Exosomes and microvesicles usually require characterization at the single-particle level. The most commonly used methods for this purpose are transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). However, atomic force microscopy (AFM) is also a promising method for the characterization of exosomes, and its opportunities seem underestimated. Here we describe the characterization of exosomes isolated from the conditioned media of human placenta cells using AFM, TEM, and NTA; we focus on the technical aspects of AFM imaging and data processing.

Periodontitis is a prevalent chronic inflammatory disease that leads to the progressive destruction of periodontal tissues and remains the primary cause of tooth loss worldwide. Despite advances in regenerative approaches—including stem cell therapy, scaffold-based tissue engineering, and guided tissue regeneration—the complete and functional restoration of the periodontal ligament remains a major clinical challenge. Stem-cell-based therapies and advanced biomaterials have emerged as promising strategies in regenerative medicine, offering potential for restoring periodontal structure and function. Among cells, periodontal-ligament-derived stem cells (PDLSCs) show exceptional regenerative potential due to their ability to differentiate into cementoblasts, osteoblasts, and other cell types essential for periodontal repair. In recent years, a variety of biomaterials with distinct specifications and properties have been utilized to repair periodontal damage. In addition to the inherent properties of biomaterials, the morphology and structural characteristics of these materials as bioequivalents for periodontal regeneration are also critical considerations. Furthermore, recent studies emphasize that mechanical stimulation plays a considerable role in directing stem cell differentiation, gene expression, matrix organization, and modulating inflammatory responses in periodontal regeneration. Canonical parameter ranges for systematic analysis indicate that cyclic stretch strain of 1–20% at 0.1–0.5 Hz (6–30 cycles/min) typically increases the expression of osteogenic markers (RUNX2, ALP, OCN) and matrix components (Col1) in PDLSCs. Conversely, higher values (>15%) often bias the response toward inflammatory pathways (IL-6, PGE2). Static compression above 2 g/cm² consistently stimulates the secretion of pro-inflammatory cytokines (IL-6, IL-8) and alters the RANKL/OPG balance in favor of osteoclastogenesis. Significant heterogeneity in response across studies will be analyzed by examining key methodological variables, including specific loading regimens (duration, frequency patterns) and culture conditions (e.g., serum/osteogenic supplements), which critically modulate mechanotransduction outcomes. This review summarizes current progress in periodontal regenerative medicine, emphasizing cellular and biomaterial considerations, as well as biofabrication techniques, with a particular focus on the influence of mechanical forces on PDLSCs. We discuss cellular responses to mechanical stimuli, including changes in gene expression, cytoskeletal organization, proliferation, and differentiation. Combining biological knowledge with advances in bioprinting and the study of mechanobiology, we finally discuss promising opportunities for improving periodontal regeneration that can be applied in the future in clinical practice.

Background: Detailed characterization of extracellular vesicles (EVs) is crucial for their application in medical diagnostics. However, the complexity of their chemical composition and the heterogeneity of EV populations make their characterization challenging. Here we describe two analytical procedures that can help overcome this challenge. Methods: Small EVs were isolated from conditioned cell culture media using ultracentrifugation and characterized using nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). Raman spectroscopy was used to assess the overall composition of the isolated samples and lipids extracted from them. Sulfophosphovanillin (SPV) colorimetric assay was used to quantify the contents of lipid. Results: Six samples of EVs were characterized. The lipid contents measured using SPV assay was in reasonable agreement with the quantitative estimates based on the particle size and concentration measured using NTA. The most peaks observed in the Raman spectra could be attributed to either proteins or lipids, and their origins was confirmed by lipid extraction. The protein-to-lipid ratio was estimated based on the Raman spectra. Conclusions: The experiential procedures described in this study will help to overcome the challenge of quick and highly informative characterization of the EVs.