Article pubs.acs.org/journal/abseba
Gold Nanorod-Collagen Nanocomposites as Photothermal Nanosolders for Laser Welding of Ruptured Porcine Intestines Russell Urie,† Sana Quraishi,† Michael Jaffe,‡ and Kaushal Rege*,† †
Chemical Engineering, Arizona State University, Tempe, Arizona 85287, United States College of Veterinary Medicine, Midwestern University, Glendale, Arizona 85308, United States
‡
S Supporting Information *
ABSTRACT: Surgical site infection and postoperative leakage are complications that may develop following colorectal surgery and result in fatal consequences. Rapid, fluid-tight wound closure through laser tissue welding (LTW) can reduce postoperative leakage and thus decrease infection. Laser tissue welding involves generation of localized heat by exposing an exogenous chromophore to near-infrared (NIR) irradiation in order to seal wounds. In this study, we generated gold nanorod (GNR)collagen nanocomposites (NCs) for laser-facilitated welding of ruptured intestinal tissue. The fluid content, stiffness, elasticity, and laser-induced temperature response of these nanocomposites were modulated to optimize laser-induced tissue fusion and minimize tissue damage. In addition, the effect of laser operating parameters including power density, femtosecond pulsed wave (PW) or continuous wave (CW) laser, and exposure duration were all studied. Laser power density and treatment duration significantly affected the temperatures reached during welding, as well as tissue weld strength and burst pressure. CW laser was found to induce significantly higher temperatures of the nanocomposites during treatment than PW laser, but the differences in weld strength and burst pressure for the two laser types were insignificant. This suggests that PW lasers can result in robust welds while minimizing potential thermal damage compared to CW lasers. The ultimate tensile strength of welded ruptured tissue was returned to as high as 68% of the native tissue strength through laser treatment, and laser treatment with these nanocomposites restored up to 64% of native tissue leak pressure and 42% of burst pressure. To the best of our knowledge, the laser power densities used (≤2.50 W/cm2) are among the lowest reported for laser tissue welding, and the laser configuration and use require very little surgical skill. Our results indicate that GNR-collagen nanocomposites are promising photothermal biomaterials in laser tissue welding applications. KEYWORDS: laser tissue welding, wound closure, gold nanorods, plasmonic nanocomposites, collagen protein matrix
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strengths,2 especially in wet wound environments.3 As an alternate method, near-infrared (NIR) irradiation can be applied to a plasmonic protein matrix to adjoin ruptured tissue by means of localized heating. This approach, called laser tissue welding (LTW), is an attractive sutureless method with application in surgeries involving intestine, blood vessels,4 nerves,5 and skin.6 In addition, LTW has the potential to reduce the skill required for performing efficient anastomosis.7 Although the mechanism behind LTW is somewhat unclear,8,9 recent research has resulted in greater understanding of lasermediated tissue bonding. Second-harmonic generation microscopy revealed a three-step thermal transition of corneal collagen denaturation, where interfibrillar proteoglycan bridges are broken at 45 °C, intramolecular collagen hydrogen bonds are broken at 60 °C, and the protein is fully denatured and homogenized at 80 °C.10 As a result, the proposed mechanism
INTRODUCTION More than 1.5 million people suffer from colorectal cancer or inflammatory bowel disease in the United States (Center for Disease Control and Prevention and National Cancer Institute). Colorectal and intestinal surgeries may necessitate resection of a portion of the colon requiring tissue anastomosis, in which disjointed sections of tissues are joined together. Intestinal anastomosis, leading to eventual tissue repair, is typically carried out using hand-placed sutures or surgical staples. These conventional techniques have associated risks of anastomotic leakage, which may result in infection, septic shock, and ultimately patient death. It is suggested that clinical leakage occurs in 17% of all colorectal anastomoses cases,1 and clinicians predict that the number of patients at risk for anastomotic leakage is likely to rise.1 Suture-free, rapid hydrosealing approaches toward anastomoses and tissue repair can decrease infection, prevent leakage, shorten operative times, improve healing rates, and minimize invasiveness. Sealants, including fibrin glues, have been limited by difficult application, poor uniformity, and low wound © 2015 American Chemical Society
Received: April 22, 2015 Accepted: August 4, 2015 Published: August 5, 2015 805
DOI: 10.1021/acsbiomaterials.5b00174 ACS Biomater. Sci. Eng. 2015, 1, 805−815
Article
ACS Biomaterials Science & Engineering
900 nm), and the synthesis was carried out such that absorption maximum (λmax) was tuned to ∼800 nm (Figure S1); absorbance was determined using a Biotek Synergy 2 plate reader. Nanorod aliquots were centrifuged (6000 rcf, 10 min) and resuspended in nanopure water to various final concentrations. Gold concentration was determined using inductively coupled plasma optical emission spectrometry (Thermo Electron Corporation). Centrifugation, decanting, and dilution steps allowed the generation of a nanorod dispersion with CTAB concentration under 0.15 mM; previous work in our laboratory determined that CTAB concentrations below 0.25 mM were optimal for elastin-like polypeptide (ELP)-based nanocomposites formed with GNRs.25 In this work, the collagen hydrogels were even more sensitive to free CTAB concentration, and additional centrifugation further reduced free CTAB from GNR dispersions to below 0.15 mM. Formation of GNR-Collagen Nanocomposites. Type I collagen was brought to 4 mg/mL using cold 2X phosphate buffered saline (PBS; pH 7.4), neutralized using 1 M NaOH, loaded in a 48-well plate, and gelled in a humid incubator at 37 °C for 1 h. The resultant hydrogels (∼2 mg collagen) were 12 mm in diameter and 10 mm in height, as determined by a digital calliper. Conventional collagen hydrogels contain as high as 99.5% fluid,26 but plastic compression can remove excess fluid to improve the mechanical properties of collagen hydrogels.26−28 Through compression, the hydrogel is decreased to
