PAMAM-PLGA nanocarrier as potential co-delivery system against liver cancer: in vitro studies

Cancer remains one of the most persistent challenges to human health, a disease defined by cells that grow and divide without stopping. While doctors have long relied on surgery, radiation, and chemical drugs to fight it, these treatments often struggle with a difficult problem: they can harm healthy tissue just as much as the tumor. Chemotherapy drugs, in particular, are like blunt instruments; they circulate through the entire body, attacking rapidly dividing cells everywhere, which leads to severe side effects and often fails to deliver a high enough dose to the tumor itself. To solve this, scientists have turned to nanotechnology, a field that builds microscopic machines to carry medicine directly to where it is needed. One promising approach involves using tiny, tree-like structures called dendrimers, which can hold drugs in their branches, and coating them with biodegradable plastics that protect the cargo and help it slip through the body's defenses. The goal is to create a delivery system that releases its medicine only when it reaches the specific, acidic environment of a tumor, sparing the rest of the body.

In a recent study, researchers set out to build such a system specifically for liver cancer, a disease that causes hundreds of thousands of deaths worldwide. They focused on the HepG2 cell line, a common model for human liver cancer, and designed a new type of nanocarrier by combining two materials: a generation 4 polyamidoamine dendrimer and a biodegradable polymer known as PLGA. The dendrimer acts as a scaffold with many branches to hold the medicine, while the PLGA coating serves as a protective shell that reduces toxicity and helps the particle move through the bloodstream. The team loaded this carrier with two different cancer-fighting agents: sorafenib, a drug that stops tumor growth signals, and curcumin, a natural compound with antioxidant properties that can help kill cancer cells. By testing this combination in a laboratory setting, the researchers aimed to see if delivering both drugs together in this tiny package would be more effective and safer than giving the drugs alone.

The first step was to confirm that the nanocarrier had been built correctly. Using various analytical tools, the team examined the chemical bonds and physical shape of their creation. They found that the two materials had successfully joined together and that the drugs were securely held within the structure. The resulting particles were roughly spherical and measured about 231 nanometers in diameter, a size small enough to travel through blood vessels but large enough to avoid being filtered out too quickly by the kidneys. When the researchers looked at the particles under a powerful electron microscope, they appeared as globular shapes ranging from 100 to 250 nanometers, confirming that the mixture was uniform and stable. They also measured how much drug the carrier could hold, finding that it successfully loaded about 5.7 percent sorafenib and 4.4 percent curcumin by weight, a promising amount for a delivery system of this size.

A critical feature of this new system is how it releases its medicine. In the human body, normal blood has a neutral pH level, while the environment inside a tumor is more acidic due to the rapid growth and metabolism of cancer cells. The researchers tested their nanocarrier in solutions that mimicked these different conditions. In a neutral environment, similar to healthy blood, the drugs were released very slowly, with only a small fraction escaping in the first two hours. However, when the environment became acidic, mimicking the inside of a tumor, the release rate increased significantly over time. While only about 7.8% of sorafenib and 5.7% of curcumin were released within the first two hours even in acidic conditions, the release accelerated as time passed, reaching over 50% for sorafenib and nearly 59% for curcumin at pH 5.0 within the same two-hour window observed in the abstract's summary of the trend, or more accurately, the study noted that release reached 51.6% for sorafenib and 58.9% for curcumin at pH 5.0, demonstrating a clear pH-sensitive response where the carrier opens up to release the medicine once it reaches the acidic microenvironment of the cancer.

The true test of the nanocarrier came when the researchers exposed liver cancer cells to it. They compared the effects of the empty carrier, the carrier with just one drug, the carrier with both drugs, and the drugs given alone. The results showed a clear pattern: the empty carrier was safe and did not harm the cells. The single-drug carriers were effective, but the carrier holding both sorafenib and curcumin was the most powerful. After treating the cancer cells with the dual-drug carrier for 24 hours, the number of living cells dropped to about 21 percent. When the treatment continued for 48 and 72 hours, the survival rate of the cancer cells fell even further, to 9.4 percent and 4.3 percent, respectively. In contrast, when the same cells were treated with the pure drugs without the nanocarrier, many more cells survived, indicating that the delivery system made the drugs much more effective at killing the cancer. Importantly, when the researchers tested the same nanocarrier on normal human cells, those cells remained largely healthy, with survival rates staying above 78 percent, suggesting that this approach could spare healthy tissue from the damage usually caused by chemotherapy.

To understand how the nanocarrier killed the cancer cells, the team looked at the genetic activity inside the cells. They measured the levels of specific genes that control cell death, known as apoptosis. The study found that the dual-drug nanocarrier caused a dramatic increase in the activity of genes that trigger cell death, such as Caspase9, P53, and Bax. The activity of these genes rose by nearly seven times compared to untreated cells. At the same time, the nanocarrier significantly reduced the activity of Bcl2, a gene that acts as a shield to prevent cells from dying. This shift in genetic activity confirms that the nanocarrier is not just stopping the cancer cells from growing, but is actively forcing them to self-destruct. The combination of the two drugs delivered together appears to work better than either drug alone, creating a stronger signal for the cancer cells to die while leaving normal cells largely untouched.

This research demonstrates that a nanocarrier made from PAMAM and PLGA polymers can successfully carry two different cancer drugs to liver cancer cells in a laboratory setting. The system proved capable of protecting the drugs, releasing them specifically in acidic conditions, and inducing a strong death response in cancer cells while remaining safe for normal cells. The study suggests that this co-delivery approach could be a valuable strategy for improving liver cancer treatment, offering a way to increase the effectiveness of existing drugs while reducing their side effects. While these findings are limited to laboratory experiments and have not yet been tested in living organisms, they provide a strong foundation for future development of targeted therapies that could one day offer a more precise and less toxic option for patients facing liver cancer.