Biomedical subjects

Michael T Harris

Publications and source records attributed to Michael T Harris.

10 recordsLinked to original sources

PubMed2006

Characterization of silica-coated tobacco mosaic virus.

The deposition of silica on the surface of tobacco mosaic virus (TMV) is achieved at a higher pH (>7) as a means to enhance its usefulness as a template for the synthesis of nanostructures. Electron energy loss spectroscopy definitively shows the presence of a silica shell on the surface of the TMV while small angle X-ray scattering differentiates successfully between silica-coated TMV and silica particles in the presence of uncoated TMV. Importantly, coating reactions done in a 50% w/v methanol/water solution produce smaller silica nanostructures during the condensation of the hydrolysis intermediates, possibly aiding in obtaining uniform coating. Furthermore, TMV-templated silica coatings are found to enhance the stability of the virus particle in methanol at conditions that would ordinarily disrupt the assembled particle. Combined these findings demonstrate that TMV can function as an efficient template for the controlled deposition of silica at neutral pH.

Journal Article↗

PubMed2006

Deposition of platinum clusters on surface-modified Tobacco mosaic virus.

Nanoscaled Pt conductors were prepared from genetically engineered Tobacco mosaic virus (TMV) templates through Pt cluster deposition on the outer surface of the TMV. Pt clusters were synthesized and deposited on the engineered TMV with surface-exposed cysteine via the in situ mineralization of hexachloroplatinate anions. This deposition was driven by the specific binding between thiols and the solid metal clusters. In addition, Pt-thiolate adducts are suggested to form on the engineered TMV in aqueous solutions that work as nucleation sites for the formation of the Pt clusters. The specific binding between Pt clusters and the engineered TMV template was investigated using UV/vis spectrophotometry and quartz crystal microbalance (QCM) analysis. The electric conductance of Pt-deposited TMV was greater than that of the uncoated TMV virion particles. This result suggests the application of metal cluster-deposited engineered TMV in future electrical devices such as rapid response sensors.

Adsorption↗

PubMed2005

Effect of CuCl2 concentration on the aggregation and mineralization of Tobacco mosaic virus biotemplate.

Aggregation of the biotemplates in mineralization processes is a considerable obstacle in preparing well-dispersed bio-inorganic hybrid materials. In this study, aggregation and mineralization of Tobacco mosaic virus (TMV) biotemplates were investigated as a function of the copper precursor (CuCl2) concentration. The mean hydrodynamic radius of TMV in an aqueous CuCl2 solution was determined by dynamic light scattering for the monitoring of the TMV aggregation. At CuCl2 concentration of 0.5 mM or higher, the mean hydrodynamic radius of TMV increased dramatically indicating aggregation of the TMV particles. Numerical calculations on the long-range interaction energy between parallel model TMV particles agreed with the experimental observations for the TMV aggregation. Mineralization of copper precursors on the TMV biotemplates was achieved only at the CuCl2 concentrations that induced considerable aggregation of the biotemplate. From the numerical calculations and experimental results, it was concluded that a dense copper cluster deposition cannot be achieved without aggregation of TMV templates.

Copper↗

PubMed2005

Surface modification of magnetic nanoparticles capped by oleic acids: characterization and colloidal stability in polar solvents.

The lyophobic surface of monodisperse magnetic nanoparticles capped by oleic acid was made to be more lyophilic by ozonolysis to increase the stability of the suspension in polar solvents like ethanol. The ozone oxidatively cleaved the double bond of oleic acid to form carbonyl and carboxyl groups on the surface of the nanoparticles. Additionally, interfacial ligand exchange of the capping molecules was applied to make the hydrophobic particle surface more hydrophilic. The magnetic particles showed enhanced miscibility and short-term stability in water after interfacial ligand exchange. The structure changes of the capping molecules on the nanoparticle surfaces were investigated using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From these spectroscopy studies, the cleavage of the oleic acid and the formations of the carboxyl and carbonyl groups on the particle surface were confirmed. The shape and the magnetic properties of the nanoparticles were maintained after the surface modification. Ozonolysis is an effective method in modifying the lyophobic surface of the magnetic nanoparticles.

Journal Article↗

PubMed2005

A finite element based algorithm for determining interfacial tension (gamma) from pendant drop profiles.

This paper introduces a robust algorithm to determine the interfacial tension (gamma) from pendant drop profiles using the Galerkin finite element method (gamma-PD-FEM) to solve the axisymmetric form of the Young-Laplace (YL) equation. In this algorithm, the theoretical profiles are generated by solving the spherical coordinate form of the YL equation. gamma-PD-FEM also solves for the parameter estimates by minimizing the difference between the theoretical and experimental surface functions, f(theta). This technique is compared to the widely used method of converting the YL equation to the three arc length-based (ALB) first-order ODEs developed by Bashforth and Adams (BA) in 1883, or as denoted in this paper, the gamma-PD-BA method. The drop apex is the initial condition for the gamma-PD-BA algorithm and the integration is terminated at a specified location along the drop profile. In contrast to techniques based on the BA approach, computation of the theoretical drop profile in gamma-PD-FEM is obtained from a second-order ordinary differential equation and requires boundary conditions at the drop apex and at the contact line of the drop to the nozzle. By incorporating both boundary conditions into the problem formulation, the algorithm can also determine if the drop shape is at static equilibrium. Results to be presented include an outline of the computer algorithm, and comparison of gamma values obtained from the gamma-PD-FEM and the traditional gamma-PD-BA method using simulated and experimental drop profile data sets.

Journal Article↗

PubMed2005

A robust algorithm for the simultaneous parameter estimation of interfacial tension and contact angle from sessile drop profiles.

The pendant and sessile drop profile analysis using the finite element method (PSDA-FEM) is an algorithm which allows simultaneous determination of the interfacial tension (gamma) and contact angle (theta(c)) from sessile drop profiles. The PSDA-FEM algorithm solves the nonlinear second-order spherical coordinate form of the Young-Laplace equation. Thus, the boundary conditions at the drop apex and contact position of the drop with the substrate are required to solve for the drop profile coordinates. The boundary condition at the position where the drop contacts the substrate may be specified as a fixed contact line or fixed contact angle. This paper will focus on the fixed contact angle boundary condition for sessile drops on a substrate and how this boundary condition is used in the PSDA-FEM curve-fitting algorithm. The PSDA-FEM algorithm has been tested using simulated drop shapes with and without the addition of random error to the drop profile coordinates. The random error is varied to simulate the effect of camera resolution on the estimates of gamma and theta(c) values obtained from the curve-fitting algorithm. The error in the experimental values for gamma from sessile drops of water on acrylic and Mazola corn oil on acrylic falls within the predicted range of errors obtained for gamma values from simulated sessile drop profiles with randomized errors that are comparable in magnitude to the resolution of the experimental setup.

Algorithms↗

PubMed2005

Patterned assembly of genetically modified viral nanotemplates via nucleic acid hybridization.

The patterning of nanoparticles represents a significant obstacle in the assembly of nanoscale materials and devices. In this report, cysteine residues were genetically engineered onto the virion surface of tobacco mosaic virus (TMV), providing attachment sites for fluorescent markers. To pattern these viruses, labeled virions were partially disassembled to expose 5' end RNA sequences and hybridized to virus-specific probe DNA linked to electrodeposited chitosan. Electron microscopy and RNAase treatments confirmed the patterned assembly of the virus templates onto the chitosan surface. These findings demonstrate that TMV nanotemplates can be dimensionally assembled via nucleic acid hybridization.

Amino Acid Substitution↗

PubMed2004

Restorative proctocolectomy for ulcerative colitis complicated by colorectal cancer.

PURPOSE: Restorative proctocolectomy with ileal pouch-anal anastomosis is widely accepted as the procedure of choice for patients requiring surgery for chronic ulcerative colitis. The role of restorative proctocolectomy in the setting of chronic ulcerative colitis complicated by colorectal carcinoma is not clear. This study was undertaken to explore the clinical outcomes of chronic ulcerative colitis patients with coexisting colorectal carcinoma who underwent restorative proctocolectomy. METHODS: A total of 756 patients with chronic ulcerative colitis were followed prospectively after restorative proctocolectomy. Forty-five (5.9 percent) were found to have invasive carcinoma of the colon (n = 31) or rectum (n = 14). These patients were followed with special attention to cancer stage, adjuvant therapy, oncologic outcome, and functional results after restorative proctocolectomy. RESULTS: Twenty-one patients (45.6 percent) had staged surgery (colon, 14; rectum, 7). Twenty-seven patients received adjuvant chemotherapy (colon, 22; rectum, 5). Fourteen patients (51.8 percent) who received chemotherapy were not diverted during this treatment. Two node-positive rectal cancer patients had pelvic radiotherapy: one before restorative proctocolectomy and one after restorative proctocolectomy. Mean time to restoration of intestinal continuity among staged patients did not differ between cancer and noncancer patients. Six patients died of metastatic disease (colon, 3; rectum, 3). Five deaths occurred among patients with Stage III disease (colon, 3/13, 23.1 percent; rectum, 2/3, 66.7 percent). One patient with Stage I cancer at the time of restorative proctocolectomy died. Thirty-nine patients are alive without evidence of disease at a mean interval from surgery of 76.5 months. Thirty-six patients have functioning pelvic pouches. Bowel frequency, continence, and complication rates are similar among restorative proctocolectomy patients with and without cancer. CONCLUSIONS: Restorative proctocolectomy as a single or staged procedure is a viable therapeutic option for selected chronic ulcerative colitis patients with associated colorectal cancers. Prognosis seems to be related to cancer stage. Adjuvant chemotherapy can safely be given to nondiverted patients. Appropriate use of preoperative and postoperative radiotherapy for rectal cancer patients who are otherwise candidates for restorative proctocolectomy is unknown. Long-term functional results for cancer patients are similar to those seen in chronic ulcerative colitis patients without cancer.

Adult↗

PubMed2003

Long-term results of salvage surgery for septic complications after restorative proctocolectomy: does fecal diversion improve outcome?

PURPOSE: Septic complications related to the ileal pouch-anal anastomosis after restorative proctocolectomy have been reported in up to 16 percent of patients in major series. Management strategies are not well established. The aim of this study was to evaluate the results of salvage surgery and to assess the impact diversion had on the outcome. METHODS: Patients who developed ileal pouch-anal anastomosis-related septic complications after restorative proctocolectomy were identified from a prospectively maintained database. Surgical procedures and follow-up data were obtained at the time of hospital and office visits. Successful salvage was defined as the absence of clinical evidence of fistula, sinus, or abscess at least three months after salvage surgery or closure of ileostomy. RESULTS: Fifty-one patients with ileal pouch-anal anastomosis-related sepsis were identified. All patients had sinus or fistulous tracts from pouch-anal anastomoses. Eighty-nine salvage procedures were performed among these 51 patients (range, 1-4 procedures per patient). Forty-eight transanal anastomotic revisions were performed in nondiverted patients. Thirty-seven transanal revisions and four abdominoperineal revisions were performed in diverted patients. At a median follow-up of 65.2 (range, 3 to 166) months after salvage surgery or closure of the diverting stoma, 21 patients (41 percent) had complete resolution of their septic problems. Bowel frequency and continence for these patients were similar to patients who had not had ileal pouch-anal anastomotic problems. Eleven (29.7 percent) of 37 transanal procedures with diversion succeeded, whereas 10 (20.8 percent) of 48 nondiverted procedures succeeded. This difference was not significant (11/37 vs. 10/48; P = 0.448). None of the four abdominoperineal revisions succeeded. Of 51 patients, 34 (66.7 percent) retained their pouches and 21 (41.2 percent) were successfully revised. Seventeen patients (33.3 percent) had pouch excision. Five (9.8 percent) had persistent fistulas and remained diverted, and 8 (15.7 percent) had persistent fistulas and were not diverted. Thus, pouch function was retained in 29 patients (56.9 percent). CONCLUSIONS: This study shows that anastomotic failure after restorative proctocolectomy is associated with a high rate of pouch failure. Ileal pouch-anal anastomosis-related fistula or sinus warrants an aggressive surgical approach in selected, highly motivated patients because acceptable functional results are possible. Multiple procedures may often be necessary to achieve complete healing. Successful repair can be achieved after one or more unsuccessful attempts. Repeat procedures can be performed safely without adversely affecting ultimate outcome.

Abscess↗

PubMed2002

Early postoperative small-bowel obstruction: a prospective evaluation in 242 consecutive abdominal operations.

PURPOSE: Early postoperative small-bowel obstruction is a common but poorly defined complication of abdominal surgery. This prospective cohort study was undertaken to examine a reproducible definition of early postoperative small-bowel obstruction, determine its incidence, evaluate potential risk factors for its development, and delineate management strategies. METHODS: Two hundred twenty-five patients undergoing 242 consecutive abdominal operations during a 9-month period were prospectively evaluated from the time of admission until Postoperative Day 30. Early postoperative small-bowel obstruction was present if, within 30 days of surgery, all of the following criteria were met after the return of intestinal function: development of crampy abdominal pain, vomiting, and radiographic findings consistent with intestinal obstruction. Patients with early postoperative small-bowel obstruction were followed up until discharge or reexploration. All patients with early postoperative small-bowel obstruction were initially treated with nasogastric decompression. RESULTS: Two hundred forty-two abdominal procedures were performed on 119 males and 123 females aged 13 to 98 (mean, 51) years. Ulcerative colitis (n = 70), malignancy (n = 59), and Crohn's disease (n = 41) were the most common diagnoses. One hundred nineteen patients (49.2 percent) had undergone previous laparotomy, and 45 patients (18.6 percent) had previously been diagnosed with intestinal obstruction. Early postoperative small-bowel obstruction occurred in 23 cases (9.5 percent). Patients with and without early postoperative small-bowel obstruction were similar with respect to diagnosis, preoperative immunosuppression, previous laparotomy or obstruction, surgery performed, and time to return of intestinal function. Twenty episodes (87 percent) resolved with nasogastric decompression alone; all but one resolved within six days or less. Three patients (13 percent) required relaparotomy; one required small-bowel resection. Two of three patients whose symptoms did not resolve with six days of nasogastric decompression required reexploration. There were no deaths and no major morbidity. CONCLUSIONS: Early postoperative small-bowel obstruction, defined by an objective data set, was observed in 9.5 percent of cases. No independent risk factors predisposing to early postoperative small-bowel obstruction were identified. Early postoperative small-bowel obstruction was safely and effectively managed by nasogastric decompression in the majority of cases, with low morbidity and no mortality. In general, reexploration should be reserved for those patients whose symptoms do not resolve within six days of nasogastric decompression.

Abdomen↗