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ANTIBACTERIAL RESORBABLE COATING OF ORTHOPAEDIC IMPLANTS: AN IN VITRO AND
IN VIVO STUDY
E. Meani1 , M. Fini2 , G. Giavaresi2 , L. Drago3 , C.L. Romanò4
1 Department of Septic Complications Surgery, Istituto Ortopedico G. Pini, Milano - Italy, 2 Department of Experimental Surgery, Istituto Ortopedico Rizzoli, Bologna - Italy, 3 Department of Microbiology, Istituto Ortopedico IRCCS Galeazzi, Milano - Italy, 4 Department of Osteo-articular Infections, Istituto Ortopedico IRCCS Galeazzi, Milano - Italy
Summary Statement: An Implant Disposable Antibacterial Coating (i-DAC®) is described, consisting of a fully
resorbable, biocompatible hydrogel, able to release antibacterial and antibiofilm agents. Direct application of the
hydrogel on implants prevented infection occurrence in an in vitro model of peri-prosthetic infection.

Introduction: Biofilm-related infections are among the main reasons for failure of joint prosthesis with high
associated social and economical costs (, , ). Bacterial adhesion and subsequent biofilm formation have been
shown to develop early after biomaterials implant into the human body, when a “race to the surface” takes place
between the host’s cells and the colonizing bacteria eventually present at the surgical site (). Providing an
antibacterial/antibiofilm coating of the implant may then play a strategic role in preventing biofilm related
infections. Here we report the results of a series of in vitro and in vivo studies, partially performed under the
European 7th Framework Programme (Implant Disposable Antibiotic Coating, IDAC, collaborative research
project # 277988), concerning a fully resorbable, biocompatible antibacterial hydrogel coating (DAC®,
Novagenit, Italy). The patented hydrogel, a co-polimer comprising of hyaluronic acid and a polylactic acid, has
been designed to be mixed with various antibacterial agents and applied directly on the implant at the time of
surgery, being fully resorbed within few days.
Patients & Methods: The tested hydrogel (DAC®, Novagenit, Italy) is a derivative of a low molecular weight
hyaluronan, grafted with poly-D,L-lactic acid and provided in powder form. At the point of care, the powder is
hydrated with the antibiotic or antibiofilm solution, thus generating the final compound to be applied onto the
implant surface. In vitro studies were conducted using DAC® coating on different biomaterials, including
titanium, chrome-cobalt and polyethylene discs. The release of different antibacterial agents, including
vancomycin, ciprofloxacin, meropenem, gentamycin, amikacin, tobramycin, clindamycin, doxycyclin, linezolid,
NAsalycilate and N-acetylcisteine, adequately mixed with the hydrogel, has been tested by means of gas
chromatography and microbiological methods. In vivo studies were then performed on 35 rabbits divided in 7
groups. Animals were implanted with an intramedullary titanium rod in their femur, with a known inoculum of
methicillin-resistant Staph. aureus and vancomycin-loaded DAC® at different concentrations (2% and 5%) and
compared with controls.
Results: Regardless of the tested material, in vitro studies showed the ability of the hydrogel to be loaded and to
sustain the release of the following antibacterial/antibiofilm compounds for up to 96 hours: vancomycin,
ciprofloxacin, meropenem, gentamycin, amikacin, tobramycin, clindamycin, doxycyclin, linezolid,
NAsalycilate, N-acetylcisteine. In vivo studies showed a bacterial load reduction ranging from 94% to 99.9%
using vancomycin-loaded DAC®, compared to controls.
Discussion/Conclusion: DAC®, a fast-resorbable antibacterial coa), showed the ability to be loaded with
various antibacterial compounds and the ability to provide a highly significant reduction of bacterial
colonization of implanted biomaterials in an animal model, opening a new pathway to local prevention and
treatment of biofilm-/implant-related infections.

References
1. Kurtz SM et al. Future clinical and economic impact of revision total hip and knee arthroplasty. JBJS 2. Bozic KJ The epidemiology of revision total hip arthroplasty in the United States. J Arthropl 2009; 3. Bozic KJ The epidemiology of revision total knee arthroplasty in the United States. CORR 2010; 4. Meani E., Romanò C.L., Crosby L., Hofmann G. (2007) Infection and local treatment in orthopaedic infections. Ed. Springer-Verlag, Heidelberg, 2007. 5. Rapporto di Prova n° 14/12 del 23/10/2012_ prova di valutazione degli effetti locali all’iniezione nel canale endomidollare femorale dell’ idrogelo “DAC” - UNI EN ISO 10993-6_IOR, Bologna.

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