* Advantages
** Some advantages to Biological and bio-hybrid drug carriers include but are not limited to offering compatibility with the human immune system, having the potential to be genetically modified, and having the capacity to hold drugs. Moreover, an essential advantage is their natural property of homing to inflammation and tumor sites. This natural property of homing to inflammation and tumor sites can enhance the targeted delivery of drugs, minimizing the risk of off-target effects and reducing the required dosage. Additionally, these systems have the potential to increase drug stability and prolong circulation time in the body, improving drug efficacy and reducing the frequency of dosing. Overall, these advantages make biological and bio-hybrid drug carriers promising for developing more effective and targeted drug delivery systems.
* Limitations
** One limitation of Biological and bio-hybrid drug carriers, especially leukocytes, is that they have a low drug-carrying capacity. A limit in the carrying capacity of a carrier means that researchers will have to use more medication to achieve the desired therapeutic effect, increasing the risk of adverse side effects and the cost of the treatment. Moreover, the short lifespan can limit their potential use for long-term drug delivery applications  [35]. Coupling this aspect with an inability to penetrate deep into tumors and the potential for genetic mutations can pose significant challenges for future drug delivery systems. Therefore, despite their advantages, further research and development are needed to address current limitations and improve their clinical feasibility.