Diffusion in a Sol−Gel-Derived Medium with a View toward Biosensor Applications

Hungerford, Graham; Rei, and Ana; Ferreira, Miguel; Suhling, Klaus; Tregidgo, Carolyn

doi:10.1021/jp066021i

Cited by 33 publications

(40 citation statements)

References 24 publications

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“…The mobilities of glass entrapped proteins have been characterized by fluorescence anisotropy [26,[59][60][61][62], tryptophan phosphorescence [63], and photobleaching experiments [62]. In addition to apoMb, enhanced conformational stability at elevated temperatures has been observed for many glass-entrapped proteins including α-lactalbumin [22], lysozyme [22,24], human serum albumin [24,26,54], creatine kinase [31], monellin [59], oncomodulin [64], cytochrome c [65], and carbonic anhydrase [66].…”

Section: Discussionmentioning

confidence: 99%

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

et al. 2008

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Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′) 3 , featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0-15%. At a fixed molar content of 5% RSi(OR') 3 , the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices.

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Section: Discussionmentioning

confidence: 99%

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

et al. 2008

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“…Ten pre-bleach scans were measured at low intensity, followed by 1 bleach scan in a region of interest (ROI) using the same laser at high power (~4mW) and then 100 post-bleach scans of the sample. 31,52 This was repeated six times for each sample viscosity. A bleach radius of 7.5, 10 and 12.5 µm was initially selected for the experiments but raw images were used to calculate the radius as explained later.…”

Section: Free Diffusion In Solutionmentioning

confidence: 99%

Influence of molecular shape, conformability, net surface charge, and tissue interaction on transscleral macromolecular diffusion

Srikantha

Mourad

Suhling

et al. 2012

Experimental Eye Research

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Purpose: To study the influence of molecular shape, conformability, net surface charge and tissue interaction on transscleral diffusion.Methods: Unfixed, porcine sclera was clamped in an Ussing chamber. Fluorophore labelled, neutral, albumin, dextran, or ficoll were placed in one hemi-chamber and the rate of transscleral diffusion was measured over 24 hours using a spectrophotometer. Experiments were repeated using dextrans and ficoll with positive, or negative, net surface charges.Fluorescence recovery after photobleaching (FRAP) was undertaken to compare transscleral diffusion with diffusion through a solution.All molecules were 70 kDa.Results: Using FRAP, mean ± SD diffusion coefficient (D) was highest for albumin, followed by ficoll, then dextran (p = 0.0005). Positive dextrans diffused fastest, followed by negative, then neutral dextrans (p = 0.0005). Neutral ficoll diffused the fastest, followed by positive then negative ficoll (p = 0.0008). For the neutral molecules, transscleral D was highest for albumin, followed by dextran, then ficoll (p < 0.0001). D was highest for negative ficoll, followed by neutral, then positive ficoll (p < 0.0001). By contrast, D was highest for positive dextran, followed by neutral, then negative dextran (p = 0.0021).Conclusions: Diffusion in free solution does not predict transscleral diffusion and the molecular-tissue interaction is important. Molecular size, shape, and charge may all markedly influence transscleral diffusion, as may conformability to a lesser degree, but all need to be considered when selecting or designing drugs for transscleral delivery.Drugs directed against vascular endothelial growth factor (VEGF) have proven efficacy in some of the most common retinal diseases. The ANCHOR and MARINA studies demonstrated efficacy in wet age-related macular degeneration (AMD), 1,2 and studies such as CRUISE, BRAVO 3,4 and several from the DRCnet Group have shown favourable results in retinal vein occlusion and diabetic macular oedema. Whilst the data in these studies have led to improved clinical care, the need for regular intravitreal injections represents a burdensome regimen of treatment. A less invasive mode of delivery would have potential advantages in terms of reduced cost, discomfort, and complication rate.Systemic administration is impeded by the blood-aqueous and blood-retinal-barriers. High drug concentrations may be required to overcome these barriers to diffusion, with the attendant risk of systemic side effects. 5 A topical route would have obvious advantages. Delivery to the retina is however difficult for several reasons, such as lacrimation, low corneal permeability to large molecules, counter directional intraocular convection, and importantly the long diffusional distance. 53 Blood flow in the conjunctiva, episclera and choroid can also reduce drug concentration. 33,50 Notwithstanding these potential difficulties, transscleral delivery has a number of potential advantages. 6,7,8,9 The sclera has a large and accessible surface area, and a high d...

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“…For NADH silica alcogel samples, stock solutions of 80 M NADH in PBS were first prepared as described previously. The alcogel itself was prepared by mixing 8 mL of TEOS with 3 mL of water and 0.2 mL of 0.01 M hydrochloric acid for 2 hours 21 . Once mixed, 1.5 mL of alcogel was added to 1.5 mL of NADH in PBS in a cuvette, which was sealed and then mixed for a further minute, where t g ~ 5 minutes.…”

Section: Sample Preparationmentioning

confidence: 99%

NADPH as a potential intrinsic probe for tumour margin estimation

Stewart

Hupp

Birch

2018

Molecular-Guided Surgery: Molecules, Devices, and Applications IV

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The fluorescent properties of the reduced coenzyme NADH and its phosphorylated derivative (NADPH) have been explored in order to assess its potential as an intrinsic probe for cancer surgery. NADPH production is increased in cancer cells to quench reactive oxygen species and meet higher demands for biosynthesis, and has attractive fluorescent properties such as emission towards the visible part of the spectrum and a relatively long fluorescence lifetime upon binding to enzymes (~ 1 -6.5 ns) that help discriminate against other endogenous species. Different environmental effects on NAD(P)H fluorescence are reported here, including an increase in lifetime upon oxygen removal, an ability to retain its fluorescent properties in a silica phantom and its fluorescence lifetime also being distinguishable in a cell environment. In addition to this, the development of a miniaturised liquid light guide filter-based time-correlated single photon counting fluorescence lifetime system is reported as a step towards time-resolved visual imaging in cancer surgery. This system has been demonstrated as being capable of measuring NAD(P)H fluorescence lifetimes in both simple solvent and cell environments.

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Diffusion in a Sol−Gel-Derived Medium with a View toward Biosensor Applications

Cited by 33 publications

References 24 publications

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Influence of molecular shape, conformability, net surface charge, and tissue interaction on transscleral macromolecular diffusion

NADPH as a potential intrinsic probe for tumour margin estimation

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