Cellular power supply for pacemakers
The human heart beats rhythmically thanks to a specialised group of cardiac cells or cardiac muscle fibres known as the pacemaker that literally sets the pace of the beat. Artificial pacemakers have batteries that currently must be replaced every five to seven years with an invasive and serious operation. Avoiding this procedure for an ageing population was the impetus behind the EU-funded project 'The development of an implantable cellular power supply based on rabbit cardiac cells' (RABBITCELLPSU). The team harnessed the power of living cardiac myocytes (muscle cells) to create the design for a new type of battery. Cardiac myocytes are long cells with a very highly organised structure. In order to confine the cells to specific channel regions, a microfluidic device with well-defined nanostructure was produced. Investigators first used primary cardiac cells to test the system, confirming the significant role of topographic features in the homogeneity and periodicity of beating of cell clusters. The team then used electrospun nanofibres with collagen as tissue scaffolds to encourage tissue growth along preferred orientations. Scientists then developed the means to cause induced pluripotent stem cells (iPSCs) to differentiate into cardiac myocytes. iPSCs are adult stem cells that have been genetically reprogrammed to an embryonic stem cell-like state. They are a powerful way to 'de-differentiate' cells from adults and then produce tissues that are a near-perfect match to minimise rejection by the immune system. The resulting cardiac myocytes have been shown to form functional tissue via the microfluidic devices or scaffolds. Exploiting them for power generation via a piezoelectric response is the next step. Zinc oxide nanowires and electrospun nanofibres from polyvinylidene fluoride, or PVDF, are both under investigation as promising piezoelectric materials. All the requisite groundwork to produce the required cellular and electrical components together with the necessary testing and measurement systems are in place. The laboratory is now routinely investigating cardiac myocytes and, in particular, their use as power devices. When ready, the cellular battery will have major impact on the quality of life of millions of people requiring surgical implantation of an artificial pacemaker.
Keywords
Cellular power supply, pacemakers, piezoelectric, cardiac cells, cardiac myocytes
