Axel Meier

A Taylor made lipophilic chlorin for Photodynamic Tumor Therapy

Abstract A new chlorin dicarboxylic acid 3 has been synthesized from the porphyrin 1 by amide acetal Claisen rearrangement. The chemical purity, photophysical properties, and its lipophilicity make the chlorin 3 promising camdidate for application in Photodynamic Tumor Therapy (PDT).

An improved method for the preparation of formyldeuteroporphyrins : synthesis of biologically relevant porphyrins

Abstract Pure 3 and 8 formyldeuteroporphyrin dimethylester isomers 3a,b have been prepared in high yield by formylation of readily accessible deuteroporphyrin dimethylester 1 with trimethyl orthoformate in trifluoroacetic acid and subsequent chromatographic separation of the mixture of isomers. The formyl-porphyrins can be transformed into synthetically and biologically useful derivatives.

Design of diamond-turned holograms incorporating properties of the fabrication process

Recently, the fabrication of computer-generated holograms by diamond face turning with a nanometer-stroke fast tool servo (nFTS) has been demonstrated. Existing methods for the design of diamond-turned holograms account for their spiral-shaped surface topology and the fact that only the phase of a wave field can be modulated. Here we present an algorithm enabling the additional consideration of two important fabrication-related properties: the shape of the diamond tool used and the limited control frequency of the nFTS. Our method is based on the generalized projections method and enables the design of holograms for the reconstruction of arbitrary intensity distributions in the far field. Experimental results are presented, demonstrating the advantages of the method.

Material aspects for the diamond machining of submicron optical structures for UV-application

The paper discusses material aspects governing the diamond machining process for submicron structures which serve as diffractive optical elements (DOE). Therefore, first the cutting process for fabrication of DOEs is introduced. The microstructured surface is generated by diamond turning using a nano Fast Tool Servo (nFTS), which enables a variation of the depth of cut up to 350 nm at a maximum frequency of 10 kHz. Such DOEs are typically used with a wavelength of 632 nm. A new application for UV-radiation with a wavelength below 350 nm requires alternative materials with sufficient reflectivity. Cutting experiments and UV-reflectivity tests were performed in order to identify suitable materials. High machining accuracy and UV-reflectivity were achieved with ultrafine grained aluminium as workpiece material.

Quantitative Phase Contrast Imaging of Microinjection Molded Parts Using Computational Shear Interferometry

Microinjection molding is an effective mass production technology to replicate microcomponents. However, compared with conventional injection molding, microinjection molding requires an adapted processing due to larger surface-area-to-volume ratios, as well as higher shear and cooling rates. Since the functionality of the final parts depends on their defect-free fabrication, a fast, robust, and reliable quality inspection of the final part is mandatory. Here, we demonstrate the applicability of computational shear interferometry (CoSI) for the quality inspection of microinjection molding parts. An analytic model based on the Jones matrix is developed to predict what information of the light field generated behind the inspected part is measured using CoSI technique. A microinjection molding part having spiral shape is inspected indicating areas with manufacturing defects, such as air bubbles, scratches, and internal stresses.

Selective synthesis and photophysical properties of tailor-made chlorins for photodynamic therapy

Photodynamic therapy (PDT) is a promising approach for the treatment of cancer, and is presently being evaluated worldwide. PDT is based on the ability of photosensitizers to accumulate selectively in tumor tissue. On irradiation fluorescence of the sensitizer allows tumor localization. Singlet oxygen formed by sensitization causes tumor destruction. Hematoporphyrin derivatives and Photofrin IIR, at the present the only practically used sensitizers in PDT, absorb light only weakly ((epsilon) approximately equals 5.000 at (lambda) equals 620 nm). It has been shown that Photofrin IIR is a multicomponent mixture of different porphyrins with only a few therapeutically active components. In contrast to porphyrins, chlorins and azachlorins have ideal photophysical properties with strong absorption ((epsilon) approximately equals 50.000) in a spectral region ((lambda) equals 650 nm) where tissue transmits much better. Molecular properties of porphinoid structures, which are responsible for tumor uptake and tumor enrichment, are connected with lipophilicity and aggregation behavior. Therefore our aim was to synthesize well defined chlorins with lipophilic properties similar to those of the active fractions of Photofrin IIR.

Diamond turned holograms for intensity reconstruction in Fresnel domains

We present a method for the design of diamond turned holograms for the reconstruction of arbitrary intensity distributions in a Fresnel domain. Existing methods are limited to the reconstruction of intensities in the far field, which imposes limitations to the optical setup. Theory and experimental verification of the new approach are presented.

Ultra Precision Machining of Non-Ferrous Metals and Nitrocarburized Tool Steel

This paper presents results for the machining of materials typically applied in ultra precision machining in comparison to a nitrocarburized tool steel. Analyzing and evaluating the machining results regarding surface integrity lead to recommendations for the ultra precision machining of this new mold material. The influence of feed, depth of cut and cutting speed on surface quality, resulting cutting forces and tool wear have been investigated. The results show that the decisive factor for the ultra precision machining of nitrocarburized tool steel are the significantly higher cutting forces. In some cases the high cutting forces lead to vibrations during the turning process deteriorating the surface integrity. Therefore, tool nose radius and depth of cut have to be reduced to minimize the cutting forces and avoid the vibrations.