Aptamers are short single-stranded nucleic acid sequences capable of binding to target molecules in a way similar to antibodies. Due to various advantages such as prolonged shelf life, low batch to batch variation, low/no immunogenicity, freedom to incorporate chemical modification for enhanced stability and targeting capacity, aptamers quickly found their potential in diverse applications ranging from therapy, drug delivery, diagnosis, and functional genomics to bio-sensing. Aptamers are generated by a process called SELEX. However, the current overall success rate of SELEX is far from being satisfactory, and still presents a major obstacle for aptamer-based research and application. The need for an efficient selection strategy consisting of defined procedures to deal with a wide variety of targets is significantly important. In this work, by analyzing key aspects of SELEX including initial library design, target preparation, PCR optimization, and single strand DNA separation, we provide a comprehensive analysis of individual steps to facilitate researchers intending to develop personalized protocols to address many of the obstacles in SELEX. In addition, this review provides suggestions and opinions for future aptamer development procedures to address the concerns on key SELEX steps, and post-SELEX modifications.

Conventional anticancer therapies, such as chemo- and/or radio-therapy are often unable to completely eradicate cancers due to abnormal tumor microenvironment, as well as increased drug/radiation resistance. More effective therapeutic strategies for overcoming these obstacles are urgently in demand. Aptamers, as chemical antibodies that bind to targets with high affinity and specificity, are a promising new and novel agent for both cancer diagnostic and therapeutic applications. Aptamer-based cancer cell targeting facilitates the development of active targeting in which aptamer-mediated drug delivery could provide promising anticancer outcomes. This review is to update the current progress of aptamer-based cancer diagnosis and aptamer-mediated active targeting for cancer therapy in vivo, exploring the potential of this novel form of targeted cancer therapy.

Non-viral vector-mediated transfection is a core technique for in vitro screening of oligonucleotides. Despite the growing interests in the development of oliogonucleotide-based drug molecules in recent years, a comprehensive comparison of the transfection efficacy of commonly used commercial transfection reagents has not been reported. In this study, five commonly used transfection reagents, including Lipofectamine 3000, Lipofectamine 2000, Fugene, RNAiMAX and Lipofectin, were comprehensively analyzed in ten cell lines using a fluorescence imaging-based transfection assay. Although the transfection efficacy and toxicity of transfection reagents varied depending on cell types, the toxicity of transfection reagents generally displayed a positive correlation with their transfection efficacy. According to our results, Lipofectamine 3000, Fugene and RNAiMAX showed high transfection efficacy, however, RNAiMAX may be a better option for majority of cells when lower toxicity is desired. The transfection efficacy of Lipofectamine 2000 was compromised by its high toxicity, which may adversely affect its application in most cells. We firmly believe that our findings may contribute to the future In vitro delivery and screening of single-stranded therapeutic oligonucleotides such as antisense oligonucleotides, antimiRs, and DNAzymes.

A targeted drug nanoparticle (NP) delivery system has shown potential as a possible cancer treatment. Given its merits, such as its selective distribution at tumor sites and its controllable drug release, drug-loaded NPs can be effectively delivered to selected organs and targeted cells, thus enhancing its antitumor efficiency and reducing its toxicity. We reported that hyaluronic acid (HA)-coated chitosan NPs promoted the drug delivery of 5-fluorouracil (5-Fu) into tumor cells that highly expressed CD44. Our new findings suggested that HA-coated chitosan NPs enhanced drug accumulation by effectively transporting NPs into CD44-overexpressed tumor cells, and they also resulted in mitochondrial damage induced by the production of reactive oxygen species (ROS). Compared to free drug and uncoated NPs, HA-coated chitosan NPs exhibited stronger inhibition rates and induced obvious apoptosis in CD44-overexpressed A549 cells. Biocompatible and biodegradable HA-coated chitosan NPs were developed to encapsulate a chemotherapeutic drug (5-Fu) to enhance drug accumulation in tumor cells and to improve the agent’s antitumor efficiency by offering targeted drug delivery via CD44.