Search PubMed⌕ Search

Biomedical subjects

M J McShane

Publications and source records attributed to M J McShane.

8 recordsLinked to original sources
PubMed2005

Application of self-assembled ultra-thin film coatings to stabilize macromolecule encapsulation in alginate microspheres.

Alginate-based hydrogels have several unique properties that have enabled them to be used as a matrix for the entrapment of a variety of enzymes, proteins and cells for applications in bioprocessing, drug delivery and chemical sensing. However, control over release rates or, in some cases, stable encapsulation remains a difficult goal, especially for small particles with high surface-area-to-volume ratios. In this work, the potential to limit diffusion of macromolecules embedded in alginate spheres with nanofilm coatings was assessed. Alginate microspheres were fabricated using an emulsification process with high surfactant concentration to form beads in the size range of 2-10 microm. Using calcium chloride for ionotropic gelation, dextran was encapsulated in the gel phase by mixing with the alginate in solution. The exterior surface was then modified with polyelectrolyte coatings using the layer-by-layer self assembly technique. Leaching studies to assess retention of dextran with varying molecular weights confirmed that the application of multi-layer thin films to the alginate microspheres was effective in reducing leaching rate and total loss of the encapsulated material from the microspheres. For the best case, the rate of release for dextran of 2,000,000 Dalton molecular weight decreased from 1% h(-1) in bare microspheres to 0.1% h(-1) in polyelectrolyte-coated microspheres. The effectiveness of nanofilms reducing loss of the encapsulated macromolecules was found to vary between different polycation materials used. These studies support the feasibility of using these microsystems for development of long-term stable encapsulated systems, such as implantable biosensors.

Alginates↗
PubMed2005

Comparison of selective attachment and growth of smooth muscle cells on gelatin- and fibronectin-coated micropatterns.

Tissue engineering research has been on going for many years, people are making all the effort to explore the cell functions in cellular level and even in molecular level. Making the cells functional in an in vitro environment is a preliminary goal for the implantation and repair of complicated tissues/organs. Fabricating artificial ECM to mimic the in vivo environment is an essential approach in tissue engineering. The work in this paper is to study how rat aorta smooth muscle cells (RASMCs) behave in two engineered cell culture scaffolds: gelatin- and fibronectin (FN)-coated micropatterns. The investigation on the initial attachment and further growth of SMCs cultured on gelatin- and FN-coated micropatterns was addressed. This study focused on both the characterization of gelatin and fibronectin assembly properties and cell responses to these two protein-coated micropatterns. Thin film patterns with gelatin and fibronectin coatings were fabricated on microscope glass slides using photolithography, electrostatic layer-by-layer self-assembly and lift-off (LbL-LO) technologies. In this work, the scaffolds were built up by commonly used polyelectrolyte materials and proteins through LbL process, containing cationic poly(diallyldimethylammonium chloride) (PDDA), poly(allylamine hydrochloride) (PAH), anionic poly(sodium 4-styrenesulfonate) (PSS), gelatin and fibronectin. The resulting polyelectrolyte thin films were characterized by contact angle (CA), quartz crystal microbalance (QCM), atomic force microscopy (AFM), and fluorescence microscopy. CA measurement shows the consistent hydrophylicity of gelatin surfaces in different number of layers with LbL deposition method. Different from our previous QCM measurement of gelatin, fibronectin does not show high electrostatic attraction to either positively or negatively charged polyelectrolytes, although it can be weakly assembled to both polyelectrolyte surfaces. AFM images show Gelatin- and FN-coated micropatterns are around 50-60 nm thick. RASMCs were cultured on these gelatin- and FN-coated micropatterns. It was observed that, for the cells cultured on gelatin-coated micropatterns, they initially landed on the gelatin-coated surface, not on the PDDA-coated surface in between. But further growth of the cells was affected by the shape of the patterns: strip pattern limited cell growth beyond the patterns, but square patterns could not. While, it was found interestingly, for the cells cultured on FN-coated micropatterns, SMCs initially landed on PDDA-coated surface, and then migrated to FN-coated both square and strip patterns. These findings indicate that both gelatin and fibronectin are adhesive proteins, but they have different effects on the initial attachment and later growth for SMCs.

Animals↗
PubMed2000

A transparent tool for seemingly difficult calibrations: the parallel calibration method.

A new easy-to-understand calibration method for the analysis of spectral data is developed. The "parallel calibration" method is logically simple and intuitive yet often provides an improvement over more complex standard calibration methods. A description of the algorithm with a technical justification for the parallel algorithm is presented, underscoring the simplicity of the approach. In addition, performance as compared to that of the standard methods of classical least-squares (CLS) and partial least-squares (PLS) regression is studied. Calibrations are carried out on a computer-generated simulation data set as well as two scientific data sets. The results show that the parallel method gives results comparable to or better than those of CLS and PLS methods in terms of mean squared error.

Algorithms↗
PubMed2000

Monte Carlo modeling for implantable fluorescent analyte sensors.

A Monte Carlo simulation of photon propagation through human skin and interaction with a subcutaneous fluorescent sensing layer is presented. The algorithm will facilitate design of an optical probe for an implantable fluorescent sensor, which holds potential for monitoring many parameters of biomedical interest. Results are analyzed with respect to output light intensity as a function of radial distance from source, angle of exit for escaping photons, and sensor fluorescence (SF) relative to tissue autofluorescence (AF). A sensitivity study was performed to elucidate the effects on the output due to changes in optical properties, thickness of tissue layers, thickness of the sensor layer, and both tissue and sensor quantum yields. The optical properties as well as the thickness of the stratum corneum, epidermis, (tissue layers through which photons must pass to reach the sensor) and the papillary dermis (tissue distal to sensor) are highly influential. The spatial emission profile of the SF is broad compared that of the tissue fluorescence and the ratio of sensor to tissue fluorescence increases with distance from the source. The angular distribution of escaping photons is more concentrated around the normal for SF than for tissue AF. The information gained from these simulations will be helpful in designing appropriate optics for collection of the signal of interest.

Algorithms↗
PubMed1999

A fluorescence-based glucose biosensor using concanavalin A and dextran encapsulated in a poly(ethylene glycol) hydrogel.

A fluorescence biosensor is described that is based on a photopolymerized poly(ethylene glycol) (PEG) hydrogel incorporating fluorescein isothiocyanate dextran (FITC-dextran) and tetramethylrhodamine isothiocyanate concanavalin A (TRITC-Con A) chemically conjugated into the hydrogel network using an alpha-acryloyl, omega-N-hydroxysuccinimidyl ester of PEG-propionic acid. In the absence of glucose, TRITC-Con A binds with FITC-dextran, and the FITC fluorescence is quenched through fluorescence resonance energy transfer. Competitive glucose binding to TRITC-Con A liberates FITC-dextran, resulting in increased FITC fluorescence proportional to the glucose concentration. In vitro experiments of hydrogel spheres in a solution of 0.1 M phosphate-buffered saline (pH 7.2) and glucose were conducted for multiple TRITC-Con A/FITC-dextran ratios. Hydrogels were characterized on the basis of the percent change in fluorescence intensity when FITC-dextran was liberated by increasing glucose concentrations. The optimum fluorescent change between 0 and 800 mg/dL was obtained with a TRITC-Con A/FITC-dextran mass ratio of 500:5 micrograms/mL PEG. Fluorescent response was linear up to 600 mg/dL. At higher concentrations, the response saturated due to the displacement of the majority of the FITC-dextran and to concentration quenching by free FITC-dextran. Dynamic fluorescent change upon glucose addition was approximately 10 min for a glucose concentration step change from 0 to 200 mg/dL.

Biosensing Techniques↗
PubMed1990

Analyzing the relationship with correspondence copying services.

Some healthcare managers think that medical record departments are not receiving the full benefits available to them from their correspondence copy service. What are they receiving and what should they be receiving? And, what are the copying service companies getting? What should they be getting? This article examines and redefines the relationship between copying services and medical record departments.

Contract Services↗
PubMedDate not supplied

Micropatterning of nanoengineered surfaces to study neuronal cell attachment in vitro.

Methods for producing protein patterns with defined spatial arrangement and micro- and nanoscale features are important for studying cellular-level interactions, including basic cell-cell communications, cell signaling, and mechanisms of drug action. Toward this end, a straightforward, versatile procedure for fabricating micropatterns of bioactive nanofilm coatings as multifunctional biological testbeds is demonstrated. The method, based on a combination of photolithography and layer-by-layer self-assembly (LbL), allows for precise construction of nanocomposite films of potentially complex architecture, and patterning of these films on substrates using a modified lift-off (LO) procedure. As a first step in evaluating nanostructures made with this process, "comparison chips," comprising two coexisting regions of square patterns with relevant proteins/polypeptides on a single substrate, were fabricated with poly(diallyldimethylammonium chloride) (PDDA) as a cell-repellent background. Using neuronal cells as a model biological system, comparison chips were produced with secreted phospholipase A2 (sPLA2), a known membrane-active enzyme for neurons, for direct comparison with gelatin, poly-l-lysine (PLL), or bovine serum albumin (BSA). Fluorescence microscopy, surface profilometry, and atomic force microscopy techniques were used to evaluate the structural properties of the patterns on these chips and show that the patterning technique was successful. Preliminary cell culture studies show that neurons respond and bind specifically to the sPLA2 enzyme embedded in the polyelectrolyte thin films and present as the outermost layer. These findings point to the potential for this method to be applied in developing test substrates for a broad array of studies aimed at identifying important biological structure-function relationships.

Animals↗