Experimental studies of sorption and transport of moisture in cement based materials with supplementary cementitious materials

Most deterioration processes in cement based materials are closely related to moisture sorption and moisture transport properties. Therefore, it is important to study these properties, both theoretically and practically. This work is an experimental investigation in this field. Nowadays, the cement industry produces cements with increasing amounts of supplementary cementitious materials (SCMs) to limit CO2 emissions from concrete production. Knowledge about the moisture properties of concrete made from these blended cements is limited. This project has therefore been an attempt to further develop our understanding of the moisture properties of cement based materials, such as sorption isotherms and sorption transport properties in the presence of SCMs. This has been done by studying sorption isotherms mainly using the sorption balance method, and moisture transport coefficients using both the cup method and a sorption dynamic method. The experimental investigations were made on three types of hydrated cement pastes and mortars (OPC, OPC + 70% slag and OPC + 10% silica fume) with three different w/b –ratios (w/b) for cement paste (0.6, 0.5, 0.4) and two different w/b for cement mortar (0.5, 0.4). Sorption isotherms were determined for cement pastes and mortars in both hygroscopic and the super-hygroscopic relative humidity ranges using the sorption balance method, and the pressure plate method. The conclusion from this part of the study was that the desorption isotherms at low RH (0-30%) for different binders and different w/b-ratios are similar. At higher RHs the samples with silica fume and slag have higher moisture content than OPC samples. This is explained by that they have a higher amount of gel pores and a lower amount of capillary pores than OPC samples. The sorption isotherm at high RHs is difficult to validate experimentally, due to the critical RH of pore solutions. Steady-state and transient measurements of transport coefficients were also made. The dynamic sorption method was used to evaluate the diffusivity in small paste samples. The results show that Fick's law cannot completely describe the transport process in such small samples and sorption behavior is therefore anomalous with two processes with different time scales. One of these is macro-diffusion into the sample, which takes place on a shorter timescale in the small samples used. The second process takes place on longer timescales and it is possibly related to the sorption in nanometer-structure of materials. To better understand the transport properties in sorption cycles, steady-state diffusion coefficients of mortar samples were measured with a newly developed cup method set-up. The measurements were done on both the absorption and desorption limbs of sorption isotherms. For OPC samples the results show a clear difference between the diffusion coefficients in absorption and desorption with vapor content as potential (Dv) and presented as a function of relative humidity (RH). The Dv in desorption is higher than absorption especially at high RHs. For samples with SCMs the dependence of Dv on RH is small. The Dv:s were also recalculated to diffusivity (Dc) using the sorption isotherms to study the effect of different potentials on the effect of hysteresis on transport properties. Key words: Cement, Concrete, Moisture transport, Hysteresis, Supplementary cementitious materials, Water vapor sorption, Sorption isotherms, Anomalous sorptio

Localization of dexamethasone within dendritic core-multishell (CMS) nanoparticles and skin penetration properties studied by multi-frequency electron paramagnetic resonance (EPR) spectroscopy

The skin and especially the stratum corneum (SC) act as a barrier and protect epidermal cells and thus the whole body against xenobiotica of the external environment. Topical skin treatment requires an efficient drug delivery system (DDS). Polymer-based nanocarriers represent novel transport vehicles for dermal application of drugs. In this study dendritic core-multishell (CMS) nanoparticles were investigated as promising candidates. CMS nanoparticles were loaded with a drug (analogue) and were applied to penetration studies of skin. We determined by dual-frequency electron paramagnetic resonance (EPR) how dexamethasone (Dx) labelled with 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PCA) is associated with the CMS. The micro-environment of the drug loaded to CMS nanoparticles was investigated by pulsed high-field EPR at cryogenic temperature, making use of the fact that magnetic parameters (g-, A-matrices, and spin-lattice relaxation time) represent specific probes for the micro-environment. Additionally, the rotational correlation time of spin-labelled Dx was probed by continuous wave EPR at ambient temperature, which provides independent information on the drug environment. Furthermore, the penetration depth of Dx into the stratum corneum of porcine skin after different topical applications was investigated. The location of Dx in the CMS nanoparticles is revealed and the function of CMS as penetration enhancers for topical application is shown

Anterior subcutaneous transposition of ulnar nerve with fascial flap and complete excision of medial intermuscular septum in cubital tunnel syndrome: A prospective patient cohort

Objective: Regarding the frequency of cubital tunnel syndrome, varieties of treatment modalities, and ambiguity of anterior subcutaneous transposition of ulnar nerve method, we aimed to evaluate the efficacy of this procedure in patients with cubital tunnel syndrome referred to Taleghani hospital between 2006 and 2009. Methods: This study was a case series including all referred patients with definite diagnosis of cubital tunnel syndrome, treated by anterior subcutaneous transposition. Treatment results were measured according to modified Bishop rating system, and were ranked into excellent, good, fair, and poor. Variables such as gender, age (less/more than 45 years), causation, and initial severity, determined by Dellon criteria preoperatively, were analyzed by Fisher’s exact test. Results: This study was performed on 26 eligible cases including 29 elbows, 38% males and 62.1% females, with mean age of 44.5 years (ranging 23–72 years). In a 12 months follow-up post-operatively, 62% showed excellent, 20.7% good, and 17.3% fair, with no poor result. In a 1–12 months follow-up post-operatively, results showed improvement, and initial severity and old age were demonstrated to significantly affect treatment results (P < 0.07). Conclusion: Though considered standard of care, the present study suggests that criteria for surgical techniques of ulnar nerve decompression, e.g. simple decompression vs. more extensive repair as in the present cohort, should be revised by controlled prospective studie

Radical Stability vs. Temporal Resolution of EPR-Spectroscopy on Biological Samples

Spin-labeling active compounds is a convenient way to prepare them for EPR spectroscopy with minimal alteration of the target molecule. In this study we present the labeling reaction of dexamethasone (Dx) with either TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) or PCA (3-(carboxy)-2,2,5,5-tetramethyl-1-pyrrolidinyloxy) with high yields. According to NMR data, both labels are attached at the primary hydroxy group of the steroid. In subsequent spin-stability measurements both compounds were applied onto HaCaT cells. When the signal of Dx-TEMPO decreased below the detection limit within 3 h, the signal of Dx-PCA remained stable for the same period of time

Drug distribution in nanostructured lipid particles

The targeted design of nanoparticles for efficient drug loading and defined release profiles is even after 25 years of research on lipid-based nanoparticles still no routine procedure. It requires detailed knowledge about the interaction of the drug with the lipid compounds and about its localisation and distribution in the nanoparticle. We present here an investigation on nano-sized lipid particles (NLP) composed of Gelucire and Witepsol as solid lipids, and Capryol as liquid lipid, loaded with Dexamethasone, a glucocorticoid used in topical treatment of inflammatory dermal diseases. The interactions of Dexamethasone, which was spin-labelled by 3-(Carboxy)-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (DxPCA), with its microenvironment are monitored by EPR spectroscopy at 94 GHz at low temperatures. The mobility of the spin-labelled drug was probed by X-band EPR at room temperature. In order to relate the magnetic and dynamic parameters deduced from EPR to the local environment of the spin probe in the NLP, investigations of DxPCA in the individual lipid compounds were carried out. The magnetic parameters reflecting the polarity of DxPCA’s environment as well as the parameters describing the mobility of the drug reveal that in the case of colloidal dispersions of the lipids and also the NLP DxPCA is attached to the surface of the nanoparticles. Although the lipophilic drug is almost exclusively associated with the NLP in aqueous solution, dilution experiments show, that it can be easily released from the nanoparticle

Nanocrystals for Improved Drug Delivery of Dexamethasone in Skin Investigated by EPR Spectroscopy

Nanocrystals represent an improvement over the traditional nanocarriers for dermal application, providing the advantages of 100% drug loading, a large surface area, increased adhesion, and the potential for hair follicle targeting. To investigate their advantage for drug delivery, compared to a base cream formulation, dexamethasone (Dx), a synthetic glucocorticoid frequently used for the treatment of inflammatory skin diseases, was covalently linked with the paramagnetic probe 3-(carboxy)-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PCA) to DxPCA. To investigate the penetration efficiency between these two vehicles, electron paramagnetic resonance (EPR) spectroscopy was used, which allows the quantification of a spin-labeled drug in different skin layers and the monitoring of the drug release. The penetration behavior in excised healthy and barrier-disrupted porcine skin was monitored by EPR, and subsequently analyzed using a numerical diffusion model. As a result, diffusion constants and free energy values in the different layers of the skin were identified for both formulations. Dx-nanocrystals showed a significantly increased drug amount that penetrated into viable epidermis and dermis of intact (factor 3) and barrier-disrupted skin (factor 2.1) compared to the base cream formulation. Furthermore, the observed fast delivery of the spin-labeled drug into the skin (80% DxPCA within 30 min) and a successive release from the aggregate unit into the viable tissue makes these nanocrystals very attractive for clinical applications

Enhanced topical delivery of dexamethasone by β-cyclodextrin decorated thermoresponsive nanogels

Highly hydrophilic, responsive nanogels are attractive as potential systems for the topical delivery of bioactives encapsulated in their three-dimensional polymeric scaffold. Yet, these drug carrier systems suffer from drawbacks for efficient delivery of hydrophobic drugs. Addressing this, β-cyclodextrin (βCD) could be successfully introduced into the drug carrier systems by exploiting its unique affinity toward dexamethasone (DXM) as well as its role as topical penetration enhancer. The properties of βCD could be combined with those of thermoresponsive nanogels (tNGs) based on dendritic polyglycerol (dPG) as a crosslinker and linear thermoresponsive polyglycerol (tPG) inducing responsiveness to temperature changes. Electron paramagnetic resonance (EPR) studies localized the drug within the hydrophobic cavity of βCD by differences in its mobility and environmental polarity. In fact, the fabricated carriers combining a particulate delivery system with a conventional penetration enhancer, resulted in an efficient delivery of DXM to the epidermis and the dermis of human skin ex vivo (enhancement compared to commercial DXM cream: ∼2.5 fold in epidermis, ∼30 fold in dermis). Furthermore, DXM encapsulated in βCD tNGs applied to skin equivalents downregulated the expression of proinflammatory thymic stromal lymphopoietin (TSLP) and outperformed a commercially available DXM cream

A Dual Fluorescence–Spin Label Probe for Visualization and Quantification of Target Molecules in Tissue by Multiplexed FLIM–EPR Spectroscopy

Simultaneous visualization and concentration quantification of molecules in biological tissue is an important though challenging goal. The advantages of fluorescence lifetime imaging microscopy (FLIM) for visualization, and electron paramagnetic resonance (EPR) spectroscopy for quantification are complementary. Their combination in a multiplexed approach promises a successful but ambitious strategy because of spin label-mediated fluorescence quenching. Here, we solved this problem and present the molecular design of a dual label (DL) compound comprising a highly fluorescent dye together with an EPR spin probe, which also renders the fluorescence lifetime to be concentration sensitive. The DL can easily be coupled to the biomolecule of choice, enabling in vivo and in vitro applications. This novel approach paves the way for elegant studies ranging from fundamental biological investigations to preclinical drug research, as shown in proof-of-principle penetration experiments in human skin ex vivo

Modeling water absorption in concrete and mortar with distributed damage

The deterioration rate of concrete structures is directly influenced by the rate of moisture ingress. Modeling moisture ingress in concrete is therefore essential for quantitative estimation of the service life of concrete structures. While models for saturated moisture transport are commonly used, concrete, during its service life, is rarely saturated and some degree of damage is often present. In this work, we investigate whether classical isothermal unsaturated moisture transport can be used to simulate moisture ingress in damaged mortar and concrete and we compare the results of numerical simulations with experimental measurements of water sorption. The effect of hysteresis of moisture retention is also considered in the numerical simulations. The results indicate that the unsaturated moisture transport models well simulate early stages of moisture ingress at all damage levels, where capillary suction is the prominent mechanism. At later stages of moisture transport, where air diffusion and dissolution have a more significant contribution, simulations that consider moisture hysteresis compare most favorably with experimental results