Recent discoveries have unfolded many powerful emerging applications in the field of drug delivery science. For the past few years, ultrasound mediated microbubble contrast agents have been an emerging modality for diagnostic and drug delivery applications. Microbubbles are small spherical bubbles composed of a gas core encapsulated by a shell with different materials. The composition of the microbubble determines its stiffness, encapsulation efficiency, stability, and clearance from the system. A gas-filled microbubble, when activated by an acoustic pulse, can produce large volumetric oscillations, and once administered intravenously, can act as a cavitating nuclei, allowing for a wide range of ultrasound-assisted drug delivery applications. Microbubbles offer a fantastic approach to ultrasound triggered drug delivery with various drug loading techniques and targeting strategies for the uptake of bioactive substances such as polynucleotides, proteins, genes, and small-molecule drugs. Microbubbles can be used for several diagnostic and therapeutic purposes for accurate detection and treatment of various life-threatening diseases.

Bacterial engineering modifies bacteria's genomic sequence using genetic engineering tools. These engineered bacteria can produce modified proteins, peptides, nucleic acids, and other biomolecules that can be used to treat various medical conditions. Engineered bacteria can target diseased tissues or organs, detect specific biomarkers in the diseased environment, and even induce specific conditions. Furthermore, a meticulously designed intracellular metabolic pathway can activate or inhibit the expression of related genes, synthesise biologically active therapeutic molecules, and precisely deliver drug payloads to diseased tissues or organs. Lactococcus (L.lactis), Salmonella (S.typhi), and E. coli (E.coli Nissle) are the most studied engineered microorganisms used as drug carriers. These have been used in vaccines to treat multifactorial diseases such as cancer, autoimmune diseases, metabolic diseases, and inflammatory conditions. Other promising strains include Bifidobacterium animalis, Listeria monocytogenes, Staphylococcus epidermidis, Staphylococcus lugdunensis, and Clostridium sporogenes. Despite the low reported risk, toxic effects associated with bacterial cells, limiting their efficacy and rapid clearance due to immune responses stimulated by high bacterial concentrations, remain major drawbacks. As a result, a better and more effective method of drug delivery must be developed by combining bacterial-based therapies with other available treatments, and more research in this area is also needed.