtiyarova et Stanislavskaya, Sellaphora gracillima Zidarova, Kopalová & Van de Vijver, S. insolita (Manguin) Hamilton et Antoniades, Stauroneis fluminopsis Van de Vijver et Lange-Bertalot were recorded for the first time in Ukraine. Besides that, Amphora hemicycla Stoermer & J. J. Yang and Sellaphora bacilloides (Hustedt) Levkov, Krstic & Nakov also were new findings in the country from the Broadleaf Forest Zone of Ukraine. Many species rare in the world flora and in Ukraine were found. A new diatom species Сaloneis albus-columba Bukhtiyarova, sp. nov., was described from the pond in stationary recreation area Kozulka. This new species possesses strongly three-undulate valves with three rhombic segments, which in morphology is most similar to Caloneis lamella Zakrzewski, however it differs from it by having rhombic distal valve segments instead of oval ones as well as noticeably smaller width of the central valve segment. The morphology of other similar species is discussed. For proper description of the new species new definitions for the raphe system morphology were grounded on functional morphology of the diatom frustule. New combinations Iconella alaskaensis (Foged) Bukhtiyarova, comb. et stat. nov., Iconella baltica (Schumann) Bukhtiyarova, comb. nov., Iconella brebissonii (Krammer & Lange-Bertalot) Bukhtiyarova, comb. nov., Iconella brightwellii (W. Smith) Bukhtiyarova, comb. nov., Iconella constricta (Grunow) Bukhtiyarova, comb. et stat. nov., Iconella didyma (Kützing) Bukhtiyarova, comb. nov. and Iconella elegans (Ehrenberg) Bukhtiyarova, comb. nov. were formally proposed. The lectotype for Eunotia glacialis F. Meister was designated here. Illustrations with light and scanning electron microscopy are presented. A primary inventory of Bacillariophyta and their subsequent study on protected territories in Ukraine is still an important task in the context of preservation of biodiversity of the country.

Partially Coherent Optical Diffraction Tomography Toward Practical Cell Study

Optical diffraction tomography (ODT) is a computational imaging technique based on refractive index (RI) contrast. Its application for microscopic imaging of weakly absorbing and scattering samples has been demonstrated by using a specially designed holographic microscope with angular scanning of the coherent sample illumination direction. Recently, an alternative low cost technique based on partially coherent sample illumination (PC-ODT), which is compatible with the conventional wide-field transmission microscope, has been established. In this case, the 3D refractive index distribution of the sample is obtained by deconvolution from a single stack of through-focus intensity images. The performance of PC-ODT has been successfully tested on various fixed specimens (diatom frustule and biological cells) and moving bacteria. Here, we demonstrate that the PC-ODT is an efficient tool for the analysis of living eukaryotic cell dynamics at short- and long-term periods. The COS-7 cells, which hail from the African green monkey kidney, have been chosen for this study. A fast data acquisition setup comprising an optical scanning module can be easily attached to the microscope, and it allows observing cell 3D organelle movements and RI variations, with the required temporal resolution. In particular, a more rapid nucleoli rotation than previously reported has been found. The long-term cell monitoring during necrosis reveals significant changes in cell dry mass concentration obtained from recovered RI contrast.

Tentative Identification of Key Factors Determining the Hemostatic Efficiency of Diatom Frustule

It is increasingly essential to develop excellent material for rapid hemorrhage control. Our previous study showed that the centric diatom frustules were superior to QuikClot® in hemostasis, however, related studies...

Physical, Chemical, and Genetic Techniques for Diatom Frustule Modification: Applications in Nanotechnology

Diatom frustules represent one of the most complex examples of micro- and nano-structured materials found in nature, being the result of a biomineralization process refined through tens of milions of years of evolution. They are constituted by an intricate, ordered porous silica matrix which recently found several applications in optoelectronics, sensing, solar light harvesting, filtering, and drug delivery, to name a few. The possibility to modify the composition and the structure of frustules can further broaden the range of potential applications, adding new functions and active features to the material. In the present work the most remarkable physical and chemical techniques aimed at frustule modification are reviewed, also examining the most recent genetic techniques developed for its controlled morphological mutation.

Modifying the thickness, pore size, and composition of diatom frustule in Pinnularia sp. with Al3+ ions

Diatoms are unicellular photosynthetic algae that produce a silica exoskeleton (frustule) which exposes a highly ordered nano to micro scale morphology. In recent years there has been a growing interest in modifying diatom frustules for technological applications. This is achieved by adding non-essential metals to the growth medium of diatoms which in turn modifies morphology, composition, and resulting properties of the frustule. Here, we investigate the frustule formation in diatom Pinnularia sp., including changes to overall morphology, silica thickness, and composition, in the presence of Al3+ ions at different concentrations. Our results show that in the presence of Al3+ the total silica uptake from the growth medium increases, although a decrease in the growth rate is observed. This leads to a higher inorganic content per diatom resulting in a decreased pore diameter and a thicker frustule as evidenced by electron microscopy. Furthermore, 27Al solid-state NMR, FIB-SEM, and EDS results confirm that Al3+ becomes incorporated into the frustule during the silicification process, thus, improving hydrolysis resistance. This approach may be extended to a broad range of elements and diatom species towards the scalable production of silica materials with tunable hierarchical morphology and chemical composition.