A novel method for the fabrication of homogeneous hydroxyapatite/collagen nanocomposite and nanocomposite scaffold with hierarchical porosity

Homogeneous nanocomposites composed of hydroxyapatite (HAp) and collagen were synthesized using a novel in situ precipitation method through dual template-driven. The morphological and componential properties of nanocomposites were investigated. The HAp particulates, in sizes of about 50–100 nm, were distributed homogeneously in the organic collagen hydrogel. Highly magnified TEM observation showed that HAp inorganic particles were composed of fine sub-particles (2–5 nm) without regular crystallographic orientation. Based on these homogeneous nanocomposites, a novel HAp/collagen nanocomposite scaffold with hierarchical porosity was prepared by multilevel freeze-drying technique. Compared to other conventional scaffolds for tissue engineering, this novel in situ method endows synthesized composite scaffolds with unique morphology—ultrafine HAp particles dispersed homogenously in collagen at nano level and the foam scaffold with hierarchical pore structures. The mechanical performance increased obviously compared with neat collagen. These results provided an efficient approach toward new biomimetic tissue scaffold for the biomedical applications with enhanced intensity/bioactivity and controlled resorption rates. This novel method, we expect, will lead to a wide application in many other hydrogel systems and may be useful for fabrication of various homogeneous inorganic/organic nanocomposites.     

Preparation of 3-D regenerated fibroin scaffolds with freeze drying method and freeze drying/foaming technique

Although three-dimensional fibroin scaffolds have been prepared with freeze drying method, the porosity and pore sizes still can not satisfy the requirement of tissue engineering. In this article, fibroin porous scaffold with high porosity and > 100μm diameter interconnected pores was firstly prepared with freeze drying method through adjusting fibroin concentration. The morphology of different scaffolds lyophilized from different fibroin concentration was observed by SEM. A novel freeze drying improved method, freeze drying/foaming technique, was also devised to prepare fibroin scaffolds at different fibroin concentrations. Using the said method, the porosity and pore size of fibroin scaffolds prepared from 12% concentration were 85.8 ± 4% and 109 ± 20 μm respectively with yield strength up to 450 ± 6 KPa while the porosity and pore size of fibroin scaffolds prepared from 8% concentration were 96.9 ± 3.6% and 120 ± 30 μm respectively with yield strength up to 30 ± 1 KPa. The freeze drying/foaming technique produced scaffolds with a useful combination of high yield strength, interconnected pores, and pore sizes greater than 100 μm in diameter. Through adjusting fibroin concentration and thawing time, the porosity, pore sizes and mechanical properties could be controlled to satisfy the different requirements of tissue engineering. The results suggested that fibroin scaffolds prepared with the above methods could be formed for utility in biomaterial application.     

A smart bilayer scaffold of elastin-like recombinamer and collagen for soft tissue engineering

Elastin-like recombinamers (ELRs) are smart, protein-based polymers designed with desired peptide sequences using recombinant DNA technology. The aim of the present study was to produce improved tissue engineering scaffolds from collagen and an elastin-like protein tailored to contain the cell adhesion peptide RGD, and to investigate the structural and mechanical capacities of the resulting scaffolds (foams, fibers and foam-fiber bilayer scaffolds). The results of the scanning electron microscopy, mercury porosimetry and mechanical testing indicated that incorporation of ELR into the scaffolds improved the uniformity and continuity of the pore network, decreased the pore size (from 200 to 20 μm) and the fiber diameter (from 1.179 μm to 306 nm), broadened the pore size distribution (from 70–200 to 4–200 μm) and increased their flexibility (from 0.007 to 0.011 kPa⁻¹). Culture of human fibroblasts and epithelial cells in ELR-collagen scaffolds showed the positive contribution of ELR on proliferation of both types of cells.     

Construction of collagen II/hyaluronate/chondroitin-6-sulfate tri-copolymer scaffold for nucleus pulposus tissue engineering and preliminary analysis of its physico-chemical properties and biocompatibility

To construct a novel scaffold for nucleus pulposus (NP) tissue engineering, The porous type II collagen (CII)/hyaluronate (HyA)–chondroitin-6-sulfate (6-CS) scaffold was prepared using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) cross-linking system. The physico-chemical properties and biocompatibility of CII/HyA–CS scaffolds were evaluated. The results suggested CII/HyA–CS scaffolds have a highly porous structure (porosity: 94.8 ± 1.5%), high water-binding capacity (79.2 ± 2.8%) and significantly improved mechanical stability by EDC/NHS crosslinking (denaturation temperature: 74.6 ± 1.8 and 58.1 ± 2.6°C, respectively, for the crosslinked scaffolds and the non-crosslinked; collagenase degradation rate: 39.5 ± 3.4 and 63.5 ± 2.0%, respectively, for the crosslinked scaffolds and the non-crosslinked). The CII/HyA–CS scaffolds also showed satisfactory cytocompatibility and histocompatibility as well as low immunogenicity. These results indicate CII/HyA–CS scaffolds may be an alternative material for NP tissue engineering due to the similarity of its composition and physico-chemical properties to those of the extracellular matrices (ECM) of native NP.     

Fabrication of three-dimensional poly(ε-caprolactone) scaffolds with hierarchical pore structures for tissue engineering

The physical properties of tissue engineering scaffolds such as microstructures play important roles in controlling cellular behaviors and neotissue formation. Among them, the pore size stands out as a key determinant factor. In the present study, we aimed to fabricate porous scaffolds with pre-defined hierarchical pore sizes, followed by examining cell growth in these scaffolds. This hierarchical porous microstructure was implemented via integrating different pore-generating methodologies, including salt leaching and thermal induced phase separation (TIPS). Specifically, large (L, 200–300 μm), medium (M, 40–50 μm) and small (S, < 10 μm) pores were able to be generated. As such, three kinds of porous scaffolds with a similar porosity of ~ 90% creating pores of either two (LS or MS) or three (LMS) different sizes were successfully prepared. The number fractions of different pores in these scaffolds were determined to confirm the hierarchical organization of pores. It was found that the interconnectivity varied due to the different pore structures. Besides, these scaffolds demonstrated similar compressive moduli under dry and hydrated states. The adhesion, proliferation, and spatial distribution of human fibroblasts within the scaffolds during a 14-day culture were evaluated with MTT assay and fluorescence microscopy. While all three scaffolds well supported the cell attachment and proliferation, the best cell spatial distribution inside scaffolds was achieved with LMS, implicating that such a controlled hierarchical microstructure would be advantageous in tissue engineering applications.     

Polyurethane (PU) scaffolds prepared by solvent casting/particulate leaching (SCPL) combined with centrifugation

This article reports an enhanced solvent casting/particulate (salt) leaching (SCPL) method developed for preparing three-dimensional porous polyurethane (PU) scaffolds for cardiac tissue engineering. The solvent for the preparation of the PU scaffolds was a mixture of dimethylformamide (DFM) and tetrahydrofuran (THF). The enhanced method involved the combination of a conventional SCPL method and a step of centrifugation, with the centrifugation being employed to improve the pore uniformity and the pore interconnectivity of scaffolds. Highly porous three-dimensional scaffolds with a well interconnected porous structure could be achieved at the polymer solution concentration of up to 20% by air or vacuum drying to remove the solvent. When the salt particle sizes of 212–295, 295–425, or 425–531 µm and a 15% w/v polymer solution concentration were used, the porosity of the scaffolds was between 83–92% and the compression moduli of the scaffolds were between 13 kPa and 28 kPa. Type I collagen acidic solution was introduced into the pores of a PU scaffold to coat the collagen onto the pore walls throughout the whole PU scaffold. The human aortic endothelial cells (HAECs) cultured in the collagen-coated PU scaffold for 2 weeks were observed by scanning electron microscopy (SEM). It was shown that the enhanced SCPL method and the collagen coating resulted in a spatially uniform distribution of cells throughout the collagen-coated PU scaffold.     

Indirect rapid prototyping of biphasic calcium phosphate scaffolds as bone substitutes: influence of phase composition,macroporosity and pore geometry on mechanical properties

While various materials have been developed for bone substitute and bone tissue engineering applications over the last decades, processing techniques meeting the high demands of scaffold shaping are still under development. Individually adapted and mechanically optimised scaffolds can be derived from calcium phosphate (CaP-) ceramics via rapid prototyping (RP). In this study, porous ceramic scaffolds with a periodic pattern of interconnecting pores were prepared from hydroxyapatite, β-tricalcium phosphate and biphasic calcium phosphates using a negative-mould RP technique. Moulds predetermining various pore patterns (round and square cross section, perpendicular and 60° inclined orientation) were manufactured via a wax printer and subsequently impregnated with CaP-ceramic slurries. Different pore patterns resulted in macroporosity values ranging from about 26.0–71.9 vol% with pore diameters of approximately 340 μm. Compressive strength of the specimens (1.3–27.6 MPa) was found to be mainly influenced by the phase composition as well as the macroporosity, both exceeding the influence of the pore geometry. A maximum was found for scaffolds with 60 wt% hydroxyapatite and 26.0 vol% open porosity. It has been shown that wax ink-jet printing allows to process CaP-ceramic into scaffolds with highly defined geometry, exhibiting strength values that can be adjusted by phase composition and pore geometry. This strength level is within and above the range of human cancellous bone. Therefore, this technique is well suited to manufacture scaffolds for bone tissue engineering.     

Novel porous scaffolds of poly(lactic acid) produced by phase-separation using room temperature ionic liquid and the assessments of biocompatibility

Here we prepared three-dimensional (3D) porous-structured biodegradable polymer scaffolds for tissue regeneration using room temperature ionic liquids (RTILs) as a novel porogen, and addressed their biological properties, including in vitro cell growth and differentiation and in vivo tissue compatibility. RTIL based on 1-butyl-3-methylimidazolium ([bmim]) bearing hydrophilic anion Cl was introduced within the polymer structure to provide a pore network. A mixture of poly(lactic acid) (PLA) with RTIL dissolved in an organic solvent formed a bi-continuous network during the drying process. Selective dissolution of the RTIL phase was facilitated in ethanol, which resulted in a porous network of the polymer phase with complete removal of the RTIL. The RTILs-assisted porous scaffolds showed a typical open-channeled network with pore sizes over 100 μm and porosities of about 86–94%. For the biocompatibility assessments of the scaffolds, mesenchymal stem cells (MSCs) derived from rat bone marrow were seeded onto the PLA scaffold, and the cell proliferation and osteoblastic differentiation behaviors were examined. Results showed a typical on-going increase in the cell population with a level comparable to that observed on the tissue culture plastic control, indicating good cell compatibility. When cultured in an osteogenic medium, the alkaline phosphatase (ALP) activity of the cells on the PLA scaffolds was stimulated to increase with time from 7 to 14 days, in a similar manner to that on the control. Moreover, the expression of genes related to osteoblasts, including collagen type I, osteocalcin and bone sialoprotein, was stimulated on the 3D PLA scaffold during culture for up to 14 days, with levels higher than those on the control, suggesting the developed scaffold provided a 3D matrix condition for osteogenesis. An in vivo pilot study conducted subcutaneously in rat for 4 weeks revealed good tissue compatibility of the scaffold, with the ingrowth of cells and formation of collageneous tissue around and deep within the pores of the scaffold and no significant inflammatory reaction. Taken together, this novel method of using RTILs as a pore generator is considered to be useful in the development of biocompatible porous polymer scaffolds for tissue regeneration.     

Preparation of three-dimensional fibroin/collagen scaffolds in various pH conditions

Three dimensional (3-D) fibroin/collagen scaffolds are the novel fibroin based scaffolds derived from aqueous solution. In this article, we investigated the effect of pH on the formation of fibroin/collagen scaffolds. In the range of pH from 4 to 8.5, the fibroin/collagen scaffolds with good porous structures can be prepared using freeze-drying method, which would facilitate the adding of other biopolymers. The structures of different fibroin-based scaffolds were investigated with FTIR and DSC, which indicated that the interaction of fibroin and collagen affected the methanol-induced transformation of fibroin from random-coil to β-sheet conformation. The mechanical properties were also studied. The results mean that all the fibroin-based scaffolds prepared in various pH values had better mechanical properties than other reported fibroin scaffolds. Since the fibroin/collagen scaffolds can be prepared in the range of pH from 4 to 8.5, it is very easy to prepare different multifunctional scaffolds such as fibroin/collagen/chitosan scaffolds and fibroin/collagen/heparin scaffolds in acidic or neutral conditions. These new fibroin-based blend materials extend the range of biomaterial properties that can promote the use in biomedical applications such as drug release and tissue engineering.     

Degradation behavior of hydrophilized PLGA scaffolds prepared by melt-molding particulate-leaching method: Comparison with control hydrophobic one

Porous PLGA/PVA scaffolds as hydrophilized PLGA scaffolds for tissue engineering applications were fabricated by a novel melt-molding particulate leaching method (non-solvent method). The prepared scaffolds exhibited highly porous and open-cellular pore structures with almost same surface and interior porosities (pore size, 200–300 μ m; porosity, about 90%). The in vitro degradation behavior of the PLGA and PLGA/PVA scaffolds was compared at 37^∘C in PBS (pH 7.4) with and without the solution change everyday to see the effect of solution pH as well as scaffold hydrophilicity on the degradation behavior. The changes in dimension, molecular weight, mechanical properties (maximum load and modulus), and morphology of the scaffolds were examined with degradation time. The degradation behavior of the PLGA and PLGA/PVA scaffolds was further investigated in vivousing a rat model (subcutaneously implantation). It was observed that both PLGA and PLGA/PVA scaffolds in decreasing pH condition (PBS no change) showed faster degradation than those in constant pH condition (PBS change everyday), owing to the enhanced intramolecular depolymerization by the increment of chain hydrophilicity caused by carboxylate groups as well as the autocatalysis of carboxylic acids accumulated in the solution by the cleavage of PLGA backbone ester bonds. The scaffolds in vivo condition also showed faster degradation than those in vitro, probably due to the aid of foreign body giant cells or enzymes. The PLGA/PVA scaffold showed slightly faster degradation than the PLGA scaffold for both in vitro and in vivo conditions. Author to whom all correspondence should be addressed.     

In vitro characterization of chitosan scaffolds: influence of composition and deacetylation degree

In this study, the influence of degree of deacetylation (DD) and composition on some structural and biological properties of chitosan scaffolds were examined in vitro. 3D chitosan scaffolds of 2% (w/v) and 3% (w/v) composition in different DDs i.e. 75–85% and >85% were prepared by freeze-drying method at −80 °C. We noticed that >85% deacetylated chitosan scaffolds of 2% (w/v) composition has a highly interconnected morphological structure having ∼100 μm pore size with 0.0917 N/mm² compression modulus. L929 fibroblastic cells were cultured on chitosan scaffolds in order to evaluate their biocompatibilities. Cell culture studies demonstrated that fibroblastic cell attachment and proliferation is affected by DD. The higher deacetylated chitosan scaffolds strongly supported the attachment and proliferation when compared with the lower deacetylated scaffolds. MTT assay indicated that >85% deacetylated chitosan scaffolds of 2% (w/v) composition, having the highest specific growth rate 0.017 h⁻¹ of all, was found to be the most suitable for cell culture studies and a potential candidate for tissue engineering with enhanced biostability and good biocompatibility.     

Stiffness Improvement of 45S5 Bioglass®‐Based Scaffolds Through Natural and Synthetic Biopolymer Coatings: An Ultrasonic Study

Due to its excellent bioactivity, 45S5 Bioglass^® is being highly considered in tissue engineering scaffold development. In order to enhance vascularization promoting tissue growth, these scaffolds typically have a highly interconnected porous structure with a porosity between 80 and >90%. Often, Bioglass^®‐based scaffolds of such a high porosity have insufficient stiffness. In order to increase the stiffness of Bioglass^®‐based scaffolds fabricated by the foam replica method, the herein investigated scaffolds were coated with a number of different biopolymers, including: collagen, gelatin, polycaprolactone (PCL), alginate and poly(l ‐lactic acid). The resulting stiffness gain was quantified by means of ultrasonic measurements. Accordingly, PCL and collagen coatings increased the scaffold stiffness, as compared to uncoated scaffolds, by 58 and 38%, respectively; while no remarkable stiffness increase was recorded for the other coatings. Additionally, scanning electron microscopy images of polymer coated scaffolds revealed that PCL coatings had not clogged the scaffold's micropores, which is deemed essential for cell seeding and to enable in‐growth of bone tissue. Thus, the application of PCL coatings represents a promising strategy for mechanical competence enhancement of Bioglass^®‐based scaffolds for bone tissue engineering.     

Silk fibroin/chitosan scaffold: preparation,characterization, and culture with HepG2 cell

Tissue engineering requires the development of three-dimensional water-stable scaffolds. In this study, silk fibroin/chitosan (SFCS) scaffold was successfully prepared by freeze-drying method. The scaffold is water-stable, only swelling to a limited extent depending on its composition. Fourier Transform Infrared (FTIR) spectra and X-Ray diffraction curves confirmed the different structure of SFCS scaffolds from both chitosan and silk fibroin. The homogeneous porous structure, together with nano-scale compatibility of the two naturally derived polymers, gives rise to the controllable mechanical properties of SFCS scaffolds. By varying the composition, both the compressive modulus and compressive strength of SFCS scaffolds can be controlled. The porosity of SFCS scaffolds is above 95% when the total concentration of silk fibroin and chitosan is below 6 wt%. The pore sizes of the SFCS scaffolds range from 100 μm to 150 μm, which can be regulated by changing the total concentration. MTT assay showed that SFCS scaffolds can promote the proliferation of HepG2 cells (human hepatoma cell line) significantly. All these results make SFCS scaffold a suitable candidate for tissue engineering.     

Hydration dynamics of collagen/PVA composites: Thermoporometric and impedance analysis

Porous scaffolds like collagen/PVA (polyvinyl alcohol) composites have potential applications in the field of biomedical engineering. The pore properties and electrical behavior of collagen/PVA composite system were investigated by thermoporometry technique and electrochemical impedance analysis. The porous composites were crosslinked by less cytotoxic genipin due to the versatility in the crosslinking reactivity between the amino groups. Different physicochemical properties like rheological behavior, thermal stability of the protein and morphological changes of the composites were investigated as a function of PVA concentration by viscosity profile, temperature dependant circular dichroic spectroscopic studies, scanning electron microscopy. Bound water constrained within the pores of collagen/PVA composites seems to provide signatures for changes induced by amount of additives on the pore diameter and distribution in composite molecules. Impedance measurements of the composites in the frequency range of 10⁻² to 10⁵ Hz reveal that concentration of the additive and crosslinking significantly influence the permittivity of the composites. The tunable physicochemical properties help to gain insight for regulating cellular events for tissue and organ regeneration.     

Fabrication and evaluation of biomimetic scaffolds by using collagen–alginate fibrillar gels for potential tissue engineering applications

Pore architecture and its stable functionality under cell culturing of three dimensional (3D) scaffolds are of great importance for tissue engineering purposes. In this study, alginate was incorporated with collagen to fabricate collagen–alginate composite scaffolds with different collagen/alginate ratios by lyophilizing the respective composite gels formed via collagen fibrillogenesis in vitro and then chemically crosslinking. The effects of alginate amount and crosslinking treatment on pore architecture, swelling behavior, enzymatic degradation and tensile property of composite scaffolds were systematically investigated. The relevant results indicated that the present strategy was simple but efficient to fabricate highly interconnected strong biomimetic 3D scaffolds with nanofibrous surface. NIH3T3 cells were used as a model cell to evaluate the cytocompatibility, attachment to the nanofibrous surface and porous architectural stability in terms of cell proliferation and infiltration within the crosslinked scaffolds. Compared with the mechanically weakest crosslinked collagen sponges, the cell-cultured composite scaffolds presented a good porous architecture, thus permitting cell proliferation on the top surface as well as infiltration into the inner part of 3D composite scaffolds. These composite scaffolds with pore size ranging from 150 to 300 μm, over 90% porosity, tuned biodegradability and water-uptake capability are promising for tissue engineering applications.     

Resorbable, porous glass scaffolds by a salt sintering process

Resorbable, porous glass scaffolds for tissue engineering were prepared by sintering borate glass with salt (sodium chloride). Subsequently, the sodium chloride was dissolved in water resulting in a highly porous material. By modifying the process parameters including salt particle size, salt volume percentage, sintering temperature and sintering time, sintered matrix structures were optimized. Analysis of the structure data indicates that the 50 vol% glass—50 vol% salt with particle sizes from 250–315 μm sintered at a temperature of 520°C for 10 min resulted in an optimum structure with 76.5% porosity and 29.3 N/cm² compressive strength. The process of HAP formation on the scaffolds in 0.25 M K₂HPO₄ solutions with pH 9.0 at 37°C was evaluated. The structural changes were analyzed by X-ray diffraction and scanning electron microscopy. An amorphous phosphate was formed on the surface of the scaffolds within 1d and crystalline hydroxyapatite (HA) within 10d.     

Robotic dispensing of composite scaffolds and in vitro responses of bone marrow stromal cells

The development of bioactive scaffolds with a designed pore configuration is of particular importance in bone tissue engineering. In this study, bone scaffolds with a controlled pore structure and a bioactive composition were produced using a robotic dispensing technique. A poly(ε-caprolactone) (PCL) and hydroxyapatite (HA) composite solution (PCL/HA = 1) was constructed into a 3-dimensional (3D) porous scaffold by fiber deposition and layer-by-layer assembly using a computer-aided robocasting machine. The in vitro tissue cell compatibility was examined using rat bone marrow stromal cells (rBMSCs). The adhesion and growth of cells onto the robotic dispensed scaffolds were observed to be limited by applying the conventional cell seeding technique. However, the initially adhered cells were viable on the scaffold surface. The alkaline phosphatase activity of the cells was significantly higher on the HA–PCL than on the PCL and control culture dish, suggesting that the robotic dispensed HA–PCL scaffold should stimulate the osteogenic differentiation of rBMSCs. Moreover, the expression of a series of bone-associated genes, including alkaline phosphatase and collagen type I, was highly up-regulated on the HA–PCL scaffold as compared to that on the pure PCL scaffold. Overall, the robotic dispensed HA–PCL is considered to find potential use as a bioactive 3D scaffold for bone tissue engineering. Seok-Jung Hong and Ishik Jeong contributed equally.     

Poröse Scaffolds aus mineralisiertem Kollagen – ein biomimetisches Knochenersatzmaterial

Porous scaffolds made from mineralised collagen – a biomimetic bone graft material Using biomimetically mineralised collagen type I, a new porous bone graft material has been developed, the composition of which mimics extracellular matrix of bone tissue. The pore structure is generated by a freeze drying process, whereas the pore size can be controlled by temperature and velocity of the freezing over a wide range. The structure is stabilized by crosslinking of the collagen with the water soluble carbodiimide derivative EDC. For the seeding with bone cells, pores with diameters of about 200 μm have turned out to be optimal. These scaffolds are elastic in the wet state which allow for cell culture experiments under mechanical stimulation.     

Influence of pore size on tensile strength, permeability and porosity of hyaluronan-collagen scaffolds

Recent investigations have shown the importance of scaffold pore size on the realisation of tissue engineered cartilage which promotes cell adhesion, proliferation and differentiation. The objective of this study was to investigate the influence of pore size on the mechanical properties, the permeability and the porosity of hyaluronan-collagen scaffolds. Hyaluronan-collagen scaffolds with three different mean pore sizes (302.5, 402.5 and 525 microm) have been produced according to a standardised protocol. The maximum stress at rupture, the Young's Moduli, permeability and porosity of the scaffolds were investigated. The permeability was determined both empirically and mathematically. Increased pore sizes indicated a larger stress at rupture as well as increased Young's Moduli. Porosity and permeability were raised by increasing pore sizes. The mathematically calculated permeability showed the same trend. The results indicate a higher mechanical stability for scaffolds with larger pores. The experimental and mathematical experiments both show increased permeability and fluid mobility for larger pores in scaffolds. Morphological changes resulting from the alteration of pore size led to non-correlation between the calculated and the experimental permeability.     

Characterisation of scaffold architecture and tendons using optical coherence tomography and polarisation-sensitive optical coherence tomography

Scaffolds play an important role in the generation of functional tissues using tissue-engineering techniques. To generate highly organised tissue, scaffolds must have specific internal and external architectures. Here, optical coherence tomography (OCT) is exploited to characterise the architectures of various scaffolds, in particular scaffolds which have been fabricated to support the formation of uniaxially orientated collagen bundle for use in tendon tissue engineering. In parallel, a polarisation-sensitive OCT (PSOCT) has been built to assess the collagen fibre organisation in human tendon and monitor the growth of engineering tendon constructs online and non-destructively. The impact of mechanical stimuli on the modulation of tendon tissue formation and organisation was also assessed. It is shown that conventional OCT is capable of characterising scaffold architecture and the pore size, porosity or microchannel dimension can be determined quantitatively and qualitatively. PSOCT generated birefringence images of human tendon and demonstrated that low birefringence images, associated with fewer microstructural variations, correlated to the presence of scar tissue or degenerated tissue; whereas the tissue-engineered tendon exhibited lower degree of birefringence.