Hemocompatible Nanostructured
Membranes for Artificial Organs
September 16, 2019
Mónica Faria
MemChem | CeFEMAMembranes, Chemical and Electrochemical Processes Group at Instituto Superior Técnico
September 16 2019
Nanoart-Hemocompatible Nanostructured Membranes for Artificial Organs (PTDC/CTM-
BIO/6178/2014)
http://cefema.tecnico.ulisboa.pt/research/group/memchem/
Mónica Faria, Vítor Geraldes, Viriato Semião, Pedro Sebastião, Maria Helena Godinho,
Pedro Brogueira, Maria Norberta de Pinho
What is an Artificial Organ?
A man-made device that is
implanted or integrated into a
human to replace a natural organ,
for the purpose of duplicating or
augmenting a specific function so the
patient may return to a normal life
as soon as possible
GEBELEIN, C.G. (1984). The Basics of Artificial Organs. In Polymeric
Materials and Artificial Organs, (American Chemical Society) 1–11.
Membrane Artificial Organs
Devices that replace the function of natural organs like AK/dialyzer and AL/MBO for the
purpose of restoring specific organ functions.
Bartolo, L.D. (2016). Membrane Artificial Organs. In Encyclopedia of Membranes, E. Drioli, and L. Giorno, eds. (Springer Berlin Heidelberg) 1152
Semipermeable membranes act as selective barriers for the removal of toxins from patient’s blood
(hemodialysis) or for gas exchange with blood (ECMO)
DIALYZER
MBO
HEMODIALYSIS ECMO
AO Development Pathway
EXTRACORPOREAL-STATIONARY INTRACORPOREALEXTRACORPOREAL-AMBULATORY
?Hemodialysis machine (Kolff, 1945)
• hinder mobility and limit
activities of daily life during
dialysis treatments
Gura, V., et al. (2016). A wearable artificial kidney for patients with end-stage renal disease. JCI Insight 1.
WAK (Gura, 2016)
• recent clinical trial (only 5 of 7
patients completed 24h
continuous treatment
• technical problems: clotting of the
blood circuit, kinked tubes, erratic
pump & batteries and
replacement of absorbent
cartridges
F3® (Fresenius, Germany)
1 µm
1 million nephrons per kidney
Human KidneyArtificial Kidney
blood
• endothelial cells (~1µm) + basement
membrane ~300nm
• filtration surface area 0,05 m2
• GFR ~100 mL/min/1.73m2 (healthy
adults <40yrs)
50 µm
State of the Art
KUF membrane hydraulic
permeability or
ultrafiltration coefficient
(mL/h/mmHg)
200 µm
F3® (microporous polysulfone Fresenius, Germany)
• Membrane wall ~50µm
• filtration surface area 1.0–2.5 m2
• KUF ~12 mL/h/mmHg
Example: if a dialysis machine generated a TMP
~200mmHg, a dialyzer with a Kuf of 12 ml/hr/mm Hg
would produce an QUF 2.4 L/hr
QUF ~6 L/hr - Over 70% the filtrate
is reabsorbed
Human LungArtificial Lung
State of the Art
300 million alveoli
• membrane wall 50-100 µm
• surface area 2-4 m2
• gas exchange 200-400 mL/min
• capillary wall ~1 µm
• surface area ~150 m2
• O2 250 mL/min
• CO2 200 mL/min
CELGARD® (3M GmbH, Germany)
microporous
polymethylpentene (PMP)
silicone rubber coating
OXYPLUS® (3M GmbH, Germany)
dense
silicone rubber
0800 SO (Medtronic, MN, USA)
microporous
polypropylene (PP)
Integral Asymmetric Membranes
HOW TO COMBINE MEMBRANE HEMOCOMPATIBILITY WITH HIGH
PERMEATION FLUXES ?
Beyond the State of the Art
Tailoring of blood contacting surface morphologies
Tailoring of the active layer thickness (minimization of UF/gas permeation resistance)
US 9181384B2 Process of synthesis asymmetric polyurethane based membranes with hemocompatibility characteristics and membranes obtained by said
process
Artificial Lung
ALungTechnologies Inc.
Pittsburgh, USA
Challenges – Artificial Lung
❑ inhibit protein and plasma leakage
❑ enhance hemocompatibility (non-hemolyctic, low platelet adhesion/activation, low
thrombus formation)
❑ high gas transfer rates > 200 mL/min
❑ inhibit gas micro bubbles into the blood
The technical and medical progress of the MBOs depends on two major factors:
2. enhancement of the flow conditions and mass transfer associated to the metabolic
functions of the lung
1. hemocompatibility of the membrane/blood interfaces
and extensively studied and show enhanced hemocompatibility properties
Membranes for the Artificial Lung
• phase inversion technique
• DMF/DEE wt.% 45/15 and solvent evaporation time 30s
• PUR/PCL wt.%: 100/0, 95/5, 90/10 and 85/15 → PEUU 100, PEUU 95, PEUU 90 and PEUU 85
Integral asymmetric bi-soft segment polyurethane membranes (PEUU) with polycaprolactone (PCL) as
the second soft segment have been prepared
Membranes for the Artificial Lung
Faria, Monica; de Pinho, Maria Norberta. 2016. "Phase segregation and gas permeation properties of poly(urethane urea) bi-soft segment
membranes". European Polymer Journal 82: 260-276
Faria, Mónica; Rajagopalan, Mahendran; de Pinho, Maria Norberta. 2012. "Tailoring bi-soft segment poly (ester urethane urea) integral asymmetric
membranes for CO2 and O2 permeation". Journal of Membrane Science 387388: 66-75.
Faria, Mónica; Geraldes, Vítor; de Pinho, Maria Norberta. 2012. "Surface Characterization of Asymmetric Bi-Soft Segment Poly(ester urethane urea)
Membranes for Blood-Oxygenation Medical Devices". International Journal of Biomaterials 2012: 1-9.
Faria, Mónica; Brogueira, Pedro; de Pinho, Maria Norberta. 2011. "Sub-micron tailoring of bi-soft segment asymmetric polyurethane membrane
surfaces with enhanced hemocompatibility properties". Colloids and Surfaces B: Biointerfaces 86 (1): 21-27.
• Enhancement of HEMOCOMPATIBILITY through tailoring of PEUU membrane surface
morphologies: The Platelet Deposition, PD, increases linearly with the sub-micron
roughness, Ra.
• Enhancement of CO2 and O2 permeation fluxes through the tailoring of the skin layer
thickness (13-24 µm).
• CO2 permeance of 0,26×10-5cm3/(cm2scmHg) for the membrane with the
thinner skin layer of 13±2 µm
CONCLUSIONS – past work
HEMOCOMPATIBLE MEMBRANES? THE ON GOING ISSUE…. ▪ The oxygen mass transfer of PEUU membranes was investigated in a system surrogate of a MBO
that allows the direct assessment to the oxygen fluxes.
▪ System consists of a slit for water circulation as a surrogate blood flow channel and a constant
pressure oxygen chamber separated by the membrane.
Membranes for the Artificial Lung
CURRENT WORK
Experimental conditions
- Water flow rates: 2.0, 2.5, 3.0 L/min
- Oxygen feed pressures: 30, 60 kPa
- Temperature: 25ºC
- Permeation area: 8.7cm2
HEMOCOMPATIBLE MEMBRANES? THE ON GOING ISSUE….
Average O2 permeation fluxes, the liquid mass transfer coeffs, the membrane mass transfer coeffs and the global mass transfer coeffs for
the PEUU10 membrane for water flow rates 2.0, 2.5, 3.0 L/min and the oxygen feed pressures 30 and 60 kPa.
Membranes for the Artificial Lung
Membrane porous layer
Membrane dense layer
𝑜2
Liquid boundary layer
Water 1
𝐾𝑜2=
1
𝑘𝑜2𝑚𝑒𝑚𝑏+
1
𝑘𝑜2𝑙𝑖𝑞
𝑘𝑜2𝑙𝑖𝑞 =𝐽𝑂2𝑙𝑖𝑞
𝑐𝑜2𝑙𝑖𝑞 − 𝑐𝑜2𝑏 𝑧
𝑘𝑜2𝑚𝑒𝑚𝑏 =𝐷𝑜2𝐻𝑆1
𝛿
• Liquid boundary layer mass transfer coefficient:
• Liquid boundary layer mass transfer coefficient:
THEORY
RESULTS
It is verified that the
resistance to the
transport of oxygen is
controlled by the liquid
boundary layer.
Faria, Mónica; Moreira, Cíntia; Mendonça Eusébio, Tiago; de Pinho, Maria Norberta; Brogueira, Pedro; Semião, Viriato. 2018. "Oxygen mass
transfer in a gas/membrane/liquid system surrogate of membrane blood oxygenators". AIChE Journal 64 (10)
The mass transfer coefficients were determined
considering a three resistances in series model
HEMOCOMPATIBLE MEMBRANES? THE ON GOING ISSUE….
Membranes for the Artificial Lung
• The resistance to the O2 transport on the liquid side can be reduced by optimizing the
circulation conditions of the liquid over the membrane surface by the deposition of fibers over
the membrane to act as boundary layer disruptors and mixing promoters.
• The synthesis of the PEUU10/PCL composites is carried out by the electrospinning of the PCL
fibers over the top surface of the PEUU10 membranes dense layer.
Top
Cross-
Section
(a) (c)
(b) (d)
• Experimental oxygen permeation fluxes of PEUU10 obtained in a surrogate system of an MBO show that the mass transfer is controlled by the liquid boundary layer;
• PEUU10/PCL composites were synthesized by depositing electrospinning PCL fibers over the PEUU10 membrane.
• As a perspective of future work, the enhancement of the O2 mass transfer by the PCL fibers will be investigated by comparing the experimental fluxes obtained for the PEUU10 membranes and for the PEUU10/PCL composites in MBO surrogate system.
Membranes for the Artificial Lung
CONCLUSIONS AND FUTURE WORK
Artificial Kidney
Science Photo Library / Brand X Pictures
• 1 million nephrons
per kidney
• Filtration in the Glomerulus: removal of 88 toxic molecules from blood while retaining blood cells and vital
blood componentes/proteins such as albumin
• Absorption in the proximal tubule: reabsorption of 65% of the filtered water, Na+, Cl−, and K+.
Renal Physiology• Passes total blood volume
every 4-5 mins
• Produces ~1.5L urine/day
J Am Soc Nephrol. 2013 Dec;24(12):2127-9
Stages of Kidney Disease
5 stages of kidney disease
Stage 1 and 2 - mild kidney damage, and usually no symptoms
Stage 3 - moderate kidney damage, swelling in the hands and feet, back pain, urinating more or less than
normal
Stage 4 – last stage before kidney failure. Start planning for dialysis or kidney transplant before reaching
kidney failure
Stage 5 – HEMODIALYSIS ORTRANSPLANT
Proteinuria (presence of protein in the urine) and GFR are the two parameters used to
detect stages of kidney disease
ESRD
TRANSPLANTATION
PORTUGAL
Em 2018 morreram 76 pessoas à espera de um órgão para
ser transplantado. Mais 49% do que em 2017.
O envelhecimento da população e, por conseguinte, dos
doentes em lista de espera ajuda a explicar o aumento
das mortes entre os doentes que aguardam por um rim.
19.01.2019
Susana Sampaio, presidente da Sociedade Portuguesa de
Transplantação.
O órgão com maior lista de espera é o rim, com cerca
de dois mil doentes dependentes de uma doação.
Hemodialysis
- most widely applied treatment for ESRD - approx. 3,000,000 patients world-wide
- bulky dialysis machines connected to arteriovenous fistula created surgically created connection
between an artery and a vein in the patient’s arm
→ UT concentrated blood flows into dialyzer
→ Dialysate flows counter current
→ wastes to diffuse from the blood in the dialyzer into the dialysate
→ dialysate is drained and replaced
Artificial Kidney - semipermeable membranes act as selective barriers for the removal of UTs from
patient’s blood
4 to 5h, 3 days/week
Artificial
Kidney /
Hemodialyzer
blood out
blood in
dialysate out
dialysate in
Artificial Kidney
polysulfone (PS)
polyacrylonitrile (PAN)
polyethersulfone (PES)
polymethylmethacrylate
(PMMA)
ethylenevinylalcohol
(EVAL)
polyesterpolymeralloy
(PEPA)
cellulosetriacetate
(CTA)
blood 50 µm
200 µm
microporous
polysulfone
surface
area
1-2 m2
F3® (Fresenius,
Germany)
Presently 88 uremic retention solutes have
been identified in ESRD patients
HD efficiently removes approx. 46% of theseFenton et al. BMC Nephrology (2018) 19:336
Transplants are more perfect but will remain a solution for the few.
So what to do?
Artificial Kidneys or Hemodialyzers on the market are inefficient
and only allow a person to survive but with very limited or low
Quality of life
Present reality
Much space for improvement/research on the Artificial Kidney
dense
active
layer
porous
surface
Tailored blood contacting
surface morphologies
Cross sections with
active layers of minimal
thickness
Hybrid
Integral
Asymmetric
Membranes
Development of new and more efficient membranes for blood purification
AIM
Two-fold goal:
1. Selective mass transfer properties: high water permeability
high permeation rates of UTs (small, middle size molecules, PBUTs)
retain albumin and other vital blood components
2. Enhanced hemocompatibility: non-hemolyctic;
low thrombosis degrees for long membrane/blood contact times
low platelet adhesion
inhibit late states of platelet activation
Methods
▪ Synthesis of high flux monophasic hybrid Cellulose Acetate/Silica (CA/SiO2) membranes by
phase inversion method coupled with sol-gel technique
▪ Casting solutions: cellulose acetate /acetone/ formamide wt.% ratio of 17/53/30
▪ SiO2 content ranging from 0 – 40 wt.%
Membrane Characterization
• Chemical structure analysis: Attenuated total reflection-infrared spectroscopy (ATR-FTIR)
• Permeability Experiments: Hydraulic Permeability(LP), Rejection coefficients to urea and BSA
• Surface morphology: Scanning Electronic Microscopy (SEM)
• Surface topography: Atomic Force Microscopy (AFM)
• Hemocompatibility: Hemolysis Index; Thrombosis degree; Platelet interaction (ISO 10993-4:2002)
G Mendes, M Faria, A Carvalho, C Gonçalves, M N Pinho, Structure of water in hybrid cellulose acetate-silica ultrafiltration membranes and
permeation properties, Carbohydrate Polymers, 189, 342-351 (2018)
ʋ(C-O), ʋ(Si-O-Si) and ʋ(Si-O-C)
• For all the CA/SiO2 membranes, the ATR-FTIR peak assigned to (Si-O-C) proves the hybrid condensation
reaction and confirms the synthesis of monophasic hybrid membranes.
Chemical structure analysis ATR-FTIR
Results
Surface morphology and cross section structure: SEMdense surface porous surface cross section
• An active dense layer, a porous layer and assymetric cross sections were identified in all membranes similar
to ones of CASiO2-18
Hydraulic Permeability (LP)
Results
obtained by the slope of the straight line of pure water permeate fluxes (Jpw) as a function of the
transmembrane pressure (∆P 0-3 bar, feed flow rate: 2.5 L/min)
• addition of 5 wt.% silica increased Lp of CA membrane from 32
to 82 L/(h.m2.bar).
• Lp increases with the addition of silica up to a content of 10
wt.% then decreased
32
82 81
57
33
0
20
40
60
80
100
CA-Si 0 CA-Si 5 CA-Si 10 CA-Si 20 CA-Si 30
Lp [
kg/(
h.m
2.b
ar)]
P 0.5 bar, feed flow rate 3.5 L/min
• Urea was fully permeated by all membranes
containing silica
• BSA was completely rejected by all membranes
containing silica
Rejection Coefficients (f) to urea and BSA
• Hemolysis Index (HI): all of the CASiO2 membranes were non-hemolytic with (HI<2)
• For blood contact time of 15 mins the thrombosis degree of all CASiO2 membranes is lower than 30% of
the positive control
• CASiO2-5 and CASiO2-11 membranes showed the lowest thrombosis degree for all blood contact times
• Thrombosis degree
RESULTS
Hemocompatibility
Results
• Platelet deposition and platelet coverage
• PD - nº platelets/104 μm2 membrane
surface
• PD decreased from ~6 for pure CA
membrane to 2.5 platelets/
platelets/104 μm2 for hybrid CASiO2
membranes
• PC - % of membrane surface covered
by platelets
• PC of the hybrid membranes
decreased by approximately one half
compared to the pure CA membrane
Glass – positive control
CASiO2-0 CASiO2-5
CASiO2-11 CASiO2-18
Hemocompatibility
Results
Platelet activation
• None of the membranes present platelets in the highest stage of activation (fully spread)
• Number of platelets in the second highest stage of activation is reduced by the introduction of silica
from 16% to <3% for the hybrid membranes
CASiO2-0 CASiO2-5
CASiO2-11 CASiO2-18
RESULTS
Hemocompatibility
Results
• A thin active dense layer and a larger porous layer were identified in all membranes.
• Membrane containing 5 wt.% silica had the highest Lp 52 L/(h.m2.bar).
• Urea was fully permeated by all hybrid CASiO2 membranes.
• BSA was totally rejected by all all hybrid CASiO2 membranes.
• All membranes were non-hemolytic with HI<2
• CASiO2-5 and CASiO2-11 membranes showed the lowest thrombosis degree for all blood contact times
• None of the membranes present platelets in the highest stage of activation (fully spread) and the
number of platelets in the second highest stage of activation is reduced by the introduction of silica from
16% to <3% for the hybrid CASiO2 membranes
CONCLUSIONSConclusions
G Mendes, M Faria, A Carvalho, C Gonçalves, M N Pinho, Structure of water in hybrid cellulose acetate-silica ultrafiltration membranes and
permeation properties, Carbohydrate Polymers, 189, 342-351, 2018
Membranes for the Artificial Kidney
• Mass transfer studies associated to the metabolic functions of the
kidney and enhancement of the flow conditions in a system
surrogate of a hemodialyzer
• Permeation experiments in surrogate system : total flux and
selective permeation of uremic toxins
• Hemocompatibility in dynamic conditions using a human blood
model
CURRENT AND FUTURE WORK
HEMOCOMPATIBLE MEMBRANES? THE ON GOING ISSUE….
ACKNOWLEDGMENTS
• FCT Fundação para a Ciência e Tecnologia, Portugal, for sponsoring PTDC/CTM-
BIO/6178/2014 project
• CeFEMA for Financial Support UID/CTM/04540/2013
Thank You