Selection of DNA Aptamers for Differentiation of Human Adipose-Derived Mesenchymal Stem Cells from Fibroblasts

Progress in Aptamer Research and Future Applications

Aptamers are short, single-stranded DNA, RNA or synthetic XNA molecules that bind to target molecules with high specificity and affinity. These intrinsically structured RNA or DNA oligonucleotides are not only substitutes for antibodies, but also show great potential for applications in diagnostics, specific drug delivery, and treatment of certain diseases. While the process of aptamer identification and its core functional mechanism known as systematic evolution of exponentially enriched ligands (SELEX), SELEX involves a number of single processes, each contributing to the success or failure of aptamer generation. Today, aptamers are widely used to facilitate basic research discoveries and clinical diagnostics. In addition, aptamers play a promising role as clinical diagnostic and therapeutic agents. This review provides recent advances in this rapidly growing field of research, with special emphasis on aptamer generation and screening, small molecule aptamers, the development of aptamer applications, and applications in clinical medicine. And it also discusses the problems that still exist today with aptamers.

Screen and Optimization of an Aptamer for Alexandrium tamarense-A Common Toxin-Producing Harmful Alga

Among all the paralytic shellfish toxins (PSTs)-producing algae, Alexandrium tamarense is one of the most widespread harmful species posing a serious threat to marine resources and human health. Therefore, it is extremely important to establish a rapid and accurate monitoring method for A. tamarense that can provide early warnings of harmful algal blooms (HABs) caused by this alga and limit the contamination due to PSTs. In this study, an ssDNA library was first obtained by whole cell systematic evolution of ligands by exponential enrichment after 18 consecutive rounds of iterative screening. After sequencing in combination with subsequent multiple alignment of sequences and secondary structure simulation, the library could be classified into 2 families, namely, Family1 and Family2, according to sequence similarity. Flow cytometry was used to test the affinity and cross-reactivity of Ata19, Ata6, Ata25 and Ata29 belonging to Family2. Ata19 was selected to be modified by truncation, through which a new resultant aptamer named as Ata19-1-1 was obtained. Ata19-1-1 with a KD of 75.16 ± 11.10 nM displayed a much higher affinity than Ata19. The specificity test showed that Ata19-1-1 has the same discrimination ability as Ata19 and can at least distinguish the target microalga from other microalgae. The observation under a fluorescence microscopy showed that the A. tamarense cells labeled with Ata19-1-1 are exhibiting bright green fluorescence and could be easily identified, factually confirming the binding of the aptamer with target cells. In summary, the aptamer Ata19-1-1 produced in this study may serve as an ideal molecular recognition element for A. tamarense, which has the potential to be developed into a novel detection method for this harmful alga in the future.

Adipose-Derived Stromal Cells for Chronic Wounds: Scientific Evidence and Roadmap Toward Clinical Practice

Chronic wounds, ie, non-healing ulcers, have a prevalence of ~1% in the general population. Chronic wounds strongly affect the quality of life and generate considerable medical costs. A fraction of chronic wounds will heal within months of appropriate treatment; however, a significant fraction of patients will develop therapy-refractory chronic wounds, leading to chronic pain, infection, and amputation. Given the paucity of therapeutic options for refractory wounds, cell therapy and in particular the use of adipose-derived stromal cells (ASC) has emerged as a promising concept. ASC can be used as autologous or allogeneic cells. They can be delivered in suspension or in 3D cultures within scaffolds. ASC can be used without further processing (stromal vascular fraction of the adipose tissue) or can be expanded in vitro. ASC-derived non-cellular components, such as conditioned media or exosomes, have also been investigated. Many in vitro and preclinical studies in animals have demonstrated the ASC efficacy on wounds. ASC efficiency appears to occurs mainly through their regenerative secretome. Hitherto, the majority of clinical trials focused mainly on safety issues. However more recently, a small number of randomized, well-controlled trials provided first convincing evidences for a clinical efficacy of ASC-based chronic wound therapies in humans. This brief review summarizes the current knowledge on the mechanism of action, delivery and efficacy of ASC in chronic wound therapy. It also discusses the scientific and pharmaceutical challenges to be solved before ASC-based wound therapy enters clinical reality.

Application of aptamers in regenerative medicine

Regenerative medicine is a discipline that studies how to use biological and engineering principles and operation methods to repair and regenerate damaged tissues and organs. Until now, regenerative medicine has focused mainly on the in-depth study of the pathological mechanism of diseases, the further development and application of new drugs, and tissue engineering technology strategies. The emergence of aptamers has supplemented the development methods and types of new drugs and enriched the application elements of tissue engineering technology, injecting new vitality into regenerative medicine. The role and application status of aptamers screened in recent years in various tissue regeneration and repair are reviewed, and the prospects and challenges of aptamer technology are discussed, providing a basis for the design and application of aptamers in long-term transformation.

Research progress of whole-cell-SELEX selection and the application of cell-targeting aptamer

BACKGROUND

Aptamers refer to the artificially synthesized nucleic acid sequences (DNA/RNA) that can bind to a wide range of targets with high affinity and specificity, which are generally generated from systematic evolution of ligands by exponential enrichment (SELEX). As a novel method of aptamers screening, whole-cell-SELEX (WC-SELEX) has gained more and more attention in many fields such as biomedicine, analytical chemistry, and molecular diagnostics due to its ability to screen multiple potential aptamers without knowing the detailed structural information of target molecules.

METHODS AND RESULTS

In recent years, with the deepening of research on application of aptamers, the traditional WC-SELEX cannot meet the practical application because of long experimental period, complicated operation process and low specificity, etc. Therefore, the development of more efficient methods for screening aptamer is always on the road. This paper summarizes the current research status of WC-SELEX for bacteria, parasites and animal cells, and reviews the latest advances of WC-SELEX techniques that are dependent on novel instruments, materials and microelectronics, including fluorescence-activated cell sorting-assisted SELEX, three-dimensional assisted WC-SELEX, and microfluidic chip system-assisted WC-SELEX. In addition, the application of aptamers targeting cells was discussed.

CONCLUSION

Taken together, this review is aimed at providing a reference for WC-SELEX selection and application of aptamer targeting cells.

Synthesis and characterization of gold nanorods coated by mesoporous silica MCM-41 as a platform bioapplication in photohyperthermia

Gold nanoparticles have been widely investigated for biomedical applications due to their optical properties. These particles present the interesting feature of absorbing light when stimulated with laser radiation to generate heating. Among the possible morphologies for synthetic gold nanoparticles, gold nanorods have properties of great interest for applications in the photohyperthermia processes. Due to their morphology, gold nanorods can absorb light at longer wavelengths comprising specific regions of the electromagnetic spectrum, such as the region of the biological window, in which laser radiation has less interaction with tissues. However, these nanoparticles present limitations in biomedical applications, such as low colloidal and thermal stabilities that can be overcome by coating the gold nanorods with silica MCM-41. The silicate covering can provide greater stability for gold nanorods and allow multifunctionality in treating different diseases through photohyperthermia. This work developed a specific chemical route through seed and growth solutions to synthesize gold nanorods with controlled particle size, rod morphology, and silica covering for photohyperthermia applications. The synthesized samples were characterized through a multi-technique approach that successfully demonstrated the presence of gold nanorods inside the silica coating, presenting high stability and desirable textural and morphological characteristics for bioapplications. Furthermore, silica-coated gold nanorods exhibit high biocompatibility and great performance in generating therapeutic heating by absorbing laser radiation in the biological window range, making the system developed in this work a promising agent in photohyperthermia.