Crosslinked HA (Crosslinked hyaluronic acid)
This document is technical information about materials. It does not recommend any procedure or product.
In brief
Hyaluronic acid chemically crosslinked into a hydrogel so that it resists enzymatic breakdown and holds shape under load. Crosslinking is what separates a filler from a plain solution of the same polysaccharide, and the degree and chemistry of that crosslinking is what product literature describes when it reports rheology.
Regulatory identity by market
COS cosmetic · MD medical device · RX drug · — not established in public sources
Identity & physical properties
| Synonyms | Crosslinked hyaluronic acid, Crosslinked HA, HA filler, Hyaluronan hydrogel |
|---|---|
| Formula | (C14H21NO11)n |
| Family | ECM component — crosslinked polysaccharide |
| Morphology | Injectable hydrogel. Rheology, in particular the elastic modulus G-prime, is the property most used in the literature to differentiate products |
| Molecular weight | Chain molecular weight and crosslink density are described separately; product behaviour follows from the network rather than from chain length alone |
Mechanism
This material supplies matrix rather than provoking the host to build it. Hyaluronan is a native component of the dermal extracellular matrix, and crosslinking is described in the literature as extending residence time by slowing enzymatic degradation. Reviews note that the gel can be removed by hyaluronidase, which is a property no other material in this atlas has.
Evidence
| PMID | Study type | Summary |
|---|---|---|
| 34882503 | review | Review of crosslinkers used in hyaluronic acid soft-tissue fillers and of alternative hydrogel fabrication routes |
| 38677707 | review | Review of the rheology of injectable hyaluronic acid hydrogels used as facial fillers |
| 30921116 | in vitro | Characterisation study of the rheologic and physicochemical properties used to differentiate hyaluronic acid filler products |
| 41199535 | review | Review of facial injectable fillers covering clinical application and safety strategies |
Regulatory identity — detail
| Market | Classification | Note | Basis |
|---|---|---|---|
| KR | medical-device | Injectable forms follow the tissue-repair biomaterial route in the MFDS device classification notice. | Legal text |
| EU | medical-device | Annex XVI, Section 3 of the MDR covers substances intended for facial or other dermal filling by injection, bringing such products under the Regulation even without an intended medical purpose. | Legal text |
| US | medical-device | Crosslinked hyaluronic acid dermal implants hold FDA premarket approval, listed with the generic name 'implant, dermal, for aesthetic use'. The earliest record found dates from December 2003 under PMA P020023. | Legal text |
| JP | unclassified | Not established from public sources as of the revision date below. | — |
| CN | unclassified | Not established from public sources as of the revision date below. | — |
| VN | unclassified | Not established from public sources as of the revision date below. | — |
Limitations & open questions
Rheologic figures such as elastic modulus are measured under laboratory conditions that do not reproduce the tissue environment, and one review cited here notes that clinical data linking these parameters to product performance are lacking. Crosslinker chemistry and residual crosslinker content differ between products and are not always disclosed. A figure reported for one gel does not describe crosslinked hyaluronic acid as a class.
All statements on this page are drawn from the cited literature. Where a market’s regulatory classification could not be established from public sources, it is marked as not established rather than inferred.
Crosslinking is the whole distinction
Hyaluronan in solution is cleared quickly. The same polysaccharide, chemically linked into a network, behaves as a gel that resists that clearance and carries load. Every property a filler is described by — firmness, cohesivity, how long it lasts — follows from the network rather than from the molecule, which is why two products made from the same raw material can behave differently.
Reversibility is unusual here
Most materials in this atlas cannot be removed once placed. Hyaluronidase degrades this one. That single property changes the risk calculus in a way that does not transfer to the polyester or ceramic biostimulators, and it is worth stating plainly rather than leaving implicit.
What the rheology numbers do and do not tell you
Elastic modulus is measured in a rheometer, not in a face. The review literature cited here is explicit that clinical evidence connecting these parameters to outcomes is thin. The numbers are useful for distinguishing products from one another; they are not a measured prediction of what happens in tissue.