Microbubbles ~ A Novel Drug Delivery System

Introduction: 

Microbubbles have been recently introduced as a promising drug delivery platform for ultrasound-guided drug delivery & gradually decrease in size due to the dissolution of interior gases by the surrounding liquid and eventually disappear, leaving some Nano-Bubbles. Ultrasound, traditionally used in diagnostic medicine, is finding a place in drug delivery in connection with these microbubbles. In addition to their non-invasive nature and the fact that they can be focused on targeted tissues, acoustic waves have been credited with releasing pharmacological agents from microbubbles, as well as rendering cell membranes more permeable. Microbubbles dispersion method was investigated to improve oxygen transfer at low agitation rates and thus reduce power consumption and shear stress on the microorganisms. The microbubbles have an average size less than that of red blood cells, so they are capable of penetrating even into the small blood capillaries and releasing drug and genes under the action of ultrasound field after reaching the specific area of interest. Recently, targeting ligands are attached to the surface of the microbubbles, which have been widely used in the cardiovascular system and tumor diagnosis and therapy. Myocardial contrast echocardiography is rapidly becoming a technique that can be utilized with intravenous with intravenous Microbubbles to detect myocardial perfusion abnormalities during stress echocardiography. This review focuses on the characteristics of the microbubbles that give diagnostic. Thus it can be concluded that this study is beneficial for knowing the significance of microbubbles in NDDS.

Definition:

Microbubbles are small gas-filled microspheres that have specific acoustic properties making them useful as a contrast agent in ultrasound imaging. First-generation microbubbles are room air microspheres, capable of passing the pulmonary capillary-bed, but cannot resist arterial pressure gradients. To increase its stability, second-generation contrast agents are filled with a heavy-molecular-weight gas.

Objectives:

Its objective is to focus on the characteristics of microbubbles that give them therapeutic properties and some important aspects of ultrasound parameters that are known to influence microbubbles-mediated drug delivery. Targeting ligands are attached to the surface of the microbubbles for target specificity and novel delivery of drugs.

Methods of preparation:

Cross-linking polymerization:

Polymer cross-linked & microbubbles float on the surface. Due to vigorously stirring of the polymer solution.

Emulsion solvent evaporation:

The emulsion is formed by surfactant based aqueous solution & polymer-based polymer solution. Inner phase droplet of microbubbles is formed which produce after vaporization of the solvent.

Atomization & Reconstitution:

Porous sphere of the surfactant solution is prepared with primary gas enclosed in it. Then the primary gas diffuses out & secondary gas diffuses in. Microbubbles are formed in saline solution.

Sonication:

Sonication is preferred for formation of microbubbles, i.e. through an ultrasound transmitting septum or by penetrating a septum with an ultrasound probe including an ultrasonically vibrating hypodermic needle.

Advantages:

·         Ultrasound imaging allows real-time evaluations of blood flow.

·         Ultrasonic molecular imaging is safer than molecular imaging modalities.

·         Targeting strategies for microbubbles are versatile and modular.

·         Since microbubbles can generate such strong signals, a lower intravenous dosage is Needed.

·         Microbubbles can cross the blood-brain barrier to deliver the drug to the target site.

Disadvantages:

·         Microbubbles don’t last very long in circulation. They have low circulation residence times.

·    Ultrasound produces more heat as the frequency increases, so the ultrasonic frequency must be carefully monitored.

Application:

·         In liver imagine

·         In gene therapy

·         In cardiac disease

·         Biochemical Application

·         Microbubbles used as diagnostic aids for:

• Organ Edge Delineation • Blood Volume and Perfusion • Inflammation • Cancer • Liver Disease • Scanning of the tumors arising in the body.

·      In the treatment of inflammation microbubbles used as the targeting molecules for inflammation center.

·        In atherosclerosis plaque targeted microbubbles used in the in vivo model.

·        In the treatment of deep vein thrombi, labella microbubbles attached to the clot

·     General application in therapy due to their small surface area and volume ratio that’s why the result is rapid.

Conclusion:

Microbubbles have a lot of promising applications since the radicals generated through it have been practically used for antibacterial, anti-smell or purification treatment of liquids. The research and practical applications concerning the microbubbles have got a good progress steadily and would make encouragement to the research and development activities.