Biomaterials and Art3ficial Organs

London, 7 March 1980

This meeting was organised by the Biomaterials Group of

the Biomaterials Group of the Biological Engineering Society

as one of their series of one day local meetings. The first

speaker, Dr. K. Gilding, Liverpool presented a paper

entitled Biocompatibility of Implant Materials. In order to

promote healing around an implant, it should be possible

to introduce an active interaction between the implant

material and the tissue and in order to achieve this the

surface characteristics of polymeric materials could be

modified by suitable attention to physical chemistry. The

key property was identified as hydrophobic/hydrophilic

balance. Capsule thickness, collagen content and cell content

were determined as an index of biocompatibility. Results

were then presented for a series of polymers, having a range

of charges and solubilities. Tracer techniques were also used

to study protein binding to the polymer surface. Using

fibrinogen, Y-globulin and albumin the competitive adsorption

of these proteins was investigated. One of the results of this

work has been the production of a synthetic collagen-type

material in which the various charged units are represented

by the monomers referred to above and this has been shown

to be perfectly accepted by the tissues with no capsule

formation being reported in 80% of the results obtained.

Dr. R. Van Noort of Sheffield, speaking on

‘Biological Tissues for Heart Valve Replacement’ compared

non-tissue and tissue valves. Typical examples of both

types of valves were then described and their characteristics

discussed. Although clinical work has been carried out using

tissue materials, there remains a lack of information about

their properties. The speaker presented results on the

variability of the strength of dura with age. Glycerol treat-

ment appeared to remove the memory of previous stress-

strain history from the material and hence provided a method

of processing the material in order to evaluate different treat-

ments given to it. The final paper of the morning session was

given by Professor J. Courtney and was entitled ‘Materials for

Artificial Kidneys’. As well as various forms of cellulose of

which the cuprammonium form is the most widely used,

various synthetic materials have also been employed. These

include acrylonitrile, polycarbonate, polyamide, poly-

sulphone and polyvinylalcohol. Evaluation of these materials

is related to their permeability, mechanical properties and

blood compatibility. He described methods for studying

permeability of membranes that have been used at

Strathclyde. A rocking test cell has been used for blood

compatibility studies. The difficulty is always to separate

evaluation of the membrane from evaluation of the device

in which it will be used. In the second part of his paper, the

author discussed the technique of haemoperfusion by which

blood can be purified, tor example, in cases of acute

poisoning. The method is not so acceptable for the use in

renal failure because urea is not removed. The forms of

charcoal used and the various polymer coatings that have

been applied were then described. Haemoperfusion resins

have been used and some of the work that has been

performed on these was then discussed.

In the afternoon session, dealing with valves and dialysis

systems, the first paper, by Mr. G. Harston from Sheffield,

was entitled ‘Development of Portable Dialysis Systems’. One

of the problems associated with the use of dialysis is the loss of

moblllty for the patient. There has thus been a considerable

incentive to develop portable units. Since conventional

units employ approximately 180 litres of dialysing fluid

over a period of 6 hours, there must be a change in concept

if portability is to be the aim. He described the development

of a system which uses only 17 litres, replaced twice during

the period of dialysis and gave results of a limited series of

clinical trials involving six dialyses extending over a two

week period.

The next speaker, Mr. T. Feest, Exeter spoke from a

clinician’s point of view and entitled his paper ‘Dialysis as

a Failure’. He saw dialysis as a stage on the road to successful

treatment with successful transplantation being the only

really effective form of treatment of renal disease. He said

that dialysis provides reasonable control over fluid electro-

lyte acid base balance, but is unselective with regard to the

excretory function of the kidney and has no contribution

to make to regulatory function and endocrine/anabolic

function. He then discussed the problems that remain after

dialysis and dealt with various types of dialysis disease. This

included the role of aluminium present in the water supply

in the incidence of encephalopathy. The needs remaining

in dialysis are that it should be shorter and easier and should

be continuously portable. He discussed the work going on

in peritoneal dialysis which were very encouraging, but

still of limited scope. The use of chronic ambulatory

peritoneal dialysis (CAPD) has changed the practice in the

U.S. and is doing so increasingly in the U.K. New membranes

have not yet had much of an impact on clinical practice,

although some new materials do show promise. He felt that

the move was away from haemodialysis to peritoneal

methods, particularly CAPD which becomes increasingly

important as renal transplantation is more possible. It is,

however, limited to one year duration. Increasing success

of transplantation (80% success for a one year graft) is

emphasising the need for a system which will enable the

patient to be established rapidly on dialysis and which has a

low capital outlay involved. The use of reverse osmosis for

water treatment has had the added advantage of improving

the bacteriological situation.

The final speaker was Dr. M. lonescu (Leeds), who

spoke on the subject of Bioprosthetic Cardiac Valves and

talked in particular of the work that he has done on the IS

pericardial xenograft valve. This uses bovine pericardium

frame mounted, which is formaldehyde sterilized and

gluteraldehyde stabilized. He discussed the differences

between this valve and other tissue valves in terms of the

flow pattern through the leaflets. Haemodynamic studies

have been carried out and the peak systolic gradient for this

and other valves has been determined. The IS pericardial

valve has a gradient 3 to 4 times lower than that shown with

the others. This is because of the good functional orifice

area compared to annulus area. Post operative haemodynamics

have been measured for up to 68 months and no significant

changes in the various parameters have been observed. The

Biomaterials 1980, Vol 1 July 173

valve, he claimed, had proven durability for up to 9 years,

representing 16788 patient months. No significant

histological changes had been observed.

As with the morning session, which provided a very

useful introduction to the concept involved in biocompati-

bility of polymeric materials, this also concentrated the

attention of biomaterials scientists upon the clinical

consequences of their work and reminded us of some of the

problems to which future attention must be given.

This meeting was organised by Dr. R. Van Noort from

Sheffield and thanks are due to him for a very interesting

and useful programme.

G.W. Hastings

First World Biomaterials Congress

Baden near Vienna, 8-12 April 1980 The Clemson Awards themselves, presented at the final

banquet, were introduced by Dr Jonathan Black from

Philadelphia. June Wilson announced the presentation to

James S. Calnan; Thomas M.S. Chang received an award

and Frank Cooke presented an award to Adam Wesolow for

his contribution to research. Student Awards had been

made to J.P. Watson of Liverpool University for his paper

‘Adhesion between soft tissue and polymer implants of

counter cations,’ and to W.A. Ryzycki of Edmonton,

Canada for ‘Fatigue failure of total hip prostheses.’

An assembly of more than 400 delegates from more than

20 countries were brought together under the auspices of

the European Society for Biomaterials, the Society for

Biomaterials of USA and the Biomaterials Group of the UK

Biological Engineering Society, and in association with the

Canadian and Japanese Societies.

The smooth integration of plenary lectures, parallel

sessions of delivered papers, council meetings, posters and a

commercial exhibition were much appreciated by all

participants. The exchange of information at research level

was evident from the discussions after papers and around

the displays of posters. As well as specific sessions on, for

example, dental implants, heart valves, or opthalmology,

Round Table discussions took place on The Behaviour of

Materials in the Biological Environment, Clinical

Considerations for Joint Replacements and Regulation

of Devices.

A report of the trends in Biomaterials research

emerging from this Congress will be published in our next

issue.

Mary Korndotffer

International Liaison During the recent World Biomaterials Congress held in

Baden, Vienna, representatives of the American Society

for Biomaterials, the U.K. Biological Engineering Society

Biomaterials Group, the European Society for Biomaterials,

the Canadian Society for Biomaterials and the Japan

Society for Biomaterials met together to discuss ways to

promote collaboration and to encourage communications

between Societies.

As a result it was decided to set up a Biomaterials

Societies International Liaison Committee and the societies

represented are to be asked to nominate representatives

‘to serve on the committee. The function of the committee

will be advisory only and it will aim to co-ordinate

activities of the member societies especially with regard to

jointly organised international scientific meetings and to

facilitate communications between member societies.

A further decision was that there will be a second

World Congress in Washington, D.C., U.S.A. from April

26th-May lst, 1984.

174 Biomatarials 1980, Vol 1 July