An Ultrasonically Actuated Fine-Needle Creates Cavitation in Bovine Liver

Ultrasonic cavitation is being used in medical applications as a way to influence matter, such as tissue or drug vehicles, on a micro-scale. Oscillating or collapsing cavitation bubbles provide transient mechanical force fields, which can, e.g., fractionate soft tissue or even disintegrate solid objects such as calculi. Our recent study demonstrates that an ultrasonically actuated medical needle can create cavitation phenomena inside water. However, the presence and behavior of cavitation and related bioeffects in diagnostic and therapeutic applications with ultrasonically actuated needles are not known. Using simulations, we demonstrate numerically and experimentally the cavitation phenomena near ultrasonically actuated needles. We define the cavitation onset within a liver tissue model with different total acoustic power levels. We directly visualize and quantitatively characterize cavitation events generated by the ultrasonic needle in thin fresh bovine liver sections enabled by high speed imaging. On a qualitative basis, the numerical and experimental results show a close resemblance in threshold and spatial distribution of cavitation. These findings are crucial for developing new methods and technologies employing ultrasonically actuated fine-needles such as ultrasound-enhanced fine-needle biopsy, drug delivery and histotripsy.Comment: 35 pages, 6 figures, under consideration at The Journal of the Acoustical Society of Americ

An Ultrasonically Actuated Needle Promotes the Transport of Nanoparticles and Fluids

Non-invasive therapeutic ultrasound methods, such as high-intensity focused ultrasound (HIFU), have limited access to tissue targets shadowed by bones or presence of gas. This study demonstrates that an ultrasonically actuated medical needle can be used to translate nanoparticles and fluids under the action of nonlinear phenomena, potentially overcoming some limitations of HIFU. A simulation study was first conducted to study the delivery of a tracer with an ultrasonically actuated needle (33 kHz) inside a porous medium acting as a model for soft tissue. The model was then validated experimentally in different concentrations of agarose gel showing a close match with the experimental results, when diluted soot nanoparticles (diameter < 150 nm) were employed as delivered entity. An additional simulation study demonstrated a threefold increase of the volume covered by the delivered agent in liver under a constant injection rate, when compared to without ultrasound. This method, if developed to its full potential, could serve as a cost effective way to improve safety and efficacy of drug therapies by maximizing the concentration of delivered entities within e.g. a small lesion, while minimizing exposure outside the lesion.Comment: 34 pages, 4 figures, under review in the Journal of the Acoustical Society of Americ

Vitamin B6 deficiency experimentally-induced bone and joint disorder: microscopic, radiographic and biochemical evidence

In the present study the effect of pyridoxine deficiency on the utrastructure and morphology of bone and its metabolism was examined in the rapidly growing chick. Pyridoxine-deficient animals had tibias of reduced dry weight and cortical thickness. Histomorphometry demonstrated a disproportionately high eroded surface, lower amount of osteoid tissue and reduced mineralized trabecular width. Anterior-posterior radiographs of the tibiotarsometatarsal joint showed reduced secondary ossification centres and coarse trabeculation. Decalcified metaphyseal cartilage showed irregular trabeculas and a markedly reduced amount of Fast-green counterstain matrix suggesting that there is less collagen present and in turn less availability for matrix to be laid down for later calcification. Plasma activity of the bone alkaline phosphatase isoenzyme (EC) 3. 1.3.1) was decreased. Plasma Ca and PO4 levels did not vary. The present bone study referring to a pseudo-lathyritic state in which collagen maturation is not completely achieved supports the hypothesis that pyridoxine is an essential nutrient for the connective tissue matri

Ultrasonic actuation of a fine-needle improves biopsy yield

Despite the ubiquitous use over the past 150 years, the functions of the current medical needle are facilitated only by mechanical shear and cutting by the needle tip, i.e. the lancet. In this study, we demonstrate how nonlinear ultrasonics (NLU) extends the functionality of the medical needle far beyond its present capability. The NLU actions were found to be localized to the proximity of the needle tip, the SonoLancet, but the effects extend to several millimeters from the physical needle boundary. The observed nonlinear phenomena, transient cavitation, fluid streams, translation of micro- and nanoparticles and atomization, were quantitatively characterized. In the fine-needle biopsy application, the SonoLancet contributed to obtaining tissue cores with an increase in tissue yield by 3-6x in different tissue types compared to conventional needle biopsy technique using the same 21G needle. In conclusion, the SonoLancet could be of interest to several other medical applications, including drug or gene delivery, cell modulation, and minimally invasive surgical procedures.Peer reviewe

Effects of Articular Cartilage Constituents on Phosphotungstic Acid Enhanced Micro-Computed Tomography

Contrast-enhanced micro-computed tomography (CE mu CT) with phosphotungstic acid (PTA) has shown potential for detecting collagen distribution of articular cartilage. However, the selectivity of the PTA staining to articular cartilage constituents remains to be elucidated. The aim of this study was to investigate the dependence of PTA for the collagen content in bovine articular cartilage. Adjacent bovine articular cartilage samples were treated with chondroitinase ABC and collagenase to degrade the proteoglycan and the collagen constituents in articular cartilage, respectively. Enzymatically degraded samples were compared to the untreated samples using CE mu CT and reference methods, such as Fourier-transform infrared imaging. Decrease in the X-ray attenuation of PTA in articular cartilage and collagen content was observed in cartilage depth of 0-13% and deeper in tissue after collagen degradation. Increase in the X-ray attenuation of PTA was observed in the cartilage depth of 13- 39% after proteoglycan degradation. The X-ray attenuation of PTA-labelled articular cartilage in CE mu CT is associated mainly with collagen content but the proteoglycans have a minor effect on the X-ray attenuation of the PTA-labelled articular cartilage. In conclusion, the PTA labeling provides a feasible CE mu CT method for 3D characterization of articular cartilage.Peer reviewe

Micro-Scale Distribution of CA4+ in Ex vivo Human Articular Cartilage Detected with Contrast-Enhanced Micro-Computed Tomography Imaging

Contrast-enhanced micro-computed tomography (CE mu CT) with cationic and anionic contrast agents reveals glycosaminoglycan (GAG) content and distribution in articular cartilage (AC). The advantage of using cationic stains (e.g., CA4+) compared to anionic stains (e.g., Hexabrix (R)), is that it distributes proportionally with GAGs, while anionic stain distribution in AC is inversely proportional to the GAG content. To date, studies using cationic stains have been conducted with sufficient resolution to study its distributions on the macro-scale, but with insufficient resolution to study its distributions on the micro-scale. Therefore, it is not known whether the cationic contrast agents accumulate in extra/pericellular matrix and if they interact with chondrocytes. The insufficient resolution has also prevented to answer the question whether CA4+ accumulation in chondrons could lead to an erroneous quantification of GAG distribution with low-resolution mu CT setups. In this study, we use high-resolution mu CT to investigate whether CA4+ accumulates in chondrocytes, and further, to determine whether it affects the low-resolution ex vivo mu CT studies of CA4+ stained human AC with varying degree of osteoarthritis. Human osteochondral samples were immersed in three different concentrations of CA4+ (3 mgI/ml, 6 mgI/ml, and 24 mgI/ml) and imaged with high-resolution mu CT at several timepoints. Different uptake diffusion profiles of CA4+ were observed between the segmented chondrons and the rest of the tissue. While the X-ray -detected CA4+ concentration in chondrons was greater than in the rest of the AC, its contribution to the uptake into the whole tissue was negligible and in line with macro-scale GAG content detected from histology. The efficient uptake of CA4+ into chondrons and surrounding territorial matrix can be explained by the micro-scale distribution of GAG content. CA4+ uptake in chondrons occurred regardless of the progression stage of osteoarthritis in the samples and the relative difference between the interterritorial matrix and segmented chondron area was less than 4%. To conclude, our results suggest that GAG quantification with CE mu CT is not affected by the chondron uptake of CA4+. This further confirms the use of CA4+ for macro-scale assessment of GAG throughout the AC, and highlight the capability of studying chondron properties in 3D at the micro scale.Peer reviewe

Delivery of Agents Into Articular Cartilage With Electric Spark-Induced Sound Waves

Localized delivery of drugs into articular cartilage (AC) may facilitate the development of novel therapies to treat osteoarthritis (OA). We investigated the potential of spark-gap-generated sound to deliver a drug surrogate, i.e., methylene blue (MB), into AC. In vitro experiments exposed bovine AC samples to either simultaneous sonication and immersion in MB (Treatment 1; n = 10), immersion in MB after sonication (Control 1; n = 10), solely immersion in MB (Control 2; n = 10), or neither sonication nor immersion in MB (Control 3; n = 10). The sonication protocol consisted of 1,000 spark-gap -generated pulses. Delivery of MB into AC was estimated from optical absorbance in transmission light microscopy. Optical absorbance was significantly greater in the treatment group up to 900 μm depth from AC surface as compared to all controls. Field emission scanning electron microscopy (FESEM), histological analysis, and digital densitometry (DD) of sonicated (n = 6) and non-sonicated (n = 6) samples showed no evidence of sonication-induced changes in proteoglycan content or collagen structure. Consequently, spark-gap -generated sound may offer a solution for localized drug delivery into AC in a non-destructive fashion. Further research on this method may contribute to OA drug therapies

Laser-ultrasonic delivery of agents into articular cartilage

Peer reviewe

Localized delivery of compounds into articular cartilage by using high-intensity focused ultrasound

Localized delivery of drugs into an osteoarthritic cartilaginous lesion does not yet exist, which limits pharmaceutical management of osteoarthritis (OA). High-intensity focused ultrasound (HIFU) provides a means to actuate matter from a distance in a non-destructive way. In this study, we aimed to deliver methylene blue locally into bovine articular cartilage in vitro. HIFU-treated samples (n = 10) were immersed in a methylene blue (MB) solution during sonication (f = 2.16 MHz, peak-positivepressure = 3.5 MPa, mechanical index = 1.8, pulse repetition frequency = 3.0 kHz, cycles per burst: 50, duty cycle: 7%). Adjacent control 1 tissue (n = 10) was first pre-treated with HIFU followed by immersion into MB; adjacent control 2 tissue (n = 10) was immersed in MB without ultrasound exposure. The MB content was higher (p 0.05). To conclude, HIFU delivers molecules into articular cartilage without major short-term concerns about safety. The method is a candidate for a future approach for managing OA.Peer reviewe