Stabilizing synthetic DNA for long-term data storage with earth alkaline salts

Rapid aging tests (70 °C, 50% RH) of solid state DNA dried in the presence of various salt formulations, showed the strong stabilizing effect of calcium phosphate, calcium chloride and magnesium chloride, even at high DNA loadings (>20 wt%). A DNA-based digital information storage system utilizing the stabilizing effect of MgCl₂ was tested by storing a DNA file, encoding 115 kB of digital data, and the successful readout of the file by sequencing after accelerated aging.

3D microtissue-derived human stem cells seeded on electrospun nanocomposites under shear stress: Modulation of gene expression

OBJECTIVE

Different microenvironments trigger distinct differentiation of stem cells. Even without chemical supplementation, mechanical stimulation by shear stress may help to induce the desired differentiation. The cell format, such as three-dimensional (3D) microtissues (MTs), MT-derived cells or single cells (SCs), may have a pivotal impact as well. Here, we studied modulation of gene expression in human adipose-derived stem cells (ASCs) exposed to shear stress and/or after MT formation.

MATERIALS AND METHODS

Electrospun meshes of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) at a weight ratio of 60:40 were seeded with human ASCs as MTs or as SCs and cultured in Dulbecco's modified Eagle's medium without chemical supplementation. After 2 weeks of static culture, the scaffolds were cultured statically for another 2 weeks or placed in a Bose® bioreactor with a flow rate per area of 0.16 mL cm^-2 min^-1. Stiffness of the scaffolds was assessed as a function of time. After 4 weeks, minimum stem cell criteria markers and selected markers of osteogenesis, endothelial cell differentiation, adipogenesis and chondrogenesis were analysed by quantitative real-time polymerase chain reaction. Additionally, cell distribution within the scaffolds and the allocation of the yes-associated protein (YAP) in the cells were assessed by immunohistochemistry.

RESULTS

MTs decayed completely within 2 weeks after seeding on PLGA/aCaP. The osteogenic marker gene alkaline phosphatase and the endothelial cell marker gene CD31 were upregulated in MT-derived ASCs compared with SCs. Shear stress realised by fluid flow perfusion upregulated peroxisome proliferator-activated receptor gamma 2 expression in MT-derived ASCs and in SCs. The nuclear-to-cytoplasmic ratio of YAP expression was doubled under perfusion compared with that under static culture for MT-derived ASCs and SCs.

CONCLUSIONS

Osteogenic and angiogenic commitments were more pronounced in MT-derived ASCs seeded on bone biomimetic electrospun nanocomposite PLGA/aCaP than in SCs seeded without induction medium. Furthermore, the static culture was superior to the perfusion regimen used here, as shear stress resulted in adipogenic commitment for MT-derived ASCs and SCs, although the YAP nuclear-to-cytoplasmic ratio indicated higher cell tensions under perfusion, usually associated with preferred osteogenic differentiation.

Hybrid nanocomposite as a chest wall graft with improved integration by adipose-derived stem cells

Surgery of the chest wall is potentially required to cover large defects after  removal of malignant tumours. Usually, inert and non-degradable Gore-Tex serves to replace the missing tissue. However, novel biodegradable materials combined with stem cells are available that stimulate the healing. Based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) and pure PLGA, a dual layer biodegradable hybrid nanocomposite was generated. Mouse adipose-derived stem cells were cultered on electrospun disks (ASCs of C57BL/6), and biomechanical tests were performed. The cell-seeded scaffolds were engrafted in C57BL/LY5.1 mice to serve as a chest wall substitute. Cell invasion into the bi-layered material, extent of CD45⁺ cells, inflammatory response, neo-vascularization and ECM composition were determined at 1 and 2 months post-surgery, respectively. The bi-layered hybrid nanocomposite was stable after a 2-week in vitro culture, in contrast to PLGA/aCaP without a PLGA layer. There was a complete biointegration and good vascularization in vivo. The presence of ASCs attracted more CD45⁺ cells (hematopoietic origin) compared to cell-free scaffolds. Inflammatory reaction was similar for both groups (±ASCs) at 8 weeks. A bi-layered hybrid nanocomposite fabricated of electrospun PLGA/aCaP and a reinforcing layer of pristine PLGA is an ideal scaffold for chest wall reconstruction. It is stable and allows a proper host tissue integration. If ASCs are seeded, they attract more CD45⁺ cells, supporting the regeneration process.

Strategies of Immobilizing Cells in Whole-cell Microbial Biosensor Devices Targeted for Analytical Field Applications

This review summarizes the development of whole-cell biosensors with a special focus on device development and cell immobilization. Integration of biosensor functions in a device will pave the way for field applications in remote areas and resource-limited settings. Firstly, an introduction to the field of whole-cell biosensors is provided, followed by examples of genetic engineering of cells in order to fulfill sensor functions. A framework of requirements to enable future field applications of biosensors is elaborated. A special focus is on different cell immobilization techniques ranging from polymers, to microfluidic devices, immobilization on paper and combinations of these methods. Looking at globally successfully implemented point of care devices such as a home pregnancy test or a blood glucose meter, we conclude the review with thoughts on long-term stability, portability, ease of use and user safety design guidelines for whole-cell biosensor devices.

Tomographic Reservoir Imaging with DNA-Labeled Silica Nanotracers: The First Field Validation

This study presents the first field validation of using DNA-labeled silica nanoparticles as tracers to image subsurface reservoirs by travel time based tomography. During a field campaign in Switzerland, we performed short-pulse tracer tests under a forced hydraulic head gradient to conduct a multisource-multireceiver tracer test and tomographic inversion, determining the two-dimensional hydraulic conductivity field between two vertical wells. Together with three traditional solute dye tracers, we injected spherical silica nanotracers, encoded with synthetic DNA molecules, which are protected by a silica layer against damage due to chemicals, microorganisms, and enzymes. Temporal moment analyses of the recorded tracer concentration breakthrough curves (BTCs) indicate higher mass recovery, less mean residence time, and smaller dispersion of the DNA-labeled nanotracers, compared to solute dye tracers. Importantly, travel time based tomography, using nanotracer BTCs, yields a satisfactory hydraulic conductivity tomogram, validated by the dye tracer results and previous field investigations. These advantages of DNA-labeled nanotracers, in comparison to traditional solute dye tracers, make them well-suited for tomographic reservoir characterizations in fields such as hydrogeology, petroleum engineering, and geothermal energy, particularly with respect to resolving preferential flow paths or the heterogeneity of contact surfaces or by enabling source zone characterizations of dense nonaqueous phase liquids.

Silica-Encapsulated DNA-Based Tracers for Aquifer Characterization

Environmental tracing is a direct way to characterize aquifers, evaluate the solute transfer parameter in underground reservoirs, and track contamination. By performing multitracer tests, and translating the tracer breakthrough times into tomographic maps, key parameters such as a reservoir's effective porosity and permeability field may be obtained. DNA, with its modular design, allows the generation of a virtually unlimited number of distinguishable tracers. To overcome the insufficient DNA stability due to microbial activity, heat, and chemical stress, we present a method to encapsulated DNA into silica with control over the particle size. The reliability of DNA quantification is improved by the sample preservation with NaN₃ and particle redispersion strategies. In both sand column and unconsolidated aquifer experiments, DNA-based particle tracers exhibited slightly earlier and sharper breakthrough than the traditional solute tracer uranine. The reason behind this observation is the size exclusion effect, whereby larger tracer particles are excluded from small pores, and are therefore transported with higher average velocity, which is pore size-dependent. Identical surface properties, and thus flow behavior, makes the new material an attractive tracer to characterize sandy groundwater reservoirs or to track multiple sources of contaminants with high spatial resolution.

Modification of silicone elastomers with Bioglass 45S5® increases in ovo tissue biointegration

Silicone is an important material family used for various medical implants. It is biocompatible, but its bioinertness prevents cell attachment, and thus tissue biointegration of silicone implants. This often results in constrictive fibrosis and implant failure. Bioglass 45S5® (BG) could be a suitable material to alter the properties of silicone, render it bioactive and improve tissue integration. Therefore, BG micro- or nanoparticles were blended into medical-grade silicone and 2D as well as 3D structures of the resulting composites were analyzed in ovo by a chick chorioallantoic membrane (CAM) assay. The biomechanical properties of the composites were measured and the bioactivity of the composites was verified in simulated body fluid. The bioactivity of BG-containing composites was confirmed visually by the formation of hydroxyapatite through scanning electron microscopy as well as by infrared spectroscopy. BG stiffens as prepared non-porous composites by 13% and 36% for micro- and nanocomposites respectively. In particular, after implantation for 7 days, the Young's modulus had increased significantly from 1.20 ± 0.01 to 1.57 ± 0.03 MPa for microcomposites and 1.44 ± 0.03 to 1.69 ± 0.29 MPa to for nanocpmosites. Still, the materials remain highly elastic and are comparably soft. The incorporation of BG into silicone overcame the bioinertness of the pure polymer. Although the overall tissue integration was weak, it was significantly improved for BG-containing porous silicones (+72% for microcomposites) and even further enhanced for composites containing nanoparticles (+94%). These findings make BG a suitable material to improve silicone implant properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1180-1188, 2019.

Nondestructive in-line sub-picomolar detection of magnetic nanoparticles in flowing complex fluids

Over the last decades, the use of magnetic nanoparticles in research and commercial applications has increased dramatically. However, direct detection of trace quantities remains a challenge in terms of equipment cost, operating conditions and data acquisition times, especially in flowing conditions within complex media. Here we present the in-line, non-destructive detection of magnetic nanoparticles using high performance atomic magnetometers at ambient conditions in flowing media. We achieve sub-picomolar sensitivities measuring ~30 nm ferromagnetic iron and cobalt nanoparticles that are suitable for biomedical and industrial applications, under flowing conditions in water and whole blood. Additionally, we demonstrate real-time surveillance of the magnetic separation of nanoparticles from water and whole blood. Overall our system has the merit of in-line direct measurement of trace quantities of ferromagnetic nanoparticles with so far unreached sensitivities and could be applied in the biomedical field (diagnostics and therapeutics) but also in the industrial sector.

Water dispersible surface-functionalized platinum/carbon nanorattles for size-selective catalysis

Selective dealloying of metal nanoparticles results in rattle-type hollow carbon nanoshells enclosing platinum nanoparticles, which are able to perform size-selective catalysis. Selective functionalization of the outer graphene-like carbon surface prevents agglomeration and leads to well dispersible nanocatalysts in aqueous solutions. The synthesis starts with the production of nanoparticles with a cobalt-platinum-alloy core surrounded by graphene-like carbon via reducing flame spray synthesis. After surface functionalization, simultaneous pore formation in the shell-wall and dissolution of the cobalt results in platinum encapsulated in hollow carbon nanospheres. Catalytic oxidation of differently sized sugars (glucose and maltoheptaose) reveales size-selective catalytic properties of these platinum nanorattles.

Selective Low-Energy Carbon Dioxide Adsorption Using Monodisperse Nitrogen-Rich Hollow Carbon Submicron Spheres

Monodisperse, nitrogen-doped hollow carbon spheres of submicron size were synthesized using hexamethoxymethylmelamine as both a carbon and nitrogen source in a short (1 h) microwave-assisted synthesis. After carbonization at 550 °C, porous carbon spheres with a remarkably high nitrogen content of 37.1% were obtained, which consisting mainly of highly basic pyridinic moieties. The synthesized hollow spheres exhibited high selectivity for carbon dioxide (CO₂) over nitrogen and oxygen gases, with a capture capacity up to 1.56 mmol CO₂ g^-1. The low adsorption enthalpy of the synthesized hollow carbon spheres permits good adsorbent regeneration. Evaluation of the feasibility of scaling up shows their potential for large-scale applications.

Gene expression in human adipose-derived stem cells: comparison of 2D films, 3D electrospun meshes or co-cultured scaffolds with two-way paracrine effects

Finding the appropriate cues to trigger the desired differentiation is a challenge in tissue engineering when stem cells are involved. In this regard, three-dimensional environments are often compared to cells' two-dimensional culture behaviour (plastic culture dish). Here, we compared the gene expression pattern of human adipose-derived stem cells (ASC) seeded in a three-dimensional (3D) electrospun mesh and on a two-dimensional (2D) film - both of exactly the same material. Additionally, we conducted experiments with a scaffold floating above a film to investigate two-way paracrine effects (co-system). Electrospun meshes (3D scaffolds) and films (2D), consisting either of pristine poly-lactic-co-glycolic acid (PLGA) or of PLGA-containing dispersed amorphous calcium phosphate nanoparticles (PLGA/aCaP), were seeded with ASCs and cultured either in Dulbecco Minimum Essential Medium (DMEM) or in osteogenic medium. After two weeks, minimum stem cell criteria markers as well as typical markers for osteogenesis, endothelial cell differentiation, adipogenesis and chondrogenesis were analysed by quantitative real-time PCR. Interestingly, mostly osteogenic genes of cells seeded on 3D meshes were upregulated compared to those on 2D films, while stem cell markers seemed to be only slightly affected. Runx2 and osteocalcin showed an especially strong upregulation under all conditions, while most other factors analysed for 2D/3D changes were highly dependent on the material composition, the culture medium and on paracrine signalling effects. The beneficial 3D environment for stem cells found in many studies has therefore not to be attributed to the third dimension alone and should carefully be compared to 2D films fabricated of the same material. Furthermore, paracrine interactions triggering differentiation are not negligible.

Effects of seeding adipose-derived stem cells on electrospun nanocomposite used as chest wall graft in a murine model

Malignant neoplasms infiltrating the chest wall often requires resection of the thoracic wall. To replace the defect, Gore-Tex^® is usually employed as the gold standard material, however, Gore-Tex^® is inert and not degradable. Novel materials are nowadays available which allow a full bio-integration due to their non-toxic degradability. Additionally, stem cell seeding has the capacity to reduce inflammatory response towards such grafts, thus integrating it better into the host organism.

Ultrapure Green Light-Emitting Diodes Using Two-Dimensional Formamidinium Perovskites: Achieving Recommendation 2020 Color Coordinates

Pure green light-emitting diodes (LEDs) are essential for realizing an ultrawide color gamut in next-generation displays, as is defined by the recommendation (Rec.) 2020 standard. However, because the human eye is more sensitive to the green spectral region, it is not yet possible to achieve an ultrapure green electroluminescence (EL) with a sufficiently narrow bandwidth that covers >95% of the Rec. 2020 standard in the CIE 1931 color space. Here, we demonstrate efficient, ultrapure green EL based on the colloidal two-dimensional (2D) formamidinium lead bromide (FAPbBr₃) hybrid perovskites. Through the dielectric quantum well (DQW) engineering, the quantum-confined 2D FAPbBr₃ perovskites exhibit a high exciton binding energy of 162 meV, resulting in a high photoluminescence quantum yield (PLQY) of ∼92% in the spin-coated films. Our optimized LED devices show a maximum current efficiency (η_CE) of 13.02 cd A^-1 and the CIE 1931 color coordinates of (0.168, 0.773). The color gamut covers 97% and 99% of the Rec. 2020 standard in the CIE 1931 and the CIE 1976 color space, respectively, representing the "greenest" LEDs ever reported. Moreover, the device shows only a ∼10% roll-off in η_CE (11.3 cd A^-1) at 1000 cd m^-2. We further demonstrate large-area (3 cm²) and ultraflexible (bending radius of 2 mm) LEDs based on 2D perovskites.

Clinical outcomes of gamma-irradiated sterile cornea in aqueous drainage device surgery: a multicenter retrospective study

PurposeThe purpose of the study was to evaluate the safety and efficacy of gamma-irradiated sterile cornea (GISC) for covering the tube in aqueous drainage device (ADD) surgery in a retrospective, multicenter case series.Patients and methodsParticipants included 297 patients (321 procedures) who had undergone ADD surgery for the first time using GISC patch at three clinic centers in the United States between April 2009 and July 2012. The medical records of those consecutive patients were reviewed. Preoperative, intraoperative, and postoperative parameters about GISC were collected and analyzed. The main outcome measures were patch graft failure (PGF) and postoperative complications related to GISC.ResultsThree hundred and nineteen eyes in 295 patients were included in the current analysis. Ten out of the 319 eyes experienced PGF with a mean follow-up of 15.4±9.8 (SD) months. The overall cumulative PGF proportion from Kaplan-Meier analysis was 2.6% (95% CI: 0.6-4.7%) at 18 months. We detected two cases of presumed endophthalmitis related to PGF.ConclusionsGISC appears to have a reasonable success rate for preventing tube exposure related to PGF over an 18-month period. This success rate, in combination with other features of GISC (transparency and storage at room temperature), makes it a viable choice for patch graft material during ADD.