Surface with antimicrobial activity obtained through silane coating with covalently bound polymyxin B

Surfaces exhibiting antimicrobial activity were prepared for potential medical application. A polycationic lipopeptide polymyxin B was selected as the bioactive agent for covalent immobilization onto the surface. First, by using sol–gel technology the inert glass substrate was functionalized by a silane coating with epoxide rings to which the peptide was coupled by means of a catalyst. Preparation of the coating and presence of the peptide on the surface were followed by FTIR, XPS and AFM analyses. The obtained material showed antimicrobial effect indicating that in spite of immobilization the peptide has retained its bioactivity. The coated surface was able to reduce bacterial cell counts of the Gram-negative bacterium Escherichia coli by more than five orders of magnitude in 24 h of incubation. It can be concluded that bioactive coatings with covalently bound polycationic peptides have potential for application on medical devices where leakage into the surrounding is not allowed in order to prevent bacterial growth and biofilm formation.     

Photon Upconversion Hydrogels for 3D Optogenetics

The ability to optically induce biological responses in 3D has been dwarfed by the physical limitations of visible light penetration to trigger photochemical processes. However, many biological systems are relatively transparent to low-energy light, which does not provide sufficient energy to induce photochemistry in 3D. To overcome this challenge, hydrogels that are capable of converting red or near-IR (NIR) light into blue light within the cell-laden 3D scaffolds are developed. The upconverted light can then excite optically active proteins in cells to trigger a photochemical response. The hydrogels operate by triplet–triplet annihilation upconversion. As proof-of-principle, it is found that the hydrogels trigger an optogenetic response by red/NIR irradiation of HeLa cells that have been engineered to express the blue-light sensitive protein Cry2olig. While it is remarkable to photoinduce the clustering of Cry2olig with blanket NIR irradiation in 3D, it is also demonstrated how the hydrogels trigger clustering within a single cell with great specificity and spatiotemporal control. In principle, these hydrogels may allow for photochemical control of cell function within 3D scaffolds, which can lead to a wealth of fundamental studies and biochemical applications.     

Microstructural development in NiAl/Ni-Si-B/Ni transient liquid phase bonds

A transmission electron microscopy (TEM) based investigation of microstructural development during transient liquid phase bonding of near-stoichiometric NiAl to commercial purity nickel is presented in this article. The work described employed Ni-4.5 wt pct Si-3.2 wt pct B (BNi-3) melt-spun interlayers. The precipitation of both Ni-Al based phases and borides within the joint and adjacent substrate regions is discussed. The article considers martensite formation (within the NiAl substrate) and the precipitation of Ll₂ type phases (both within the joint and at the interface with the NiAl substrate). The relative roles of the two substrate materials (NiAl and Ni) in the isothermal resolidification process are identified. The preferential formation of Ni₃B boride phases in the Ni substrate near the original location of the Ni substrate-joint interface is discussed and contrasted with the absence of similar events in the NiAl substrate.     

Spontaneous in vivo reversion to normal of an inherited mutation in a patient with adenosine deaminase deficiency

Somatic mosaicism in genetic disease generally results from a de novo deleterious mutation during embryogenesis. We now describe a somatic mosaicism due to the unusual mechanism of in vivo reversion to normal of an inherited mutation. The propositus was an adenosine deaminase-deficient (ADA-) child with progressive clinical improvement and unexpectedly mild biochemical and immunologic abnormalities. Mosaicism due to reversion was evidenced by absence of a maternally transmitted deleterious mutation in 13/15 authenticated B cell lines and in 17% of single alleles cloned from blood DNA, despite retention of a maternal 'private' ADA polymorphism linked to the mutation. Establishment of significant somatic mosaicism following reversion to normal could modify any disorder in which revertant cells have a selective advantage.     

Breast carcinoma: MR imaging before re-excisional biopsy

PURPOSE: To investigate the role of magnetic resonance (MR) imaging in the examination of patients after excisional biopsy of breast carcinoma before re-excision. MATERIALS AND METHODS: Forty-seven patients underwent contrast material-enhanced MR imaging after initial excisional biopsy of breast carcinoma before further surgery. RESULTS: The positive predictive value of MR imaging for predicting residual disease was 82%; the negative predictive value was 61%. Fourteen patients had multifocal (n = 6) or diffuse (n = 8) carcinoma. The extent of tumor was correctly identified with MR imaging alone in nine of the 14 patients, with both mammography and MR imaging in three patients, with mammography alone in one patient, and with no imaging modality in one patient. In four of the 14 patients, management was altered from re-excision to mastectomy (n = 3) or from breast-conservation therapy to mastectomy (n = 1). CONCLUSION: MR imaging has a high positive predictive value for predicting residual tumor after excisional biopsy. The identification of mammographically and clinically unsuspected multifocal or extensive residual tumor may lend support for mastectomy rather than re-excision. However, false-negative findings due to postsurgical changes and false-positive findings due to enhancement of granulation tissue and benign breast tissue remain limitations.     

Multicoil array for high resolution imaging of the breast

An RF multicoil array for high resolution imaging of the breast is presented. The RF multicoil is incorporated into a dedicated breast imaging apparatus that holds either breast in gentle compression during imaging. Simulations and imaging experiments demonstrate the high sensitivity and RF homogeneity of the multicoil array. Direct comparisons are made between the multicoil and a surface coil. In vivo images are presented to demonstrate the homogeneity of the RF field of the multicoil over the entire breast. An in vivo image of both high temporal and spatial resolution is shown, which demonstrates the sensitivity of the RF multicoil array that may be achieved in a practical imaging experiment.