An Aptamer-Functionalized DNA Circuit to Establish an Artificial Interaction between T Cells and Cancer Cells.

Nongenetic strategies that enable control over the cell-cell interaction network would be highly desired, particularly in T cell-based cancer immunotherapy. In this work, we developed an aptamer-functionalized DNA circuit to modulate the interaction between T cells and cancer cells. This DNA circuit was composed of recognition-then-triggering and aggregation-then-activation modules. Upon recognizing target cancer cells, the triggering strand was released to induce aggregation of immune receptors on the T cell surface, leading to an enhancement of T cell activity for effective cancer eradication. Our results demonstrated the feasibility of this DNA circuit for promoting target cancer cell-directed stimulation of T cells, which, consequently, enhanced their killing effect on cancer cells. This DNA circuit, as a modular strategy to modulate intercellular interactions, could lead to a new paradigm for the development of nongenetic T cell-based immunotherapy.

Aptamer-Based Analysis and Manipulation of the Protein Activity in Living Cells.

Directly analyzing and precisely manipulating the activity of target proteins without altering their natural structure and expression would be essential to decoding many protein-dominant cellular processes. To meet this goal, we used streptavidin as the carrier to develop an aptamer-based nanoplatform for monitoring the activation process of specific proteins in living cells. Our results showed that this nanoplatform could efficiently enter the cellular cytoplasm and specifically report the presence of RelA in the activated state. Meanwhile, with incorporation of a photoresponsive module, this aptamer-based nanoplatform was able to manipulate the nuclear translocation behavior of active RelA, enabling control over related downstream signaling events.

Photolytic Removal of Red Blood Cell Membranes Camouflaged on Nanoparticles for Enhanced Cellular Uptake and Combined Chemo-Photodynamic Inhibition of Cancer Cells.

Biomimetic therapeutics offer great potential for drug delivery that avoids immune recognition. However, the coated cell membrane usually hinders the cellular uptake of nanoparticles; thus, structure-changeable formulations have attracted increasing attention. Herein, we report photolytic pyropheophorbide a (PA)-inserted red blood cell (RBC) membrane-camouflaged curcumin dimeric prodrug (CUR2-TK)-poly(lactic-co-glycolic acid) (PLGA) nanoparticles [(CUR2-TK)-PLGA@RBC-PA] for enhanced cancer therapy. In these nanoparticles, the inner core was constructed using PLGA and loaded with our synthesized reactive oxygen species (ROS)-responsive cleavable curcumin dimeric prodrug (CUR2-TK). The nanoparticles generated ROS in response to the light irradiation attributed to the incorporated PA. The ROS further triggered the lysis of the cell membrane and exposed the nanoparticles for enhanced tumor cellular uptake, and the ROS also cleaved CUR2-TK for controlled CUR drug release. Moreover, the ROS performed photodynamic therapy (PDT). The chemotherapy and PDT produced a combined effect in the treatment of cancer cells, thus enhancing anticancer therapeutic efficacy.

Aptamer-Pyropheophorbide a Conjugates with Tumor Spheroid Targeting and Penetration Abilities for Photodynamic Therapy.

Pyropheophorbide a (Pyro) is a widely used photosensitizer for photodynamic therapy (PDT). However, poor water solubility, aggregation-induced fluorescence quenching, and lack of selectivity to targeted cells seriously limit its application. In this work, we prepared aptamer-Pyro conjugates (APCs) by linking Pyro to hydrophilic nucleic acid aptamer to enhance its water solubility and endow it with protein tyrosine kinase 7 (PTK7) overexpressed tumor spheroid specific targeting and penetration abilities for photodynamic therapy. The molecular conjugate was successfully synthesized and dissolved well in an aqueous solution. The APCs showed strong near-infrared fluorescence in the aqueous solution and produced singlet oxygen both in the solution and cells under laser irradiation, indicating its generation of singlet oxygen during PDT was guaranteed. Owing to the cancer cell targeting ability of the aptamer, the APCs specifically bound with PTK7 overexpressed cancerous cells and showed fluorescence signal for tumor cell imaging and diagnosis. The APCs exhibited favorable enhanced phototoxicity to target tumor cells compared with control cells. More importantly, due to the small size of the molecular conjugate, the APCs efficiently penetrated into the interior of multicellular tumor spheroids (MCTS) and caused cell damage. All these results indicated that the robust aptamer-Pyro conjugate is a promising selective tumor-targeting and penetrable molecule for cancer photodynamic therapy.

Aptamer-Functionalized Nanovaccines: Targeting In Vivo DC Subsets for Enhanced Antitumor Immunity.

Cancer vaccines, which directly pulsed in vivo dendritic cells (DCs) with specific antigens and immunostimulatory adjuvants, showed great potential for cancer immunoprevention. However, most of them were limited by suboptimal outcomes, mainly owing to overlooking the complex biology of DC phenotypes. Herein, based on adjuvant-induced antigen assembly, we developed aptamer-functionalized nanovaccines for in vivo DC subset-targeted codelivery of tumor-related antigens and immunostimulatory adjuvants. We chose two aptamers, iDC and CD209, and tested their performance on DC targeting. Our results verified that these aptamer-functionalized nanovaccines could specifically recognize circulating classical DCs (cDCs), a subset of DCs capable of priming naïve T cells, noting that iDC outperformed CD209 in this regard. With excellent cDC-targeting capability, the iDC-functionalized nanovaccine induced potent antitumor immunity, leading to effective inhibition of tumor occurrence and metastasis, thus providing a promising platform for cancer immunoprevention.

Aptamer-Based Targeted Drug Delivery Systems: Current Potential and Challenges.

Aptamers are single-stranded DNA or RNA with 20-100 nucleotides in length that can specifically bind to target molecules via formed three-dimensional structures. These innovative targeting molecules have attracted an increasing interest in the biomedical field. Compared to traditional protein antibodies, aptamers have several advantages, such as small size, high binding affinity, specificity, good biocompatibility, high stability and low immunogenicity, which all contribute to their wide application in the biomedical field. Aptamers can bind to the receptors on the cell membrane and mediate themselves or conjugated nanoparticles to enter into cells. Therefore, aptamers can be served as ideal targeting ligands for drug delivery. Since their excellent properties, different aptamer-mediated drug delivery systems had been developed for cancer therapy. This review provides a brief overview of recent advances in drug delivery systems based on aptamers. The advantages, challenges and future prospectives are also discussed.

Metal-organic frameworks for stimuli-responsive drug delivery.

Metal-organic framework (MOF), a novel hybrid porous material which is composited by metal ions and organic linkers, has drawn increasing attention and became a promising material in the biomedical field owing to their unique properties including large pore volume, high surface area, tunable pore size, versatile functionality and high drug loading efficiency. However, the MOF families and members, and the drug release mechanisms in MOF-based stimuli-responsive drug delivery systems (DDSs) are rarely summarized. Here, we systematically classified the families of MOF and introduced some representative members in MOF families. Moreover, the underlying drug release mechanisms were interpreted according to endogenous stimuli (include pH, glutathione (GSH), adenosine-triphosphate (ATP), ion, glucose, enzyme, H2S, and etc.) and the exogenous stimuli (include light, temperature, pressure, and etc.). Furthermore, the remaining challenges and future directions of DDSs based on MOF are discussed and proposed. This review revealed the relationship between the structure and properties of MOF. A better understanding of these release mechanisms under different stimuli would benefit the designing of sophisticated DDSs based on the promising material of MOF.

Metal-organic frameworks for virus detection.

Virus severely endangers human life and health, and the detection of viruses is essential for the prevention and treatment of associated diseases. Metal-organic framework (MOF), a novel hybrid porous material which is bridged by the metal clusters and organic linkers, has become a promising biosensor platform for virus detection due to its outstanding properties including high surface area, adjustable pore size, easy modification, etc. However, the MOF-based sensing platforms for virus detection are rarely summarized. This review systematically divided the detection platforms into nucleic acid and immunological (antigen and antibody) detection, and the underlying sensing mechanisms were interpreted. The nucleic acid sensing was discussed based on the properties of MOF (such as metal ion, functional group, geometry structure, size, porosity, stability, etc.), revealing the relationship between the sensing performance and properties of MOF. Moreover, antibodies sensing based on the fluorescence detection and antigens sensing based on molecular imprinting or electrochemical immunoassay were highlighted. Furthermore, the remaining challenges and future development of MOF for virus detection were further discussed and proposed. This review will provide valuable references for the construction of sophisticated sensing platform for the detection of viruses, especially the 2019 coronavirus.

Dynamic DNA Assemblies in Biomedical Applications.

Deoxyribonucleic acid (DNA) has been widely used to construct homogeneous structures with increasing complexity for biological and biomedical applications due to their powerful functionalities. Especially, dynamic DNA assemblies (DDAs) have demonstrated the ability to simulate molecular motions and fluctuations in bionic systems. DDAs, including DNA robots, DNA probes, DNA nanochannels, DNA templates, etc., can perform structural transformations or predictable behaviors in response to corresponding stimuli and show potential in the fields of single molecule sensing, drug delivery, molecular assembly, etc. A wave of exploration of the principles in designing and usage of DDAs has occurred, however, knowledge on these concepts is still limited. Although some previous reviews have been reported, systematic and detailed reviews are rare. To achieve a better understanding of the mechanisms in DDAs, herein, the recent progress on the fundamental principles regarding DDAs and their applications are summarized. The relative assembly principles and computer-aided software for their designing are introduced. The advantages and disadvantages of each software are discussed. The motional mechanisms of the DDAs are classified into exogenous and endogenous stimuli-triggered responses. The special dynamic behaviors of DDAs in biomedical applications are also summarized. Moreover, the current challenges and future directions of DDAs are proposed.

Tumor microenvironment and NIR laser dual-responsive release of berberine 9-O-pyrazole alkyl derivative loaded in graphene oxide nanosheets for chemo-photothermal synergetic cancer therapy.

A berberine 9-O-pyrazole alkyl derivative, a chemical compound (called B3) previously synthesized by our group, shows anti-cancer activity. However, B3 lacks targeting cytotoxicity to cancer cells, leading to obvious toxic side effects on normal cells. To solve this problem, here, we prepared a drug delivery system, namely, AS1411-GO/B3 for tumor targeting, in which nano-graphene oxide (GO) sheets were employed as the drug carrier, and the aptamer AS1411 was conjugated onto GO for tumor targeting. GO also had a photothermal effect, which helped the release of B3 from GO as well as the thermal cytotoxicity to cells. We found that the release of B3 could respond to acid conditions, indicating that the tumor intracellular environment could promote the release of B3, thus allowing it to perform chemotherapy effects. This system could also release B3 in response to photothermal heating, moreover, combined photothermal therapy and chemotherapy to improve the anticancer activity was achieved. This AS1411-GO/B3 platform with chemo-photothermal synergetic therapy provides a very promising treatment for tumors.

Advances in aptamer screening technologies.

Systematic evolution of ligands by exponential enrichment (SELEX) is a well-established technology for the screening of aptamers binding to various targets with relatively high specificity and affinity. The screened aptamers have shown great achievements in bio-sensing and targeted therapeutics, which in turn stimulate continuous development of SELEX technology. To date, many SELEX technologies have been established, such as cell-SELEX, mag-SELEX, capillary electrophoresis SELEX and some novel modifications of SELEX. This review highlights current screening technologies and comprehensively pinpoints their principles, pros and cons. Some main aptamers screened by SELEX or involved in clinical trials are summarized. While, there are still challenges in obtaining of aptamer with high affinity and in an efficient way. The limitations and possible future directions on the screening of aptamers are also outlined.