Solid-phase synthesis is, to date, the preferred method for the manufacture of oligonucleotides, in quantities ranging from a few micrograms for research purposes to several kilograms for therapeutic or commercial use. But for large-scale oligonucleotide manufacture, scaling up and hazardous waste production pose challenges that necessitate the investigation of alternate synthetic techniques. Despite the disadvantages of glass supports, using soluble supports as a substitute presents difficulties because of their high overall yield and complex purification steps. To address these challenges, various independent approaches have been developed; however, other problems such as insufficient cycle efficiency and synthesis of oligonucleotide chains of desired length continue to exist. In this study, we present a review of the current developments, advantages, and difficulties of recently reported alternatives to supports based on controlled pore glass, and discuss the importance of a support choice to resolve issues arising during oligonucleotide synthesis.

Here, we link approved and emerging nucleic acid-based therapies with the expanding universe of small non-coding RNAs (sncRNAs) and the innate immune responses that sense oligonucleotides taken up into endosomes. The Toll-like receptors (TLRs) 3, 7, 8, and 9 are located in endosomes and can detect nucleic acids taken up through endocytic routes. These receptors are key triggers in the defense against viruses and/or bacterial infections, yet they also constitute an Achilles heel towards the discrimination between self- and pathogenic nucleic acids. The compartmentalization of nucleic acids and the activity of nucleases are key components in avoiding autoimmune reactions against nucleic acids, but we still lack knowledge on the plethora of nucleic acids that might be released into the extracellular space upon infections, inflammation, and other stress responses involving increased cell death. We review recent findings that a set of single-stranded oligonucleotides (length of 25-40 nucleotides (nt)) can temporarily block ligands destined for endosomes expressing TLRs in human monocyte-derived dendritic cells. We discuss knowledge gaps and highlight the existence of a pool of RNA with an approximate length of 30-40 nt that may still have unappreciated regulatory functions in physiology and in the defense against viruses as gatekeepers of endosomal uptake through certain routes.

Oligonucleotide is emerging as a novel class of therapeutics due to its high specificity, and ability to manage the incorrigible diseases with targeted action. The expedited growth evident from past few decades unveils the potentiality of the oligonucleotide as the future medicine. Various studies based on the vector-based system have shown the superiority of the lipid over other non-viral vectors. The lipid-based systems are most often exploited for the development of safe and efficient gene delivery systems. The factors influencing the structure, stability, internalization, and transfection of the lipoplex required for effective lipoplex delivery system are being explored. Furthermore, safety considerations and the status of lipoplex clinical trials are also addressed. The need of more scalable methods, which can be applied at industrial level, is identified and exploited. The aim is to manufacture products with long-term shelf life to support clinical trials and their subsequent market use. The design of lipoplexes leads to efficient entrapment of nucleic acid with enhanced in-vitro and in-vivo milieu stability, facilitating uptake and cellular targeting. The increasing number of entry of lipoplex-based gene therapy in the clinical trials shows the potential of lipoplex as a well-characterized system with consistent quality and reliable performance. The concomitant development of novel lipids, enhanced understanding of the uptake mechanism and formulation design characteristics have increased lipoplex-based oligonucleotide delivery system access to and success in the clinical trials and regulatory nod.

MicroRNAs (MiRNAs) play multiple crucial regulating roles in cell which can regulate one third of protein-coding genes. MiRNAs participate in the developmental and physiological processes of human body, while their aberrant adjustment will be more likely to trigger diseases such as cancers, kidney disease, central nervous system diseases, cardiovascular diseases, diabetes, viral infections and so on. What\'s worse, for the detection of miRNAs, their small size, high sequence similarity, low abundance and difficult extraction from cells impose great challenges in the analysis. Hence, it\'s necessary to fabricate accurate and sensitive biosensing platform for miRNAs detection. Up to now, researchers have developed many signal-amplification strategies for miRNAs detection, including hybridization chain reaction, nuclease amplification, rolling circle amplification, catalyzed hairpin assembly amplification and nanomaterials based amplification. These methods are typical, feasible and frequently used. In this review, we retrospect recent advances in signal amplification strategies for detecting miRNAs and point out the pros and cons of them. Furthermore, further prospects and promising developments of the signal-amplification strategies for detecting miRNAs are proposed.