Aptamer guided nanomedicine shows great promise in targeted cancer therapies. However the loss of targeting capacity during in vivo or clinical trials has largely hindered its popularity and there are no systematic studies to elucidate the causes. Herein, we investigated such loss of targeting capacity by examining how the physiological milieu affected targeting effect. Aptamer functionalized gold nanoparticle (AuNP) was chosen as the model and exposed to human blood serum that is used to mimic physiological milieu. Dynamic light scattering (DLS), flow cytometry and label-free liquid chromatography tandem mass spectrometry (LC-MS/MS) were employed to determine variations of NPso surface chemistry and biological identities changes after serum exposure. Results showed that the targeting ability loss was caused by protein corona blocking, replacement and enzymatic cleavage of surface aptamer targeting ligands. Noteworthy, the aggregation issue is critical for the smaller NPs. Analysis of the protein corona profile indicated the accumulation of immune-related proteins on the surface of aptamer-conjugated NPs, which could induce immune response, resulting in rapid clearance of NPs.

Graphitic nanomaterials have unique, strong, and stable Raman vibrations that have been widely applied in chemistry and biomedicine. However, utilizing them as internal standards (ISs) to improve the accuracy of surface-enhanced Raman spectroscopy (SERS) analysis has not been attempted. Herein, we report the design of a unique IS nanostructure consisting of a large number of gold nanoparticles (AuNPs) decorated on multilayered graphitic magnetic nanocapsules (AGNs) to quantify the analyte and eliminate the problems associated with traditional ISs. The AGNs demonstrated a unique Raman band from the graphitic component, which was localized in the Raman silent region of the biomolecules, making them an ideal IS for quantitative Raman analysis without any background interference. The IS signal from the AGNs also indicated superior stability, even under harsh conditions. With the enhancement of the decorated AuNPs, the AGN nanostructures greatly improved the quantitative accuracy of SERS, in particular the exclusion of quantitative errors resulting from collection loss and non-uniform distribution of the analytes. The AGNs were further utilized for cell staining and Raman imaging, and they showed great promise for applications in biomedicine.

Ultrathin two-dimensional (2D) porous Zn(OH)₂ nanosheets (PNs) were fabricated by means of one-dimensional Cu nanowires as backbones. The PNs have thickness of approximately 3.8 nm and pore size of 4–10 nm. To form "smart" porous nanosheets, DNA aptamers were covalently conjugated to the surface of PNs. These ultrathin nanosheets show good biocompatibility, efficient cellular uptake, and promising pH-stimulated drug release.

Cancer chemotherapy has been limited by its side effects and multidrug resistance (MDR), the latter of which is partially caused by drug efflux from cancer cells. Thus, targeted drug delivery systems that can circumvent MDR are needed. Here, we report multifunctional DNA nanoflowers (NFs) for targeted drug delivery to both chemosensitive and MDR cancer cells that circumvented MDR in both leukemia and breast cancer cell models. NFs are self-assembled via potential co-precipitation of DNA and magnesium pyrophosphate generated by rolling circle replication, during which NFs are incorporated using aptamers for specific cancer cell recognition, fluorophores for bioimaging, and doxorubicin (Dox)-binding DNA for drug delivery. NF sizes are tunable (down to ~200 nm in diameter), and the densely packed drug-binding motifs and porous intrastructures endow NFs with a high drug-loading capacity (71.4%, wt/wt). Although the Doxloaded NFs (NF-Dox) are stable at physiological pH, drug release is facilitated under acidic or basic conditions. NFs deliver Dox into target chemosensitive and MDR cancer cells, preventing drug efflux and enhancing drug retention in MDR cells. NF-Dox induces potent cytotoxicity in both target chemosensitive cells and MDR cells, but not in nontarget cells, thus concurrently circumventing MDR and reducing side effects. Overall, these NFs are promising tools for circumventing MDR in targeted cancer therapy.

Chlorin e6-pHLIP_ss-AuNRs, a gold nanorod-photosensitizer conjugate containing a pH (low) insertion peptide (pHLIP) with a disulfide bond which imparts extracellular pH (pH_e)-driven tumor targeting ability, has been successfully developed for bimodal photodynamic and photothermal therapy. In this bimodal therapy, chlorin e6 (Ce6), a second-generation photosensitizer (PS), is used for photodynamic therapy (PDT). Gold nanorods (AuNRs) are used as a hyperthermia agent for photothermal therapy (PTT) and also as a nanocarrier and quencher of Ce6. pHLIPss is designed as a pHe-driven targeting probe to enhance accumulation of Ce6 and AuNRs in cancer cells at low pH. In Ce6-pHLIP_ss-AuNRs, Ce6 is close to and quenched by AuNRs, causing little PDT effect. When exposed to normal physiological pH 7.4, Ce6-pHLIP_ss-AuNRs loosely associate with the cell membrane. However, once exposed to acidic pH 6.2, pHLIP actively inserts into the cell membrane, and the conjugates are translocated into cells. When this occurs, Ce6 separates from the AuNRs as a result of disulfide bond cleavage caused by intracellular glutathione (GSH), and singlet oxygen is produced for PDT upon light irradiation. In addition, as individual PTT agent, AuNRs can enhance the accumulation of PSs in the tumor by the enhanced permeation and retention (EPR) effect. Therefore, as indicated by our data, when exposed to acidic pH, Ce6-pHLIP_ss-AuNRs can achieve synergistic PTT/PDT bimodality for cancer treatment.

Early and accurate diagnosis and treatment of cancer depend on rapid, sensitive, and selective detection of tumor cells. Current diagnosis of cancers, especially leukemia, relies on histology and flow cytometry using single dye-labeled antibodies. However, this combination may not lead to high signal output, which can hinder detection, especially when the probes have relatively weak affinities or when the receptor is expressed in a low concentration on the target cell surface. To solve these problems, we have developed a novel method for sensitive and rapid detection of cancer cells using dye-doped silica nanoparticles (NPs) which increases detection sensitivity in flow cytometry analyses between 10- and 100-fold compared to standard methods. Our NPs are ~60 nm in size and can encapsulate thousands of individual dye molecules within their matrix. We have extensively investigated surface modification strategies in order to make the NPs suitable for selective detection of cancer cells using flow cytometry. The NPs are functionalized with polyethylene glycol (PEG) to prevent nonspecific interactions and with neutravidin to allow universal binding with biotinylated molecules. By virtue of their reliable and selective detection of target cancer cells, these NPs have demonstrated their promising usefulness in conventional flow cytometry. Moreover, they have shown low background signal, high signal enhancement, and efficient functionalization, either with antibody- or aptamer-targeting moieties.

Advanced bioanalysis, including accurate quantitation, has driven the need to understand biology and medicine at the molecular level. Bioconjugated silica nanoparticles have the potential to address this emerging challenge. Particularly intriguing diagnostic and therapeutic applications in cancer and infectious disease as well as uses in gene and drug delivery, have also been found for silica nanoparticles. In this review, we describe the synthesis, bioconjugation, and applications of silica nanoparticles in different bioanalysis formats, such as selective tagging, barcoding, and separation of a wide range of biomedically important targets. Overall, we envisage that further development of these nanoparticles will provide a variety of advanced tools for molecular biology, genomics, proteomics and medicine.