Laser fabrication and spectroscopy of organic nanoparticles.

In working with nanoparticles, researchers still face two fundamental challenges: how to fabricate the nanoparticles with controlled size and shape and how to characterize them. In this Account, we describe recent advances in laser technology both for the synthesis of organic nanoparticles and for their analysis by single nanoparticle spectroscopy. Laser ablation of organic microcrystalline powders in a poor solvent has opened new horizons for the synthesis of nanoparticles because the powder sample is converted directly into a stable colloidal solution without additives and chemicals. By tuning laser wavelength, pulse width, laser fluence, and total shot number, we could control the size and phase of the nanoparticles. For example, we describe nanoparticle formation of quinacridone, a well-known red pigment, in water. By modifying the length of time that the sample is excited by the laser, we could control the particle size (30-120 nm) for nanosecond excitation down to 13 nm for femtosecond irradiation. We prepared beta- and gamma-phase nanoparticles from the microcrystal with beta-phase by changing laser wavelength and fluence. We present further results from nanoparticles produced from several dyes, C(60), and an anticancer drug. All the prepared colloidal solutions were transparent and highly dispersive. Such materials could be used for nanoscale device development and for biomedical and environmental applications. We also demonstrated the utility of single nanoparticle spectroscopic analysis in the characterization of organic nanoparticles. The optical properties of these organic nanoparticles depend on their size within the range from a few tens to a few hundred nanometers. We observed perylene nanoscrystals using single-particle spectroscopy coupled with atomic force microscopy. Based on these experiments, we proposed empirical equations explaining their size-dependent fluorescence spectra. We attribute the size effect to the change in elastic properties of the nanocrystal. Based on the results for nanoparticles of polymers and other molecules with flexible conformations, we assert that size-dependent optical properties are common for organic nanoparticles. While "electronic confinement" explains the size-dependent properties of inorganic nanoparticles, we propose "structural confinement" as an analogous paradigm for organic nanoparticles.

[Staged surgical palliations for hypoplastic left heart syndrome with poor preoperative conditions].

A 2.8 kg-female newborn diagnosed as hypoplastic left heart syndrome was transferred to our hospital after resuscitation against systemic circulatory failure due to closure of the ductus arteriosus. Her systemic circulation was stabilized after alprostadil (lipo-PGE1) and inotorpic agent infusion along with mechanical ventilation support. On admission, signs of a pulmonary high-flow and low systemic perfusion were evident. Impaired coagulation aspect was gradually noted. Because a surgical palliation with cardiopulmonary bypass was considered to be at high-risk, a bilateral pulmonary artery banding was indicated. Through a median sternotomy, the right and left pulmonary arteries were individually banded. The patient was continued on the same ventilation strategy. Cardiac, hepatic and renal dysfunctions were improved over next few days and the patient weaned from ventilatory support. She underwent combined Norwood stage I and II repair at 4 months of age with weight of 4.8 kg. Postoperative course has been uneventful and the patient is now followed up in preparation for Fontan operation.

[Comparison of right ventricular function between prevention and enlargement of pulmonary valve annulus after repair of tetralogy of Fallot; mid-term results].

Total of 41 patients with tetralogy of Fallot (TOF) who underwent intracardiac repair from 1993 to 1998 were divided into 2 groups: preservation (n = 14) or enlargement (n = 27) of the pulmonary valve annulus. The procedure was decided on the Z value of the annular size: above or under -2 SD of the standard value. Although postoperative right ventricular (RV) diastolic volume (RVEDV) and cardiothoracic ratio (CTR) were larger than the preservation group and pulmonary regurgitation (PR) existed in the enlargement group, RV pressure was decreased and central venous pressure (CVP) was low and RV contraction was preserved. The exercise capacity was also good and no significant arrhythmia was recognized. Our mid-term results showed that appropriate enlargement of the pulmonary valve annulus preserved good RV function in patients with TOF.

[Differences in postoperative course by preoperative left ventricular volume after closure of ventricular septal defect during early infancy].

A total of 38 early infants with ventricular septal defect (VSD) were divided into 2 groups by preoperative LVEDV. The group A (n=14, LVEDV>250% N) showed significantly longer period of intubation, cathecholamine drip, and hospitalization compared with the group B (n=28, LVEDV<250% N). At dischage, both groups showed significant lowered right ventricular (RV) pressure, but LVSF in the group A was significantly lower than that in the group B. The patients with larger left ventricular (LV) volume preoperatively were thought to be potential high-risk groups in cardiac and pulmonary function and their postoperative course was prolonged and recovery of LV function was worse. In such patients, special care is mandatory to do postoperative management and to decide timing of operation.

[Off-pump coronary artery bypass grafting for severe acute coronary syndrome].

UNLABELLED: Off-pump coronary artery bypass grafting (off-pump CABG: OPCAB) has become a standard procedure, but the indication for the patients with severe acute coronary syndrome (ACS) has not been established. The purpose of this study is to evaluate the role of OPCAB for patients with acute myocardial infarction (AMI) and impending myocardial infarction (IMI). Clinical indication of OPCAB for acute coronary syndrome between November 1997 and December 2002, 14 patients diagnosed ACS out of 220 CABG cases underwent surgery. Twelve male and 2 female with a mean age of 66.3 +/- 7.5 were NYHA grade IV condition before surgery. Three of nine AMI cases and 4 of 5 IMI cases underwent OPCAB. Thirteen cases needed intra-aortic balloon pumping (IABP) support pre-operation, in 1 AMI and 2 IMI cases IABP had to be weaned during operation. The mean graft number was 2.6. Except one AMI case with severe cardiac damage, 13 cases were discharged in NYHA grade I-II condition. CONCLUSION: In early onset cases with still rising CK-MB, operative risk and result is difficult to evaluate pre-operatively. Equal results could be seen in IMI cases with no previous myocardial damage. We suggest, that in cases without severe myocardial damage, OPCAB could be one alternative treatment.

Tuberculous abdominal aortic pseudoaneurysm penetrating the left psoas muscle after BCG therapy for bladder cancer.

We describe a case of a 75-year-old man with abdominal aortic and right femoral tuberculous pseudoaneurysms 32 months after intravesical bacillus Calmette-Guerin therapy for bladder cancer. These aneurysms were probably brought on by systemic infection by Mycobacterium bovis. The infrarenal aorta and right common femoral artery were successfully replaced with an in situ expanded polytetrafluoroethylene graft. Tuberculous pseudoaneurysm after bacillus Calmette-Guerin therapy for malignancy is very rare, and we review the related literature.

Primary photoreaction of photoactive yellow protein studied by subpicosecond-nanosecond spectroscopy.

The primary photochemical event of photoactive yellow protein (PYP) was studied by laser flash photolysis experiments on a subpicosecond-nanosecond time scale. PYP was excited by a 390-nm pulse, and the transient difference absorption spectra were recorded by a multichannel spectrometer for a more reliable spectral analysis than previously possible. Just after excitation, an absorbance decrease due to the stimulated emission at 500 nm and photoconversion of PYP at 450 nm were observed. The stimulated emission gradually shifted to 520 nm and was retained up to 4 ps. Then, the formation of a red-shifted intermediate with a broad absorption spectrum was observed from 20 ps to 1 ns. Another red-shifted intermediate with a narrow absorption spectrum was formed after 2 ns and was stable for at least 5 ns. The latter is therefore believed to correspond to I1 (PYP(L)), which has been detected on a nanosecond time scale or trapped at -80 degrees C. Singular value decomposition analysis demonstrated that the spectral shifts observed from 0.5 ps to 5 ns could be explained by two-component decay of excited state(s) and conversion from PYP(B) to PYP(L). The amount of PYP(L) at 5 ns was less than that of photoconverted PYP, suggesting the formation of another intermediate, PYP(H). In addition, the absorption spectra of these intermediates were calculated based on the proposed reaction scheme. Together, these results indicate that the photocycle of PYP at room temperature has a branched pathway in the early stage and is essentially similar to that observed under low-temperature spectroscopy.

Morphology, fluorescence properties, and their photothermal changes of poly(substituted thiophene) films revealed by near-field fluorescence microspectroscopy.

The morphology and fluorescence spectrum of poly(3-[2-(N-dodecylcarbamoyloxy)ethyl]thiophene-2,5-diyl) film were examined with spatial resolution of 100 nm using near-field fluorescence microspectroscopy. Fluorescence spectra observed at protruding domains were blue-shifted compared with flat areas, and further blue-shift was observed there more appreciably by long-time irradiation via a near-field scanning optical microscope probe. It is considered that the polymer chains at the protruding domains take disordered conformations, in which conjugated lengths are shorter and further disordering can be induced more easily by irradiation compared with those in the flat areas.

Nanometer-nanosecond oscillatory expansion and contraction behavior of polymer films induced by 248 nm excimer laser excitation.

Microregional mechanical measurements of a poly[methylmethacrylate) film can be made by a combined probe/measurement laser system, as represented in the picture. The localized nature of the laser systems allow quantification of the degree of expansion and contraction processes, as well as the glass-rubber transition. Such nondestructive techniques lead to the elucidation of polymer morphological dynamics.

Analysis of radiation pressure exerted on a metallic particle within an evanescent field.

Radiation pressure induced by an evanescent field was experimentally analyzed for a single submicrometer-sized gold particle. The force measurement was based on a thermodynamic analysis of Brownian motion by use of a three-dimensional position-sensing technique. The lateral radiation pressure could be ascribed to a scattering force, which was oriented in the same direction as the propagation vector of the incident laser beam. The potential profile in the longitudinal direction indicated that the gold particle was attracted to the high-intensity region of the evanescent field by a gradient force.

Evaluation of Annuloaortic Ectasia by Angioscopy and IVUS "Report of 2 cases".

We attempted combined use of angioscopy and intravascular ultrasonography (IVUS) to localize the coronary ostia and determine the aortic segment to be replaced in patients with annuloaortic ectasia, because these preoperative informations are important for selection of an appropriate technique for reconstructing the coronary artery, to prevent complications, and also to postoperative follow-up. Two cases with annuloaortic ectasia underwent angioscopy and IVUS both pre- and post-operatively. Structure of aortic cusps, position of coronary ostia, the extent of ectasia with very thin wall were clearly observed by IVUS. Angioscopy showed milky white luminal surface of the ectasic segment. After Cabrol's operation, the sutured portion of native aorta and graft was clearly identified by IVUS and mural thrombus and naked surface of graft were observed by angioscopy. Complications were observed in none. The results indicate feasibility of combined use of angioscopy and IVUS for determination of surgical approach and follow-up in patients with AAE.

[Reoperation of tetralogy of Fallot for the transannular patch neo-intimal stenosis: a case report].

A 3-year-old male patient underwent right ventricular outflow tract reconstruction with a glutaraldehyde-preserved equine pericardium for tetralogy of Fallot. Because of progressive severe pulmonary restenosis with over systemic right ventricular pressure, tricuspid regurgitation, and abnormal high echoic shadow in the distal main pulmonary artery on echocardiogram, he required reoperation a year after the first correction. In the reoperative findings, the pseudointima was thickened heavily and detached from glutaraldehyde-preserved equine pericardial patch. The patch was removed and the right ventricular outflow was reconstructed widely to the pulmonary bifurcation with porcine pericardial patch again. Patho-histological findings showed foreign body giant cells and macrophages in the pseudointima. Four years after the reoperation, echocardiogram shows 41 mmHg for the right ventricular pressure and 22 mmHg for the pressure gradient of right ventricular outflow tract, and the patient is doing well now.

Blind-deconvolution analysis of transient curves by the use of a convolved autoregressive model.

A new method is proposed for analyzing a transient curve as a multiexponential decay convolved with an instrumental response function and for estimating the decay constants and amplitudes without knowledge of the response function. The method requires a single-exponential reference curve observed with the same response function as that for a sample curve, whereas its decay-constant and amplitude values are not necessary for the estimation. The sample and reference curves are analyzed with a convolved autoregressive model, which is based on a linear least-squares algorithm. This method has the advantage of a short computation time when compared with a conventional nonlinear least-squares fitting technique. Double-exponential curves are also acceptable as the reference, if two curves with different decay parameters can be provided for the analysis.

In situ measurements of ion-exchange processes in single polymer particles: laser trapping microspectroscopy and confocal fluorescence microspectroscopy.

Ion-exchange processes of a cationic dye (Rhodamine B; RhB) were studied for individual polymer particles (diameter of 16-20 µm) by laser trapping microspectroscopy and confocal fluorescence laser microspectroscopy. The absorbance of RhB at 565 nm adsorbed on a cation-exchange particle increased linearly with the concentration of RhB in the aqueous phase, while it was independent of the particle diameter. Fluorescence intensity profile measurements of RhB along the particle diameter by confocal fluorescence microspectroscopy directly proved that ion exchange took place in the surface layer (∼2-µm thickness) of the particle in the initial stage (1 h). Diffusion of RhB in the particle was very slow, and ion exchange proceeded gradually to the inner volume in the order of days. The ion-exchange processes were analyzed on the basis of simulation of the time course of the concentration profile of RhB in the particle, and the diffusion coefficient of RhB was determined to be (2-4) × 10(-11) cm(2)·s(-1).

Absorption effects on total-internal-reflection fluorescence spectroscopy.

A theoretical consideration is made for transverse-electric polarization vectors of a transmitted field in an optically absorbing sample to derive a fluorescence intensity formula as a function of the absorption index of the sample as well as incident and observation angles in total-internal-reflection fluorescence spectroscopy. These equations are experimentally confirmed. It is shown that the angular spectrum of fluorescence intensity is the Laplace transformation of the effective penetration depth, even for the absorbing sample. High resolution of the depth profile is expected for an absorbing sample compared with a nonabsorbing one.

Pattern formation and flow control of fine particles by laser-scanning micromanipulation.

A novel micromanipulation technique is proposed for aligning fine particles on micrometer-scale spatial patterns and for moving the particles continuously along the formed patterns. This technique is based on the repetitive scanning of a focused trapping laser beam. The velocity of the particle flow can be controlled by scan speed and laser power. The origin of the driving force is considered theoretically and experimentally.

Analysis of transient emission curves by a convolved autoregressive model.

A new method is developed for estimating the decay parameters of transient emission curves convolved with an instrumental response function. This method is based on the convolved autoregressive model, which we originally proposed. The computation time of the method is much shorter than that of the conventional nonlinear least-squares method. Results of analyses for simulated and real data are shown to demonstrate a high potential of the developed method.

Laser photolysis and fluorescence studies on pyrene-thiazide and pyrene-diazoxide systems.

The laser photolysis studies on pyrene, pyrene-thiazides and pyrene-diazoxide systems in acetonitrile revealed that thiazides and diazoxide can scavenge the photoejected electron. It was found that the pyrene fluorescence is quenched by the present diuretics and related compounds and both static and dynamic quenching constants were obtained. Thiazides quench the fluorescence through both static and dynamic mechanism, while the small static quenching constant and no lifetime shortening of pyrene were observed in the case of diazoxide quencher. This difference may correspond to the difference of their diuretic activity.