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Experimental studies demonstrated antibodies against matrix and coating of polyester-based vascular prostheses. Thus, this study examined associations of these antibodies with serum cytokines (IL-2, IL-4, and IL-10) and local inflammatory reactions. Rats (n = 8/group) intramuscularly received prosthesis segments [PET-C, PET-G, and PET-A groups: polyethylene terephthalate (PET)-based prostheses coated with bovine collagen and gelatin or human serum albumin, respectively; uncoated polytetrafluoroethylene-based (PTFE) prosthesis], with sham-operated controls. Blood was drawn pre-operatively and weekly until day 22. Polymer-specific or coating-specific antibodies and cytokines were detected by enzyme immunoassays, inflammatory reactions were immunohistochemically evaluated on day 23. Polymer-specific antibodies were detected in all PET-groups using uncoated PET as antigenic target, but not for PTFE or controls, coating-specific antibodies only for PET-A. IL-10 was increased in all PET-groups and correlated with polymer-specific antibodies for PET-G and PET-A. IL-2 was increased for PET-A, but overall correlated with PET-specific antibodies. IL-4 remained unchanged in all groups. Intense local inflammatory reactions (ED1+ /ED2+ macrophages and T lymphocytes) were found within all PET-groups, but only minor for PTFE or controls. In conclusion, PET-specific antibodies were associated with increased IL-10 and along with concurrent coating-specific antibodies also with increased IL-2, indicating a specific T cell response. Thus, matrix and/or coating of polymeric vascular prostheses elicit distinct systemic immune reactions, probably influencing local inflammatory reactions.

Biomaterials can cause a chronic local inflammation called foreign body reaction, with formation of foreign body giant cells (FBGC) by monocyte/macrophage fusion. However, FBGC appearance and role for biomaterials with different physicochemical properties are not yet fully understood. This study aimed at examining FBGC and inflammatory cells after intramuscular implantation of poly(l-lactide-co-d/l-lactide) (PLA) as membranes and uncoated electro-spun fiber meshes or meshes with a positively charged plasma-polymer coating into rats. After 7, 14 and 56 days, CD68+ and CD163+ macrophages, T lymphocytes, MHC-II+ cells, FBGC, and nestin-stained tissue area as regeneration marker were morphometrically analyzed. FBGC occurrence was primarily determined by material morphology, as their numbers for meshes were 10-fold higher during acute and 50-fold higher during chronic inflammation than for membranes but comparable between uncoated and coated meshes. CD68+ macrophages decreased around and within meshes, while CD163+ macrophages and MHC-II+ cells increased within meshes. T lymphocytes within meshes were higher for coated meshes, suggesting that the peri-implant tissue immunological response is also influenced by surface chemistry. FBGC were predominantly CD68+ and CD163- , and nestin-stained tissue area was negatively correlated with CD68+ monocytes/macrophages numbers and positively correlated with CD163+ macrophages numbers, highlighting differing roles in FBGC formation and tissue regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2726-2734, 2018.

Combining collagen, an established regenerative biomaterial, and copper (Cu) with its known antibacterial and angiogenic effects could improve wound healing. However, Cu is also cytotoxic. Thus, this study aimed at examining the tissue reactions after simultaneous intramuscular implantation of collagen discs either without Cu (controls) or impregnated in 2, 20, or 200 mmol/L Cu acetate in 24 rats. After 7, 14, and 56 days, implants with peri-implant tissue were retrieved from 8 rats/day for immunohistochemical detection of CD68+ monocytes/macrophages and CD163+ macrophages, MHC-II+ cells, T lymphocytes and nestin as tissue regeneration marker. CD68+ monocytes/macrophages around implants increased with Cu amount but decreased over time except for the highest Cu amount, while CD163+ macrophages increased over time around and within implants. MHC-II+ cells were similar to CD68+ monocytes/macrophages. T lymphocyte numbers around implants were higher for Cu-impregnated samples vs. controls on day 7 and highest on day 14, but declined afterwards. Nestin expression around and within implants was largely unaffected by Cu. In conclusion, pro-inflammatory reactions around implants were dose-dependently influenced by Cu but mostly decreased over time, while Cu did not negatively affect anti-inflammatory and regenerative reactions. These results suggest that Cu-impregnated collagen could be beneficial in wound treatment.

Copper (Cu) could be suitable to create anti-infective implants based on Titanium (Ti), for example by incorporating Cu into the implant surface using plasma immersion ion implantation (Cu-PIII). The cytotoxicity of Cu might be circumvented by an additional cell-adhesive plasma polymerized allylamine film (PPAAm). Thus, this study aimed to examine in vivo local inflammatory reactions for Ti6Al4V implants treated with Cu-PIII (Ti-Cu), alone or with an additional PPAAm film (Ti-Cu-PPAAm), compared to untreated implants (Ti). Successful Cu-PIII and PPAAm treatment was confirmed with X-ray Photoelectron Spectroscopy. Storage of Ti-Cu and Ti-Cu-PPAAm samples in double-distilled water for five days revealed a reduction of Cu release by PPAAm. Subsequently, Ti, Ti-Cu and Ti-Cu-PPAAm samples were simultaneously implanted into the neck musculature of 24 rats. After 7, 14 and 56 days, peri-implant tissue was retrieved from 8 rats/day for morphometric immunohistochemistry of different inflammatory cells. On day 56, Ti-Cu induced significantly stronger reactions compared to Ti (tissue macrophages, antigen-presenting cells, T lymphocytes) and to Ti-Cu-PPAAm (tissue macrophages, T lymphocytes, mast cells). The response for Ti-Cu-PPAAm was comparable with Ti. In conclusion, PPAAm reduced the inflammatory reactions caused by Cu-PIII. Combining both plasma processes could be useful to create antibacterial and tissue compatible Ti-based implants.

Surface modification of Titanium (Ti) by low-temperature plasma influences cell-material interactions. Therefore, this study aimed at examining serum cytokine levels and associations after intramuscular implantation (n = 8 rats/group) of Ti-plates with Plasma Polymerized Allyl Amine (Ti-PPAAm), Plasma Polymerized Acrylic Acid (Ti-PPAAc), and without such layers (Ti-Controls). Pro-inflammatory (IL-2, IFNγ, IL-6) and anti-inflammatory (IL-4, IL-10, IL-13) cytokines were measured weekly for 56 days. Ti-PPAAm caused increased IL-2 (d7-14, d35), increased IFNγ (d35) and decreased IL-10 (d35, d49-56). Ti-PPAAc induced divergent anti-inflammatory cytokine changes with increased IL-4 (d28-56) and decreased IL-10 (d42-56). Ti-Controls elicited increased IL-2 (d42) and IFNγ (d35-42, d56). IL-6 was not detected and IL-13 only in three samples, thus they do not influence the response against these Ti implants. Correlation analysis revealed surface-dependent associations between cytokines indicating the involvement of different inflammatory cell populations. Concluding, different plasma modifications induce specific serum cytokine profiles and associations indicating distinct inflammatory responses.

Titanium (Ti) is an established biomaterial for bone replacement. However, facilitation of osteoblast attachment by surface modification with chemical groups could improve the implant performance. Therefore, this study aimed to evaluate the effect of a plasma polymerized allylamine (PPAAm) layer on the local inflammation in a rat model. Three series (RM76AB, RM78AB, RM77AB) of PPAAm-treated Ti plates were prepared using different plasma conditions. Twelve male LEW.1A rats received one plate of each series and one uncoated control plate implanted into the back musculature. After 7, 14 and 56 days, four rats were euthanized to remove the implants with surrounding tissue. Total monocytes/macrophages, tissue macrophages, T-cells and MHC-class-II-positive cells were morphometrically counted. On day 14, the macrophage/monocyte number was significantly higher for the controls than for the PPAAm samples. On day 56, the RM76AB and RM78AB samples had significantly lower numbers than RM77AB and the controls. The same was found for the tissue macrophages. No change over time and no differences between the implants were found for the T-cells. For the number of MHC-class-II-positive cells, a significant decrease was found only for the RM78AB implants between day 14 and day 56. Physico-chemical analysis of the PPAAm implants revealed that the RM77AB implants had the lowest water absorption, the highest nitrogen loss and the lowest oxygen uptake after sonication. These results demonstrate that the PPAAm samples and the controls were comparable regarding local inflammation, and that different plasma conditions lead to variations in the material properties which influence the tissue reaction.

Calcium phosphate (CaP) preparations are established coatings for titanium-based medical implants used for bone reconstruction. However, biodegradation of the coating can result in microparticles that subsequently cause inflammatory reactions. The present study was therefore aimed at investigating the inflammatory response to two series of CaP-coated titanium plates: Ti-brushite (Ti-B) and Ti-hydroxyapatite (Ti-H) implants. Fifteen male LEW.1A rats received one plate of each series and a pellet (5 × 2 mm) of sol–gel derived silica/CaP (SCP implants) implanted into the back musculature. After 7, 14 and 28 days, five rats were killed and the implants were removed with the surrounding tissue. Quantitative immunohistochemistry was performed on frozen sections. Total monocytes/macrophages, tissue macrophages, T-cells, MHC-class-II-positive cells and proliferating cells were counted. For the Ti-B implants, the number of monocytes/macrophages remained constant while the other cell populations increased. In contrast, for the Ti-H implants the number of monocytes/macrophages decreased while the other cell populations remained constant. The SCP implants demonstrated degradation and scattering into smaller particles with an increase for all cell populations except the proliferating cells. Human mesenchymal stem cells demonstrated adherence and a flat morphology on Ti-B and Ti-H implants and no remarkable difference between both implants. Taken together, the in vivo data demonstrate that the short-term inflammatory response against a hydroxyapatite coating is lower in comparison to a brushite coating, and that the morphology of cells growing in vitro is similar on both layers.

The study was aimed at investigating the local tissue reactions through a histological examination of β-1-integrin expression and neointima formation, and humoral immune responses by detection of prosthesis-specific antibodies, after functional implantation of vascular prostheses. In three groups of pigs, the infrarenal aorta was replaced with segments of collagen-impregnated Dacron®-prostheses: M-prosthesis—medium primary porosity, double velour layer, crimping; C-prosthesis—low primary porosity, no velour, crimping; T-prosthesis—high primary porosity, no velour, no crimping. For each prosthesis type, one series with four animals was used for examining the tissue reactions, and a second series with eight animals was used to study the antibody response, both until 116 days postoperative. In the first three weeks, the M-prosthesis caused the highest tissue reactions and the highest antipolyester antibodies, but the lowest anticollagen antibodies, whereas the T-prosthesis caused the highest anticollagen antibodies, but the least tissue response and antipolyester antibodies in the early phase. On day 116, the C-prosthesis caused the highest tissue reactions and highest polyester-specific antibodies. These results indicate a possible association between local inflammatory reactions and humoral immune responses, influenced by properties of vascular grafts. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008

Implantation of biomaterials can cause complications often associated with inflammatory reactions. However, repeated evaluation of the implant site would be burdening for patients. Alternatively, blood examinations with analysis of inflammatory serum markers could potentially be useful to reflect the local cellular response for detection and/or prediction of inflammation-related complications. Therefore, following intramuscular implantation of surface-modified Ti implants in rats, this study aimed at examining possible associations between the post-implantation time course of pro-inflammatory (INFγ, IL-2) and anti-inflammatory (IL-4, IL-10) cytokine serum concentrations and the local peri-implant tissue response after 56 days (pro-inflammatory CD68-positive monocytes/macrophages, anti-inflammatory CD163-positive macrophages, MHC class II-positive cells, activated natural killer cells and mast cells). Multivariate correlation analysis revealed a significant interaction between serum IFNγ and peri-implant tissue CD68-positive monocytes/macrophages (p = 0.001) while no interactions were found for other cytokines and cell types. Additional Pearson correlation analysis of IFNγ serum concentrations on each experimental day vs. the CD68-positive monocytes/macrophages response on day 56 demonstrated a consistently positive correlation that was strongest during the first three weeks. Thus, high early pro-inflammatory IFNγ serum concentration was associated with high late number of pro-inflammatory CD68-positive monocyte/macrophages and low early serum IFNγ with low late CD68-positive monocyte/macrophage numbers. Further studies aimed at examination of patient samples could establish the relevance of this association to predict clinical complications. After implantation of titanium samples, high early IFNγ serum concentrations were associated with a pronounced late pro-inflammatory CD68-positive monocyte/ macrophage (red circle) response, while no correlation was found for other investigated cytokines and inflammatory cells (green circle). In contrast, low early IFNγ serum concentrations were correlated with low late monocyte/ macrophage numbers.

In the "Materials and methods" chapter of the article given above, in section 2.1 titled "Implant samples and preparation" on page 2 (top paragraph of the right column), an incorrect value of 1 μg mm-2 for the average Cu load of the surface was inadvertently specified. This was due to an accidental mix-up of electronic data sets from examination of different implant series. The correct value is 0.2 μg mm-2. No other data given in the article are affected. The authors kindly apologize for this mistake.

Copper (Cu) based coatings can reduce infections for titanium (Ti) implants. However, Cu is also cytotoxic. To examine the balance of antibacterial versus adverse tissue effects, this study aimed at evaluating a Cu coating regarding in vivo Cu release and local inflammatory reactions for 72 h. TiAl6V4 plates received either plasma electrolytic oxidation only (Ti), or an additional galvanic Cu deposition (Ti-Cu). No Staphylococcus aureus were found in vitro on Ti-Cu after 24 h. Following simultaneous intramuscular implantation of two Ti and two Ti-Cu plates into nine rats, serum Cu was elevated until 48 h and residual Cu on explanted samples reduced accordingly after 48 h. Total and tissue macrophages around implants increased until 72 h for both series, and were increased for Ti-Cu. As numbers of total and tissue macrophages were comparable, macrophages were probably tissue-derived. MHC-class-II-positive cells increased for Ti-Cu only. T-lymphocytes had considerably lower numbers than macrophages, did not increase or differ between both series, and thus had minor importance. Tissue reactions increased beyond Cu release, indicating effects of either surface-bound Cu or more likely the implants themselves. Altogether, Ti-Cu samples possessed antibacterial effectiveness in vitro, released measurable Cu amounts in vivo and caused a moderately increased local inflammatory response, demonstrating anti-infective potential of Cu coatings.

Copper (Cu) could serve as antibacterial coating for Ti6Al4V implants. An additional cell-adhesive layer might compensate Cu cytotoxicity. This study aimed at in vitro and in vivo evaluation of low-temperature plasma treatment of Ti6Al4V plates with Ti/Cu magnetron sputtering (Ti6Al4V–Ti/Cu), plasma-polymerized ethylenediamine (Ti6Al4V–PPEDA), or both (Ti6Al4V–Ti/Cu–PPEDA). Ti6Al4V–Ti/Cu and Ti6Al4V–Ti/Cu–PPEDA had comparable in vitro Cu release and antibacterial effectiveness. Following intramuscular implantation of Ti6Al4V–Ti/Cu, Ti6Al4V–PPEDA, Ti6Al4V–Ti/Cu–PPEDA and Ti6Al4V controls for 7, 14 and 56 days with 8 rats/day, peri-implant tissue was immunohistochemically examined for different inflammatory cells. Ti6Al4V–PPEDA had more mast cells and NK cells than Ti6Al4V, and more tissue macrophages, T lymphocytes, mast cells and NK cells than Ti6Al4V–Ti/Cu–PPEDA. Ti6Al4V–Ti/Cu had more mast cells than Ti6Al4V and Ti6Al4V–Ti/Cu–PPEDA. Results indicate that PPEDA-mediated cell adhesion counteracted Cu cytotoxicity. Ti6Al4V–Ti/Cu–PPEDA differed from Ti6Al4V only for mast cells on day 56. Altogether, implants with both plasma treatments had antibacterial properties and did not increase inflammatory reactions.

Implantation of biomaterials like titanium (Ti) causes inflammatory reactions possibly affecting implant functionality. Surface modifications could improve biocompatibility and functionality of implants. Biomembrane-derived phospholipids might be useful as implant coating due to their biomimetic properties. In vitro studies demonstrated beneficial effects for 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphoethanolamin (POPE) as coating regarding interactions with cells and bacteria. Therefore, this in vivo study aimed at examining local inflammatory reactions after implantation of POPE-coated Ti plates. Ti implants with POPE attached non-covalently or covalent via octadecylphosphonic acid (OPA), with OPA alone and uncoated controls were simultaneously implanted intramuscularly in rats for 7, 14 and 56 days. The peri-implant tissue was quantitatively analyzed by immunohistochemistry for total macrophages, tissue macrophages, T cells, antigen-presenting cells and proliferating cells. Overall, both POPE-coated series were comparable to the controls. Furthermore, no differences were found between POPE coating on a covalently linked OPA monolayer and POPE coating dried from solution. Together with earlier in vitro results, this demonstrates the potential of phospholipids for implant surface modification.

In recent experimental studies, we could demonstrate the occurrence of antibodies against the prosthesis matrix and coating following implantation of polyester-based vascular grafts. Therefore, this study aimed at evaluating the biocompatibility of a new absorbable polymer coating by detection of antibodies against the coating and the polyester matrix. Two polyester vascular prostheses coated either with the polymer (PP-prosthesis) or with gelatine (PG-prosthesis) were functionally implanted into sheep (n = 22 per group). Blood was drawn on days 1 (pre-OP) and 7, 14, 28, 56, 84, 140 (post-OP). Homogenates from both prostheses (PP-target or PG-target) or from an uncoated prosthesis (P-target) were used as assay targets in a particle-based immunoassay. The antibody binding against the P-target was significantly higher in the PP-group than in the PG-group on days 7-56, but not on days 84 and 140. Within both groups, no significant differences but a significant correlation between the binding against the P-target and the coated target was found. Therefore, the absorbable polymer did not induce a specific humoral immune response. In conclusion, the overall immunogenicity of the polymer-coated graft was comparable to the gelatine-coated graft. The detection of prosthesis-specific antibodies seems to be useful for in vivo biocompatibility testing.

Intima hyperplasia, resulting from extracellular matrix (ECM) secretion, can lead to vascular prosthesis occlusion and is a major problem in vascular surgery. Fibronectin might contribute to ongoing ECM secretion. However, the exact role of fibronectin and its influence on neointima formation remains unclear. This study was aimed at investigating the time course of the fibronectin area fraction and neointima formation following the functional implantation of three different polyester vascular prostheses into pigs. The infrarenal aorta from 15 animals (n = 5/group) was replaced by prosthesis segments with low, medium and high primary porosity. After 7, 14, 21, 28 and 116 days, the prostheses were morphometrically examined. Overall, the fibronectin area fraction was inversely correlated with the neointima thickness, demonstrating high fibronectin levels in the early phase (days 7 and 14) and low levels in the later phase with almost complete neointima formation (days 21-116). Throughout the study, fibronectin levels were highest at the proximal anastomosis region. The low porosity prosthesis had the highest fibronectin area fraction and a delayed neointima formation in the middle phase (days 21 and 28) but the highest neointima lining on day 116. The results indicate a relationship between fibronectin and neointima formation with the prosthesis porosity, demonstrating the importance of the textile design for tissue reactions following implantation.