Per Kjellin - Academia.edu (original) (raw)
Papers by Per Kjellin
PubMed, Jun 1, 2022
Purpose: To investigate the biomechanical and immunological reactions to coated and non-coated bl... more Purpose: To investigate the biomechanical and immunological reactions to coated and non-coated blasted PEEK implants in vivo after 12 weeks and review the associated literature. Methods: Two osteotomy sites were performed in each proximal tibia of 10 lop-eared rabbits (n= 4 per rabbit). Each rabbit received a randomly placed (1) blasted zirconium phosphate nano-coated PEEK- (nano-ZrP), (2) blasted PEEK- (PEEK) and (3) titanium implant (Ti) and an empty sham site. At 12 weeks, removal torque of all implants and biological investigation with qPCR was performed. The implant surfaces were analyzed prior to insertion with interferometry, SEM and XPS. Results: The interferometry analysis showed that there was no difference in roughness for the uncoated PEEK compared to the ZrP coated PEEK implants. The titanium implants were considerably smoother (Sa= 0.23 µm) than the uncoated Sa= 1.11 µm) and ZrP coated PEEK implants (Sa= 1.12 µm). SEM analysis on the PEEK implants corroborated the interferometry results; no difference in structure between the uncoated vs. the ZrP coated PEEK was visible on the micrometer level. At higher magnifications, the ZrP coating was visible in the SEM as a thin, porous network. All tested implants displayed osseointegration with the highest RTQ for nano-ZrP (18.4 Ncm) followed by PEEK (14.5 Ncm) and Ti (11.5 Ncm). All implants activated the immune system, with elevated macrophage and M2 macrophage qPCR markers at 12 weeks compared to the sham site. Clinical significance: Nano-ZrP coating improves osseointegration of blasted PEEK implants at 12 weeks of follow-up. Osseointegration of titanium, PEEK and nano-ZrP PEEK is not a normal bone healing process, but rather a shield-off mechanism that appears to be regulated by the innate immune system.
Journal of Materials Science: Materials in Medicine, Sep 30, 2022
Journal of Functional Biomaterials
Leukocyte–platelet-rich fibrin (L-PRF) contains growth factors that stimulate bone regeneration. ... more Leukocyte–platelet-rich fibrin (L-PRF) contains growth factors that stimulate bone regeneration. This study evaluated the bone repair in a tibia rat model around two implant surfaces in combination or not with L-PRF by assessing microtomographic and histomorphometric parameters. A total of 48 female rats were used in the study, in which 24 received implants with two types of surface treatments (dual acid etched—DAE or nanohydroxyapatite—nanoHA), and the other 24 received the same mini implants with L-PRF, which was collected by cardiac puncture, centrifugated, and inserted in the bone bed. The animals were euthanized 7 and 30 days after implant placement, and the retrieved samples were prepared for microtomographic and histomorphometric (bone-to-implant contact—BIC; and Bone Area Fraction Occupancy—BAFO) analyses. The adhesion of the nanoHA surface onto the implant surface was investigated by insertion and removal in simulated bone medium (Sawbones). The adhesion evaluation revealed...
Nanomaterials
This study evaluated the effect of smoke exposure on the expression of genes related to bone meta... more This study evaluated the effect of smoke exposure on the expression of genes related to bone metabolism in implants coated with nanohydroxyapatite (NHA). A total of 36 rats were exposed to cigarette smoke for 60 days. The animals were allocated into three groups: machined implants (MAC), dual acid-etched implants (DAE), and NHA-coated implants (NHA). Implants were installed in the left tibia of the rats after 30 days of smoke exposure. The implants were retrieved 7 and 30 days after implantation, and the adjacent bone analyzed using a real-time polymerase chain reaction for gene expression of alkaline phosphatase (ALP), osteopontin (OPN), receptor activator of the nuclear factor kappa ligand (RANKL), osteoprotegerin (OPG), the RANKL/OPG ratio, osteocalcin (OCN) and runt-related transcription factor 2 (Runx2). After 7 days, Runx2, OPN and OPG expression demonstrated significantly higher levels for the NHA surface treatment relative to DAE and MAC surfaces. NHA presented the lowest RA...
Un phosphate de calcium cristallin nanometrique et synthetique, particulierement un hydroxyapatit... more Un phosphate de calcium cristallin nanometrique et synthetique, particulierement un hydroxyapatite, ayant une zone de surface specifique allant de 150 m2/g a 300 m2/g. Le phosphate de calcium cristallin nanometrique peut etre sous forme de poudre ou d'un revetement sur une surface. Un procede de production de la poudre de phosphate de calcium cristallin nanometrique ou son revetement. Le procede consiste a former une phase cristalline liquide dans une solution d'eau de calcium, de phosphore et un tensio-actif, placer la phase dans un milieu a l'ammoniac de maniere a former des cristaux nanometriques, puis soit retirer le tensio-actif avec un solvant et recouvrir les cristaux nanometriques afin d'obtenir la poudre, soit diluer la phase cristalline liquide traitee par ammoniac avec un solvant organique hydrophobe afin de creer une micro-emulsion des cristaux liquides nanometriques dans l'eau, immerger la surface revetue d'une couche d'oxyde d'un objet d...
Nano Letters, 2002
... Zach, MP; Ng, KH; Penner, RM Science2000, 290, 2120−2123. ... Manipulation and Organization o... more ... Zach, MP; Ng, KH; Penner, RM Science2000, 290, 2120−2123. ... Manipulation and Organization of Ferromagnetic Nanowires by Patterned Nematic Liquid Crystals. Clayton P. Lapointe, Daniel H. Reich and Robert L. Leheny. Langmuir 2008 24 (19), 11175-11181. ...
Journal of Power Sources, 2007
This thesis concerns effects of polymeric surfactants on the crystal growth of inorganic structur... more This thesis concerns effects of polymeric surfactants on the crystal growth of inorganic structures. The crystal growth of calcium carbonate on steel surfaces was studied with a heat exchanger cell and with an electrochemical method. Two copolymeric surfactants, differing in hydrophobic / hydrophilic ratio, were synthesised and their effect on the crystallisation was investigated. It was found that the more hydrophobic of the polymers prevented CaCO3 crystallisation most efficiently. The same results were obtained with the electrochemical method. Lignin, a biopolymer occurring naturally in wood, was evaluated in the heat exchanger cell and its efficiency as an antiscalant was assessed. Lignin had a similar antiscaling efficiency as poly(acrylic acid), but it had only a minor effect on which polymorph that formed. In the second part of this thesis, synthesis of CaCO3, SrCO3, Ag and CdS with the use of liquid crystalline phases as templates, is described. Synthesis of CaCO3 was made i...
Synthetic nano-sized crystalline calcium phosphate, particularly hydroxyapatite, having a specifi... more Synthetic nano-sized crystalline calcium phosphate, particularly hydroxyapatite, having a specific surface area in the range of 150 m 2 fg to 300 m 2 /g, is described. The nano-sized crystalline calcium phosphate may be in the form of a powder or in the form of a coating on a surface. A method of producing a nano-sized crystalline calcium phosphate powder or coating is also described. The method comprises formation of a liquid crystalline phase in a water solution of calcium, phosphorous precursor and a surfactant, placing the phase in an ammonia atmosphere so that nano-sized crystals are formed, followed by either removal of the surfactant with a solvent and recovering the nano-sized crystals to obtain the powder, or diluting the ammonia-treated liquid crystalline phase with a hydrophobic organic solvent to create a microemulsion of the nano-sized crystals in water, dipping an oxide layer-coated surface of an object into the microemulsion, or alternatively saving the step of ammoni...
Ceramics International, 2016
Synthetic calcium phosphates are used in for example bone cements and implant coatings to increas... more Synthetic calcium phosphates are used in for example bone cements and implant coatings to increase biocompatibility. The common method to produce tricalcium phosphate (TCP) uses high temperatures, which creates large crystals with low specific surface areas. In order to investigate new methods to produce TCP at lower temperatures, the reaction between calcium propionate and triethyl phosphate conducted at 220 degrees C was studied. The method had a near 100% conversion rate, the main synthesis products were calcium phosphate and ethyl propionate. The formed calcium phosphate polymorph could be controlled depending on the water content of the precursor mixture. Anhydrous conditions created amorphous calcium phosphate. As the concentration of water increased, beta-TCP was formed, followed by calcium deficient hydroxyapatite and monetite. The particle size increased with the water content, from 20 to 40 nm for amorphous calcium phosphate to tenths of micrometers for monetite. The specific surface areas varied between 209 m(2)/g for the amorphous product to 3.6 m(2)/g for the monetite product.
Nordic Pulp and Paper Research Journal, 2006
Journal of biomedical materials research. Part A, 2018
A nanosized hydroxyapatite (HA) modification on polyetheretherketone (PEEK) using a novel spin co... more A nanosized hydroxyapatite (HA) modification on polyetheretherketone (PEEK) using a novel spin coating technique was investigated in a rabbit model. Spin coating technique creates a 20-40 nm thick layer of nanosized HA particles with similar shape, size, and crystallinity as human bone. Some implants were designed with a perforating hole in the apical region to mimic a fusion chamber of a spinal implant. The coating nano-structures were assessed using a scanning electron microscope. The in vivo response to HA-PEEK was compared to untreated PEEK with respect to removal torque, histomorphometry, and computed microtomography. The HA-coated and pure PEEK implants were inserted in the tibia and femur bone according to simple randomization. The rabbits were sacrificed 20 weeks after implantation. Removal torque analysis showed significantly higher values for HA-PEEK. Qualitative histological evaluation revealed an intimate contact between PEEK and the bone at the threads and perforated ho...
PubMed, Jun 1, 2022
Purpose: To investigate the biomechanical and immunological reactions to coated and non-coated bl... more Purpose: To investigate the biomechanical and immunological reactions to coated and non-coated blasted PEEK implants in vivo after 12 weeks and review the associated literature. Methods: Two osteotomy sites were performed in each proximal tibia of 10 lop-eared rabbits (n= 4 per rabbit). Each rabbit received a randomly placed (1) blasted zirconium phosphate nano-coated PEEK- (nano-ZrP), (2) blasted PEEK- (PEEK) and (3) titanium implant (Ti) and an empty sham site. At 12 weeks, removal torque of all implants and biological investigation with qPCR was performed. The implant surfaces were analyzed prior to insertion with interferometry, SEM and XPS. Results: The interferometry analysis showed that there was no difference in roughness for the uncoated PEEK compared to the ZrP coated PEEK implants. The titanium implants were considerably smoother (Sa= 0.23 µm) than the uncoated Sa= 1.11 µm) and ZrP coated PEEK implants (Sa= 1.12 µm). SEM analysis on the PEEK implants corroborated the interferometry results; no difference in structure between the uncoated vs. the ZrP coated PEEK was visible on the micrometer level. At higher magnifications, the ZrP coating was visible in the SEM as a thin, porous network. All tested implants displayed osseointegration with the highest RTQ for nano-ZrP (18.4 Ncm) followed by PEEK (14.5 Ncm) and Ti (11.5 Ncm). All implants activated the immune system, with elevated macrophage and M2 macrophage qPCR markers at 12 weeks compared to the sham site. Clinical significance: Nano-ZrP coating improves osseointegration of blasted PEEK implants at 12 weeks of follow-up. Osseointegration of titanium, PEEK and nano-ZrP PEEK is not a normal bone healing process, but rather a shield-off mechanism that appears to be regulated by the innate immune system.
Journal of Materials Science: Materials in Medicine, Sep 30, 2022
Journal of Functional Biomaterials
Leukocyte–platelet-rich fibrin (L-PRF) contains growth factors that stimulate bone regeneration. ... more Leukocyte–platelet-rich fibrin (L-PRF) contains growth factors that stimulate bone regeneration. This study evaluated the bone repair in a tibia rat model around two implant surfaces in combination or not with L-PRF by assessing microtomographic and histomorphometric parameters. A total of 48 female rats were used in the study, in which 24 received implants with two types of surface treatments (dual acid etched—DAE or nanohydroxyapatite—nanoHA), and the other 24 received the same mini implants with L-PRF, which was collected by cardiac puncture, centrifugated, and inserted in the bone bed. The animals were euthanized 7 and 30 days after implant placement, and the retrieved samples were prepared for microtomographic and histomorphometric (bone-to-implant contact—BIC; and Bone Area Fraction Occupancy—BAFO) analyses. The adhesion of the nanoHA surface onto the implant surface was investigated by insertion and removal in simulated bone medium (Sawbones). The adhesion evaluation revealed...
Nanomaterials
This study evaluated the effect of smoke exposure on the expression of genes related to bone meta... more This study evaluated the effect of smoke exposure on the expression of genes related to bone metabolism in implants coated with nanohydroxyapatite (NHA). A total of 36 rats were exposed to cigarette smoke for 60 days. The animals were allocated into three groups: machined implants (MAC), dual acid-etched implants (DAE), and NHA-coated implants (NHA). Implants were installed in the left tibia of the rats after 30 days of smoke exposure. The implants were retrieved 7 and 30 days after implantation, and the adjacent bone analyzed using a real-time polymerase chain reaction for gene expression of alkaline phosphatase (ALP), osteopontin (OPN), receptor activator of the nuclear factor kappa ligand (RANKL), osteoprotegerin (OPG), the RANKL/OPG ratio, osteocalcin (OCN) and runt-related transcription factor 2 (Runx2). After 7 days, Runx2, OPN and OPG expression demonstrated significantly higher levels for the NHA surface treatment relative to DAE and MAC surfaces. NHA presented the lowest RA...
Un phosphate de calcium cristallin nanometrique et synthetique, particulierement un hydroxyapatit... more Un phosphate de calcium cristallin nanometrique et synthetique, particulierement un hydroxyapatite, ayant une zone de surface specifique allant de 150 m2/g a 300 m2/g. Le phosphate de calcium cristallin nanometrique peut etre sous forme de poudre ou d'un revetement sur une surface. Un procede de production de la poudre de phosphate de calcium cristallin nanometrique ou son revetement. Le procede consiste a former une phase cristalline liquide dans une solution d'eau de calcium, de phosphore et un tensio-actif, placer la phase dans un milieu a l'ammoniac de maniere a former des cristaux nanometriques, puis soit retirer le tensio-actif avec un solvant et recouvrir les cristaux nanometriques afin d'obtenir la poudre, soit diluer la phase cristalline liquide traitee par ammoniac avec un solvant organique hydrophobe afin de creer une micro-emulsion des cristaux liquides nanometriques dans l'eau, immerger la surface revetue d'une couche d'oxyde d'un objet d...
Nano Letters, 2002
... Zach, MP; Ng, KH; Penner, RM Science2000, 290, 2120−2123. ... Manipulation and Organization o... more ... Zach, MP; Ng, KH; Penner, RM Science2000, 290, 2120−2123. ... Manipulation and Organization of Ferromagnetic Nanowires by Patterned Nematic Liquid Crystals. Clayton P. Lapointe, Daniel H. Reich and Robert L. Leheny. Langmuir 2008 24 (19), 11175-11181. ...
Journal of Power Sources, 2007
This thesis concerns effects of polymeric surfactants on the crystal growth of inorganic structur... more This thesis concerns effects of polymeric surfactants on the crystal growth of inorganic structures. The crystal growth of calcium carbonate on steel surfaces was studied with a heat exchanger cell and with an electrochemical method. Two copolymeric surfactants, differing in hydrophobic / hydrophilic ratio, were synthesised and their effect on the crystallisation was investigated. It was found that the more hydrophobic of the polymers prevented CaCO3 crystallisation most efficiently. The same results were obtained with the electrochemical method. Lignin, a biopolymer occurring naturally in wood, was evaluated in the heat exchanger cell and its efficiency as an antiscalant was assessed. Lignin had a similar antiscaling efficiency as poly(acrylic acid), but it had only a minor effect on which polymorph that formed. In the second part of this thesis, synthesis of CaCO3, SrCO3, Ag and CdS with the use of liquid crystalline phases as templates, is described. Synthesis of CaCO3 was made i...
Synthetic nano-sized crystalline calcium phosphate, particularly hydroxyapatite, having a specifi... more Synthetic nano-sized crystalline calcium phosphate, particularly hydroxyapatite, having a specific surface area in the range of 150 m 2 fg to 300 m 2 /g, is described. The nano-sized crystalline calcium phosphate may be in the form of a powder or in the form of a coating on a surface. A method of producing a nano-sized crystalline calcium phosphate powder or coating is also described. The method comprises formation of a liquid crystalline phase in a water solution of calcium, phosphorous precursor and a surfactant, placing the phase in an ammonia atmosphere so that nano-sized crystals are formed, followed by either removal of the surfactant with a solvent and recovering the nano-sized crystals to obtain the powder, or diluting the ammonia-treated liquid crystalline phase with a hydrophobic organic solvent to create a microemulsion of the nano-sized crystals in water, dipping an oxide layer-coated surface of an object into the microemulsion, or alternatively saving the step of ammoni...
Ceramics International, 2016
Synthetic calcium phosphates are used in for example bone cements and implant coatings to increas... more Synthetic calcium phosphates are used in for example bone cements and implant coatings to increase biocompatibility. The common method to produce tricalcium phosphate (TCP) uses high temperatures, which creates large crystals with low specific surface areas. In order to investigate new methods to produce TCP at lower temperatures, the reaction between calcium propionate and triethyl phosphate conducted at 220 degrees C was studied. The method had a near 100% conversion rate, the main synthesis products were calcium phosphate and ethyl propionate. The formed calcium phosphate polymorph could be controlled depending on the water content of the precursor mixture. Anhydrous conditions created amorphous calcium phosphate. As the concentration of water increased, beta-TCP was formed, followed by calcium deficient hydroxyapatite and monetite. The particle size increased with the water content, from 20 to 40 nm for amorphous calcium phosphate to tenths of micrometers for monetite. The specific surface areas varied between 209 m(2)/g for the amorphous product to 3.6 m(2)/g for the monetite product.
Nordic Pulp and Paper Research Journal, 2006
Journal of biomedical materials research. Part A, 2018
A nanosized hydroxyapatite (HA) modification on polyetheretherketone (PEEK) using a novel spin co... more A nanosized hydroxyapatite (HA) modification on polyetheretherketone (PEEK) using a novel spin coating technique was investigated in a rabbit model. Spin coating technique creates a 20-40 nm thick layer of nanosized HA particles with similar shape, size, and crystallinity as human bone. Some implants were designed with a perforating hole in the apical region to mimic a fusion chamber of a spinal implant. The coating nano-structures were assessed using a scanning electron microscope. The in vivo response to HA-PEEK was compared to untreated PEEK with respect to removal torque, histomorphometry, and computed microtomography. The HA-coated and pure PEEK implants were inserted in the tibia and femur bone according to simple randomization. The rabbits were sacrificed 20 weeks after implantation. Removal torque analysis showed significantly higher values for HA-PEEK. Qualitative histological evaluation revealed an intimate contact between PEEK and the bone at the threads and perforated ho...