focus, focus, focus

So after all that reading, note taking, quoting, and searching I have come up with my final questions.

1. Why do we need to use tissue engineering for ACL scaffolding?

• background on injury rates, number of surgeries performed annually
• why does the ACL not heal on its own?
• problems with past and current methods of treatment- allograft, autograft, prosthesis- commercial ones (Carbon Fiber Prostheses, Gore Tex, Darcon, Leeds-Keio Artificial Ligament, Kennedy Ligament Augmentation)
  
• more specific- why do women have a higher risk of tearing their ACLs?

2. What components will be used?

• Use design from "Fiber-based tissue-engineered scaffold for ligament replacement:
  design considerations and in vitro evaluation
  James A. Cooper a,b,c,d, Helen H. Luf, Frank K. Koe, Joseph W. Freemana,
  Cato T. Laurencin a,b,c,d,*"
  
• Polymeric fibers of polyactide-co-glycolide 10:90 (PLGA fibers)
• Biodegradable materials
  
• 3-D braiding technology
• Braiding geometry
• TABLE 1- effects of braiding geometry on other parameters- "Results from the porosimetry analyses of the PLAGA
  circular and rectangular braided scaffolds are summarized
  in Table 1. The effects of braiding geometry on the
  linear density, mode pore diameter, median pore
  diameter, surface area, braiding angle, and porosity of
  the scaffolds can be derived from Table 1."
• Braiding angle
  
• Advantages of this design- controlled pore diameter promote tissue infiltration throughout scaffold, custom design with 3-D braiding, 3-D braiding prevents catastrophy from one tiny break

3. How does it work?

• design from Cooper et. al.
  
• Surgical implant, instead of the basically 2 procedures using an autograft (remove tissue from one area and put it in ACL), only one (just put in new scaffold)
  
• Architecture
• Porosity
• Degradability
• Cell Source
• IDEAL "The ideal ACL replacement scaffold should be
  biodegradable, porous, biocompatible, exhibit sufficient
  mechanical strength, and able to promote the formation
  of ligamentous tissue." from article mentioned above
• 3 regions- "The objective
  was to design a scaffold that provides the newly
  regenerating tissue with a temporary site for cell
  attachment, proliferation, and mechanical stability. As
  shown in Fig. 1, the 3-D braided scaffold was comprised
  of three regions: femoral tunnel attachment site,
  ligament region, and tibial tunnel attachment site. The
  attachment sites had high angle fiber orientation at the
  bony attachment ends and lower angle fiber orientation
  in the intraarticular zone. This pre-designed heterogeneity
  in the grafts was aimed to promote the eventual
  integration of the graft with bone tissue. The scaffold
  was composed of PLAGA fiber with diameter similar to
  that of type I collagen fiber."
• Cell adhesion
• Cells spread across fiber
• Cell migration and attachment
  

4. What will the strength be?

• evaluating the design described in Cooper et. al.
  
• ultimate tensile strengths tested- "The ultimate tensile strengths ranged
  from ~100 to 400 MPa"
• circular geometry was stronger than rectangular - "When the same number of yarns was
  used for the rectangular and circular braids the circular
  braid geometry showed a significant increase in maximum
  tensile load. The 3-D circular fibrous scaffold was
  able to withstand tensile loads of 907N (SD7132 N),
  which was greater than the level for normal human
  physical activity that is estimated to range between 67
  and 700N"
• Table 2- Maximum loads and ultimate tensile strength
  

5. How can it be improved?

• keep going with design from Cooper et. al.
  
• optimal braiding angle, pore size, biocompatibility
• "Future studies will focus on the scaffold’s initial
  mechanical properties as compared to a rabbit model
  and in vitro characterization of the cellular response and
  interaction with the braided tissue-engineered ligament
  scaffold."