Unlike external machines, implanting parts internally triggers the body's powerful defenses. The immune system attacks foreign objects, and blood forms clots around non-native surfaces. These two biological responses are the biggest design hurdles for internal replacement parts, problems that external devices like dialysis machines don't face.

Digital computers have separate units for processing (CPU) and memory (RAM). In biological computation, this distinction dissolves. The strength and pattern of connections between neurons *is* the memory, and the electrical firing (spiking) across these same connections *is* the processing.

The primary motivation for biocomputing is not just scientific curiosity; it's a direct response to the massive, unsustainable energy consumption of traditional AI. Living neurons are up to 1,000,000 times more energy-efficient, offering a path to dramatically cheaper and greener AI.

The supply chain for neurons is not the main problem; they can be produced easily. The true challenge and next major milestone is "learning in vitro"—discovering the principles to program neural networks to perform consistent, desired computations like recognizing images or executing logic.

The danger of AI creating harmful proteins is not in the digital design but in its physical creation. A protein sequence on a computer is harmless. The critical control point is the gene synthesis process. Therefore, biosecurity efforts should focus on providing advanced screening tools to synthesis providers.

Contrary to sci-fi imagery, the living neurons for biocomputing platforms are not extracted from animals. They are created from commercially available stem cells, which are originally derived from human skin. This process avoids the ethical and practical issues tied to using primary tissue.

Companies like Cortical Labs are growing human brain cells on chips to create energy-efficient biological computers. This radical approach could power future server farms and make personal 'digital twins' feasible by overcoming the massive energy demands of current supercomputers.

Instead of seizing human industry, a superintelligent AI could leverage its understanding of biology to create its own self-replicating systems. It could design organisms to grow its computational hardware, a far faster and more efficient path to power than industrial takeover.

There's a qualitative difference between neurons grown in vitro from stem cells and those found in an adult brain. The scientific community discusses whether lab-grown neurons are less mature, like "infant" neurons, and may lack some receptors. The "perfect" neuron for computation is an open research question.