Week 1 HW: Final Project Ideas
(1) Target Product and Motivation
The target product is a 3D-bioprinted bioactive bilayer hydrogel dressing engineered to
accelerate wound healing, promote blood vessel growth, and eliminate infections in patients
suffering from Diabetic Foot Ulcers (DFUs).
The dressing consists of two main synergistic layers:
• Structural & Antimicrobial Base: A biocompatible matrix composed of Chitosan
(derived via bacterial conversion) and human Fibrin. Chitosan serves as an innate
antimicrobial barrier against common DFU pathogens like Staphylococcus aureus,
while fibrin promotes fast angiogenesis (new blood vessel formation) to restore
microcirculation in ischemic diabetic tissues [1].
• Regenerative Matrix: Encapsulated recombinant human Epidermal Growth Factor
(hEGF) to actively stimulate fibroblast proliferation and rapid re-epithelialization of the
wound [2].
Motivation: In Guatemala, diabetic foot complications represent a massive public health
crisis. Current standard treatments in public hospitals are heavily reliant on archaic,
aggressive physical debridement (“raspar la herida”). Due to deficient long-term postoperative care, a vast number of these cases inevitably result in painful lower-limb
amputations. This project aims to revolutionize local medical care by providing an advanced,
accessible biomaterial that prevents infection, drastically reduces wound-closure times, and
stops preventable amputations.
(2) Living System (Manufacturing Chassis)
To ensure maximum bio-safety, high purity, and scalable cost-efficiency, we propose a dual
living-system workflow that avoids volatile extraction from wild animals
(tilapia/crustaceans):
• Primary Chassis: Pichia pastoris (methylotrophic yeast)
o Role: Production of recombinant hEGF and human Fibrinogen (cleaved
enzymatically into fibrin during bioprinting).
o Mechanism: The system is fed an engineered carbon source regimen
(Glycerol for rapid biomass growth, followed by Methanol to induce the highly
efficient AOX1 promoter). P. pastoris synthesizes and correctly folds the
complex human proteins, secreting them directly into the extracellular media
[2].
o Output: High-yield, purified hEGF and fibrinogen proteins ready to form the
printable bio-ink.
• Secondary Chassis: Escherichia coli
o Role: Expressing bacterial Chitin Deacetylase enzymes to convert raw, lowcost industrial chitin (from regional shrimp shell waste) into high-purity,
biomedical-grade Chitosan [1].
(3) Automation Strategy
We will implement an integrated two-phase automated ecosystem combining liquid handling
and robotic tissue testing to eliminate slow, error-prone manual steps:
• Automated Screening via Desktop Liquid Handler (e.g., Opentrons OT-2):
o The robot will automatically mix varying concentrations of Chitosan, Fibrin,
and hEGF inside multi-well plates. This allows us to systematically screen
hundreds of unique bio-ink formulations per day to optimize mechanical
viscosity and growth factor release profiles [3].
• High-Throughput Robotic Skin-Model Testing (Pre-clinical Simulation):
o The automated liquid handler will seed human keratinocytes and fibroblasts
onto 3D-bioprinted matrices to grow artificial human skin layers [4].
o An automated module will induce uniform “wounds” in these printed tissues.
The robot will then apply our various formulated dressings and monitor
cellular migration rates via automated high-content imaging systems to find
the ultimate healing formulation before proceeding to the mandatory Human
Clinical Trials.
(4) Scale and Timeline Calculations (Back-of-the-Envelope)
(a) How Much? (Scale of Production)
• Target Population: We will target 15,000 active DFU patients per year in Guatemala
(representing ~10% of the calculated high-risk diabetic population).
• Treatment Parameters: An average DFU patient requires 20 dressings over a 2-month
treatment cycle (1 dressing changed every 3 days).
• Total Dressings Required:
15,000 patients × 20 dressings/patient = 300,000dressings/year15,000 patients×20 dressings/patient=𝟑𝟎𝟎,𝟎𝟎𝟎 dressings/year
• Dressing Dimensions & Mass: A standard DFU patch is 10 cm × 10 cm × 0.2 cm
(Volume = 20 cm³ or 20 mL of hydrogel matrix).
o Hydrogels are ~ 95% water. The solid matrix consists of 3% Chitosan/Fibrin
matrix (~ 0.6 g) and a therapeutic dose of 10 μg of hEGF per dressing [4].
• Total Annual Raw Material Requirements:
o hEGF Needed: 300,000 ×10𝜇g =3,000,000𝜇g =𝟑 grams of pure hEGF/year
o Chitosan/Fibrin Matrix Needed: 300,000×0.6g =𝟏𝟖𝟎 kg of matrix
polymer/year
(b) How Long? (Production Timeline)
• Yeast Fermentation Yields: Standard industrial P. pastoris fed-batch fermentations
yield roughly 1.5 g/L of recombinant protein after a 5-day cycle (including growth,
induction, and purification) [2].
• Bioreactor Sizing: To yield 3 g of pure hEGF and the necessary human fibrinogen
fractions, a small 10-Liter pilot benchtop bioreactor running just one single 5-day
batch can produce the entire country’s yearly supply of growth factors.
• Bio-printing Output Rate: An automated industrial multi-nozzle 3D-bioprinter can
output 1 dressing every 2 minutes (30 dressings/hour) [4].
o Operating continuously across 2 parallel commercial bio-printing lines:
30060dressings/hour
,000dressings
= 5,000hours of printing
o Running 24/7, 5,000 hours/24hours/day =𝟐𝟎𝟖 consecutive days of
manufacturing
(5) Clinical Application and Technical Unknowns
Clinical Application Protocol
To prevent the hydrogel from shifting or forming a bacterial breeding ground due to body heat
and moisture, the application follows a strict clinical protocol [4]:
• Primary Hydrogel Layer: The chitosan-fibrin matrix will undergo a mild enzymatic
crosslinking during printing using transglutaminase to give it a natural, nonaggressive tackiness.• Secondary External Bandage: To protect the bio-printed patch from shifting, it will be
secured externally using a breathable, antimicrobial secondary polyurethane film
or a light compression bandage.
• Periodic “Curaciones” & Changes: The dressing must be completely replaced every
72 hours. Before applying a new patch, the medical professional must perform a
standard cleaning and necessary light debridement (“curación”) to remove dead
tissue, clear residual exudate, and inspect wound improvement.
Major Technical Unknowns and Bottlenecks
Protein Stability during Crosslinking: hEGF is a highly sensitive peptide. We do not
know if the mechanical shear stress of the 3D-printing nozzle or the chemical process
of crosslinking the hydrogel will denature or deactivate the growth factor [4].
Cold Chain Logistics in Tropical Climates: Guatemala has diverse, high-humidity,
and hot tropical climates. Hydrogels are prone to bacterial contamination and
dehydration. Developing a sterile packaging technique that keeps the dressing viable
at room temperature without requiring a strict -20°C clinical cold chain is a massive
hurdle.
Local Regulatory Pathways for Bio-Engineered GMs: The Guatemalan Ministry of
Health (Ministerio de Salud Pública) lacks an established regulatory framework for
approving 3D-bioprinted human tissues incorporating genetically modified microbial
outputs.
References
[1] D. Archana, P. K. Dutta, and C. Chavalitnitikul, “Chitosan‐poly(vinyl pyrrolidone)‐nano
silver oxide composite coatings for chronic wound healing applications,” Int. J. Biol.
Macromol., vol. 57, pp. 137–144, Jun. 2013, doi: 10.1016/j.ijbiomac.2013.03.019.
[2] H. Duan, H. Jiao, and W. Wang, “High-level expression, purification, and characterization of
bioactive human epidermal growth factor (hEGF) in Pichia pastoris,” J. Ind. Microbiol.
Biotechnol., vol. 45, no. 5, pp. 321–329, May 2018, doi: 10.1007/s10295-018-2028-1.
[3] Opentrons, “Automation protocols for high-throughput biomaterial screening and liquid
handling using the OT-2 platform,” Opentrons Labworks Inc., Tech. Rep., 2021. [Online].
Available: https://opentrons.com
[4] Z. Yao, X. Niu, and J. Zhang, “3D bioprinting of bioactive hydrogel dressings encapsulating
growth factors for accelerated diabetic wound healing,” Adv. Healthc. Mater., vol. 9, no. 12, p.
2000377, Jun. 2020, doi: 10.1002/adhm.202000377.