Kim Cheng Tan

Fused deposition modeling of novel scaffold architectures for tissue engineering applications.

Fused deposition modeling, a rapid prototyping technology, was used to produce novel scaffolds with honeycomb-like pattern, fully interconnected channel network, and controllable porosity and channel size. A bioresorbable polymer poly(epsilon-caprolactone) (PCL) was developed as a filament modeling material to produce porous scaffolds, made of layers of directionally aligned microfilaments, using this computer-controlled extrusion and deposition process. The PCL scaffolds were produced with a range of channel size 160-700 microm, filament diameter 260-370 microm and porosity 48-77%, and regular geometrical honeycomb pores, depending on the processing parameters. The scaffolds of different porosity also exhibited a pattern of compressive stress-strain behavior characteristic of porous solids under such loading. The compressive stiffness ranged from 4 to 77 MPa, yield strength from 0.4 to 3.6 MPa and yield strain from 4% to 28%. Analysis of the measured data shows a high correlation between the scaffold porosity and the compressive properties based on a power-law relationship.

Mechanical properties and cell cultural response of polycaprolactone scaffolds designed and fabricated via fused deposition modeling.

A number of different processing techniques have been developed to design and fabricate three-dimensional (3D) scaffolds for tissue-engineering applications. The imperfection of the current techniques has encouraged the use of a rapid prototyping technology known as fused deposition modeling (FDM). Our results show that FDM allows the design and fabrication of highly reproducible bioresorbable 3D scaffolds with a fully interconnected pore network. The mechanical properties and in vitro biocompatibility of polycaprolactone scaffolds with a porosity of 61 +/- 1% and two matrix architectures were studied. The honeycomb-like pores had a size falling within the range of 360 x 430 x 620 microm. The scaffolds with a 0/60/120 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 41.9 +/- 3.5 and 3.1 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 29.4 +/- 4.0 and 2.3 +/- 0.2 MPa, respectively. In comparison, the scaffolds with a 0/72/144/36/108 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 20.2 +/- 1.7 and 2.4 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 21.5 +/- 2.9 and 2.0 +/- 0.2 MPa, respectively. Statistical analysis confirmed that the five-angle scaffolds had significantly lower stiffness and 1% offset yield strengths under compression loading than those with a three-angle pattern under both testing conditions (p < or = 0.05). The obtained stress-strain curves for both scaffold architectures demonstrate the typical behavior of a honeycomb structure undergoing deformation. In vitro studies were conducted with primary human fibroblasts and periosteal cells. Light, environmental scanning electron, and confocal laser microscopy as well as immunohistochemistry showed cell proliferation and extracellular matrix production on the polycaprolactone surface in the 1st culturing week. Over a period of 3-4 weeks in a culture, the fully interconnected scaffold architecture was completely 3D-filled by cellular tissue. Our cell culture study shows that fibroblasts and osteoblast-like cells can proliferate, differentiate, and produce a cellular tissue in an entirely interconnected 3D polycaprolactone matrix.

Cranioplasty After Trephination Using a Novel Biodegradable Burr Hole Cover:Technical Case Report

OBJECTIVE AND IMPORTANCE: We have developed novel biodegradable polymer implants by using the rapid prototyping technology fused deposition modeling. Early results of a clinical pilot study for cranioplasty are presented. CLINICAL PRESENTATION: Five patients with the diagnosis of chronic subdural hematoma were included in the study. After trephination and evacuation of the subdural hematoma, burr holes (diameter, 14 mm) were closed using a biodegradable implant made of polycaprolactone. Implants were computer designed with an upper rim diameter of 16 mm and a 14 mm body diameter with a fully interconnected, honeycomb-like architecture of 400 to 600 &mgr;m in pore size. INTERVENTION: Postoperative computed tomographic scans indicated that the plugs were stably anchored in the osseous host environment with no fluid collection detectable. The postoperative course was uneventful, and patients were discharged after 5 days. Follow-up scans after 3, 6, and 12 months showed that the implants were well integrated in the surrounding calvarial bone with new bone filling the porous space. CONCLUSION: These novel polymer scaffolds made of the slow-degrading material polycaprolactone represent a suitable implant for closure of post-trephination defects.

Distributed rapid prototyping – a framework for Internet prototyping and manufacturing

This paper focuses on the development of a distributed rapid prototyping system via the Internet to form a framework of Internet prototyping and manufacturing for the support of effective product development. The proposed methodology is targeted at a wide audience using a disparate range of computer systems to access remotely located rapid prototyping facilities via the Internet for prototype fabrication. The methodology is useful for both educational research for teaching evolving rapid prototyping technologies and remote scientific visualization. This approach is based on the merger of object‐oriented modular software architecture and client server communications for the remote control of rapid prototyping hardware (called fused deposition modeling) via the Internet. Other Web tools are used to allow the remote user to have higher interactivity with the server applications that have a direct link with the front‐end terminals controlling the rapid prototyping hardware.

Composite PLDLLA/TCP Scaffolds for Bone Engineering: Mechanical and In Vitro Evaluations

Bone tissue engineering scaffolds have two challenging functional tasks to play; to be bioactive by encouraging cell proliferation and differentiation, and to provide suitable mechanical stability upon implantation. Composites of biopolymers and bioceramics unite the advantages of both materials resulting in better processibility, enhanced mechanical properties through matrix reinforcement and osteoinductivity. Novel composite blends of poly(L-lactide-co-D,L-lactide)/tricalcium phosphate (PLDLLA/TCP) were fabricated into scaffolds by an extrusion deposition technique customised from standard rapid prototyping technology. PLDLLA/TCP composite material blends of various compositions were prepared and analysed for their mechanical properties. PLDLLA/TCP (10%) was optimised and fabricated into scaffolds. Compressive mechanical properties for the composite scaffolds were performed. In vitro studies were conducted using porcine bone-marrow stromal cells (BMSCs). Cell-scaffold constructs were induced using osteogenic induction factors for up to 8 weeks. Cell proliferation, viability and differentiation capabilities were assayed using phase contrast light microscopy, scanning electron microscopy, PicoGreen DNA quantification, AlamarBlue metabolic assay; FDA/PI fluorescent assay and western blot analysis for osteopontin. Microscopy observations showed BMSCs possessed high proliferative capabilities and demonstrated bridging across the pores of the scaffolds. FDA/PI staining as well as AlamarBlue assay showed high viability of BMSCs cultured on the composite scaffolds Cell numbers, based on DNA quantitation, was observed to increase continuously up to the 8th week of study. Western blot analysis showed increased osteopontin synthesis on the scaffolds compared to tissue culture plastic. Based on our results the PLDLLA/TCP scaffolds exhibit good potential and biocompatibility for bone tissue engineering applications.

The value simulation‐based learning added to machining technology in Singapore

This study seeks to understand the value simulation‐based learning (SBL) added to the learning of Machining Technology in a 15‐week core subject course offered to university students. The research questions were: (1) How did SBL enhance classroom learning? (2) How did SBL help participants in their test? (3) How did SBL prepare participants for workshop practice? The findings suggest that SBL enlivened the learning of Machining Technology, and promoted autonomous and mastery learning. SBL made a deep impression on the participants’ visual experience, helping them remember the machine processes. SBL also helped learners to conceptualize their answers and provided them with opportunities to become familiar with the conventional machines before workshop practice. An infusion of SBL has the potential to add value to the learning of Machining Technology.