The Mechanical properties of Biological Materials Eds. J.F.V. Vincent and J.D. Currey Cambridge University Press, 1980,513 pp f 30.00

This well produced book is number 24 in the series of

Symposia published by the Society for Experimental

Biology and arises from a symposium held in Leeds,

September 1979. It comprises eighteen chapters and also

the abstracts of eleven posters presented at the meeting.

These chapters all contain mathematical treatments which

may cause apprehension but perseverance will be rewarded

and they are necessary in order to develop the depth of

understanding needed.

In his own inimitable style, J.E. Gordon in the first

chapter ‘Biomechanics: the last stronghold of vitalism’

highlights some central principles although it is only scene

setting for what follows. He reminds us that the safety of

structures living and otherwise depends on attention to

detail. The rest of the book helps in providing that detail.

The book provides fundamental materials science in

chapters on Fracture (E.H. Andrews) Composite Materials

(B. Harris) Rubber Elasticity (L. Mullins) and viscoelasticity

(K.L. Dorrington). These tend to be straightforward treat-

ments of the subject with limited application to biological

systems, although the origins of the viscoelasticity chapter

are more clearly in biology, but this is not so surprising

since as Bryan Harris points out in his chapter, ‘attempts to

apply composite theories to biological materials have so

far been less successful and perhaps this is not surprising

as it is far less easy to set up sensible model experiments’.

The major group of chapters deals specifically with a

range of biological materials and include mollusc shell,

(Currey), teeth (Waters), bone (Katz), wood (Jeronimidis),

insect cuticle (Vincent), keratin (Fraser and Macrae),

silks (Denny), plant cell walls (Sellen), proteins (Gosline),

mucus (Pain), cartilage (Swanson) and tendon (Kasletic and

Baer). The value of each of each of these chapters is that they

are authoritative reviews rather than the usual limited

experimental presentations common to many conference

proceedings. They present what is known as well as pointing

to the problems and the gaps in our knowledge and thereby

serve a useful function. The worker in clinical biomaterials

and in other natural materials will find this a good reference

source.

This book deserves to become established as a

reference text for all interested in research or teaching these

aspects of biological materials and the editors have brought

together a set of authors to provide a first rate book.

G .W. Hastings

Controlled Release of Bioactive Agents Ed. Richard Baker Academic Press 1980 473 pp $34.50

This work is based on the papers presented at the 6th

International Meeting of the Controlled Release Society in

New Orleans, Louisiana, August 1979 and though it omits

a considerable number of the papers presented in the

proceedings of the meeting, is still a very interesting and

useful compilation of data by experts in the field of controlled

release. The volume comprises two distinct sets of chapters -

those dealing with pharmaceutical applications and those

dealing with non-medical topics. The twenty-seven chapters

are too many to list individually so the following selection

according to this reviewer’s personal taste, will provide an

indication for the reader of the scope of the volume.

Heller and Baker present a simple theoretical analysis

of the release from bioerodable devices, indicate that these

can provide zero order release and can be useful for the

release of high molecular weight species. This is followed

by Pitt (et al.) who reviews the nature of biodegradable

polyesters and points out the importance of usefully changing

diffusion coefficients by the change in glass transition

temperature, molecular weight and polymer structure.

Langer (et al.) in one paper shows that, contrary to widely

held views, high molecular weight polymers such as insulin

can diffuse out of inert polymer films into which they

were initially incorporated in a matrix form. This is in spite

of the fact that they will not diffuse through the film not

containing the hormone! In another paper he demonstrates

how the rapidly decaying release rate with time of spheres

and cylinders can be chanyed to a reasonably constant rate

by coating most of the surface of matrix devices. Lee

provides a simplified mathematical analysis allowing both

diffusion and partition coefficients to be determined easily

from simple experiments involving absorption of a solution

into a hydrogel or other polymer. Good (et al.) describes

the preparation of two phase hydrogels based on hydroxy-

ethyl methacrylate with polybutadiols capped with two

double bonds. These were made as small spheres in saturated

salt solution. The description of cleaning, drug charging and

a mathematical analysis of solvent interaction with cross-

linked networks and the diffusion equations are usefully

provided.

Both sections also contain many interesting papers

covering topics such as the release of active species from

polymers to which they are covalently attached, how to

obtain constant rates of release from hydrogel monoliths

by providing a more densely crosslinked exterior layer

which becomes rate controlling, how to incorporate heparin

and prostaglandin E2 into HEMA hydrogels to render them

non-thrombogenic, the disruption of mating amongst low

density forest pests, such as the Western Pine Shoot Borer,

by the use of a confusing background level of sex attractant

pheromone release from hollow fibres, the reduction of

face-fly breeding in cattle faeces by use of encapsulated

Dimilin added to the feed, and many more.

This is a book for specialists in the field of controlled

release and will be a welcome addition to the libraries of

the increasing number of organisations working in this

field. Though much of it will date very quickly there are

valuable, clearly explained, theoretical sections which will

stand the test of time.

N.B. Graham

Bioma terials 1982, Vol3 January 59