Modeling of microbubble dissolution in aqueous medium

Aqueous suspensions of microbubbles find use in various biomedical and pharmaceutical applications. Microbubbles of size from 1-10 μm, comprise of a gas core and a shell made of protein, SDS or polymeric material. Most of the biomedical applications involve intravenous administrations of microbubbles. Once administered in body, microbubbles start dissolving in the body media. The effectiveness of these microbubbles depends on their circulation time in blood. The circulation time (or persistence time) of these microbubbles largely depends upon the kinetics of their dissolution in body media. It is therefore necessary to know/predict the time for which the microbubbles made from a particular formulation will circulate in blood. Accordingly, the objectives of this work were to model microbubble dissolution and predict dissolution time. There are several models available in the literature aimed at attempting the modeling of microbubble dissolution. However, it was found that, the existing models do not take into account either the shell elasticity or the variation in surface tension with change in microbubble size. In this work, attempt has been made to account for these factors which may affect microbubble dissolution process greatly. The model for microbubble dissolution in an aqueous medium saturated with gas used to make microbubble has been developed. The values of shell resistance, elasticity and initial surface tension have been regressed by comparing model with the experimental data available I literature. It is found that, the shell resistance and elasticity of shell increases with number of carbon atom in lipids, thus dissolution time of the microbubble increases with number of carbon atoms in lipids. The dissolution time also increases with level of saturation and initial radius of the microbubble. As the Ostwald coefficient decreases, it is also observed that the dissolution time increases. The life time of gas with lower Ostwald coefficient microbubble is higher. The degree of variations in shell resistance and surface tension also increases with number of carbon atom in lipid. However, based on the regressed shell properties, SDS can be considered as inelastic material as the variation in surface tension and shell resistance is negligible. The model for dissolution of microbubble in multi gas environment in water and in blood has also been developed. Two way diffusion of core gas to the bulk and the diffusion of air dissolved in the bulk to the gas core have been considered. The growth in microbubble was observed during its dissolution due to higher influx of gases dissolved in the aqueous medium than outflux of gas used to make microbubble. The shell resistance of gases and surface tension of the microbubble first decreases and then increases. The dissolution time increases with number of carbon atom in a lipid molecule, initial radius and level of saturation of the aqueous medium.by Jignesh Rajendrakumar JoshiM.Tech

Modeling of microbubble dissolution in aqueous medium

A mathematical model for microbubble dissolution in an aqueous medium containing dissolved gases is presented. None of the models available in the literature take into account the influence of shell elasticity (Es), variation in surface tension (σ) at the gas–liquid interface and shell resistance (Ω) on the kinetics of microbubble dissolution. Moreover, values of these shell parameters are not known/available and hence arbitrary values for these variables have been assumed in many of the reports for estimation of dissolution kinetics. Therefore, in this work, a mathematical model is developed to describe microbubble dissolution which takes into account the effect of shell elasticity (Es), shell resistance (Ω), surface tension (σ) and their variation, on the microbubble dissolution. The values of these shell parameters have then been estimated using the proposed model and the experimental data available in literature. The proposed model accurately predicts the experimental microbubble dissolution data using estimated values of shell parameters. Analysis of the results further show that the surface tension and shell resistances change drastically during the microbubble dissolution process and the variation in these parameters during the dissolution process is highly dependent on the shell elasticity which in turn affects the microbubble dissolution times. The methodology developed in this work can be used to estimate shell parameters for any microbubble formulation, to accurately predict in-vitro/in-vivo dissolution of microbubbles, and hence to design a microbubble system with desired characteristics and performance.by Sameer V. Dalvi and Jignesh R. Josh

Evaluation of surgically treated primary spinal cord tumors in a single Indian institution: A case series study of 178 patients

Introduction: Primary spinal cord tumors are rare tumors that are usually heterogeneous having variable histopathological subtypes. Rapidly, growing space-occupying lesions in the spinal canal cause severe loss of function. This study aimed to analyze all adult patients diagnosed with primary spinal cord tumors and to describe their location, symptoms, histopathological types, surgical outcome, complications, recurrence in a single institution, and prognostic factors. Materials and Methods: The study was a retrospective study of 178 patients with spinal tumor who underwent surgical intervention at the department of neurosurgery at a tertiary care institute from 2014 to 2021. Patient demographic characteristics, symptoms, radiological features, spinal level of tumor, spinal compartment, preoperative and postoperative McCormick grade, and complications were recorded, and a comparison of outcomes after surgical intervention was done. Results: In our study, 97 patients were males and the rest of the 81 patients were females. The mean age at the time of surgery was 43.5 years. The thoracic region of the spinal canal was the most involved with 67 (37.64%) cases, whereas intradural extramedullary was the most common (65.73%). Schwannoma was the most common histopathological subtype (46.06%). Total excision was achieved in 154 cases. A total of 37 patients were in Grades 4 and 5 of modified McCormick’s grade preoperatively. However, postoperatively, there were only 17 patients in this group. Two patients with cervical intramedullary tumor expired in the postoperative period. Conclusion: Early surgical intervention with sound microneurosurgical skills gives good outcomes independent of the type and location of tumor. Better outcomes are seen in extradural tumors, early surgical intervention, tumors better amenable to total resection, and in patients with better preoperative neurological status

Infections in Infants with SCID: Isolation, Infection Screening, and Prophylaxis in PIDTC Centers.

PurposeThe Primary Immune Deficiency Treatment Consortium (PIDTC) enrolled children with severe combined immunodeficiency (SCID) in a prospective natural history study of hematopoietic stem cell transplant (HSCT) outcomes over the last decade. Despite newborn screening (NBS) for SCID, infections occurred prior to HSCT. This study's objectives were to define the types and timing of infection prior to HSCT in patients diagnosed via NBS or by family history (FH) and to understand the breadth of strategies employed at PIDTC centers for infection prevention.MethodsWe analyzed retrospective data on infections and pre-transplant management in patients with SCID diagnosed by NBS and/or FH and treated with HSCT between 2010 and 2014. PIDTC centers were surveyed in 2018 to understand their practices and protocols for pre-HSCT management.ResultsInfections were more common in patients diagnosed via NBS (55%) versus those diagnosed via FH (19%) (p = 0.012). Outpatient versus inpatient management did not impact infections (47% vs 35%, respectively; p = 0.423). There was no consensus among PIDTC survey respondents as to the best setting (inpatient vs outpatient) for pre-HSCT management. While isolation practices varied, immunoglobulin replacement and antimicrobial prophylaxis were more uniformly implemented.ConclusionInfants with SCID diagnosed due to FH had lower rates of infection and proceeded to HSCT more quickly than did those diagnosed via NBS. Pre-HSCT management practices were highly variable between centers, although uses of prophylaxis and immunoglobulin support were more consistent. This study demonstrates a critical need for development of evidence-based guidelines for the pre-HSCT management of infants with SCID following an abnormal NBS.Trial registrationNCT01186913