Recent studies have demonstrated that exosomes serve as biocompatible drug carriers, offering enormous advantages over conventional synthetic carriers and holding immense potential for therapeutic applications. The development of nanocarriers capable of effectively delivering loaded cargos to target sites without systemic toxicity remains challenging and is of significance to facilitate therapeutic effectiveness. Drug carriers that are specifically designed to respond to the acidic and reductive environments of tumors are of great interest. These carriers can effectively release loaded cargos at tumor-specific sites. In addition, noninvasive cancer therapies such as sonodynamic therapy (SDT) and photodynamic therapy (PDT) have recently emerged as an effective modality and an alternative to traditional cancer therapies, which can effectively minimize side effects and improve treatment efficacy. In pursuit of this aim, this dissertation focuses on the design and preparation of exosome-based drug carriers for the safe and efficient delivery of therapeutic agents for tumor targeting, bioimaging capacity, and anticancer effects. Herein, the conjugation of cancer-targeting ligands into exosome surface could improve the accumulation of sonosensitizer into tumors and thus enhance cancer-specificity of exosomes. As a result, the nanosystems demonstrated higher sonotoxicity against cancer cells (Chapter 2). The development of stimuli-responsive exosomes to deliver dual therapeutic agents was illustrated in Chapter 3 and Chapter 4. In particular, sodium bicarbonate (SBC) was loaded into exosomes to render pH-responsive exosomes capable of delivering dual sonosensitizer and anticancer drug to cancer cells for chemo-SDT (Chapter 3). In response to acid pH in the endo/lysosomal compartment, SBC significantly generated CO₂ bubbles and caused the exosome membrane to burst, followed by the effective release of loaded cargo. Consequently, the nanosystem exhibited efficient anticancer activity against human breast cancer cells in vitro and in vivo owing to the combination of chemo-SDT. Furthermore, taking the feature of over-expressed glutathione (GSH) in the tumor microenvironment, redox-cleavable diselenide linker-bearing lipids were embedded into exosomes to trigger drug release in response to high GSH concentrations in tumors. Bioreducible exosomes effectively suppressed tumor growth in mice without significant systemic toxicity, via a combination of mitochondria-targeted SDT and energy metabolism-targeted therapy (Chapter 4). Moreover, exosomes produced from brain endothelial cells (bEVs) were employed as a biocompatible nanoplatform to deliver photosensitizers into brain tumors, crossing the blood-brain barrier (BBB). Mitochondria-targeting photosensitizer-loaded bEVs significantly suppressed the growth of glioblastoma without resulting in adverse systemic effects (Chapter 5). The engineered exosomes in this dissertation successfully empowered the inherent therapeutic agents, overcoming their disadvantages via conferring good biocompatibility, high drug loading capacity, improved stability, and efficient tumor targeting ability. Moreover, this dissertation offers an in-depth understanding on the possible mechanisms for tumor-targeted delivery of exosome-based nanosystems with various state-of-the-art material designs.