Biocompatibility of Injectable Microspheres

Gottfried Lemperle*

Received: January 16, 2018;   Published: January 23, 2018

DOI: 10.26717/BJSTR.2018.02.000682

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Abstract

The increasing need for long lasting injectable soft tissue fillers for the treatment of wrinkles and skin defects, gastric reflux, urinary and fecal incontinence, and other indications requires a critical discussion of biocompatibility based on science. Since biological fillers made of collagen will be absorbed over time, medium- and long-lasting biomaterials have been developed in recent years. Particles of irregular shape and rough surface structure tend to initiate severe and early foreign body reactions with scattered giant cells (“frustrated macrophages”). On the other hand, biologically inert microspheres with smooth surfaces are encapsulated by macrophages and fibrous tissue and will be kept in place. A review of the literature shows that most injected microspheres and particles of different chemical nature and a diameter of 20 to 65μm are phagocytosed by macrophages. Particles smaller than 20μm are also phagocytosed but are transported by macrophages to regional lymph nodes, liver and/or lungs. Since 1 gram of medium size microspheres of 40μm has a surface area twice as large as 1 gram of microspheres of 125μm in diameter, the stimulus for associated tissue in growth is doubled. Therefore, approximately 75% of the filler volume of a medium size microsphere implant consists of the body’s own connective tissue, whereas only 40% of the filler volume encapsulating larger beads is made up of fibrous tissue.

Abbreviations: GERD: Gastro-Esophageal Reflux Disease; PI: Propidium Iodine; PSF: Polysulfone; RES: Reticulo-Endothelial System; SEM: Scanned Electron Microscopy; PMA: Polymethylacrylate; PLLA: Polylactic Acid; PTFE: Polytetrafluoroethylene

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