TABLE 2.

Sealants and adhesives used for clinical pulmonary applications

	Composition	Examples	Mechanism of action	Characteristics	References
Lung volume reduction
PVA	Aminated PVA Glutaraldehyde	AeriSeal (PulmonX Corp, CA, USA)	Local delivery and in situ polymerisation induces inflammatory responses, fibrosis and scar tissue formation, promoting atelectasis	Degradable, and invokes inflammatory responses	[27, 29, 31]
Autologous blood	Autologous blood Fibrinogen Thrombin		Blood clot formation is instigated at site which supports plugging of emphysematous tissue	Low cost, higher risk of infection and usually used as a last-resort treatment	[40–43]
Sealing air/fluid leaks
Fibrin	Fibrinogen Thrombin Factor XIII	Vivostat Fibrin Sealant (Vivostat A/S Alleroed, Denmark); Tisseel (Baxter International, IL, USA)	Upon administration, fibrinogen is converted to fibrin in the presence of thrombin; fibrin forms clots which covalently bond with tissue with the help of factor XIII; this process is accelerated by addition of calcium ions	Neo-angiogenesis, normal wound healing, degradable, risk of disease transmission or allergic reactions as a derivative of human/animal plasma, unclear efficiency in wet environment and poor mechanical properties	[38, 44]
Cyanoacrylates	N-butyl cyanoacrylate Methacryloxysulpholane 2-octyl cyanoacrylate Butyl lactoyl cyanoacrylate	Glubran2 (GEM, Tuscany, Italy); Omnex (Ethicon, NJ, USA)	Cyanoacrylates upon application polymerise in the presence of weak bases found in bodily fluids and blood including water and amines	Wet adhesion, rapid curing, low cost, inflammatory reactions induced, degradable, exothermic polymerisation and toxic byproducts	[45–47]
Albumin	Albumin Glutaraldehyde PEG	BioGlue (CryoLife, GA, USA); Progel (BD, NJ, USA)	Lysine molecules in albumin, extracellular matrix, and cell surfaces crosslink upon glutaraldehyde exposure	Degradable, instigate inflammatory response, rigid, cytotoxic	[44, 48–51]
PEG	PEG Polylactic acid Polytrimethylene carbonate	FocalSeal (Genzyme Corp, MA, USA); Coseal (Cohesion Technologies, CA, USA)	PEG is modified with degradable functionalities or crosslinked with degradable polymers to confer adhesiveness and tissue bonding	Controlled degradation, flexibility, high adhesion strength and biocompatibility, high swelling ratio and low cohesive strength and brittleness	[38, 52]
Collagen	Collagen	Peri-Strips (Synovis Life Technologies, MN, USA)	Presents an adhesive matrix to provide additional clotting factors and to control bleeding; the matrix covalently binds to the tissue	Lower risk of disease transmission and composed of the most abundant extracellular matrix protein	[48]

PVA: polyvinyl alcohol; PEG: polyethylene glycol.