width=5 Abstract    


Sueli Suzigan, Gilberto Goissis, Diderot Rodrigues Parreira, Helder Chaves, Kassim M. K. Hussain, Selma R. O. Raymundo.

Depto. Quím. Fís. Molec., Inst. Quím. São Carlos (IQSC) – Universidade de São Paulo (USP), SP, Brasil. Faculdade de Medicina de São José do Rio Preto (FAMERP) – São José do Rio Preto, SP, Brasil.  

IV-CVHAP 2001 POSTER-E - 046

Fecha recepción: 04/02/2001
Fecha publicación: 01/04/2001
 Evaluación: Ver "Taller de Patología Experimental"

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width=5 Título
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   Polymeric mesh are recently the most recommended materials for the reconstruction of the abdominal wall, with special emphasis for polypropylene mesh. This work describes the preparation, characterization and the biocompatibility studies on polypropylene mesh coated with anionic collagen or in the form of a double layer with poly (vinyl chloride), as a biomaterials for the reconstruction of the abdominal wall. Materials were characterized by electron scanning microscopy, differential scanning calorimetry and by microscopic study of their implantation in the abdominal wall of sheep for periods from 01 to 18 weeks. The results showed that the double layer of polypropyleno:poly (vinyl chloride) was the most biocompatible and less susceptible in relation to intestine adhesion, suggesting its potential use as a permanent biomaterial for abdominal wall reconstruction. For the same reasons poly (vinyl chloride) by itself, particularly due to the lack of intestine adhesion after 9 weeks, may constitute in an efficient and low cost biomaterial for short term abdominal wall repair. In the case of anionic collagen coated polypropylene, the biological response was associated with an anomalous metaplastic ossification surrounding the polypropylene making the material improper for the purpose intended in this work. Although we do not have a plausible explanation for this anomalous tissue response, due to the well known good behavior of collagen implants, we think that this may be associated to the significant higher dielectric properties of anionic collagen in comparison to native collagen biomaterials. In vivo this property is closely related to bone tissue growth and remodeling.

Key words: polypropylene | poly (vinyl chloride) | anionic collagen | abdominal wall | reconstruction  metaplastic ossification

Palabras clave: polipropileno | poli (cloruro de vinilo) | colágeno aniónico | pared abdominal | reconstrucción | osificación metaplásica



Figura 1: :Scanning electron micrograph. a) polypropylene mesh (1000X); b) polypropylene: anionic collagen (500x);

Figura 1a y 1b

Figure 2: Histologic findings of the tissular response of polypropylene (PLP) and PLP:anionic collagen (AC) composite after 18 weeks from implantation. a - PLP, intense fibrosis around the implant (top center), Gomori´s trichrome stain, 40x; b - PLP:AC, associated to fibrosis and new bone formation (right), H.E., 40x;

Figura 2a y 2b

Figure 2: Histologic findings of the tissular response of polypropylene (PLP) and PLP:anionic collagen (AC) composite after 18 weeks from implantation. Primitive bone (center), close to PLP (left), H.E., 100x; d - Bone trabeculae with a lacunae at the central region, H.E., 400x;

Figura 2c y 2d

Figure 2: Histologic findings of the tissular response of polypropylene (PLP) and PLP:anionic collagen (AC) composite after 18 weeks from implantation. e -  Osteoblasts at the surface of the primary spicule (inner surface), H.E., 400x.

Figura 2e

Figura 1c.- Scanning electron micrograph: polypropylene: anionic collagen  (5000x)

Figura 1c



   MarlexÒ, ProleneÒ and TrelexÒare polypropylene (PLP) mesh


   Being the most widely used materials for hernia repair and abdominal wall reconstruction

   Repair mechanism:

  • Just as mechanical reinforcement (sublay technique) or
  • The induction of a scar tissue around the polymeric mesh

   Cause for failures:

  • Inappropriate surgical techniques
  • Mechanical changes in the mechanical properties of the implant during or after implantation
  • The persistence of a active and constant inflammatory process leading to irregular scar tissue formation of low intensity


   Low integration of the implant at the interface of the regeneration tissue


  • Minor
    • Seromes (30-50%)                            
    •  Indisposition (10-20%)
    • Restriction of the mobility of the abdominal wall (25%)
  • Major
    • Bowel adhesion at the surface of the implant

    In spite of the problems mentioned above, polypropylene mesh are still the most efficient artificial materials for abdominal wall reconstruction

    The ideal implant: It should incorporate to the native tissue during tissue remodeling by means of a milder inflammatory response


The use of biodegradable biomaterials that include:

  • PLP: peritoneum sandwiches
  • Poliésteres: polyglycolic acid
  • Polyester mesh : fluoroapassivated gelatins
  • Crosslinked bovine pericardium



   Purpose of this work:

   The development and the characterization (physicochemical and tissue response) of polypropylene mesh modified by coating with anionic collagen (AC) and intended for short and long term abdominal wall repair


   What is expected is a material with the appropriate mechanical properties of PLP associated with less intense bowel adhesion due to the high biocompatibility demonstrated for anionic collagen Þ more favorable inflammatory responses.


Collagen preparation: AC was prepared and characterized as described in Goissis, G. et alli. “Biocompatibility studies of anionic collagen membranes with different degree of glutaraldehyde cross-linking”. Biomaterials., v.20, p.27-34, 1999. No glutaraldehyde was used for collagen crosslinking.

Polypropylene: was commercially available and of medical for uses in the repair of abdominal wall.

Anionic collagen coating: coating of the PLP mesh was preformed with 1% (w/w) AC gels by immersion under vacuum

Material characterization

Anionic collagen: polyacrylamide-SDS gel electrophoresis, infrared spectroscopy and differential scanning calorimetry.

Polypropylene: Scanning electron microscopy anddifferential scanning calorimetry.


Materials were sterilized with ethylene oxide and implant (PLP and PLC:AC) were performed on male sheep with re-operations at 1, 9 e 18 weeks from implantation. Evaluation of the implants were done in relation  to bowel adhesion and tissue response, on microscopic examination (Hematoxylin and Eosin, Von Kossa and Gomori´s Trichrome stain).



   Material Characterization:

Anionic collagen: as expected anionic collagen was of the type I with an a1/ a2 of 1.95 and a molecular mass ~100000 D; Infrared spectroscopy 1235/1450 cm-1= 1,07 and a thermal stability of 53.2±0,7 °C suggesting the preservation of collagen triple helix structure.

Polypropylene: melt temperature = 171.7 ±0.8°C.

Polypropylene: anionic collagen composite:

Thermal analysis: thermal transitionsat50.8±0.3 °C (AC) and 173,1±0.4 °C (PLP) in accord with the values determined for PLP and anionic collagen alone

Scanning electron microscopy: Those for PLP, and PLP:AC composites are shown respectively by Figura 1a, 1b and Figure 1c

   Biological evaluation:


  • Non infection or displacement of suture
  • Serome Þonly one animal with one PLP implant (9 weeks)
  • Bowel adhesion (Jenkinsonsclassification):
  1. PLP: minimal after 1 and 9 weeks (level 1); moderate to intense after 18 weeks (level 2).
  2. PLP:AC: no adhesion after 1 and 9 weeks (level 0). Minimal after 18 weeks (level 1).

    Biological evaluation:

Microscopic pathology of the explants

Microscopic evaluation of polypropylene and polyprolpylene:anionic collagen implant on the abdominal wall of sheep are shown at Table 1 and Figure 2ab, Figure 2cd and Figure 2e. Figures and Table.


    Polypropylene implant:

  • Near-implant fibrosis: Moderate (3+/5) independent from implantation time;
  • Near-implant inflammation: Moderate (2+/5) after 9 weeks Þ intense (4+/5) after 18 weeks.
  • Type of inflammatory reaction: Foreign body-type giant cell reaction, with the predominance of histiocytes and multinucleated giant cells (Figure 2a).

   Polypropylene: anionic collagen implant:

  • Near-implant fibrosis: On a comparative basis, it was more intense in comparison to PLP (4+/5).
  • Near-implant inflammation: Opposite to that observed wit PLP: Week 1 Þ 3+/5; weeks 9 and 18 Þ 1+/5. Qualitatively the tissular reaction was similar to that observed for PLP, except that a metaplastic ossification or primary ossification was detected around the implant (Figure 1b through 1e).


Spicules of primitive fiberbone ( 2+/5) Þ (5+/5) was detected after 01, 09 and 18 weeks in the form of a belt surrounding the implant, with the characteristics of new bone formation (Figure 2ab, Figure 2cd, Figure 2e).


   (i) Although PLP coated with anionic collagen was characterized by lower bowel adhesion and improved tissue response in comparison to PLP alone, the formation of new bone tissue around the implant does not recommend its use for the repair of the abdominal wall defects. Nevertheless this response is an indication for osteoinductive properties of the anionic collagen coating, important for biomaterials for in bone reconstruction. 

   (ii) This response may be related to the improved dielectric properties determined for anionic collagen, particularly when associated with polarized poly(vinylidene fluoride)/trifluorethylene composites (Plepis, A.M.G.; Goissis, G.; Das-Gupta D.K. Dielectric and pyroelectric characterization of anionic and native collagen. Pol. Eng. Sci., 36, 2932 (1996).; Goissis, G, Piccirilli, L., Plepis, AMG, Das-Gupta, DK. Preparation and characterization of anionic collagen P(VDF-TrFE) composites. Polymer Engineering Science, 39, 474-482 (1999). (PVDF), due to their ability of these materials to respond with electrical currents upon thermal or mechanical stimulus.



Acknowledgements to: João Vicente de Paiva, Domingos Zanchetta Netto and FAPESP.


Correspondencia: Sueli Suzigan. Laboratório Larpac - Phone / fax 55 - 17 - 232 02 03. Rua Voluntários de São Paulo 3117 . 15.015-200 - São José do Rio Preto - SP - Brazil. e-mail: larpac@riopreto.com.br


1. PLEPIS AMG, GOISSIS G, DAS-GUPTA DK - Dieletric and pyroeletric characterization of anionic and native collagen. Polymer Engineering Science, 36:2932, 1996.

2. GOISSIS G, SUZIGAN S, PARREIRA DR, RAPOSO LS, MANIGLIA JV, PLEPIS AMG - Characterization and chemical reactivity of acellular collagen intended for implant materials. Anais I Congresso Latinoamericano de Órgãos Artificiais e Biomateriais, Belo Horizonte, 1998.

3. GOISSIS G, PICCIRILLI L, PEPLIS AMG, DAS-GUPTA DK - Preparation and characterization of anionic collagen P (VDF-TrFE) composites. Polymer Engineering Science, 39:474-482, 1999.

4. GOISSIS G, ET AL - Biocompatibility studies of anionic collagen membranes with different degree of glutaraldeyde cross-linking. Biomaterials, 20:27-34,1999.

5. GOISSIS G, SUZIGAN S, PARREIRA DR,MANIGLIA JV, BRAILE DM, RAYMUNDO S- Preparation and characterization of collagen-elastin matrices from blood vessels intended as small diameter vascular grafts. Artificial Organs, 24 (3):217-223, 2000.

6. SUZIGAN S, GOISSIS G , PARREIRA DR - Calcification studies in bovine pericardium crosslinked with glutaraldehyde acetals. III Congreso Virtual Hispanoamericano de Anatomia Patologica. http://conganat.uniovi.es/posters/120/texto.htm:1-7, 2000.