An Injectable and Drug-loaded Supramolecular Hydrogel for Local Catheter Injection into the Pig Heart

The overall goal of this procedure is to minimal invasively, inject a drug loaded supramolecular hydrogel into an infarcted pig heart using a long, flexible catheter. This is accomplished by first preparing a formulation of hydrogel later and the desired drug. The second step is to investigate the properties of the hydrogel and the rate of drug release in an in vitro setting.

Then four weeks after myocardial infarction, an electromechanical map of the pig's left ventricle is made using data points taken from the endocardial surface. Then the so-called hibernating myocardium is targeted for local injections with drug loaded hydrogel. This convenient formulation and application procedure can lead to uncovering new therapies for myocardial infarction and so forth.

The main advantage of this technique over existing percutaneous approaches like intra coronary effusion are one, the catheter application of the hydrogel, and two, the possibility of treatment planning, which allows us to guide catheter to the area of interest. This method can help answer key questions in the study and treatment of myocardial infarction, such as potential advantages of injecting a mechanically supporting material and the effectiveness of sustained local drug delivery. The Implications of this technique extend to our therapy and myocardial infarction because the electro mechanical mapping allows for identification of the infarcted region and subsequent guided site-specific injection of hydrogel allows for local drug delivery.

Generally, individuals knew that this method will struggle because this technique requires practical skills with subtle movements of the catheter while monitoring stability parameters. Visual demonstration of this method is critical as both formulation of drug load IDE gels. Anti injection via a catheter are challenging procedures that are difficult to perform without experience In preparation formulate a milliliter of 10%weight by volume hydrogel.

Begin with dissolving 100 milligrams of up hydrogel later in 900 microliters of PBS at pH 11.7. In case the hydrogels are formulated for injection into animals, all steps should be performed wearing gloves. Then stir the hydrogel into the PBS at 70 degrees Celsius for an hour.

Once the solution has cooled, check the pH. It should be around nine. The solution is good for several days.

Now pipette the drug or molecule of interest into the solution and let it stir for 10 minutes in case the hydrogel will be injected into an animal. Complete the preparation by UV sterilizing the solution for an hour. The text protocol reviews how the hydrogel can be analyzed.

First, prepare a plastic hanging cell culture insert for a 24 well plate by covering its bottom with parfum to prevent leakage. Then transfer 100 microliters of the prepared viscous solution into the insert, and immediately add 1.4 microliters of one molar hydrochloric acid. The pH will drop to a neutral value and in 30 minutes the hydrogel will cure.

Now remove the para film and place the inserts into a well plate, and at 800 microliters of PBS at pH 7.4, load the empty wells with PBS and seal the plate with paraform to reduce evaporation. Then let the plates incubate with gentle agitation at 37 degrees Celsius. Periodically refreshing the PBS and analyzing the removed PBS for released compounds by up hydrogel erosion and drug release.

Demonstrating the procedure will be Dr.Ton from the urich where he is an interventional cardiologist. Four weeks after inducing a myocardial infarction, plan the electromechanical mapping procedure and set up the system in the cath lab. First place the external reference patch on the back of the anesthetized pig, then secure vascular access via the femoral artery by the standard protocol.

To construct the electromechanical map of the LV endocardial surface, use an ultra low magnetic field energy source and a sensor tipped catheter. Next, use a power injector to obtain a biplane left ventricular angiogram in the 25 degree right anterior oblique and 40 degree left anterior oblique view. Use these views to estimate the size of the lv.

Now give the animal 75 units per kilogram of heparin. Then advance a number eight French mapping catheter under fluoroscopic guidance into the left ventricle via the descending aorta, aortic arch, and a aortic valve. The catheter can have a D or F curve.

Then orientate the tip of the catheter to the apex of the left ventricle. To acquire the first data, continue collecting data on the outflow tract, lateral and posterior points to form A 3D silhouette, defining the borders of the ventricle. Next, drag the mapping catheter over the endocardium and sequentially.

Acquire the location of the tip while it is in contact with the endocardium. Ultimately, collect data from all the endocardial segments. Then remove the mapping catheter using the data.

Define the target area. It is where electrical activity is near normal and mechanical movement is impaired. The so-called hibernating myocardium for the intra myocardial injection.

Plan to use an injection catheter composed of a 27 gauge needle and core lumen in a number eight French catheter to deliver specific amounts. Lotus syringe with approximately one milliliter of the hydrogel solution, and place it in a syringe pump to ensure that the myocardial wall is not punctured by the needle. Adjustments are done according to minimal wall thickness of the ventricle measured on a recent echocardiogram.

Adjust the needle extension to zero degrees and to 90 degrees. Then fill the dead space in the system with the hydrogel solution. Next, place the injection catheter tip across the aortic valve and into the target area to fulfill the first injection criteria.

That is perpendicularity of the catheter to the LV wall. Second, it must have excellent loop stability as calculated by the EMM system. Thirdly, the target area must have an underlying voltage of at least 6.9 millivolts.

If these criteria are met, then advance the needle into the myocardium. Now, check a fourth criteria. There must be a premature ventricular contraction of the left ventricle.

With all criteria met inject 0.1 to 0.3 milliliters of the hydrogel at a constant rate. Repeat the injection at six to 10 different positions that are as diffusely positioned as possible for the hydrogel to function as a drug delivery system. Erosion must occur gradually release of a small drug pirfenidone and a fluorescent protein, and ruby two were studied.

In vitro the small drug released within a day while bigger molecules like M ruby two released over a week. There was no apparent burst release of large molecules to locate the target region for the drug injection. Real-time 3D myocardial mapping was used to create a reconstruction of the left ventricle.

It continuously displays as voltage potentials on a graded color scale whereafter it is adjusted to the selected threshold. The local linear shortening or LLS function quantifies regional wall motion by obtaining the average change in distance between sample site and adjacent points at systole and end diastole. These values are then calculated for each segment and displayed in the polar map.

Infarcted areas are characterized by impaired mechanical sensitivity or having an LLS value below 4%and they are characterized abnormal or low unipolar potentials that are less than six millivolts Once mastered, this technique can be done in one and a half to two hours While doing this procedure. It's important to plan it properly and to have a team of experienced people Following this procedure. Variations in the treatment can be implemented to answer additional questions such as optimal hydrogel formulation, desired rate of drug release, and effectiveness of different kind of drugs.

After watching this video, you should have a good understanding on how to formulate a drug loaded super molecular hydrogel and how to carefully plan and execute the electromechanical mapping and the inter myocardial injection procedures. Do not forget that working with lab animals such as pigs requires approval from the experimental committee and should be performed according to local welfare regulations.