Quantification of Iron (Fe) in Lithium Niobate by Optical Absorption

A quantitative method, based solely on optical absorption, to determine the total iron (Fe) concentration in Fe : LiNbO3 is proposed. Absorption spectra of several samples doped by thermal diffusion with different concentrations and different [Fe2+]/[Fe3+] ratios show an isosbestic point at 342 nm. At this wavelength the absorption is proportional to the total Fe concentration and does not depend on the oxidation state. Thanks to the large number of samples covering a wide range of concentrations, in this work it was possible to estimate an effective absorption cross-section relating the absorbance of a given sample to its iron content. The main advantage of the proposed method is in its simplicity and the fact that the result does not depend on the reduction degree of the sample. As it is known that the absorbance of Fe:LN at another wavelength (532 nm) gives information on the amount of Fe2+ present in the sample, our method makes it possible to characterize both the total Fe amount and its reduction degree within a single optical absorption measurement

Diffusion of iron in lithium niobate: a secondary ion mass spectrometry study

Iron-doped X-cut lithium niobate crystals were prepared by means of thermal diffusion from thin film varying in a systematic way the process parameters such as temperature and diffusion duration. Secondary Ion Mass Spectrometry was exploited to characterize the iron in-depth pro- files. The evolution of the composition of the Fe thin film in the range between 600\ub0C and 800\ub0C was studied, and the diffusion coefficient at different temperatures in the range between 900\ub0C and 1050\ub0C and the activation energy of the diffusion process were estimated

Lithium niobate crystals doped with iron by thermal diffusion: Relation between lattice deformation and reduction degree

We report, to our knowledge for the first time, on the experimental observation that the maximum lattice deformation induced at the surface of iron doped lithium niobate crystal by thermal diffusion depends on both the Fe concentration and the reduction degree of the doped layer itself. By exploiting a simple linear model, we suggest a description of this experimental evidence and we point out a procedure that allows the characterization of the in-depth profile of the Fe2+/Fe3+ ratio

In-vivo biological activity and glycosylation analysis of a biosimilar recombinant human follicle-stimulating hormone product (Bemfola) compared with its reference medicinal product (GONAL-f).

Recombinant human follicle-stimulating hormone (r-hFSH) is widely used in fertility treatment. Although biosimilar versions of r-hFSH (follitropin alfa) are currently on the market, given their structural complexity and manufacturing process, it is important to thoroughly evaluate them in comparison with the reference product. This evaluation should focus on how they differ (e.g., active component molecular characteristics, impurities and potency), as this could be associated with clinical outcome. This study compared the site-specific glycosylation profile and batch-to-batch variability of the in-vivo bioactivity of Bemfola, a biosimilar follitropin alfa, with its reference medicinal product GONAL-f. The focus of this analysis was the site-specific glycosylation at asparagine (Asn) 52 of the α-subunit of FSH, owing to the pivotal role of Asn52 glycosylation in FSH receptor (FSHR) activation/signalling. Overall, Bemfola had bulkier glycan structures and greater sialylation than GONAL-f. The nominal specific activity for both Bemfola and GONAL-f is 13,636 IU/mg. Taking into account both the determined potency and the nominal amount the average specific activity of Bemfola was 14,522 IU/mg (105.6% of the nominal value), which was greater than the average specific activity observed for GONAL-f (13,159 IU/mg; 97.3% of the nominal value; p = 0.0048), although this was within the range stated in the product label. A higher batch-to-batch variability was also observed for Bemfola versus GONAL-f (coefficient of variation: 8.3% vs 5.8%). A different glycan profile was observed at Asn52 in Bemfola compared with GONAL-f (a lower proportion of bi-antennary structures [~53% vs ~77%], and a higher proportion of tri-antennary [~41% vs ~23%] and tetra-antennary structures [~5% vs <1%]). These differences in the Asn52 glycan profile might potentially lead to differences in FSHR activation. This, together with the greater bioactivity and higher batch-to-batch variability of Bemfola, could partly explain the reported differences in clinical outcomes. The clinical relevance of the differences observed between GONAL-f and Bemfola should be further investigated

Depth-resolved photorefractive characterization of lithium niobate doped with iron by thermal diffusion

Iron doping of lithium niobate crystals by thermal diffusion is a well-established technique for the realization of spatially confined photorefractive stages in integrated optical devices. In this paper we present an innovative method able to realize depth-resolved holographic measurements inside the iron-diffused layer, so that in-depth profiles of the main photorefractive parameters can be derived without the need of any waveguide. By means of this technique it is possible to achieve a better knowledge of the influence of different surface treatments on the photorefractive performances of iron-diffused layers and to link them to the results of other depth-resolved characterization techniques in the framework of microscopic models of photorefractivity