Ultrasound-enhanced ocular delivery of dexamethasone sodium phosphate: An in vivo study

Background The eye\u27s unique anatomy and its physiological and anatomical barriers can limit effective drug delivery into the eye. Methods An in vivo study was designed to determine the effectiveness and safety of ultrasound application in enhancing drug delivery in a rabbit model. Permeability of a steroid ophthalmic drug, dexamethasone sodium phosphate, was investigated in ultrasound- and sham-treated cases. For this study, an eye cup filled with dexamethasone sodium phosphate was placed on the cornea. Ultrasound was applied at intensity of 0.8 W/cm2 and frequency of 400 or 600 kHz for 5 min. The drug concentration in aqueous humor samples, collected 90 min after the treatment, was determined using chromatography methods. Light microscopy observations were done to determine the structural changes in the cornea as a result of ultrasound application. Results An increase in drug concentration in aqueous humor samples of 2.8 times (p \u3c 0.05) with ultrasound application at 400 kHz and 2.4 times (p \u3c 0.01) with ultrasound application at 600 kHz was observed as compared to sham-treated samples. Histological analysis showed that the structural changes in the corneas exposed to ultrasound predominantly consisted of minor epithelial disorganization. Conclusions Ultrasound application enhanced the delivery of an anti-inflammatory ocular drug, dexamethasone sodium phosphate, through the cornea in vivo. Ultrasound-enhanced ocular drug delivery appears to be a promising area of research with a potential future application in a clinical setting

Thermal safety of ultrasound-enhanced ocular drug delivery: A modeling study

PURPOSE: Delivery of sufficient amounts of therapeutic drugs into the eye for treatment of various ocular diseases is often a challenging task. Ultrasound was shown to be effective in enhancing ocular drug delivery in the authors’ previous in vitro and in vivo studies. METHODS: The study reported here was designed to investigate the safety of ultrasound application and its potential thermal effects in the eye using PZFlex modeling software. The safety limit in this study was set as a temperature increase of no more than 1.5 °C based on regulatory recommendations and previous experimental safety studies. Acoustic and thermal specifications of different human eye tissues were obtained from the published literature. The tissues of particular interest in this modeling safety study were cornea, lens, and the location of optic nerve in the posterior eye. Ultrasound application was modeled at frequencies of 400 kHz–1 MHz, intensities of 0.3–1 W/cm(2), and exposure duration of 5 min, which were the parameters used in the authors’ previous drug delivery experiments. The baseline eye temperature was 37 °C. RESULTS: The authors’ results showed that the maximal tissue temperatures after 5 min of ultrasound application were 38, 39, 39.5, and 40 °C in the cornea, 39.5, 40, 42, and 43 °C in the center of the lens, and 37.5, 38.5, and 39 °C in the back of the eye (at the optic nerve location) at frequencies of 400, 600, 800 kHz, and 1 MHz, respectively. CONCLUSIONS: The ocular temperatures reached at higher frequencies were considered unsafe based on current recommendations. At a frequency of 400 kHz and intensity of 0.8 W/cm(2) (parameters shown in the authors’ previous in vivo studies to be optimal for ocular drug delivery), the temperature increase was small enough to be considered safe inside different ocular tissues. However, the impact of orbital bone and tissue perfusion should be included in future modeling efforts to determine the safety of this method in the whole orbit especially regarding potential adverse optic nerve heating at the location of the bone

Ultrasound Stimulation of Insulin Release from Pancreatic Beta Cells

OBJECTIVE : Type 2 diabetes mellitus is a complex metabolic disease that has reached epidemic proportions. Controlling type 2 diabetes is often difficult as pharmacological management routinely requires complex therapy with multiple medications, and loses its effectiveness over time. Thus, new modes of therapy are needed that will directly target the underlying causes of impaired glucose homeostasis. The objective of this study is to explore a novel, non-pharmacological approach that utilizes the application of ultrasound energy to augment insulin release from pancreatic beta cells. METHODS: Our experiments focus on determination of effectiveness and safety of ultrasound application in stimulation of insulin release from pancreatic beta cells. ELISA insulin release assay was used to determine and quantify the effects of ultrasound on insulin release in cultured INS-1 beta cells. Effects of ultrasound on cell viability were assessed by trypan blue exclusion method. Planar ultrasound transducers with center frequencies of 400 kHz,600 kHz, 800 kHz and 1 MHz were used to expose cells for a duration of 5 minutes at an intensity of 1 W/cm2. Insulin release and cell viability results were studied as a function of temperature increase and non-thermal activity as measured experimentally and simulated using PZFlex modeling software. RESULTS: Our results indicated that cell viability was not significantly affected during and for up to 30 minutes after treatment when cells were exposed to ultrasound frequencies of 800 kHz and 1 MHz. However, cell viability was highly reduced (by around 80-90%) when the cells were exposed to ultrasound frequencies of 400 kHz and 600 kHz(p \u3c 0.001). ELISA results showed that significant amounts of insulin were released from beta cells exposed to 400kHz and 600 kHz ultrasound at the cost of cell viability (p \u3c 0.05). Cell exposure to ultrasound at frequency of 800 kHz resulted in approximately 4-fold increase in insulin release (p \u3c 0.005). Cell exposure to ultrasound at frequency of 1MHz also showed increased insulin release (around 50%) though no statistical significance was achieved when compared to sham treatment CONCLUSIONS: If shown successful our approach may eventually lead to new methods in the treatment of diabetes and other secretory diseases. Our future studies will focus on application of ultrasound to human pancreatic islets to determine whether it would be possible to stimulate beta cells without stimulating other endocrine and exocrine cells of the pancreas

Ultrasound-Enhanced Drug Delivery for Treatment of Onychomycosis

More than 32 million Americans are currently suffering from onychomycosis—an unattractive and potentially dangerous fungal nail disorder. There is currently no effective treatment for onychomycosis. The oral antifungal drugs take over 6 months to work and have overall failure rates of over 30% along with dangerous side effects including elevated liver function tests and hepatitis. The other current treatment option is the application of antifungal drugs to the top of the nail in a nail polish form. This treatment plan has been preferred by many patients as the drug has only non-serious, infrequently reported side-affects. However, the medicated nail polish also needs to be applied for 6 months and has a low cure rate of only up to 36%. Our hypothesis is that ultrasound application can lead to the increased effectiveness of delivery of topically applied antifungal drugs and reduce the necessary time of application for successful treatment. Our preliminary studies indicate that the use of ultrasound increases nail permeability by 50% for a drug mimicking compound. Additionally, we developed and tested a novel ultrasound device for treatment of onychomycosis that can be used to apply therapeutic ultrasound at different clinically-relevant parameters. Our ongoing research efforts focus on optimizing ultrasound parameters for nail drug delivery by utilizing a diffusion cell setup. People who would benefit the most from this treatment are those in their 60s or older, particularly those who suffer from diabetes, poor circulation, immunosuppressive diseases, or have cancer that is being treated with radiation

Low-Frequency, Low-Intensity Ultrasound as a Potential Treatment for Type 2 Diabetes

OBJECTIVE: The objective of this study was to explore the safety and efficacy of a potential new treatment method that utilizes a non-invasive application of ultrasound energy to induce exocytosis of insulin from pancreatic beta cells. Amperometric measurements offer confirmation of secretion as well as data that could lead to optimization in controlling the release via ultrasound application. Finite-element modeling studies provide information regarding the thermal and mechanical effects of therapeutic ultrasound in the human abdomen. METHODS: Initial experiments focused on detecting exocytotic secretions from pancreatic beta cells in response to ultrasound stimulation using carbon fiber amperometry. Neurotransmitters, specifically dopamine and its precursor L-DOPA, were loaded into secretory vesicles in beta cells and co-released with insulin. Cells were stimulated at 800 kHz and an intensity of 0.5 W/cm2 for 5 s, 10 s, and 15 s at various time intervals. Secretion of insulin was detected by proxy through the oxidation of these neurotransmitters using commercially available carbon fiber electrodes. A negative control group was included in which cells were not loaded with the dopamine and L-DOPA, however still exposed to ultrasound. Calcium dependence was evaluated by stimulating cells in the presence of an extracellular calcium chelator, EGTA. In parallel with these experiments, a finite-element modeling study to determine the safety of therapeutic levels of ultrasound to the human pancreas in vivo without adverse mechanical or thermal effects in the surrounding tissues. RESULTS: Immediate secretory amperometric readings were recorded after application of ultrasound at the parameters described above. With the application of consecutive ultrasound pulses, a prolonged response was recorded for a prolonged stimulation. In experiments where Ca2+ dependence was explored, a statistically significant lower response was observed (p \u3c 0.01). Consequently, the negative control group with unloaded cells did not produce an amperometric response. Ongoing work is focusing on finding the optimal acoustic windows for ultrasound applications in patients through simulations. CONCLUSIONS: These results confirm that ultrasound stimulation induces secretory events in beta cells, and points towards a Ca2+ dependent process. Ongoing work is looking at the elucidation of mechanisms of ultrasound in the stimulation of insulin release and determining safety and effectiveness of this method in clinically relevant models including human pancreatic islets and in vivo diabetic rat model. Our proposed technology would directly target beta cell dysfunction, one of the underlying causes of insulin deficiency in Type 2 Diabetes, potentially resulting in a new therapeutic approach for the treatment of Type 2 Diabetes

Amperometric Detection of Ultrasound-Induced Secretory Events in Potential Treatment of Type 2 Diabetes

OBJECTIVE:The objective of this study was to explore a potential new treatment method that utilizes a non-invasive application of ultrasound energy to induce exocytosis of insulin from pancreatic beta cells. Our amperometric measurements can not only provide confirmation of secretion, but also data that could lead to optimization in controlling the release via ultrasound application. METHODS: Our experiments focused on detecting exocytotic secretions from pancreatic beta cells in response to ultrasound stimulation using carbon fiber amperometry. Exocytosis of insulin is measured via amperometric readings of the oxidation of dopamine. Dopamine that is loaded into cells is released via vesicles along with insulin. Results were obtained with commercially available electrodes as well as electrodes fabricated in-house. A sham group was included in which cells were loaded with dopamine but not stimulated for secretion. RESULTS: To confirm the functionality of the in-house made electrodes, a triangular waveform was run through the electrode, and using an oscilloscope, the original signal was compared to the one from the electrode. Consequently, the amperometry experiments were run with both the in-house made electrodes and commercial electrodes. Similar results were obtained. Secretory amperometric readings were recorded after application of ultrasound at 800kHz and 1MHz with an intensity of 1W/ cm2. The ultrasound pulse was applied for 5s, 10s and 15s at various time intervals. There is an immediate response of secretion after application of the 800kHz pulse for 5s at three intervals (t=180s, 360s and 540s). Similar results were obtained at 1KHz. With application of consequent 5s, 10s and 15s ultrasound pulses, a prolonged response was recorded for a prolonged stimulation. These results confirm that ultrasound stimulation induces secretory events in beta cells. Ongoing experiments focus on exploring the impact of varying parameters such as ultrasound intensity and pulse length on exocytotic events. CONCLUSIONS: Our proposed technology would directly target beta cell dysfunction, one of the underlying causes of insulin deficiency in Type 2 Diabetes, and could result in the development of a new therapeutic approach for the treatment of Type 2 Diabetes

Hidden Bleed Ultrasound Phantom

Every year, GW hospital treats 300 gunshot wound victims and, per protocol, doctors and nurses will calculate a patient’s ankle brachial index (ABI) to determine whether or not the injuries sustained by the lower extremities require surgery to repair any internal bleeding. If a patient scores a 0.9 or above on the ABI, they are further examined for damage to the vasculature of their legs. However, patients that score closely to a 0.9 are prematurely sent home from hospitals because their ABI score is within the normal range but post injury internal bleeding can be extremely slow and not affect the ABI value. This is dangerous since their internal bleedings injuries can worsen and have to seek treatment again. Our group proposes using ultrasound as a diagnostic tool to detect internal pseudoaneurysms if a patient scores close to a 0.9 on the ABI. To test the effectiveness of ultrasound in pseudoaneurysm detection, we are developing a tissue ultrasound phantom of the leg with a femoral artery to test ultrasound in this application. We are going to create and develop multiple leg tissue phantoms with femoral arteries, which consist of the same acoustic properties of real tissue and blood. Then, we will mimic different potential gunshot induced pseudoaneurysm scenarios on these phantoms to observe their effects. The phantom will be attached to a peristaltic pump to facilitate blood flow and a pressure sensor will collect data which will allow the maximum and minimum pressures within the artery, ABI and BPM to be calculated via a microcontroller. After ultrasound imaging is performed on the phantom, the image is analyzed using ImageJ and the pseudoaneurysm can be detected and measured. When the femoral artery is punctured, we expect to see the blood mimicking fluid slowly ooze from the puncture site and pool around the artery within the gel. The gel and blood mimicking fluid will contain a similar acoustic attenuation to real blood and soft tissue. This will prove that the gels are biomimetic and can be used in future research to study sonography and produce an algorithm that self detects trauma induced pseudoaneurysms while minimizing the user variability associated with ultrasound in clinical settings