title: Sutureless Microsurgical Anastomosis Using an Optimized Thermoreversible Intravascular Poloxamer Stent.
abstract: BACKGROUND
  Sutureless microvascular anastomosis has great translational potential to simplify microvascular surgery, shorten operative times, and improve clinical outcomes. The authors developed a transient thermoreversible microvascular stent using a poloxamer to maintain vessel lumen patency before application of commercially available adhesives to seal the anastomosis instead of sutures. Despite technical success, human application necessitates bovine serum albumin removal from existing formulations; rapid poloxamer transition between states; and increased stiffness for reliable, reproducible, and precise microvascular approximation.
  
  
  METHODS
  Two commercially available poloxamers were used in this study (P407 and P188). After removing bovine serum albumin, each poloxamer was tested at varying concentrations either alone or in combination to determine the optimal preparation for sutureless microvascular anastomosis. Transition temperature and formulation stiffness were tested in vitro by rheometry, with the most promising combinations tested in an established in vivo model.
  
  
  RESULTS
  Increasing poloxamer concentration resulted in an increase in stiffness and decrease in transition temperature. Pure P188 without bovine serum albumin, dissolved in phosphate-buffered saline to a 45% concentration, demonstrated desirable rheologic behavior, with precise gel transition and increased gel stiffness compared with our previous formulation of 17% P407 (96 kPa versus 10 kPa). These characteristics were optimal for microsurgical intravascular use, offering surgical precision and control between liquid and solid states, depending on the surgically controlled local temperature.
  
  
  CONCLUSIONS
  Use of 45% P188 without bovine serum albumin demonstrated optimal rheologic and translational properties as a microvascular stent for sutureless anastomosis. Rapid transition, increased stiffness, and safety profile demonstrate safe translational application for human clinical trials.
authors.affiliation: Stanford, Calif. From the Hagey Laboratory for Pediatric Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Davis
authors.forename: C Travis
authors.initials: CT
authors.lastname: Rappleye
authors.forename: Peter A
authors.initials: PA
authors.lastname: Than
authors.forename: Melanie
authors.initials: M
authors.lastname: Rodrigues
authors.forename: Michael W
authors.initials: MW
authors.lastname: Findlay
authors.forename: Sarah N
authors.initials: SN
authors.lastname: Bishop
authors.forename: Arnetha J
authors.initials: AJ
authors.lastname: Whitmore
authors.forename: Zeshaan N
authors.initials: ZN
authors.lastname: Maan
authors.forename: Rory B
authors.initials: RB
authors.lastname: McGoldrick
authors.forename: Adriaan O
authors.initials: AO
authors.lastname: Grobbelaar
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Gurtner
mesh_terms: D000714:Anastomosis, Surgical / Q000379:methods; D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery*; D002417:Cattle; D004195:Disease Models, Animal; D008297:Male; D008866:Microsurgery / Q000379:methods*; D020442:Poloxamer; D011474:Prosthesis Design; D051381:Rats; D017207:Rats, Sprague-Dawley; D015607:Stents; D013536:Suture Techniques; D013696:Temperature; D014656:Vascular Surgical Procedures / Q000379:methods*
chemical_list: D020442:Poloxamer
references.citation: Chang EI, Galvez MG, Glotzbach JP, et al. Vascular anastomosis using controlled phase transitions in poloxamer gels. Nat Med. 2011;17:1147–1152
references.citation: Qiu Y, Park K. Environment-sensitive hydrogels for drug delivery. Adv Drug Deliv Rev. 2001;53:321–339
references.citation: Singh-Joy SD, McLain VC. Safety assessment of poloxamers 101, 105, 108, 122, 123, 124, 181, 182, 183, 184, 185, 188, 212, 215, 217, 231, 234, 235, 237, 238, 282, 284, 288, 331, 333, 334, 335, 338, 401, 402, 403, and 407, poloxamer 105 benzoate, and poloxamer 182 dibenzoate as used in cosmetics. Int J Toxicol. 2008;27(Suppl 2):93–128
references.citation: Yong CS, Choi JS, Quan QZ, et al. Effect of sodium chloride on the gelation temperature, gel strength and bioadhesive force of poloxamer gels containing diclofenac sodium. Int J Pharm. 2001;226:195–205
references.citation: Choi H, Lee M, Kim M, Kim C. Effect of additives on the physicochemical properties of liquid suppository bases. Int J Pharm. 1999;190:13–19
references.citation: Artzi N, Shazly T, Baker AB, Bon A, Edelman ER. Aldehyde-amine chemistry enables modulated biosealants with tissue-specific adhesion. Adv Mater. 2009;21:3399–3403
references.citation: Lang N, Pereira MJ, Lee Y, et al. A blood-resistant surgical glue for minimally invasive repair of vessels and heart defects. Sci Transl Med. 2014;6:218ra6
references.citation: Grist EP. Transmissible spongiform encephalopathy risk assessment: The UK experience. Risk Anal. 2005;25:519–532
references.citation: Rassing J, Attwood D. Ultrasonic velocity and light-scattering studies on the polyoxyethylene-polyoxypropylene copolymer pluronic F127 in aqueous solution. Int J Pharm. 1982;13:47–55
references.citation: Schild H. Poly(N-isopropylacrylamide): Experiment, theory and application. Prog Polym Sci. 1992;17:163–249
references.citation: Mortensen K, Perdersen J. Structural study on micelle formation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in aqueous solution. Macromolecules. 1983;26:805–812
references.citation: Edwards CM, Heptinstall S, Lowe KC. Pluronic F-68 inhibits agonist-induced platelet aggregation in human whole blood in vitro. Artif Cells Blood Substit Immobil Biotechnol. 1998;26:441–447
references.citation: Lechmann T, Reinhart WH. The non-ionic surfactant Poloxamer 188 (RheothRx) increases plasma and whole blood viscosity. Clin Hemorheol Microcirc. 1998;18:31–36
references.citation: Toth K, Wenby RB, Meiselman HJ. Inhibition of polymer-induced red blood cell aggregation by poloxamer 188. Biorheology. 2000;37:301–312
references.citation: Dumortier G, Grossiord JL, Agnely F, Chaumeil JC. A review of poloxamer 407 pharmaceutical and pharmacological characteristics. Pharm Res. 2006;23:2709–2728
references.citation: Radivojša M, Grabnar I, Ahlin Grabnar P. Thermoreversible in situ gelling poloxamer-based systems with chitosan nanocomplexes for prolonged subcutaneous delivery of heparin: Design and in vitro evaluation. Eur J Pharm Sci. 2013;50:93–101
references.citation: Johnston TP, Nguyen LB, Chu WA, Shefer S. Potency of select statin drugs in a new mouse model of hyperlipidemia and atherosclerosis. Int J Pharm. 2001;229:75–86
references.citation: Johnston TP, Beris H, Wout ZG, Kennedy JL. Effects on splenic, hepatic, hematological, and growth parameters following high-dose poloxamer 407 administration to rats. Int J Pharm. 1993;100:279–284
references.citation: Francis GL. Albumin and mammalian cell culture: Implications for biotechnology applications. Cytotechnology. 2010;62:1–16
references.citation: Bouchot O, Berger RL, Berne JP, Brunotte F, Brenot R. Clinical experience with a novel thermosensitive temporary coronary artery occluder (LeGoo). Ann Thorac Surg. 2010;89:1912–1917
references.citation: Shalhoub J, Thapar A, Davies AH. The use of reverse thermosensitive polymer (LeGoo) for temporary vessel occlusion in clampless peripheral vascular surgery. Vasc Endovascular Surg. 2011;45:422–425
references.citation: Wimmer-Greinecker G, Bouchot O, Verhoye JP, et al. Randomized clinical trial comparing a thermosensitive polymer (LeGoo) with conventional vessel loops for temporary coronary artery occlusion during off-pump coronary artery bypass surgery. Ann Thorac Surg. 2011;92:2177–2183
references.citation: Molina WR, Pompeo A, Sehrt D, Pohlmann G, Kim FJ. Use of a polymeric gel to prevent retropulsion during intracorporeal lithotripsy (in Spanish). Actas Urol Esp. 2013;37:188–192
references.citation: Rane A, Bradoo A, Rao P, et al. The use of a novel reverse thermosensitive polymer to prevent ureteral stone retropulsion during intracorporeal lithotripsy: A randomized, controlled trial. J Urol. 2010;183:1417–1421
references.citation: Brunkwall J, Ruemenapf G, Florek HJ, Lang W, Schmitz-Rixen T. A single arm, prospective study of an absorbable cyanoacrylate surgical sealant for use in vascular reconstructions as an adjunct to conventional techniques to achieve haemostasis. J Cardiovasc Surg (Torino). 2007;48:471–476
references.citation: Gu JH, Ge JB, Li M, Xu HD, Wu F, Qin ZH. Poloxamer 188 protects neurons against ischemia/reperfusion injury through preserving integrity of cell membranes and blood brain barrier. PLoS One. 2013;8:e61641
references.citation: Grindel JM, Jaworski T, Emanuele RM, Culbreth P. Pharmacokinetics of a novel surface-active agent, purified poloxamer 188, in rat, rabbit, dog and man. Biopharm Drug Dispos. 2002;23:87–103
references.citation: Grindel JM, Jaworski T, Piraner O, Emanuele RM, Balasubramanian M. Distribution, metabolism, and excretion of a novel surface-active agent, purified poloxamer 188, in rats, dogs, and humans. J Pharm Sci. 2002;91:1936–1947
references.citation: Orringer EP, Casella JF, Ataga KI, et al. Purified poloxamer 188 for treatment of acute vaso-occlusive crisis of sickle cell disease: A randomized controlled trial. JAMA. 2001;286:2099–2106
references.citation: Willcox ML, Newman MM, Paton BC. A study of labeled pluronic F-68 after intravenous injection into the dog. J Surg Res. 1978;25:349–356