Simple Substrates Research Articles

Enantioselective Rhodium-Catalyzed Cycloisomerization of 1,6-Allenynes to access 5/6-Fused Bicycle[4.3.0]nonadienes

Transition-metal-catalyzed cycloisomerization of 1,n-allenynes represents a powerful synthetic tool to rapidly assemble complex polycyclic skeletons from simple linear substrates. Nevertheless, there are no reports of the asymmetric version of these reactions. Moreover, most of these reactions proceed through a 6-endo-dig cyclization pathway, which preferentially delivers the distal product (via 5/5 rhodacyclic intermediate) rather than the proximal one (via 6/5 rhodacyclic intermediate). Herein, we report an enantioselective rhodium(I)-catalyzed cycloisomerization of 1,6-allenynes to provide the proximal product 5/6-fused bicycle[4.3.0]nonadienes in good yields and with excellent enantioselectivities. Remarkably, this chemistry works perfectly for 1,6-allenynes having a cyclic substituent within the allene component, thereby affording synthetically formidable tricyclic products with excellent enantioselectivities. Moreover, extensive DFT calculations suggest an uncommon pathway involving 5-exo-dig cycloisomerization, ring-expansion, rate-determining alkene isomerization involving Csp3-H activation, C-C activation of the cyclobutene moiety and finally reductive elimination. Deuterium labeling experiments support the rate-determining step involving the C–H bond activation in this transformation.

Rhodium-Catalyzed Synthesis of Silicon-Bridged 1,2-Dialkenylbenzenes via 1,4-Rhodium Migration.

An efficient synthesis of 1,3-dialkylidene-2,3-dihydro-1 H-benzo[ c]siloles, a new type of silicon-bridged π-conjugated compounds, was developed from a simple substrate combination of dialkynylsilanes and arylboronic acids under rhodium catalysis through the use of 1,4-rhodium migration. The reaction pathway was probed by deuterium-labeling experiments, and the use of o-tolylboronic acids led to the formation of 6-membered silacycles via 1,5-rhodium migration.

Multi-branch sandwich piezoelectric energy harvester: mathematical modeling and validation

Energy harvesting from ambient environment has attracted intensive attention over the years for powering low-power autonomous electronic devices. A conventional piezoelectric energy harvester (CPEH) can hardly meet the requirements of effective energy harvesting from wideband, low frequency and low amplitude vibration sources due to its simple substrate and single resonant peak response. Using sandwich structure comprised of a soft-core layer and two thin skins can drastically reduce the natural frequency and increase voltage output of the harvester. The stiffness of sandwich harvester and consequently its resonant frequency can be tuned more flexibly than the CPEH by choosing different materials and adjusting the geometric dimensions of the core and skins. In this paper, a novel multi-branch sandwich piezoelectric energy harvester (MSPEH) is proposed to harvest energy from wideband, low frequency and low amplitude vibration sources. The proposed harvester comprises of a main sandwich beam as substrate with a patch of piezoelectric layer bonded over it. Multiple inner single branches with tip masses are connected to the main substrate to generate multiple resonant peaks and tune the range of the interested frequency. Firstly, a mathematical model of the proposed harvester is presented, and the electromechanical coupling equations are obtained. Subsequently, a prototype of MSPEH with two inner single branches is fabricated and tested under harmonic base excitation to study its performance. When tested at a low harmonic excitation of 0.02 g, the harvester generates 2.48 V, 6.21 V and 1.55 V at three resonant frequencies of 18.18 Hz, 24.74 Hz and 28.12 Hz, respectively. Finally, the accuracy of derived mathematical model is verified by comparing with the predictions from finite element simulation and experimental results. The novel MSPEH offers excellent design flexibility to adjust resonant frequencies by choosing inner single branches and tip masses and thus it has potential to generate sufficient power output from wideband, low frequency and low amplitude vibration sources.

Signalling Growth through Lipid Kinases

Phosphoinositides form a group of signalling glycerophospholipids whose physiological function in cells is closely linked to their spatial distribution and turnover. Cells employ a network of enzymes to robustly maintain basal lipid levels and modulate their activity in response to a multitude of incoming signals. However, the mechanisms governing these molecular interactions are unclear. Our study describes how during growth factor stimulation, the cross-talk between two enzymes linked to the turnover of two very low abundance lipid species mediates optimal cellular growth signalling. Upon insulin receptor activation, Class I PI3-Kinase (PI3K) generates phosphatidylinositol 3,4,5-trisphosphate (PIP3) at the plasma membrane, which directs key downstream signalling events leading to cell growth and proliferation. We found another lipid-kinase PIP4K, which controls the level of phosphatidylinositol 5-phosphate (PI5P), was linked to the levels of PIP3. Biochemical studies indicate that PIP4K can use PI5P to produce the substrate (PIP2) for Class I PI3K to produce PIP3. However, imaging using lipid-binding probes and high-sensitivity mass spectrometry measurements showed inverse correlations of the PIP3 with PIP4K protein levels in cells, suggesting that a simple substrate channelling mechanism was insufficient to link the activity of these kinases. Using a combination of genetics and microscopy in Drosophila cells we found that PIP4K functions along with an additional negative feedback loop to control PIP3 levels. This was further corroborated by quantitative live-cell imaging of PIP3 dynamics ex vivo in salivary glands where PIP4K regulated class I PI3K activity. Finally, we show that PIP4K functions at the plasma membrane, proximal to receptor activation. Overall, the study proposes that receptor activation can directly trigger opposing activities to ensure controlled signal transduction at short time scales. Future studies will involve quantitative modeling and experimental approaches to understanding the how these kinases are connected spatio-temporally.

A simple paper-based surface enhanced Raman scattering (SERS) platform and magnetic separation for cancer screening

Early and precise diagnosis of cancer is critical for a better prognosis. Here, we describe a simple and cost-effective plasmonic paper as a surface enhanced Raman scattering (SERS) substrate in combination with magnetic separation for cancer screening. The plasmonic paper was fabricated by immersing plain filter paper into gold nanorod solution and the SERS property of the paper was evaluated using 4-mercaptobenzoic acid (4-MBA) and rhodamine 6 G (R6 G), which showed an enhancement factor (EF) in the range of 106–108. HT-29, a colorectal cancer cell line that highly expresses epithelial cell adhesion molecule (EpCAM), served as the target cells; non-EpCAM-expressing cells, namely fibroblasts and red blood cells (RBCs), were used as negative controls. Intrinsic SERS spectra of the target and control cells showed distinctive patterns on the plasmonic paper due to differences in their structure and components. A combination of principal component analysis (PCA) and k-nearest-neighbor algorithm (k-NN) was employed to analyze and distinguish the acquired HT-29 and fibroblast SERS spectra, demonstrating a diagnostic sensitivity and specificity of 84.8% and 82.6%, respectively, whereas the differentiation between HT-29 and RBCs SERS spectra showed a sensitivity and specificity of 96.4% and 100%, respectively. The magnetic separation was applied to capture the target cells from cell mixtures followed by PCA and k-NN analysis. The identification of the captured cells as cancerous cells from the HT-29 and fibroblast mixture indicated an accuracy of 83.7%, while that from a mixture of HT-29 and RBCs was 98.2%. Thus, the simple paper-based SERS substrate with the assistance of magnetic enrichment and multivariate analysis offers a potent new platform for cancer cell detection and screening.

Stereoselective Insertion of Benzynes into Lawsones: Synthesis of Biologically Important Benzannulated Bicyclo[3.3.0]octanes.

An ideal stereoselective insertion of in situ generated benzynes into lawsones through domino formal [2+2]-cycloaddition followed by rearrangement is disclosed. The reaction allowed for the preparation of biologically important benzannulated bicyclo[3.3.0]octanes in good yields and with excellent selectivities by using simple substrates and conditions.

Developing cysteamine-modified SERS substrate for detection of acidic pigment with weak surface affinity.

In this paper, we developed cysteamine-modified surface-enhanced Raman scattering (SERS) substrate for detecting detect trace amount of acidic pigment that shows weak affinity with gold nanoparticles (Au NPs). To realize sensitive and reproducible detection of pigment with weak affinity, the SERS substrate was prepared by attaching cysteamine (CA) to the Au NPs, the acidic pigment molecule could rapidly reached to the surface of Au NPs because of the formation of multi‑hydrogen-bond and electrostatic interaction between the pigment and CA molecule. The proposed method allowed us to detect five kinds of acidic pigment with a limit of 1.0 ppm, which is below the strictest safety limit. Compared with the previous methods, the advantages of the present substrate were its simple substrate preparation, high reproducibility and good universality. Furthermore, the reliable and enough accurate results had been obtained by using of the proposed substrates in the assay of trace pigment in real samples.

Synthetic WSe2 monolayers with high photoluminescence quantum yield.

In recent years, there have been tremendous advancements in the growth of monolayer transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). However, obtaining high photoluminescence quantum yield (PL QY), which is the key figure of merit for optoelectronics, is still challenging in the grown monolayers. Specifically, the as-grown monolayers often exhibit lower PL QY than their mechanically exfoliated counterparts. In this work, we demonstrate synthetic tungsten diselenide (WSe2) monolayers with PL QY exceeding that of exfoliated crystals by over an order of magnitude. PL QY of ~60% is obtained in monolayer films grown by CVD, which is the highest reported value to date for WSe2 prepared by any technique. The high optoelectronic quality is enabled by the combination of optimizing growth conditions via tuning the halide promoter ratio, and introducing a simple substrate decoupling method via solvent evaporation, which also mechanically relaxes the grown films. The achievement of scalable WSe2 with high PL QY could potentially enable the emergence of technologically relevant devices at the atomically thin limit.

Directed assembly of photonic crystals through simple substrate patterning.

We present molecular dynamics simulations of the epitaxial growth of high quality crystalline films for photonics applications from triblock Janus colloids. With a featureless substrate, the film morphologies were qualitatively similar to previously reported experimental results, with two stacking polymorphs appearing in nearly equal proportion. However, with a patterned substrate deliberately designed to be easy to fabricate by standard photolithography techniques, both the grain size and selectivity towards the photonically active polymorph were greatly improved. We also evaluated the effect of particle flux to find that lower flux led to higher quality crystals, while higher flux led to frustrated films with smaller crystalline domains. Our results suggest that carefully engineered but simple to manufacture patterned substrates could yield self-assembled single crystals of sufficient quality to exhibit a complete photonic bandgap.

Periphyton consumption by an invasive snail species is greater in simplified than in complex habitats

Habitat complexity may stabilize consumer–resource interactions and reduce the probability of invasion in aquatic habitats. We tested the hypotheses that (i) higher habitat complexity reduces resource consumption independently of grazer species, but that (ii) invasive grazers have a greater influence on decreasing resources independently of habitat complexity. We performed an experiment using artificial substrates to simulate different complexity levels. We evaluated Melanoides tuberculata (O.F. Müller, 1774) and Aylacostoma chloroticum Hylton Scott, 1954 consumption of specific algal groups and the interaction between habitat complexity and grazer species. Moreover, we evaluated grazer activity on the different substrates during the experiment. The results support only the first hypothesis and indicate lower resource consumption on complex substrates compared with simpler substrates. Additionally, the effect of the grazing of the invasive species on taxon richness was greater in simplified than in complex habitats. The grazing activity on the substrate suggests a relationship between resource exploitation and habitat complexity in which the invasive grazing species visited the simple habitat less frequently. However, the effects of invasive grazers on food resources were higher on the simple substrate. The effects of grazing activity on food resources depend on the interaction between habitat complexity and grazer species. In this way, the introduction of an invasive species may have negative impacts on the structure and function of periphytic communities, mainly in simplified aquatic ecosystems.

A Novel Methodology for Gain Enhancement of the Fabry-Pérot Antenna

A significant problem that is encountered with the traditional Fabry-Perot cavity (FPC) antenna is the nonuniform phase distribution inside the cavity, which adversely affects the radiation characteristics of the antenna. In this paper, a novel methodology is proposed to further enhance the gain of the FPC antenna. A metasurface with a controllable reflection phase is designed to correct the phase distribution to a nearly uniform distribution, thereby enhancing the antenna gain. The unit cell of the metasurface is a simple substrate with two patches. The top layer patch is sufficiently large to provide high reflectivity, whereas the bottom layer patch has a variable size to tune the reflection phase of the unit cell. Using the proposed formula, a metasurface with a reflection phase correction is designed. The antenna gain is further enhanced, and high aperture efficiency is obtained. A prototype antenna is fabricated and measured. The measured results are in very good agreement with the simulated results. The measured results show that the antenna has a 3 dB gain bandwidth of 4% (9.8 GHz- 10.2 GHz). On average, a 2 dB gain enhancement is obtained Compare to the reference antenna. The maximum gain of the antenna reaches 19.7 dBi at 10 GHz with an aperture efficiency of 82.5%.

Broadband Coaxial Rotary Joint With Simple Substrate Integrated Waveguide Feeder

This paper presents a broadband coaxial rotary joint with simple single-layer substrate integrated waveguide (SIW) feeder. The annular slot etched on the surface of SIW can effectively convert TE10 mode in the rectangle SIW into the rotational symmetric TEM mode in the coaxial line. Broadband impedance matching can be achieved because the additional capacitive coupling between the short-circuited circular metallic patch and coaxial line. Comparing with previous SIW fed rotary joints, the proposed design has the advantages of wider bandwidth and simpler feeding structure. The equivalent circuit is given to explain the design. A prototype centered at 12 GHz is fabricated with the 10-dB impedance matching bandwidth of 24.9% and the minimum insertion loss of 0.3 dB.

Flow of condensed particles around a packing front visualized by drying colloidal suspensions on a tilted substrate.

A gravity effect was demonstrated for 10 nm particles drying in colloidal suspensions. The particles were well-dispersed and did not sediment. However, when a suspension was dried on a tilted directional cell, a clear downward flow of particles was observed around the packing front, which was the boundary between the packed particles layer and the suspension. Three particle sizes (10-110 nm) were examined, with the most pronounced effect being on the 10 nm particles. The primary origin of the downflow was attributed to condensation of particles near the packing front and the subsequent increase in the overall density of the condensed layer. Because of the flow, the packing front was not parallel to the drying interface and tilted cracks formed in the packed layer. A mathematical model was proposed that considered conservation of the suspended particles in the condensed layer. Three competing factors of particle transport (advection, particle consumption by packing, and particle transport by the downward flow) were used to explain the experimental results. Overall, the results suggested that simple substrate tilting would be useful to evaluate whether suspended particles are easily packed or not during drying.

Copper‐Mediated Radiofluorination of Aryl Pinacolboronate Esters: A Straightforward Protocol by Using Pyridinium Sulfonates

Radiofluorination of arylboronic acids pinacol esters (arylBPin) mediated by copper triflate pyridine complex is one of the more promising synthetic approaches for the direct introduction of nucleophilic [18F]fluoride into non‐activated arenes and heteroarenes. However, the application of this method to the production of positron emission tomography (PET) radiotracers in automated synthesizers remains a challenging task. The choice of phase‐transfer catalyst (PTC) and corresponding base used for the generation of reactive [18F]fluoride species has a profound impact on the efficiency of the 18F‐fluorination process. Herein we report the development of a simple procedure involving trapping of the aqueous [18F]fluoride on a weak anion‐exchange resin (WAX) and its release by elution with pyridinium sulfonate in dimethyl acetamide. Obtained reactive [18F]fluoride was used as‐is in a copper‐catalyzed fluorination reaction employing pyridinium salt as both PTC and base. High radiochemical conversion rates (RCCs) achieved for a series of simple arylBPin substrates and 4‐[18F]fluoro‐D,L‐phenylalanine demonstrate the efficiency of this novel 18F‐processing approach. Notably, the proposed method obviates conventional azeotropic drying steps, solvents evaporation and/or changeover and can be implemented on commercial automated synthesizers.

In(OTf)3-Catalyzed Cascade Cyclization for Construction of Oxatricyclic Compounds.

A highly diastereoselective cascade cyclization reaction has been developed for establishing a series of oxatricyclic compounds using Chan's diene and simple keto alkynal substrates with only 1 mol % of In(OTf)3 as the catalyst in 82-92% yields. The potential utility of this synthetic strategy has been demonstrated in model studies for the construction the core structures of 1α,8α:4α,5α-diepoxy-4,5-dihydroosmitopsin and cortistatin A.

Highly Atom-Economic, Catalyst-Free, and Solvent-Free Synthesis of Phthalazinones

Herein a simple, catalyst- and solvent-free system for highly atom-economic synthesis of phthalazinones has been developed using phthalaldehydic acid, 2-acyl-benzoic acid, and substituted hydrazine as simple substrates. The reaction time was shortened to 20–60 min. Structurally diverse phthalaldehydic acids, 2-acyl-benzoic acids, and hydrazines were transformed into phthalazinones with a nearly 100% yield regardless of the aggregate state and electronic nature of the substituents. The transformation was demonstrated to be amenable for scale-up with multiple liquid and solid materials. In addition, isolation and purification of the crude products can be simply done with only crystallization. The heavy metal pollution was also eliminated from the source.

Dynamic control of hydrogel crosslinking via sortase-mediated reversible transpeptidation

Cell-laden hydrogels whose crosslinking density can be dynamically and reversibly tuned are highly sought-after for studying pathophysiological cellular fate processes, including embryogenesis, fibrosis, and tumorigenesis. Special efforts have focused on controlling network crosslinking in poly(ethylene glycol) (PEG) based hydrogels to evaluate the impact of matrix mechanics on cell proliferation, morphogenesis, and differentiation. In this study, we sought to design dynamic PEG-peptide hydrogels that permit cyclic/reversible stiffening and softening. This was achieved by utilizing reversible enzymatic reactions that afford specificity, biorthogonality, and predictable reaction kinetics. To that end, we prepared PEG-peptide conjugates to enable sortase A (SrtA) induced tunable hydrogel crosslinking independent of macromer contents. Uniquely, these hydrogels can be completely degraded by the same enzymatic reactions and the degradation rate can be tuned from hours to days. We further synthesized SrtA-sensitive peptide linker (i.e., KCLPRTGCK) for crosslinking with 8-arm PEG-norbornene (PEG8NB) via thiol-norbornene photocrosslinking. These hydrogels afford diverse softening paradigms through control of network structures during crosslinking or by adjusting enzymatic parameters during on-demand softening. Importantly, user-controlled hydrogel softening promoted spreading of human mesenchymal stem cells (hMSCs) in 3D. Finally, we designed a bis-cysteine-bearing linear peptide flanked with SrtA substrates at the peptide’s N- and C-termini (i.e., NH2-GGGCKGGGKCLPRTG-CONH2) to enable cyclic/reversible hydrogel stiffening/softening. We show that matrix stiffening and softening play a crucial role in growth and chemoresistance in pancreatic cancer cells. These results represent the first dynamic hydrogel platform that affords cyclic gel stiffening/softening based on reversible enzymatic reactions. More importantly, the chemical motifs that affords such reversible crosslinking were built-in on the linear peptide crosslinker without any post-synthesis modification. Statement of SignificanceCell-laden ‘dynamic’ hydrogels are typically designed to enable externally stimulated stiffening or softening of the hydrogel network. However, no enzymatic reaction has been used to reversibly control matrix crosslinking. The application of SrtA-mediated transpeptidation in crosslinking and post-gelation modification of biomimetic hydrogels is innovative because of the specificity of the reaction and reversible tunability of crosslinking kinetics. While SrtA has been previously used to crosslink and fully degrade hydrogels, matrix softening and reversible stiffening of cell-laden hydrogels has not been reported. By designing simple peptide substrates, this unique enzymatic reaction can be employed to form a primary network, to gradually soften hydrogels, or to reversibly stiffen hydrogels. As a result, this dynamic hydrogel platform can be used to answer important matrix-related biological questions that are otherwise difficult to address.

NIR-Active Plasmonic Gold Nanocapsules Synthesized Using Thermally Induced Seed Twinning for Surface-Enhanced Raman Scattering Applications.

Hollow and porous core-shell nanostructures with defined interior nanogaps are of great significance in the field of surface-enhanced Raman scattering (SERS) applications because of the presence of intrinsic electromagnetic (EM) hot spots, multipolar resonances, and multiple facets. Further, nanomaterials having extinction in the near-infrared (NIR) region are particularly important for SERS and biomedical applications, and thus it is highly desirable to synthesize NIR-active plasmonic nanostructures. Herein, we report the synthesis of gold nanocapsules having a solid Au bead as core and a thin-porous rod-shaped shell with extinction in both NIR I and NIR II regions. Thermally induced twinned seeds were used for the silver-free synthesis of pentatwinned Au bead, which served as the foundation for the directed growth of Ag nanorods, which was finally converted to Au nanocapsules following galvanic replacement reaction (GRR). Detailed investigation was carried out to understand the effect of thermal treatment duration in the seed morphology and its subsequent growth to anisotropic Au beads. Ag overgrowth on Au beads yielded uniform Au-bead@Ag nanorods whose size can be tuned by varying the Ag precursor. Five different sized Au-bead@Ag nanorods were studied, and they were converted to Au nanocapsules following GRR. We explored the size-dependent SERS activity of the prepared Au nanocapsules along with their comparison with solid pentatwinned Au beads and found that the smallest sized Au nanocapsules were the best SERS performers. Finite-difference time-domain simulation revealed the presence of intense EM hot spots in the smallest sized Au nanocapsule and corroborated the experimental SERS data. Finally, we fabricated a simple flexible cellulose-based SERS substrate by using the smallest sized Au nanocapsules and investigated its SERS sensing ability for the detection of 2-napthalenethiol (2-NT), as a model analyte, and were able to achieve its detection down to 1 fM concentration.

Mechanical response of an epithelial island subject to uniaxial stretch on a hybrid silicone substrate.

The mechanical response of large multi-cellular collectives to external stretch has remained largely unexplored, despite its relevance to normal function and to external challenges faced by some tissues. Here, we introduced a simple hybrid silicone substrate to enable external stretch while providing a physiologically relevant physical micro-environment for cells. We micropatterned epithelial islands on the substrate using a stencil to allow for a circular island shape without restraining island edges. We then used traction force microscopy to determine the strain energy and the inter-cellular sheet tension within the island as a function of time after stretch. While the strain energy stored in the substrate for unstretched cell islands stayed constant over time, a uniaxial 10% stretch resulted in an abrupt increase, followed by sustained increase in the strain energy of the islands over tens of minutes, indicating slower dynamics than for single cells reported previously. The sheet tension at the island mid-line perpendicular to the stretch direction also more than doubled compared to unstretched islands. Interestingly, the sheet tension at the island mid-line parallel to the stretch direction also reached similar levels over tens of minutes indicating the tendency of the island to homogenize its internal stress. We found that the sheet tension within large epithelial islands depends on its direction relative to that of the stretch initially, but not at longer times. We suggest that the hybrid silicone substrate provides for an accessible substrate for studying the mechanobiology of large epithelial cell islands.

Reduced-Particle-Size Wheat Bran Is Efficiently Colonized by a Lactic Acid-Producing Community and Reduces Levels of Enterobacteriaceae in the Cecal Microbiota of Broilers.

In the present study, we investigated whether reducing the particle size of wheat bran affects the colonizing microbial community using batch fermentations with cecal inocula from seven different chickens. We also investigated the effect of in-feed administration of regular wheat bran (WB; 1,690 μm) and wheat bran with reduced particle size (WB280; 280 μm) on the cecal microbial community composition of broilers. During batch fermentation, WB280 was colonized by a lactic acid-producing community (Bifidobacteriaceae and Lactobacillaceae) and by Lachnospiraceae that contain lactic acid-consuming butyric acid-producing species. The relative abundances of the Enterobacteriaceae decreased in the particle-associated communities for both WB and WB280 compared to that of the control. In addition, the community attached to wheat bran was enriched in xylan-degrading bacteria. When administered as a feed additive to broilers, WB280 significantly increased the richness of the cecal microbiota and the abundance of bacteria containing the butyryl-coenzyme A (CoA):acetate CoA-transferase gene, a key gene involved in bacterial butyrate production, while decreasing the abundances of Enterobacteriaceae family members in the ceca. Particle size reduction of wheat bran thus resulted in the colonization of the bran particles by a very specific lactic acid- and butyric acid-producing community and can be used to steer toward beneficial microbial shifts. This can potentially increase the resilience against pathogens and increase animal performance when the reduced-particle-size wheat bran is administered as a feed additive to broilers.IMPORTANCE Prebiotic dietary fibers are known to improve the gastrointestinal health of both humans and animals in many different ways. They can increase the bulking capacity, improve transit times, and, depending on the fiber, even stimulate the growth and activity of resident beneficial bacteria. Wheat bran is a readily available by-product of flour processing and is a highly concentrated source of (in)soluble dietary fiber. The intake of fiber-rich diets has been associated with increased Firmicutes and decreased Proteobacteria numbers. Here, we show that applying only 1% of a relatively simple substrate which was technically modified using relatively simple techniques reduces the concentration of Enterobacteriaceae This could imply that in future intervention studies, one should take the particle size of dietary fibers into account.