An Overview of Soft Tissue Fillers for Cosmetic Dermatology: From Filling to Regenerative Medicine

Abstract

Hyaluronic acid (HA)-based injectable filling agents are at the forefront of the current demand for noninvasive dermatological procedures for the correction of age-related soft tissue defects. The present review aims to summarize currently available HA-based products and critically appraise their differences in rheological nature and clinical application. Linear HA (LHA) gels may be supplemented with amino acids, lipoic acid, vitamins, nucleosides, or minerals for synergistic antiaging and antioxidant benefits (polycomponent LHA). HA hydrogels can be generated via chemical or physical crosslinking, which increases their elasticity and decreases viscosity. The performance of crosslinked fillers depends on HA concentration, degree of crosslinking, elastic modulus, cohesivity, and type of crosslinking agent employed. PEG-crosslinked LHA displays improved elasticity and resistance to degradation, and lower swelling rates as compared to BDDE-crosslinked LHA. Physical crosslinking stabilizes HA hydrogels without employing exogenous chemical compounds or altering hyaluronans’ natural molecular structure. Thermally stabilized hybrid cooperative HA complexes (HCC) are a formulation of high- and low-molecular-weight (H-HA and L-HA) hyaluronans, achieving high HA concentration, low viscosity with optimal tissue diffusion, and a duration comparable to weakly cross-linked gel. Our critical analysis evidences the importance of understanding different fillers’ properties to assist physicians in selecting the most appropriate filler for specific uses and for predictable and sustainable results.

Bioinspired Hydrogels as Platforms for Life-Science Applications: Challenges and Opportunities

“…The new HA hydrogels are soft and moist materials, but also it is necessary to confer a certain strength, allowing them to maintain a given shape. Due to its excellent biocompatibility and ability to form hydrogels by various chemical modifications, during the last years extensive studies were reported on HA innovative materials for various biomedical applications, such as skin biorevitalizing [230], advanced wound healing [231,232], cartilage friction reduction [233], controlled drug delivery systems [234,235], polymer scaffolds [236], and 3D bioprinting constructs [136,237].…”

Synthesis of the Types and Trends of Review Articles

“…However, the term "overview" is utilized as a non-discriminant term for reviews of changing rigor and quality [7]. In this regard, the Cochrane Collaboration took measures to distinguish "systematic overview," employed synonymously for "systematic review," from other forms of overview that typically lack systematic approaches and detailed reporting [7] (for some strong recent examples of medicine-related overview, see [56,57]).…”

Enzymatically Triggered Deprotection and Cross-Linking of Thiolated Alginate-Based Bioinks

“…Numerous different polymer cross-linking methods have been developed and explored for generating hydrogels, including both covalent − chemistries and noncovalent strategies. − The former results in hydrogels with long-term structural robustness, whereas the latter allows for dynamic remodulation of the materials by cells. Noncovalently cross-linked hydrogels are also often shear thinning, which is an attractive feature for three-dimensional (3D) bioprinting and other applications requiring syringe extrusion of the materials, such as in cell-injection therapy and soft-tissue filler treatments. − …”