Depth profile of free volume in a mixture and copolymers of poly(N-vinyl-pyrrolidone) and poly(ethylene glycol) studied by positron annihilation spectroscopy.

Effect of hydrogen bonding on the depth profile of the free-volume in a mixture (weight ratio of 65:35) of poly(N-vinyl-pyrrolidone) (PVP) and poly(ethylene glycol) (PEG) and the copolymers of vinyl pyrrolidone with poly(ethylene glycol) diacrylate (PVP-PEGDA) and monomethacrylate (PVP-PEGMMA) was studied using positron annihilation spectroscopy. Doppler broadening energy spectra of annihilation radiation and positron annihilation lifetime were measured as a function of positron incident energy (0-30 keV). Significant variations of the free-volume depth profile in terms of the S parameter, ortho-positronium lifetime, intensity, and lifetime distribution are observed as a result of the hydrogen-bonding replacement of covalent bonds. The polymer mixture with hydrogen bonding through two sides of PEG short chains has a larger free volume and a wider distribution than the comb-structured PVP-PEGMMA and the network structured PVP-PEGDA. A longer ortho-positronium lifetime is observed near the surface than in the bulk. This is interpreted in terms of surface effect, free volume, and hydrogen bonding for drug delivery applications of polymeric materials.

Fluidics cube for biosensor miniaturization.

To create a small, portable, fully automated biosensor, a compact means of fluid handling is required. We designed, manufactured, and tested a "fluidics cube" for such a purpose. This cube, made of thermoplastic, contains reservoirs and channels for liquid samples and reagents and operates without the use of any internal valves or meters; it is a passive fluid circuit that relies on pressure relief vents to control fluid movement. We demonstrate the ability of pressure relief vents to control fluid movement and show how to simply manufacture or modify the cube. Combined with the planar array biosensor developed at the Naval Research Laboratory, it brings us one step closer to realizing our goal of a handheld biosensor capable of analyzing multiple samples for multiple analytes.

High-resolution finite element models with tissue strength asymmetry accurately predict failure of trabecular bone.

The ability to predict trabecular failure using microstructure-based computational models would greatly facilitate study of trabecular structure-function relations, multiaxial strength, and tissue remodeling. We hypothesized that high-resolution finite element models of trabecular bone that include cortical-like strength asymmetry at the tissue level, could predict apparent level failure of trabecular bone for multiple loading modes. A bilinear constitutive model with asymmetric tissue yield strains in tension and compression was applied to simulate failure in high-resolution finite element models of seven bovine tibial specimens. Tissue modulus was reduced by 95% when tissue principal strains exceeded the tissue yield strains. Linear models were first calibrated for effective tissue modulus against specimen-specific experimental measures of apparent modulus, producing effective tissue moduli of (mean+/-S.D.) 18.7+/-3.4GPa. Next, a parameter study was performed on a single specimen to estimate the tissue level tensile and compressive yield strains. These values, 0.60% strain in tension and 1.01% strain in compression, were then used in non-linear analyses of all seven specimens to predict failure for apparent tensile, compressive, and shear loading. When compared to apparent yield properties previously measured for the same type of bone, the model predictions of both the stresses and strains at failure were not statistically different for any loading case (p>0.15). Use of symmetric tissue strengths could not match the experimental data. These findings establish that, once effective tissue modulus is calibrated and uniform but asymmetric tissue failure strains are used, the resulting models can capture the apparent strength behavior to an outstanding level of accuracy. As such, these computational models have reached a level of fidelity that qualifies them as surrogates for destructive mechanical testing of real specimens.

Array biosensor for detection of biohazards.

A fluorescence-based biosensor has been developed for simultaneous analysis of multiple samples for multiple biohazardous agents. A patterned array of antibodies immobilized on the surface of a planar waveguide is used to capture antigen present in samples; bound analyte is then quantified by means of fluorescent tracer antibodies. Upon excitation of the fluorophore by a small diode laser, a CCD camera detects the pattern of fluorescent antibody:antigen complexes on the waveguide surface. Image analysis software correlates the position of fluorescent signals with the identity of the analyte. This array biosensor has been used to detect toxins, toxoids, and killed or non-pathogenic (vaccine) strains of pathogenic bacteria. Limits of detection in the mid-ng/ml range (toxins and toxoids) and in the 10(3)-10(6) cfu/ml range (bacterial analytes) were achieved with a facile 14-min off-line assay. In addition, a fluidics and imaging system has been developed which allows automated detection of staphylococcal enterotoxin B (SEB) in the low ng/ml range.

Modeling of the drug delivery from a hydrophilic transdermal therapeutic system across polymer membrane.

A mathematical simulation is presented which describes the in vitro drug delivery kinetics from hydrophilic adhesive water-soluble poly-N-vinylpyrrolidone (PVP)-polyethylene glycol (PEG) matrices of transdermal therapeutic systems (TTS) across skin-imitating hydrophobic Carbosil membranes. Propranolol is employed as the test drug. The contributions of the following physicochemical determinants to drug delivery rate control have been estimated: the drug diffusion coefficients both in the matrix and the membrane; the membrane-matrix drug partition coefficient: the drug concentration in the matrix and the membrane thickness. Drug transfer from the hydrophilic matrix across the membrane is shown to be controlled by the drug partitioning from the matrix into the membrane. The best correlation between simulation data and experimental results is obtained when the effect of membrane hydration is taken into consideration during in vitro drug release.

Array biosensor for simultaneous identification of bacterial, viral, and protein analytes.

The array biosensor was fabricated to analyze multiple samples simultaneously for multiple analytes. The sensor utilized a standard sandwich immunoassay format: Antigen-specific "capture" antibodies were immobilized in a patterned array on the surface of a planar waveguide and bound analyte was subsequently detected using fluorescent tracer antibodies. This study describes the analysis of 126 blind samples for the presence of three distinct classes of analytes. To address potential complications arising from using a mixture of tracer antibodies in the multianalyte assay, three single-analyte assays were run in parallel with a multianalyte assay. Mixtures of analytes were also assayed to demonstrate the sensor's ability to detect more than a single species at a time. The array sensor was capable of detecting viral, bacterial, and protein analytes using a facile 14-min assay with sensitivity levels approaching those of standard ELISA methods. Limits of detection for Bacillus globigii, MS2 bacteriophage, and staphylococcal enterotoxin B (SEB) were 10(5) cfu/mL, 10(7) pfu/mL, and 10 ng/mL, respectively. The array biosensor also analyzed multiple samples simultaneously and detected mixtures of the different types of analytes in the multianalyte format.

An array immunosensor for simultaneous detection of clinical analytes.

A fluorescence-based immunosensor has been developed for simultaneous analysis of multiple samples. A patterned array of recognition elements immobilized on the surface of a planar waveguide is used to "capture" analyte present in samples; bound analyte is then quantified by means of fluorescent detector molecules. Upon excitation of the fluorescent label by a small diode laser, a CCD camera detects the pattern of fluorescent antigen:antibody complexes on the sensor surface. Image analysis software correlates the position of fluorescent signals with the identity of the analyte. This immunosensor was used to detect physiologically relevant concentrations of staphylococcal enterotoxin B (SEB), F1 antigen from Yersinia pestis, and D-dimer, a marker of sepsis and thrombotic disorders, in spiked clinical samples.

Array biosensor: optical and fluidics systems.

Optical and fluidics systems have been developed as central components for an automated array biosensor. Disposable planar waveguides are patterned with immobilized capture antibodies using a physically isolated patterning (PIP) method. The PIP method enables simultaneous deposition of several antibodies and completely circumvents cross-immobilization problems encountered with other array deposition processes. A multi-channel fluidics cell allows numerous assays to be performed on the patterned waveguide. The sensing arrays are optically interrogated using a diode laser with a tailored output to optimize coupling to and maximize excitation uniformity within the waveguide. A patterned cladding is employed to optically isolate the waveguide from perturbations induced by the permanently attached flow cells. Compact optics image the evanescently excited fluorescence onto a large area, cooled CCD array. The image data is processed and automated signal analysis corrects for local background and noise variations.

Modeling of percutaneous drug transport in vitro using skin-imitating Carbosil membrane.

A comparative study of the barrier function of human skin and polydimethylsiloxane-polycarbonate block copolymer Carbosil membrane was performed in vitro using 14 drugs spanning a wide range of structures and therapeutic classes. The drug permeability coefficients across the skin and the Carbosil membrane wee examined as an explicit dependence of permeant molecular weight, melting point, solubility in aqueous solution in aqueous solution and octanol-water partition coefficient. Owing to heterophase and heteropolar structure, Carbosil membranes and human skin epidermis share a common solubility-diffusion mechanism of drug transport. This synthetic membrane is shown to provide a mechanistically substantiated model for percutaneous drug absorption. Carbosil membrane can be used both foe quantitative prediction for transdermal drug delivery rate and as a skin-imitating standard membrane in the course of in vitro drug delivery kinetics evaluation.

Histopathology of human coronary atherosclerosis by quantifying its chemical composition with Raman spectroscopy.

BACKGROUND: Lesion composition, rather than size or volume, determines whether an atherosclerotic plaque will progress, regress, or rupture, but current techniques cannot provide precise quantitative information about lesion composition. We have developed a technique to assess the pathological state of human coronary artery samples by quantifying their chemical composition with near-infrared Raman spectroscopy. METHODS AND RESULTS: Coronary artery samples (n=165) obtained from explanted recipient hearts were illuminated with 830-nm infrared light. Raman spectra were collected from the tissue and processed to quantify the relative weights of cholesterol, cholesterol esters, triglycerides and phospholipids, and calcium salts in the examined artery location. The artery locations were then classified by a pathologist and grouped as either nonatherosclerotic tissue, noncalcified plaque, or calcified plaque. Nonatherosclerotic tissue, which included normal artery and intimal fibroplasia, contained an average of approximately 4+/-3% cholesterol, whereas noncalcified plaques had approximately 26+/-10% and calcified plaques approximately 19+/-10% cholesterol in the noncalcified regions. The average relative weight of calcium salts was 1+/-2% in noncalcified plaques and 41+/-21% in calcified plaques. To make this quantitative chemical information clinically useful, we developed a diagnostic algorithm, based on a first set of 97 samples, that demonstrated a strong correlation of the relative weights of cholesterol and calcium salts with histological diagnoses of the same locations. This algorithm was then prospectively tested on a second set of 68 samples. The algorithm correctly classified 64 of these new samples, thus demonstrating the accuracy and robustness of the method. CONCLUSIONS: The pathological state of a given human coronary artery may be assessed by quantifying its chemical composition, which can be done rapidly with Raman spectroscopic techniques. When Raman spectra are obtained clinically via optical fibers, Raman spectroscopy may be useful in monitoring the progression and regression of atherosclerosis, predicting plaque rupture, and selecting proper therapeutic intervention.

Open-label phase I study of combination therapy with zidovudine and interferon-beta in patients with AIDS-related Kaposi's sarcoma: AIDS Clinical Trials Group Protocol 057.

The aim of this study was to identify a safe and tolerable dose of recombinant interferon-beta (IFN-beta) used in conjunction with a fixed dose of zidovudine in patients with early-stage, good-prognosis AIDS-related Kaposi's sarcoma. We conducted a phase I, dose-escalation controlled trial of 22.5, 45 of 90 million units of IFN-beta given by daily subcutaneous injection with 500 mg per day of oral zidovudine. At the time of this study, this was standard of care for HIV infection. Patients were sequentially enrolled at three medical centers. Tumor response, drug tolerance, antiviral studies and CD4 changes were assessed. Four patients were enrolled at each dose level, and escalation proceeded when at least four patients had tolerated two weeks of therapy without dose-limiting toxicity. ACTG Kaposi's sarcoma tumor response criteria were used to assess response. Fifteen patients were enrolled. The combination of IFN-beta and zidovudine was well tolerated, and the dose-limiting toxicities were local skin necrosis and systemic symptoms. Despite generally good prognostic characteristics, only two patients achieved a clinical complete response and three addition patients had stable disease for a prolonged period of time (range 24-44 weeks). There was no correlation between baseline CD4 cell counts and tumor response, nor between the antiviral effect of IFN-beta as measured by decreases in immune-complex dissociated p24 antigen and tumor response. Higher doses of IFN-beta did not result in more tumor responses or in greater antiviral activity. The maximum tolerated dose of IFN-beta in combination with 500 mg per day of zidovudine was 45 million units by subcutaneous injection per day. IFN-beta is well tolerated in patients with AIDS-related Kaposi's sarcoma when used in conjunction with zidovudine. However, the antitumor response rate in good-prognosis patients is low. Further studies of this agent should be in the context of four-drug antiretroviral regimens where viral suppression is greatest and any antitumor activity of IFN-beta may be observed.

Oncology nurses and chronic compounded grief.

Oncology nurses have repeated confrontations with death. To suggest that oncology nurses have emotional needs in response to the demands of caring for cancer patients has not been popular even among the nurses themselves. Indeed, there is little written in the professional literature describing the grief experiences of nurses caring for dying patients. To study the grief of oncology nurses, the Grief Experience Inventory (GEI), a multi-dimensional measure of grief that is sensitive to the longitudinal evolution of the process of bereavement, was selected. In addition, a demographic questionnaire to identify professional, personal, and supportive influences that might affect nurses' grief experiences was developed. Data were collected from June 1991 through May 1992, from a total of 50 professional nurses (termed Stayers and Leavers) on adult oncology units in a comprehensive cancer center and in an urban medical center. The findings indicated that both Stayers and Leavers are above the norms in despair, social isolation, and somatization. Implications for education and practice as well as suggestions for education and practice as well as suggestions for further research are discussed.

Weekly oral etoposide in patients with Kaposi's sarcoma associated with human immunodeficiency virus infection: a phase I multicenter trial of the AIDS Clinical Trials Group.

We conducted a Phase I trial to evaluate the safety, maximally tolerated dose (MTD), antitumor activity, and pharmacology of once-weekly oral etoposide in patients with Kaposi's sarcoma (KS) and AIDS. From September 1990 to October 1991, 27 eligible patients with biopsy-confirmed KS were treated at six etoposide dose levels, ranging from 150 to 400 mg weekly. Patients were treated until their tumor progressed or until unacceptable toxicity developed. On the first day of therapy, etoposide plasma concentrations were measured by high-performance liquid chromatography. The MTD was defined as the etoposide dose that induced reversible grade 3 toxicity in three of six patients during the first 4 weeks. Although dose-limiting toxicity was uncommon during the first 4 weeks of treatment (three of 27 patients), and the MTD was not reached, with longer treatment > 50% of patients developed dose-limiting toxicities, most commonly neutropenia. Responses were observed at all dosage levels (except 350 mg weekly), with partial tumor regression documented in nine (36%) of 25 evaluable patients. There was marked variability in etoposide area under the plasma concentration versus time curve, elimination half-time (t1/2), and urinary excretion. These pharmacokinetic features were not, however, associated with the presence of gastrointestinal symptoms, the severity of side effects, or tumor response. We conclude that weekly oral etoposide can be safely administered to patients with AIDS and KS. The observed antitumor effects over a wide range of doses support further studies with very low and minimally toxic etoposide doses, alone or in combination with other agents.

Lung scan evaluation of thrombolytic therapy for pulmonary embolism.

UNLABELLED: Data from three trials of thrombolytic therapy for pulmonary embolism (PE) were combined to assess the utility of perfusion lung scan defect scoring in predicting the response to thrombolytic therapy. METHODS: Pre- and post-therapy lung scans and duration of symptoms were available for a total of 221 patients, 167 were treated with various thrombolytic regimes and 54 were treated with heparin alone. RESULTS: Improvement in the lung scan defect score was correlated with larger initial defect score (r = 0.53), segmental appearance (r = 0.31) and shorter duration of symptoms (r = 0.20). There was no significant residual correlation between improvement and segmental appearance in a multiple regression analysis after accounting for initial defect score and duration of symptoms. Two lung scan scoring methods (segmental and anterior-posterior method) provided similar results with low interobserver variability (r = 0.90 for both methods). CONCLUSION: This study indicates that the baseline perfusion lung scan defect severity helps to predict the response to thrombolytic therapy.

Phase I AIDS Clinical Trials Group (075) study of adriamycin, bleomycin and vincristine chemotherapy with zidovudine in the treatment of AIDS-related Kaposi's sarcoma.

OBJECTIVE: To determine the toxicity and maximum tolerated dose of doxorubicin (adriamycin) in combination with fixed doses of bleomycin, vincristine (ABV) and zidovudine in patients with advanced AIDS-related Kaposi's sarcoma. PATIENTS AND METHODS: Twenty-six HIV-seropositive men with Kaposi's sarcoma were treated daily with 100 mg zidovudine orally every 4 h, along with combination chemotherapy using bleomycin 10 U/m2 and vincristine 1.4 mg/m2 (maximum, 2 mg) given intravenously in 2-week cycles. In addition, three successive cohorts of eight patients received escalating doses of doxorubicin each beginning with no doxorubicin (level I), doses of 10 mg/m2 (level II), and 15 mg/m2 (level III). RESULTS: The major dose-limiting toxicity experienced with the combination therapy was severe neutropenia in eight patients, four of whom received level III doxorubicin (15 mg/m2). Therefore, 10 mg/m2 of doxorubicin in combination with zidovudine and BV chemotherapy was defined as the maximum tolerated dose. Other dose-limiting toxicities included neuropathy (n = 2), cutaneous toxicity associated with bleomycin (n = 1), and diarrhea (n = 1). Seventeen patients (71%; 95% confidence interval, 46-85) experienced either partial (n = 13) or clinical complete remission (n = 4) to therapy after a median of five cycles (range, 2-9). CONCLUSION: The maximum tolerated dose of doxorubicin is 10 mg/m2 when given in combination with zidovudine and BV chemotherapy. Response rates observed with the combined antiretroviral and chemotherapy regimen are similar to those previously reported with ABV chemotherapy alone.

Fundamental dilemmas of the randomized clinical trial process: results of a survey of the 1,737 Eastern Cooperative Oncology Group investigators.

PURPOSE: We studied oncologists' attitudes and behavior with regard to their participation in randomized clinical trials. METHODS: We surveyed the 1,737 physician members of the Eastern Cooperative Oncology Group (ECOG) using the Physician Orientation Profile (POP), a self-administered mailed questionnaire. A response rate of 86% was achieved (1,485 of 1,737); each physician's actual patient accrual was recorded. RESULTS: All respondents indicated that they had a systematic pattern of patient preselection for entry onto trials beyond the formal inclusion/exclusion trial criteria. Eighty-nine percent stated that improving patient quality of life rather than prolonging survival was more personally satisfying. Sixty-two percent did not enter a single patient during the 12-month period following the survey, while 10% entered 80% of all patients during that time. Physicians overestimated their accrual rate by a factor of 6. Eighty-three percent defined randomization and adherence to trial protocol as a serious challenge to their ability to make individualized treatment decisions. CONCLUSION: This study raises questions regarding the following: (1) the perceived generalizability of trial findings, (2) the role of end points other than survival for clinical trials, (3) the consequences of physician overestimation of patient accrual, and (4) the impact of randomized trials on the behavior of clinicians. Further investigation into these critical issues will provide meaningful recommendations to enhance the future design, implementation, and conduct of randomized clinical trials in cancer.

Two trials of reduced bolus alteplase in the treatment of pulmonary embolism. An overview.

The Bolus Alteplase Pulmonary Embolism (BAPE) Group and a consortium of French investigators utilized essentially the same investigational protocol to test reduced dose bolus alteplase vs full dose 100 mg/2 h alteplase in the treatment of pulmonary embolism (PE). The principal hypothesis was that reduced dose bolus alteplase (n = 96) would result in fewer bleeding complications than full dose 100 mg of 2 h alteplase (n = 44) administered as a continuous infusion to hemodynamically stable patients with PE. To provide data on bolus alteplase's safety profile in a larger sample size than would have been feasible in either trial alone, we present an overview of the BAPE and French trials. There were no differences between the reduced dose bolus and full dose 2 h rt-PA groups with respect to bleeding complications. Therefore, the principal hypothesis of these two randomized controlled trials could not be confirmed. Efficacy was similar in the two treatment groups. Interpretation of the results will vary because the increased convenience and cost savings from using a reduced dose of bolus alteplase may be offset by a higher mortality rate. However, a trial that compared the mortality rates of the two treatment regimens would have required more than 800 patients.