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