| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Liu, D. C., et al.
(author)
-
The Human Stratum Corneum Prevents Small Gold Nanoparticle Penetration and Their Potential Toxic Metabolic Consequences
- 2012
-
In: Journal of Nanomaterials. - : Hindawi Limited. - 1687-4110 .- 1687-4129.
-
Journal article (peer-reviewed)abstract
- Nanoparticles are being used inmultiple applications, ranging from biomedical and skin care products (e. g., sunscreen) through to industrial manufacturing processes (e. g., water purification). The increase in exposure has led to multiple reports on nanoparticle penetration and toxicity. However, the correlation between nanoparticle size and its penetration without physical/chemical enhancers through the skin is poorly understood-with studies instead focusing primarily on skin penetration under disrupted conditions. In this paper, we investigate the penetration and metabolic effects of 10 nm, 30 nm, and 60 nm gold nanoparticles within viable excised human skin after 24-hour exposure usingmultiphoton tomograph-fluorescence lifetime imaging microscopy. After 24 hour treatment with the 10, 30, and 60 nm gold nanoparticles, there was no significant penetration detected below the stratum corneum. Furthermore, there were no changes in metabolic output (total NAD(P) H) in the viable epidermis posttreatment correlating with lack of penetration of nanoparticles. These results are significant for estimating topical nanoparticle exposure in humans where other model systems may overestimate the exposure of nanoparticles to the viable epidermis. Our data shows that viable human skin resists permeation of small nanoparticles in a size range that has been reported to penetrate deeply in other skin models.
|
|
| 5. |
- Sundh, Henrik, 1976, et al.
(author)
-
Development of intestinal ion-transporting mechanisms during smoltification and seawater acclimation in Atlantic salmon Salmo salar
- 2014
-
In: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1227-1252
-
Journal article (peer-reviewed)abstract
- This study investigated the expression of ion transporters involved in intestinal fluid absorption and presents evidence for developmental changes in abundance and tissue distribution of these transporters during smoltification and seawater (SW) acclimation of Atlantic salmon Salmo salar. Emphasis was placed on Na+, K+-ATPase (NKA) and Na+, K+, Cl- co-transporter (NKCC) isoforms, at both transcriptional and protein levels, together with transcription of chloride channel genes. The nka alpha 1c was the dominant isoform at the transcript level in both proximal and distal intestines; also, it was the most abundant isoform expressed in the basolateral membrane of enterocytes in the proximal intestine. This isoform was also abundantly expressed in the distal intestine in the lower part of the mucosal folds. The protein expression of intestinal Nka alpha 1c increased during smoltification. Immunostaining was localized to the basal membrane of the enterocytes in freshwater (FW) fish, and re-distributed to a lateral position after SW entry. Two other Nka isoforms, alpha 1a and alpha 1b, were expressed in the intestine but were not regulated to the same extent during smoltification and subsequent SW transfer. Their localization in the intestinal wall indicates a house-keeping function in excitatory tissues. The absorptive form of the NKCC-like isoform (sub-apically located NKCC2 and/or Na+, Cl(-)co-transporter) increased during smoltification and further after SW transfer. The cellular distribution changed from a diffuse expression in the sub-apical regions during smoltification to clustering of the transporters closer to the apical membrane after entry to SW. Furthermore, transcript abundance indicates that the mechanisms necessary for exit of chloride ions across the basolateral membrane and into the lateral intercellular space are present in the form of one or more of three different chloride channels: cystic fibrosis transmembrane conductance regulator I and II and chloride channel 3.
|
|
| 6. |
- Sundh, M., et al.
(author)
-
Formation of Supported Lipid Bilayers at Surfaces with Controlled Curvatures: Influence of Lipid Charge
- 2011
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 115:24, s. 7838-7848
-
Journal article (peer-reviewed)abstract
- We have developed and characterized novel biomimetic membranes, formed at nanostructured sensor substrates with controlled curvatures, motivated by the many biological processes that involve membrane curvature. Model systems with convex nanostructures, with radii of curvatures (ROCs) of 70, 75, and 95 nm, were fabricated utilizing colloidal assembly and used as substrates for supported lipid bilayers (SLBs). The SLBs were formed via vesicle adsorption and rupture, and the vesicle deposition pathway was studied by means of quartz crystal microbalance with dissipation (QCM-D) and fluorescence microscopy. SLBs conforming to the underlying nanostructured surfaces, which exhibit increased surface area with decreased ROC, were confirmed from excess mass, monitored by QCM-D, and excess total fluorescence intensities. The formation of SLBs at the nanostructured surfaces was possible, however, depending on the ROC of the structures and the lipid vesicle charge the quality varied. The presence of nanostructures was shown to impair vesicle rupture and SLB formation was progressively hindered at surfaces with structures of decreasing ROCs. The introduction of a fraction of the positively charged lipid POEPC in the lipid vesicle membrane allowed for good quality and conformal bilayers at all surfaces. Alternatively, for vesicles formed from lipid mixtures with a fraction of the negatively charged lipid POPS, SLB formation was not at all possible at surfaces with the lowest ROC. Interestingly, the vesicle adsorption rate and the SLB formation were faster at surfaces with nanostructures of progressively smaller ROCs at high ratios of POPS in the vesicles. Development of templated SLBs with controlled curvatures provides a new experimental platform, especially at the nanoscale, at which membrane events such as lipid sorting, phase separation, and protein binding can be studied.
|
|
| 7. |
- Sundh, M., et al.
(author)
-
Influence of phase separating lipids on supported lipid bilayer formation at SiO2 surfaces
- 2010
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12:2, s. 453-460
-
Journal article (peer-reviewed)abstract
- The importance of the lipid phase on the formation of supported lipid bilayers (SLBs) via vesicle fusion and on the resulting SLB homogeneity at SiO2 surfaces has been studied by the quartz crystal microbalance with dissipation (QCM-D) monitoring technique. Physiologically relevant lipid compositions were chosen to correspond to different regions (l(d), l(o) and coexistence of phases) in established phase diagrams of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), N-palmitoyl-D-erythro-sphingosylphosphorylcholine (PSM) and cholesterol. For most compositions, SLBs formed through vesicle rupture in a critical-surface-coverage dependent manner. Inclusion of PSM and cholesterol into POPC vesicles significantly impaired the vesicle rupture process such that a higher critical concentration of vesicles on the surface was needed before the rupture process started. When increasing the cholesterol content the vesicles formed SLBs containing more defects in the form of intact vesicles adsorbed on the surface up to a point (lo phase) where vesicles did not break at all but formed supported vesicular layers. The hampering of vesicle rupture is interpreted in terms of the ability of cholesterol to accommodate vesicle deformation. Experiments using elevated temperatures to alter the lipid membrane into a more fluid phase significantly improved the quality of the SLB showing the importance of both cholesterol content and the lipid phase on SLB homogeneity.
|
|
| 8. |
- Sundh, M., et al.
(author)
-
Supported Lipid Bilayers With Controlled Curvature via Colloidal Lithography
- 2011
-
In: IEEE Transactions on Nanobioscience. - 1536-1241. ; 10:3, s. 187-193
-
Journal article (peer-reviewed)abstract
- Supported lipid bilayers (SLBs) at surfaces provide a route to quantitatively study molecular interactions with and at lipid membranes via different surface-based analytical techniques. Here, a method to fabricate SLBs with controlled curvatures, in the nanometer regime over large areas, is presented, utilizing lipid vesicle rupture onto nanostructured sensor substrates. Heat treated colloidal particle masks were used as templates to produce silicon dioxide films with systematically varied radius of curvature (ROC, 70 to 170 nm are demonstrated) and quartz crystal microbalance with dissipation monitoring (QCM-D) was used to confirm vesicle rupture onto such structured surfaces. Fluorescence microscopy was used to show fluidity of the supported membranes. The formation of confluent SLBs is demonstrated at the nanostructured surfaces from vesicles composed of POPC lipids. However, at surfaces with decreasing ROCs, vesicle rupture was hindered but with an increasing fraction of the positively charged lipid POEPC in the vesicles, it was possible to form good quality supported bilayers on all curvatures studied. Curved SLBs open up the possibility to systematically study the influence of curvature on molecular interactions at lipid membranes.
|
|
| 9. |
- Vandenput, Liesbeth, 1974, et al.
(author)
-
Serum Estradiol Levels are Inversely Associated with Cortical Porosity in Older Men
- 2014
-
In: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 99:7
-
Journal article (peer-reviewed)abstract
- Context: The key role of serum estradiol (E2) for bone health in men is well established. The effect of serum sex steroids on bone microstructure, measured by high-resolution peripheral quantitative computed tomography (HRpQCT), remains unknown in elderly men. Objective: To examine the associations between serum sex steroids and bone microstructural parameters in older men. Methods: Trabecular and cortical bone microstructure at the tibia was measured by HRpQCT in 440 men (mean 80 years of age) participating in the population-based MrOS Sweden cohort. Serum levels of E2 and testosterone (T) were analyzed with mass spectrometry and free E2 and free T levels were calculated using law-of-mass-action equations. Results: Age-adjusted models demonstrated that E2 and free E2 but not T or free T associated significantly inversely with cortical porosity. The associations between E2 and free E2 and cortical porosity remained significant after further adjustment for height, weight, physical activity, calcium intake and smoking. Models including both serum E2 and T demonstrated that E2 (standardized beta= -0.12, P<0.05) but not T associated independently with cortical porosity. A similar independent association was found for free E2 (standardized beta= -0.12, P<0.05) but not free T. Free E2 associated significantly with trabecular bone volume fraction in age-adjusted models but this association did not remain significant after further adjustment. Conclusions: Serum E2 levels associated inversely with cortical porosity in 80-year-old men. We propose that low serum E2 may reduce cortical bone strength, at least partly by increasing cortical porosity, and, thereby, increase fracture risk in older men.
|
|
