or laser-based (LBB) bioprinting [5, 6]. EBB uses pneumatic or
mechanical extrusion to print the cell suspension in the required
pattern. DBB, which ejects the cell-laden droplets, is mediated by
piezoelectric, acoustic, thermal, or electrostatic actuation [7]. In
LBB, a laser energy-absorbing material evaporates after irradiation,
followed by deposition on a layer of biological ink. EBB is preferred
to fabricate mechanically enhanced tissue constructs, although
DBB and LBB offer greater precision. One concern of bioprinting
is the cell viability after printing. Shear stresses in EBB, thermal
stresses in DBB, and irradiation energy in LBB are the major causes
of cell death in bioprinted constructs [8].
Despite the limitations, bioprinted constructs can be an important tool in preclinical in vitro testing of pharmaceuticals [9]. Certain drugs can cause tissue-specific toxicity, which can be
investigated at the early stages of development. Drug toxicity has
been routinely assessed in critical organs or tissues of the body,
especially liver [10]. An increase in antibiotic-resistant bacterial
strains has driven the development of new antibiotics; however,
chondrotoxicity is one of the major concerns for the safe use of
antibiotics. Bioprinted chondrocyte constructs can be used in the
preclinical phase to determine the toxic effects of a drug on cartilage tissue [4].
In this chapter, a novel method for microfabrication of scalable
tissue strands as building units will be presented. Cell aggregation
and fusion are achieved without the use of liquid printing medium
or an external mold. The scaffold-free cartilage tissue model presented in this work closely recapitulates the articular cartilage biology and physiology to enable the use of such tissues in toxicology
studies in vitro.
2 Materials
All solutions were prepared using ultrapure water and analytical
grade reagents.
2.1 Sodium Alginate
Preparation
1. Sodium alginate solution: powder treated with ultraviolet
(UV) light for sterilization with three 30-min cycles, 4% w/v
in sterilize deionized water, stir overnight in a magnetic stirrer.
2. CaCl 2 solution: powder treated with UV light for sterilization
with three 30-min cycles, 4% w/v in sterilize deionized water
(see Note 1).
3. Sodium citrate solution: powder treated with UV light for
sterilization with three 30-min cycles, 4% w/v in sterilize deionized water.
176
Pallab Datta et al.
mechanical extrusion to print the cell suspension in the required
pattern. DBB, which ejects the cell-laden droplets, is mediated by
piezoelectric, acoustic, thermal, or electrostatic actuation [7]. In
LBB, a laser energy-absorbing material evaporates after irradiation,
followed by deposition on a layer of biological ink. EBB is preferred
to fabricate mechanically enhanced tissue constructs, although
DBB and LBB offer greater precision. One concern of bioprinting
is the cell viability after printing. Shear stresses in EBB, thermal
stresses in DBB, and irradiation energy in LBB are the major causes
of cell death in bioprinted constructs [8].
Despite the limitations, bioprinted constructs can be an important tool in preclinical in vitro testing of pharmaceuticals [9]. Certain drugs can cause tissue-specific toxicity, which can be
investigated at the early stages of development. Drug toxicity has
been routinely assessed in critical organs or tissues of the body,
especially liver [10]. An increase in antibiotic-resistant bacterial
strains has driven the development of new antibiotics; however,
chondrotoxicity is one of the major concerns for the safe use of
antibiotics. Bioprinted chondrocyte constructs can be used in the
preclinical phase to determine the toxic effects of a drug on cartilage tissue [4].
In this chapter, a novel method for microfabrication of scalable
tissue strands as building units will be presented. Cell aggregation
and fusion are achieved without the use of liquid printing medium
or an external mold. The scaffold-free cartilage tissue model presented in this work closely recapitulates the articular cartilage biology and physiology to enable the use of such tissues in toxicology
studies in vitro.
2 Materials
All solutions were prepared using ultrapure water and analytical
grade reagents.
2.1 Sodium Alginate
Preparation
1. Sodium alginate solution: powder treated with ultraviolet
(UV) light for sterilization with three 30-min cycles, 4% w/v
in sterilize deionized water, stir overnight in a magnetic stirrer.
2. CaCl 2 solution: powder treated with UV light for sterilization
with three 30-min cycles, 4% w/v in sterilize deionized water
(see Note 1).
3. Sodium citrate solution: powder treated with UV light for
sterilization with three 30-min cycles, 4% w/v in sterilize deionized water.
176
Pallab Datta et al.