Biomedical subjects

C Mauli Agrawal

Publications and source records attributed to C Mauli Agrawal.

At least 19 recordsLinked to original sources

PubMed2007

Preventing diabetic foot ulcer recurrence in high-risk patients: use of temperature monitoring as a self-assessment tool.

OBJECTIVE: The purpose of this study was to evaluate the effectiveness of a temperature monitoring instrument to reduce the incidence of foot ulcers in individuals with diabetes who have a high risk for lower extremity complications. RESEARCH DESIGN AND METHODS: In this physician-blinded, randomized, 15-month, multicenter trial, 173 subjects with a previous history of diabetic foot ulceration were assigned to standard therapy, structured foot examination, or enhanced therapy groups. Each group received therapeutic footwear, diabetic foot education, and regular foot care. Subjects in the structured foot examination group performed a structured foot inspection daily and recorded their findings in a logbook. If standard therapy or structured foot examinations identified any foot abnormalities, subjects were instructed to contact the study nurse immediately. Subjects in the enhanced therapy group used an infrared skin thermometer to measure temperatures on six foot sites each day. Temperature differences >4 degrees F (>2.2 degrees C) between left and right corresponding sites triggered patients to contact the study nurse and reduce activity until temperatures normalized. RESULTS: The enhanced therapy group had fewer foot ulcers than the standard therapy and structured foot examination groups (enhanced therapy 8.5 vs. standard therapy 29.3%, P = 0.0046 and enhanced therapy vs. structured foot examination 30.4%, P = 0.0029). Patients in the standard therapy and structured foot examination groups were 4.37 and 4.71 times more likely to develop ulcers than patients in the enhanced therapy group. CONCLUSIONS: Infrared temperature home monitoring, in serving as an "early warning sign," appears to be a simple and useful adjunct in the prevention of diabetic foot ulcerations.

Adult↗

PubMed2006

Coronary stents: a materials perspective.

The objective of this review is to describe the suitability of different biomaterials as coronary stents. This review focuses on the following topics: (1) different materials used for stents, (2) surface characteristics that influence stent-biology interactions, (3) the use of polymers in stents, and (4) drug-eluting stents, especially those that are commercially available.

Alloys↗

PubMed2006

Surface modification of functional self-assembled monolayers on 316L stainless steel via lipase catalysis.

Lipase catalyzed esterification of therapeutic drugs to functional self-assembled monolayers (SAMs) on 316L stainless steel (SS) after assembly has been demonstrated. SAMs of 16-mercaptohexadecanoic acid (-COOH SAM) and 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS, and lipase catalysis was used to attach therapeutic drugs, perphenazine and ibuprofen, respectively, on these SAMs. The reaction was carried out in toluene at 60 degrees C for 5 h using Novozyme-435 as the biocatalyst. The FTIR spectra after surface modification of -OH SAMs showed the presence of the C=O stretching bands at 1745 cm(-1), which was absent in the FTIR spectra of -OH SAMs. Similarly, the FTIR spectra after the reaction of the -COOH SAM with perphenazine showed two peaks in the carbonyl region, a peak at 1764 cm(-1), which is the representative peak for the C=O stretching for esters. The second peak at 1681 cm(-1) is assigned to the C=O stretching of the remaining unreacted terminal COOH. XPS spectra after lipase catalysis with ibuprofen showed a photoelectron peak evolving at 288.5 eV which arises from the carbon (C=O) of the carboxylic acid of the drug (ibuprofen). Similarly for -COOH SAMs, after esterifiation we see a small, photoelectron peak evolving at 286.5 eV which corresponds to the C in the methylene groups adjacent to the oxygen (C-O), which should evolve only after the esterification of perphenazine with the -COOH SAM. Thus, lipase catalysis provides an alternate synthetic methodology for surface modification of functional SAMs after assembly.

Catalysis↗

PubMed2006

Implantation of oxygen enhanced, three-dimensional microporous L-PLA polymers: a reproducible porcine model of chronic total coronary occlusion.

We have hypothesized that oxygen enhanced three-dimensional microporous poly-L-lactic acid (L-PLA) bioabsorbable polymer constructs could be implanted to produce a subacute occlusion in a porcine coronary artery, forming a thrombofibrotic occlusion containing microvascular channels. Chronic total occlusion (CTO) is increasingly prevalent in patients who present for percutaneous interventions. No reproducible animal coronary model simulating human CTOs has previously been developed. Swine coronary arteries were cannulated and a microporous L-PLA polymer pledget was advanced into a preselected segment of coronary. The coronary arteries were angiographically re-imaged at day 3, day 10, and day 28, to document the presence or absence of an occlusion. Histopathology was also performed at each time point to evaluate the lesion characteristics. A novel three-dimensional L-PLA microporous polymer construct, when implanted into porcine coronary arteries, reproducibly results in the development of a CTO at day 3. The histopathology in this porcine coronary model of CTO at day 28 closely mimics human coronary CTO, including the presence of microvascular channels and dense collagen and elastic tissue in the occlusion.

Absorbable Implants↗

PubMed2005

Correlating subjective and objective descriptors of ultra high molecular weight wear particles from total joint prostheses.

A total of 750 images of individual ultra-high molecular weight polyethylene (UHMWPE) particles isolated from periprosthetic failed hip, knee, and shoulder arthroplasties were extracted from archival scanning electron micrographs. Particle size and morphology was subsequently analyzed using computerized image analysis software utilizing five descriptors found in ASTM F1877-98, a standard for quantitative description of wear debris. An online survey application was developed to display particle images, and allowed ten respondents to classify particle morphologies according to commonly used terminology as fibers, flakes, or granules. Particles were categorized based on a simple majority of responses. All descriptors were evaluated using a one-way ANOVA and Tukey-Kramer test for all-pairs comparison among each class of particles. A logistic regression model using half of the particles included in the survey was then used to develop a mathematical scheme to predict whether a given particle should be classified as a fiber, flake, or granule based on its quantitative measurements. The validity of the model was then assessed using the other half of the survey particles and compared with human responses. Comparison of the quantitative measurements of isolated particles showed that the morphologies of each particle type classified by respondents were statistically different from one another (p<0.05). The average agreement between mathematical prediction and human respondents was 83.5% (standard error 0.16%). These data suggest that computerized descriptors can be feasibly correlated with subjective terminology, thus providing a basis for a common vocabulary for particle description which can be translated into quantitative dimensions.

Joint Prosthesis↗

PubMed2005

Wear and biomechanical characteristics of a novel shear-reducing insole with implications for high-risk persons with diabetes.

OBJECTIVE: This study was designed to measure pressure and shear reduction of a novel insole design. METHODS: We compared three multilayer viscoelastic insoles to a novel insole design (Glide-Soft, Xilas Medical, Inc., San Antonio, TX). The bottom pad of each insole was fabricated from firm-density Plastazote [Apex Foot Products (now Aetrex), South Hackensack, NJ] with an upper of Plastazote, ethyl vinyl acetate, or PORON (Langer Biomechanics Group, Inc., Deer Park, NY). The GlideSoft design used the same materials with two intervening thin sheets of a low friction material. We measured foot pressures, shear, and material stiffness prospectively as the insoles aged during daily usage in 30 healthy adults. We used the F-Scan (Tekscan, Inc., Boston, MA) to determine in-shoe foot pressures and the Automated Stress-relaxation Creep Indenter System (Xilas Medical) to measure material stiffness. To evaluate shear force, the insole was placed on the slide assembly of a custom-designed shear tester equipped with a reciprocating mechanism and force transducers. RESULTS: The GlideSoft exhibited 57% less peak shear force than the standard insole (P < 0.05) in laboratory testing under simulated conditions. Ethyl vinyl acetate had higher compressive stiffness values than Plastazote and PORON at all test intervals (P < 0.05). There were no statistical differences between any of the insoles for peak in-shoe pressure measurements (P > 0.05). CONCLUSIONS: The GlideSoft design demonstrated a significant reduction in shear while maintaining equivalent pressure reduction compared with standard insole designs with three different material combinations for up to 320,000 steps.

Diabetic Foot↗

PubMed2005

Pullout forces of sutures in muscle lacerations.

The purpose of this study was to determine if complex suture techniques had higher pullout forces from muscle tissue than conventional stitching. Using transected cadaver muscle bellies, we performed repairs with various suture techniques and measured pullout forces. Epimyseal repair with conventional stitches (Kessler, figure eight, horizontal mattress) was inferior to complex stitches (modified Mason-Allen, perimeter). The combined complex stitches (perimeter and Mason-Allen) were strongest. Conventional stitches failed longitudinally through the muscle, whereas complex stitches failed transversely across the muscle. The complex combination of perimeter and Mason-Allen stitches had superior pullout resistance compared to conventional stitches.

Biomechanical Phenomena↗

PubMed2004

Diffusion in musculoskeletal tissue engineering scaffolds: design issues related to porosity, permeability, architecture, and nutrient mixing.

The field of tissue engineering continues to advance with the discovery of new biomaterials, growth factors and scaffold fabrication techniques. However, for the ultimate success of a tissue engineered construct the issue of nutrient transport to the scaffold interior needs to be addressed. Often, the requirements for adequate nutrient supply are at odds with other scaffold design parameters such as mechanical properties as well as scaffold fabrication techniques, leading to incongruities in finding optimal solutions. The goal of this review article is to provide an overview of the various engineering design factors that promote movement of nutrients, waste and other biomolecules in scaffolds for musculoskeletal tissue engineering applications. The importance of diffusion in scaffolds and how it is influenced by porosity, permeability, architecture, and nutrient mixing has been emphasized. Methods for measuring porosity and permeability have also been outlined. The different types of biomaterials used, scaffold fabrication techniques implemented and the pore sizes/porosities obtained over the past 5 years have also been addressed.

Animals↗

PubMed2004

Interaction of hydroxyapatite-titanium at elevated temperature in vacuum environment.

In this study, the interaction between hydroxyapatite (HA) and titanium (Ti) at elevated temperature in vacuum environment was investigated. The 80 wt% HA-20 wt% Ti powder mixtures and 90 wt% HA-10 wt% Ti powder mixtures were dry pressed and heat-treated at 1100 degrees C in vacuum environment. HA powders and the commercially pure Ti powders were used as controls. The heat-treated samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscope (SEM) and energy disperse spectra. XRD and SEM indicated densification of metallic Ti specimens during the in-vacuum heat treatment. Heat treatment of HA specimens in vacuum resulted in the loss of hydroxyl groups as well the formation of a secondary beta-tricalcium phosphate phase. Metallic Ti was not observed in the in-vacuum heat-treated HA-Ti specimens. However, alpha-tricalcium phosphate, tetracalcium phosphate and calcium titanium oxide were observed for the in-vacuum heat-treated HA-Ti specimens. It was concluded that the in-vacuum heat-treatment process completely converted the metal-ceramics composites to ceramic composites.

Coated Materials, Biocompatible↗

PubMed2004

Home monitoring of foot skin temperatures to prevent ulceration.

OBJECTIVE: To evaluate the effectiveness of at-home infrared temperature monitoring as a preventative tool in individuals at high risk for diabetes-related lower-extremity ulceration and amputation. RESEARCH DESIGN AND METHODS: Eighty-five patients who fit diabetic foot risk category 2 or 3 (neuropathy and foot deformity or previous history of ulceration or partial foot amputation) were randomized into a standard therapy group (n = 41) or an enhanced therapy group (n = 44). Standard therapy consisted of therapeutic footwear, diabetic foot education, and regular foot evaluation by a podiatrist. Enhanced therapy included the addition of a handheld infrared skin thermometer to measure temperatures on the sole of the foot in the morning and evening. Elevated temperatures (>4 degrees F compared with the opposite foot) were considered to be "at risk" of ulceration due to inflammation at the site of measurement. When foot temperatures were elevated, subjects were instructed to reduce their activity and contact the study nurse. Study subjects were followed for 6 months. RESULTS: The enhanced therapy group had significantly fewer diabetic foot complications (enhanced therapy group 2% vs. standard therapy group 20%, P = 0.01, odds ratio 10.3, 95% CI 1.2-85.3). There were seven ulcers and two Charcot fractures among standard therapy patients and one ulcer in the enhanced therapy group. CONCLUSIONS: These results suggest that at-home patient self-monitoring with daily foot temperatures may be an effective adjunctive tool to prevent foot complications in individuals at high risk for lower-extremity ulceration and amputation.

Diabetes Complications↗

PubMed2003

Efficacy of glow discharge gas plasma treatment as a surface modification process for three-dimensional poly (D,L-lactide) scaffolds.

Gas plasma surface modification of three-dimensional poly (D,L-lactide) scaffolds fabricated by a novel vibrating particle fabrication technique was demonstrated to enhance cell adhesion, proliferation, and differentiation over 10 days in culture using human embryonic palatal mesenchyme cells. Characterization of corresponding two-dimensional treated surfaces revealed decreased contact angle measurements of 54.2 +/- 0.6 degrees for treated surfaces compared to 72.3 +/- 0.7 degrees for control surfaces (p < 0.05). SEM of treated surfaces revealed increased surface roughness combined with marked pitting and erosion. This may contribute to increased cell adhesion. WST-1 cell proliferation assay measurements as an index of cell numbers revealed a statistically significant increase in proliferation activity on treated surfaces on days 1 and 4 compared with controls. There was a fivefold increase in WST-1 activity for both control and treated groups over 10 days. Confocal laser micrographs revealed increased cell numbers on treated specimens throughout all layers of the scaffold, indicating that the glow discharge process enhanced cell proliferation throughout the entire scaffold architecture. Scanning electron micrographs demonstrated increased cell adhesion for treated specimens at the polymer surface most evident after days 1 and 4 of culture. Alkaline phosphatase (ALP)-specific activity peaked by day 7 for control and treated surfaces, indicating cellular differentiation. There was a trend for increased protein production on the treated specimens compared with controls at the initial time points although the differences were not statistically significant. These results demonstrated that gas plasma surface modification enhances osteoblast-like cell function in a three-dimensional scaffold model.

Absorbable Implants↗

PubMed2003

Effect of post-deposition heating temperature and the presence of water vapor during heat treatment on crystallinity of calcium phosphate coatings.

In this study, radiofrequency sputtered calcium phosphate (CaP) coatings were evaluated after 1h post-deposition heat treatment at either 350 degrees C, 400 degrees C, 450 degrees C, 500 degrees C or 600 degrees C in the presence or absence of water vapor. X-ray diffraction analyses indicated the as-sputtered coatings to be amorphous. With different post-deposition heat treatments used, in this study, crystallinity of CaP coatings was observed to be in the range of 0-68%. The 400 degrees C and 450 degrees C heat-treated CaP coatings in the absence of water vapor were poorly crystalline, exhibiting a crystallinity of 2+/-1%. In comparison to heat treatments at 450 degrees C in the absence of water vapor, the presence of water vapor at 450 degrees C heat treatment resulted in a significant increase in coating crystallinity. However, this effect was not observed at higher temperatures. A coating crystallinity of 60-68% was observed for coatings heat treated at 450 degrees C in the presence of water vapor, and at 500 degrees C and 600 degrees C in the presence or absence of water vapor. In addition, increases in the degree of coating crystallinity were observed to be consistent with the increasing number of PO(4) peaks observed as a result of different post-deposition heat treatments. It was concluded that the presence of water vapor at 450 degrees C post-deposition heat treatment significantly affect the crystallinity of CaP coatings, whereas an increase to temperature higher than 450 degrees C and in the presence of water vapor has no significant effect on crystallinity.

Calcium Phosphates↗

PubMed2003

Age-related changes of noncalcified collagen in human cortical bone.

It is well known that osteoid, which contains a noncalcified collagenous matrix, is formed during the initial stage of bone formation during the bone remodeling process. Thus, synthesis of defective collagen molecules in osteoid may cause abnormal bone formation, thereby leading to changes in bone quality. The objective of this study was to investigate age-related changes in noncalcified collagen molecules in osteoid and its likely effects on the mechanical integrity of human cortical bone. Thirty human cadaveric femurs were divided into three age groups: young adults, middle age, and the elderly, respectively. A novel high performance liquid chromatography approach was employed to quantify the denaturation of noncalcified collagenous matrix in addition to mechanical tests of bone. Bulk concentrations of both enzymatic and nonenzymatic collagen cross links in bone also were measured. Moreover, the number of newly formed osteons per unit area and the bony area fraction of these osteons were estimated. The results of this study indicate that denaturation of the noncalcified collagenous matrix in bone increases with increasing age. In addition, such collagen denaturation in osteoid exhibited a correlation with nonenzymatic collagen cross links as well as the strength and toughness of bone. These results suggest that age-related changes in the noncalcified collagenous matrix induced by bone remodeling may have likely effects on bone quality.

Adult↗

PubMed2002

Collagen and bone viscoelasticity: a dynamic mechanical analysis.

The purpose of this study was to explore the effects of changes in Type I collagen on the viscoelasticity of bone. Bone coupons were heated at either 100 or 200 degrees C to induce the thermal denaturation of Type I collagen. Half of these specimens were rehydrated after heat treatment; the other half were tested in a dry condition. The degree of denatured collagen (DC%) was analyzed by a selective digestion technique with the use of alpha-chymotrypsin. Isothermal (37 degrees C) and variable temperature tests (scans from 35 to 200 degrees C) were performed with the use of a dynamic mechanical analyzer to evaluate changes in bone viscoelastic properties as a function of collagen damage, specifically, changes in the loss factor (tan delta) and storage modulus (E') were assessed. Significant collagen denaturation occurred only when bone was heated at 200 degrees C irrespective of the hydration condition. Also, DC% did not show a significant effect on tan delta. However, higher values of tan delta were observed in wet samples compared to dry specimens. The temperature-scan tests revealed that the hydration condition, but not DC%, significantly affected the behavior of tan delta. However, E' was not strongly influenced either by DC% or by water content. These results suggest that at a constant frequency the denaturation of collagen triple-helical molecules may have few effects on the viscoelasticity of bone, but moisture may play a prominent role in determining this property.

Biomechanical Phenomena↗

PubMed2002

Standardized analysis of UHMWPE wear particles from failed total joint arthroplasties.

Periprosthetic tissue obtained at revision surgery from eight total hip replacement cases was hydrolyzed, and polyethylene debris particles were isolated from each case. Individual particles were analyzed by scanning electron microscopy (SEM) and computerized image analysis in accordance with ASTM F1877-98, a standard for quantitative description of wear debris. For comparison, periprosthetic tissues from eight total knee revision and four total shoulder revision cases were processed and analyzed with identical methods. A total of 2599 hip, 4345 knee, and 1200 shoulder particles were analyzed. The morphologies of the isolated polyethylene particles from the total hip specimens were distinctly different from the total knee and total shoulder particles. The mean equivalent circle diameter (ECD) for hip particles was 0.694 microm +/- 0.005; knee particles measured 1.190 microm +/-0.009; and shoulder particles 1.183 microm +/- 0.017. The ECD was significantly different between hip particles and those from the shoulder and knee. The mean aspect ratio (AR) for the hip particles was 1.626 +/- 0.015, compared to the knee particles at 1.935 +/- 0.015 and shoulder particles at 2.082 +/- 0.033. The AR was statistically different among all three groups. Other descriptors from the ASTM standard, elongation (E), form factor (FF), and roundness (R) were all significantly different among the three groups of joints. This study demonstrates the utility of ASTM F1877-98 in differentiating wear debris particles from different sources.

Adult↗

PubMed2002

Age-related changes in the collagen network and toughness of bone.

The hypothesis of this study is that the mechanical integrity of the collagen network in bone deteriorates with age, and such adverse changes correlate with the decreased toughness of aged bone. To test the hypothesis, 30 human cadaveric femurs from donors ranging from 19 to 89 years of age were tested to determine the age-related changes in the mechanical properties of demineralized bone and fresh bone samples. Along with bone porosity, bone density, and weight fractions of the mineral and organic phases, collagen denaturation and concentrations of collagen cross-links (HP, hydroxylysylpyridinoline; LP, lysylpyridinoline; PE, pentosidine) were determined for these bone specimens as a function age. Analysis of variance (ANOVA) showed that age-dependent changes were reflected in the decreased strength, work to fracture, and fracture toughness of bone; in the decreased strength, elastic modulus, and work to fracture of the collagen network; as well as in the increased concentration of pentosidine (a marker of nonenzymatic glycation) and increased bone porosity. Regression analyses of the measured parameters showed that the age-related decrease in work to fracture of bone (especially its postyield portion) correlated significantly with deterioration in the mechanical integrity of the collagen network. The results of this study indicate that the adverse changes in the collagen network occur as people age and such changes may lead to the decreased toughness of bone. Also, the results suggest that nonenzymatic glycation may be an important contributing factor causing changes in collagen and, consequently, leading to the age-related deterioration of bone quality.

Adult↗

PubMed2001

Comparison of UHMWPE particles in synovial fluid and tissues from failed THA.

The size and morphology of ultra high molecular weight polyethylene (UHMWPE) wear particles isolated from synovial fluid and periprosthetic tissues from three failed total hip arthroplasties were evaluated. Hip capsule, femoral canal tissue, and synovial fluid were collected at the time of revision surgery. The polyethylene wear particles were isolated and then imaged using a scanning electron microscope. The size and morphology of the particles were quantified using an image analysis protocol. Five shape descriptors were defined for each particle: equivalent circle diameter (ECD, a measure of size having units of length), aspect ratio (AR), elongation (E), roundness (R), and form factor (FF). The size and shape of the polyethylene particles differed depending on the source. Femoral tissue particles had the lowest equivalent circle diameter (0.697 +/- 0.009 mm), aspect ratio (1.577 +/- 0.016), and elongation (1.912 +/- 0.030), but the highest values for roundness (0.715 +/- 0.005) and form factor (0.874 +/- 0.003). Hip capsule particles had the highest equivalent circle diameter (0.914 +/- 0.019 mm), aspect ratio (1.764 +/- 0.025), and elongation (2.488 +/- 0.053), but the lowest values for roundness (0.642 +/- 0.006) and form factor (0.803 +/- 0.005). The size and shape descriptors for synovial fluid particles (equivalent circle diameter: 0.763 +/- 0.012 mm; aspect ratio: 1.700 +/- 0.029; elongation: 2.212 +/- 0.054; roundness: 0.681 +/- 0.006; and form factor: 0.841 +/- 0.004) were intermediate among the femoral tissue and hip capsule particles. These data suggest that larger particles may become lodged in the hip capsule, while smaller particles may migrate to more distant tissues and subsequently cause aseptic loosening and osteolysis.

Aged↗

PubMedDate not supplied

Angiogenic bFGF expression from gas-plasma treated scaffolds.

PURPOSE: In vivo experiments indicate that gas-plasma-treated D,L-polylactide polymers expressing basic fibroblast growth factor (bFGF) exhibit enhanced angiogenesis. bFGF is not a single entity, but it is instead a family of isoforms. Consequently, we sought to determine which bFGF isoforms and levels initiate angiogenesis in nude mice peritoneums. METHODS: Cytoplasmic and nuclear bFGF were characterized for nude mice peritoneums incubated with nontreated scaffolds containing HAEC (CW), its respective polymer-only scaffolds (Cp) and gas-plasma treated scaffolds with HAEC (TW) and without cells (Tp). NuPAGE electrophoresis and WesternBreeze Chemiluminescent kits were used to analyze relative bFGF densities and molecular weights. VEGF was quantified using ImageJ. RESULTS: bFGF bands were located at molecular weights of 24, 48, 58, 72 and 80 kDa, depending on whether they were from cytoplasms or nuclei. At 12, 24 and 72 days, 58-kDa bFGF bands were observed from nuclei of TW and Tp, 80-kDa bFGF bands were only observed in cytoplasmic fractions < or = 24 days. Total cytoplasmic and nuclear bFGF intensities increased from 12 to 24 days, then declined by 72 days. CONCLUSIONS: (1) Gas-plasma treated scaffolds up-regulate bFGF isoforms. (2) bFGF was expressed in the nuclei; however, 80-kDa bFGF was seen only in cytoplasms.

Animals↗