Feasibility of in vitro calcification plaque disruption using ultrasound-induced microbubble inertial cavitation.

Percutaneous transluminal coronary angioplasty (PTCA) is a clinical method in which plaque-narrowed arteries are widened by inflating an intravascular balloon catheter. However, PTCA remains challenging to apply in calcified plaques since the high pressure required for achieving a therapeutic outcome can result in balloon rupture, vessel rupture, and intimal dissection. To address the problem with PTCA, we hypothesized that a calcified plaque can be disrupted by microbubbles (MBs) inertial cavitation induced by ultrasound (US). This study proposed a columnar US transducer with a novel design to generate inertial cavitation at the lesion site. Experiments were carried out using tubular calcification phantom to mimic calcified plaques. After different parameters of US + MBs treatment (four types of MBs concentration, five types of cycle number, and three types of insonication duration; n = 4 in each group), inflation experiments were performed to examine the efficacy of cavitation for a clinically used balloon catheter. Finally, micro-CT was used to investigate changes in the internal structure of the tubular plaster phantoms. The inflation threshold of the untreated tubular plaster phantoms was > 11 atm, and this was significantly reduced to 7.4 ± 0.7 atm (p = 5.2E-08) using US-induced MBs inertial cavitation at a treatment duration of 20 min with an acoustic pressure of 214 kPa, an MBs concentration of 4.0 × 108 MBs/mL, a cycle number of 100 cycles, and a pulse repetition frequency of 100 Hz. Moreover, micro-CT revealed internal damage in the tubular calcification phantom, demonstrating that US-induced MBs inertial cavitation can effectively disrupt calcified plaques and reduce the inflation threshold of PTCA. The ex vivo histopathology results showed that the endothelium of pig blood vessels remained intact after the treatment. In summary, the results show that US-induced MBs inertial cavitation can markedly reduce the inflation threshold in PTCA without damaging blood vessel endothelia, indicating the potential of the proposed treatment method.

Purification and properties of genetically engineered protein containing the repeating sequence in the glycophorin-binding protein of malaria merozoite

A protein containing the glycophorin-binding sequence, M3R, has been genetically engineered in E. coli, and a method of its purification from the bacterial source has been established. The method involvers: a) extraction, b) heat treatment at 80' for 3 min, c) concentration of M3R by acid precipitation, d) HPLC on a reverse-phase C8 column, and e) purification by reverse-phase C4 chromatography. The purified protein migrates as a single band of Mw=22000. M3R has been assayed by the rabbit antibody raised against a synthetic peptide containing a partial sequence of the protein. The overall yield has been approximately 20 mg of pure protein from 100 gm of bacterial paste. Automated sequence analysis has confirmed the purity as well as the identity of the protein as M3R; its sequence of 15 residues from the NH2-terminus agrees with that predicted from the gene sequence. Structural analyses of its peptide fragments have further confirmed correctness of its sequence. Rabbit antibody prepared against M3R has been found to react with the merozoite of P.falcipurm merozoite