In this work we report the development of the tri-functionalized mesoporous silica nanoparticles (MSNs) for use as theranostic compounds that orchestrate the trio of imaging, target and therapy in a single particle. The MSNs are functionalized in sequence with (1) contrast agents that enable traceable imaging of particle targeting, (2) drug payloads for therapeutic intervention and, (3) biomolecular ligands for highly-targeted particle delivery. Traceable imaging of nanoparticles was accomplished by directly incorporating a near-infrared (NIR) fluorescent contrast agent, ATTO647N, into the silica framework of MSNs, to exploit the relative transparency of most tissues at NIR wavelengths and maximize MSN surface area available for the subsequent conjugating drugs and targeting ligands. An oxygen-sensing, palladium-porphyrin based photosensitizer (Pd-porphyrin; PdTPP) was incorporated into the MSN's nanochannels, to enable photodynamic therapy (PDT). cRGDyK peptides, tiling the outermost surfaces of MSNs, were used for targeting the overexpressed α_vβ₃ integrins of cancer cells, and to ensure the internalization of the photosensitizer PdTPP. In vitro cell evaluation of the theranostic platform demonstrated not only excellent targeting specificity and minimal collateral damage, but highly potent therapeutic effect as well.

Gene-based therapies have emerged as a new modality for combating a myriad of currently incurable diseases. However, the fragile nature of gene therapeutics has significantly hampered their biomedical applications. Correspondingly, the development of gene-delivery vectors is of critical importance for gene-based therapies. To date, a variety of gene-delivery vectors have been created and utilized for gene delivery. In general, they can be categorized into viral- and non-viral vectors. Due to safety issues associated with viral vectors, non-viral vectors have recently attracted much more research focus. Of these non-viral vectors, polymeric vectors, which have been preferred due to their low immunogenicity, ease of production, controlled chemical composition and high chemical versatility, have constituted an ideal alternative to viral vectors. In particular, biodegradable polymers, which possess advantageous biocompatibility and biosafety, have been considered to have great potential in clinical applications. In this context, the aim of this review is to introduce the recent development and progress of biodegradable polymers for gene delivery applications, especially for their chemical structure design, gene delivery capacity and additional biological functions. Accordingly, we first define and categorize biodegradable polymers, followed by describing their corresponding degradation mechanisms. Various types of biodegradable polymers resulting from natural and synthetic polymers will be introduced and their applications in gene delivery will be examined. Finally, a future perspective regarding the development of biodegradable polymer vectors will be given.

Functionalization of mesoporous silica nanoparticles (MSNs) with Pd-porphyrins for cancer cell photodynamic therapy is reported. The composite platform, MSN–PdTPP, expands the role of Pd-porphyrins from their routine use as phosphorescence probes for oxygen sensing/imaging (diagnostics) to that of novel nano-photosensitizers for cancer cell phototherapy (therapeutics). The utility of MSN–PdTPP in the phototherapeutic treatment of MDA-MB-231 breast cancer cells is also evaluated, suggesting it is a promising cancer theranostic platform.