Protein adsorption on soft contact lenses

Proteina~orption on soft contact lenses III.

Much.

E.J. Ciao,

J.L. Koenig,J+M.~der~on* and N. Jenny t

Departments of Macr5m5lacufar Science, Patho/5gy and Pediatrics, Case Western Reserve Untiersity, Ctevefand, Oh/o 4.4 106. USA (Received 2 January 1985; accepted 25 September t985)

Adsorption of bovine submaxillary mucin (BSM) on three different soft contact surfaces, lathe cut (LC) and spin cast (SC) crosslinked poly-Z-hydro~ethylmethac~late and spin cast poly{Z-hydro~ethylmethac~late/methac~lie acid) (PREMISE), was studied. The in vitro process was foflowed by attenuated total reflectance-Fourier t~nsfo~ infrared spectroscopy (ATR-AIR). A three-layer structure is envisaged for the adsorbed BSM: a very thin surface layer of strongly hound and conformationally altered mucin constitutes the surface layer. A random to B-sheet structural transition activated by the hydrogel surface is proposed for this layer. Glycoprotein hydrogen-bonding with the polymer hydroxyls and interaction of charged and hydrophobic groups with hydrogel surfaces are important in stabilizing this layer. Most of the adsorbed BSM (99%) is found in the middle and top layers which are formed by a different degree of associated BSM (their ~onfo~ation is minimally changed or not changed at all, respectively) and are weakly adsorbed to the lens surfaces. Surface morphololgy and chemical composition of the lenses are important adsorption parameters only for the reversibly adsorbed BSM. Keywords: Contact lenses. ATR-FTIR, BSM (bovine submaxillary mucinl, adsorption

The irreversible migration of organic and inorganic molecules from the tear solution to the lens surface is the underlying phenomenon in contact lens spoilage’,‘. Tear proteins usually adsorb firmly to the polymeric surface’*‘. Some mechanisms have been postulated in order to explain this spoiling phenomenon3s4 but none of them have been unequivocally proved. Surface active substances can be used as preventive measures5,6 but only papain or trypsin enzymatic digestion of the adsorbed protein has been of practical use6. Among the tear com~nents, ocular mucin has been found in largeamounts in secretions of contact lens users7**. In fact, scanning electron microscopy (SEM) analysis of ‘in vivo’ spoiled contact lenses have shown that after the insertion of hydrophilic or hydrophobic lenses, substantial mucous coating develops on the anterior lens surface*,‘. Dreyer et a/.“. using SEM and X-ray photoelectron spectroscopy (ESCA) reported that mucopolysacchandes were found on more than 70% of the analysed lenses. Tripathi ef af.” studied more than 300 in viva spoiled soft contact lenses by different analytical techniques. They found a complex mucoprotein-lipid deposit on most of the lenses. It is suggested

*To whom correspondence should be addressed: At the Department of Pathology. ‘At the Department of Pediatrics. Q 1986

6u~e~o~h

EsCo (Publishers) Ltd. 0142-96

12/86/01

that the mucin coating could be an immunological response of the eye to entrap and eventually expel the foreign bodyg. Human ocular mucin (HOM) is usually found at the interface between the tear and the cornea1 epithelium; it is secreted by goblet and non-goblet cells distributed throughout the conjunctiva and spread over the surface of the eye by the action of blinking’** 13. Its main function is to increasethe wettability of the hydrophobic cornea”, 13. Tear film mucin has also been considered to play a role in the maintenance of low su~acetension by masking and removing lipid contaminants which can migrate to the epithelial-tear interface from the outer tear layer14. More recently, a cleaning function by a foreign particle trapping mechanism has also been attributed to HOM’. It has been postulated that contrary to the ordinary belief of the harmful effects of the adsorption of proteins onto the contact lens, a selective weak adsorption of the mucin should occur in order to assure lens biocompatibility’ 5_ Recently, Proust and coworkers’” studied bovine submaxillary mucin (BSM) adsorbed on surface-oxidized polyethylene films; its amount increasing with the degree of polymer oxidation. They also found a loosely bound adsorbed mucin layer. The same group also studied BSM adsorption on silicone lenses grafted with poly(vinyl pyrrolidone) (PVP)17. Similar results were obtained: the amount of

~OS-08$03.00 Bi5material.s f986,

Val 7 January

9

Adsorption on soft contact lenses: E.J. Castiflo at al.

adsorbed mucin was proportional to the PVP content. These findings indicate that the polymer hydrophilicity may play a role in the mucin adsorption process. There is no reported data about the conformational state of adsorbed giycoproteins. It has been argued that because they have higher solubility and stability than simple proteins, no denaturation would be expected for the mucins at inte~a~es18, Previous work’Q-2’ has shown the feasibili~ of using the ATR-FTIR technique to study protein conformations after adsorption on hydrogel surfaces. In vitro tear protein experiments20~2r have shown that both serum albumin and lysozyme adsorb irreversibly on soft contact lenses by changing their con~guration. An altered structure has been detected for both proteins; this is reflected by increases of the @-sheet proportion, and participation of the charged and hydrophobic side chain residues. The structural changes observed are similar to those experienced after heat denaturatior?*~*‘. The purpose of the present investigation is toelucidate the role of mucin as a component of the protein layer adsorbed to soft contact lenses and determine the importance of the hydrophili~i~ and the surface quality of the hydrogel as controlling parameters in the BSM adsorption. Due tothe lack of purified and well identified HOM, this work was carried out with ESM which had been functionally compared to HOM, as a macromolecular lachrymal surfactant22, and was better characterized than HOM23-26.

The instrumental conditions and the protein adsorption procedure has been described elsewhere20’2’. Neve~heless for the sake of clarity, some details will be given here. BSM was purified according to the procedure of Nisizawa and Pigman and purchased from Sigma Labs (St Louis, MO). Porcine submaxillary mucin (PSM) was kindly provided by Dr Neil Jentoft. For the PSM sample a purification procedure described by DeSalegui and Plonska*’ was followed. The BSM was dissolved (0.8 mg/cc) in phosphate buffer solution (PBS), pH 7.3T3 and adsorbed for different periods of time on soft contact lenses of the PHEMA type. Desorption studies werecarried out by immersing the lenses in static PBS solutions. The soft contact lenses were provided by the National Patent Development Corp. (New 8runswi~k, NJ). Internal reflection spectra were obtained from a Digilab FTS-20 FTIR spe~trophotometerwitha Wilks ATR attachment. A Ge crystal of 60” incidence angle was used. For the transmission spectra, powdered samples were diluted in KBr. BSM (0.01 %) in buffer solutions was analysed in a sp~tro~larimeterJASCO-40 to obtain the circular dichroism (CD) spectra. Quartz ceils with 1 cm of pathlength were used. The machine was calibrated with samples of d-10 camphor-sulphonic acid.

RESULTS AND DlSCUSSlON Figure f shows the transmission i.r. spectra of two types of mucin i.e. BSM and PSM. The positions of the major bands suggest different features in their structure. Amide I, II and Ill bands appear at 1657, 1645 and 1242 cm-’ respectively for BSM. Similar bands for PSM are found at 1650, 1549 and 1236 cm-‘. There is also a major spectral difference in the carbohydrate region as denoted by the

10

~iomate~~/s

1986, Vol 7 Jenuary

0

Figure I l.r. spectra of much powders extracted from different sour&es. Bottom: bovine submaxillary much. Top: porcine submaxillary much.

intensity of the complex band centred at 1100 cm-’ for the BSM spectrum. Hence, compositional and structural differences exist be~een the two mucins. Reported data ‘a* 2s shows that both PSM and BSM are basically constituted by the same type and relatively the same proportions of amino acids (serine, threon~ne, glutamic acid, glycine and valine). Although, the arrangement of the components obviously influences the structure of the glycoprotein molecule, we speculate that the spectral differences are mainly produced by the different isolation and purification methods. Sugar microheter~enei~ is usually found for mucins from different sources’*. Supporting this point of view, our BSM spectra show some differences with respect to the spectrum of BSM obtained by a different method and reported some years ago25z2Q. A 1725 cm-’ peak present in that BSM spectra and due too-acetyl groups of the sialic acid, a major carbohydrate component, is detected only as a shoulder in Figure t. figure 2 shows BSM spectra in PBS buffer and in the solid state. After its dissolution, the positions of the amide I and II bands change in the usual fashion found for serum albumin, lysozyme and ~-globulin20,z~~3s: (i) shifting of the amide I and II bands in opposite directions, and (ii) sharpening of both bands. Sugar bands experience a significant decrease and the s(CH,) backbone vibration also shifts from 1448 to 1458 cm-‘. These changes indicate different conformations in the solid and solution state. The observed shifts of the amide I band from 1657 to 1653cm-’ and for the amide II band from 1545 to 1548 cm-’ may not be due to a definite conformational change from one type of secondary structure to another, but

Adsorption on soft contact lenses: E.J. Castillo et a/.

Table 1

Amide I and II shifts for different proteins after dissolution’

Protein

(KBr )

II band

: 0

in detecting states.

the spectroscopic be sensitive the

800

smaller

dihedral

Figure 2 1.r. spectral comparison of bovine submaxillary mucin (BSMJ in two different states. Top: transmission spectrum of BSM powder. Bottom: ATR spectrum of a buffer solution of BSM after digital subtraction of the buffer ATR spectrum.

rather reflect

changes

bonding

of the glycoprotein

charged

groups;

chain

in: (1) the degree backbone3’;

(2) the ionization

complete

bonding of this

perhaps

could

or (3) internalization

of hydrophobic

of

side-

from the solid to the solution

state can be correlated

amount

of p-sheet

and a-helices

Figure

3

the

shows

lysozyme2’,

y-globulin3’,

P-lactoglobulin3’.

found when

factor

I.r. bands ational band

states results

bending

shows

a straight

assigned from

(60%)

and

shifting

It is observed

of 0.95

ordered

However,

albuminzO,

position

while

different

bond

will

have

leading

to a

will be formed3’. is that

structure.

An important the

low a-helix

random

content

this high P-sheet

P-sheet

and a

content

II shift.

of BSM

Using

8

conse-

bands

has a hrgh proportion (Figure

thee Greenfield

conformational

45%

strained

water-protein

chain stresses

The CD spectra

P-sheet,

of the amide

and

of the conformational

BSM

the

Apparently

produce

from the amide

position

no major

and

composition

structure

and

of 4) of

7% a-

has been found for PSM34.

content

I peak which

does not agree with the denotes

that the higher

ribonuclease3’

that

a larger

shift

is

in the protein.

line was fitted for the data and a

to the different

protein

absorptions3’. of

stretching

and in-plane

that the amide

helix. Similar

procedures

in solution

band will

distance,

was obtained.

I band involves C=O

(10%)

with the structure.

for

is detected

a combination C-N

protein

haemoglobin3’,

are not ‘pure’

while the amide stretching

II

a larger 6 contribution

As a first approach correlation

amide

in the

arise from

however

protein-protein

approach33,

is: 48%

to different

in the solid state

phenomenon

reveal BSM

due

the a-helices

arrangement;

be predicted

structure.

little

46 50 90

distinguish

relieves the internal

‘unordered’ Fasman

of the amide II band

that

15 10 5

in the C = 0 bond distance.

more regular structure

indicates

residues. It should be noted that the shifting

and

of hydrogen

than

atomic

is expected

quence

2

differences

dissolution

angles

The frequency might

will

the drying and lyophilization hydrogen

10 22

in the inter-atomic

after

stiff C-N-H

The

changes

sensitivity

absorption

Therefore,

layers.

Wavenumbers

75 28 55

nature of each band. A stretching

angles.

change 1200

B-Sheet (%)

-1

structural Such

to changes

bending

more 1600

6 2 8 7 10 13 20

3 1 0

*Band shifts are expressed in cm

aggregation

2000

Amide II shift a-Helix (%)

1

Haemoglobin3’ Lysozyme3g Albumin3’ Albumln3’ Ribonuclease” B_Lacto910bulin3’ y-Globul,n3’ SOLID

I shift

Amide

The

the

(40%)

amide

in-plane

II

N-H

contributions,

stretching

N-H bending

conform-

(80%),

C-N

0

(1 O%)32. Tab/e 7

I band is not as sensitive

as the amide

4

6 0

20

I

I

I

40

60

80 I

% P-Sheet Figure 3 Correlation of the shifting of the amide II band for the solid statesolution state transition with the b-sheet content for different types of proteins.

240

220 Wavelength Figure 4

(nm)

CD spectrum of bovine submaxillary mucin in buffer solution.

Biometerials

1986, Vol 7 January

11

Adsorption on soft contact lenses: E.J. Castillo et al.

proportion will be given by a random structure. If Figure 3 is utilized to calculate the percentage of P-sheet present in the mucin structure, the contribution of each component is as follows: 7% a-helix, 3% P-sheet, and 90% random. When BSM is adsorbed on hydrophilic surfaces an altered i.r. spectrum is obtained. Figures 5 and 6 show the spectra of the adsorbed glycoprotein on lathe cut (LC) and spin cast (SC) PHEMA soft contact lenses after different periods of adsorption and followed by 1 min rinsing instatic PBS. A splitting of the amide II band,from a single peak in the solution spectrumat 1549 cm-’ to 1554and 1530 cm-’ is found at short adsorption times; this band splitting is less noticeable at longer adsorption times. The amide I band experiences two changes: (a) shoulders appear at 1672 and 1636cm-’ (b road ening) and (b) peak maxima shift from 1653 to 1649 cm-‘. These spectral changes indicate that the structure of the adsorbed glycoprotein is different from that present either in solution or in the solid state. The shape

U

I

I

10

1

1400

G 1000

a

Wavenumbers Figure 5 AT??-IR spectra of adsorbed bovine submaxillary mucin on lathe cut PHEMA lens surfaces for different periods of time followed by 1 min of rinsing in buffer solution.

1651 fi

1549

and position of theamide I and II bands suggestan increased amount of p-sheet content for the adsorbed BSM. A random to P-sheet transition is suggested for the adsorbed glycoprotein because of the above CD and i.r. conformational data. Similar changes in the spectra are found when BSM adsorbs to a chemically different hydrophilic surface. Figure 7 shows the spectra of the glycoprotein adsorbed on PHEMA/MAA: amide I broadening and appearance of shoulders on the amide I band are observed. Nevertheless spectral changes after the short-time are not as conspicuous as in the case of the SC and LC PHEMA surfaces. As will be described later, PHEMA/MAA lenses adsorbed rapidly increased amounts of reversibly desorbed BSM masking conformational changes in the spectra. A growing band at 1336 cm-’ (Figure 7) is a significant difference from the spectra of BSM adsorbed on PHEMA. This peak is assigned to the C-OH vibration from the sugar moieties35; the appearance of this band may be due to the interaction of the -COOH groups of the methacrylic acid with the attached sugar molecules of the BSM. From Figures 5-7, it is evident that the observed spectral changes are a function of the adsorption time or more correctly, a function of the amount of BSM present on the lenses. Splitting of the amide II band, broadening and appearance of shoulders in the amide I band, are very obvious at short-times disappearing almost completely at longertimes. Also, the shifting of the amide II band to higher frequencies is maximized at short-times, from 1 548 cm-’ (PBS solution) to 1555 + 1 cm-’ at shorter times and 1549 cm-’ at longer times. This specific band shifting may indicate a different kind of hydrogen-bonding, for the N-H backbone groups of the BSM, from the solution state where most of the NH groups are hydrogen bonded to water to a hydrogen bonding with the hydroxyl branches of the polymer. These spectral changes (see Tab/e 2) and the time dependence probably means that only the initial glycoprotein molecules (short adsorption times) interact strongly with the polymeric surface. As a result of this interaction a different structure at the interface is formed. Further molecules are deposited on top of these first conformationally changed BSM layers and only interact amongst themselves.

t

L

71 h

I t

24 h

8h

4h

2h 1400

1400 Wavenumbers Figure 6 ATR-IR spectra of adsorbed bovine submaxillary mucin on spin cast PHEMA lens surfaces for different periods of time followed by 1 min of rinsing in buffer solution.

12

Biomateriels

1986, Vol 7 January

Wavenumbers Figure 7 ATR-IR spectra of adsorbed bovine submaxillary mucin on spin cast PHEMA/MAA lens surfaces for different periods of time followed by 1 min of rinsing in buffer solution.

Adsorption on soft contact lenses: E.J. Castiilo et al.

Tab/e 2 Frequencies* of rhe coniormat~onal bands forbovine serum muck in different states Solid

Solution

Adsorption (long-time)

Adsorption (short-time)

1653 1548 1242

1651 ?r 2 15492 1

1649 k 1 1555k2

NO

NO

-Amide I Amide II Amide III

1657 1545 1242

*Frequencies are given in cm-‘.

NO, Not detected.

It is well known that mucins aggregate easily under certain conditions36,37. One hypothesis is that buffer salts may be important for the structuring of mucin gels37,38. In the longer adsorption time spectra of Figures 5-7, a new peak at 1095 cm -’ is present. This peak can be assigned to the s(C-0) of the sugar groups, although this peak appears at 1080 cm-l and has a much smaller intensity in the native spectra. The 1095 cm--’ peak also may be assigned to the s(P-0) vibration. If this is correct, the buffer salts are adsorbed jointly in this step and may inititate BSM aggregation. These gels constitute the weakly bound layers of BSM to the lens surface. A singular feature that characterizes the BSM adsorption on soft contact lenses from the corresponding adsorption of serum albumin, lysozyme and y-globufin20~2’~39 is the large amount of easily desorbed glycoprotein. Baszkin et a/.17, utilizing an ‘in situ’ radioactive labelling technique to follow BSM adsorption on silicone grafted contact lenses, have reported similar results. These deposits can be observed with the naked eye and most of them are instantaneously desorbed when the lenses are placed in PBS solution. It is doubtful that most of the BSM is really adsorbed on the contact lens. As we have said before, buffer salts can initiate BSM aggregation; also prolonged heating may induce degradation and crosslinking. Possible aggregation mechanisms are given by saccharide-saccharide interactions37 and/or intermolecular disulphide bonding4’. Hence the resultant insoluble BSM gels will be deposited on the lens surfaces merely by the force of gravity. Figure 8 shows the amounts of mucin adsorbed for different periods of time on the different types of lenses, followed by PBS desorption for only 1 min. A calibration curve was previously obtained by the measurement of the

amide If area of lens samples containing known amounts of BSM20,21. It was observed that surface quality and chemcial composition exerted some influence on the process. LCPHEMA lenses adsorb significantly larger amounts of BSM than either SC-PHEMA or SC-PHEMA/MAA lenses. An interpretation of the results obtained follows. SC-PHEMA lenses possess better surface finish than the LC-PHEMA lenses due to the fabrication prccess. Lathe processing produces numerous marks on the lenses4’, 42; these surface defects may increase the lens surface area, mainly after its water swelling. Conversely, SC processing IS claimed to be a ‘surface-free defects technique’43. Accordingly, sutiace irregularities may induce additional sites for the deposition of BSM molecules. Similar results have been previously found for the albumin and lysozyme adsorption on the same type of lenses2’, 21. Drastic alterations of the spectra of BSM are observed for the irreversibly adsorbed glycoprotein. Figures 3, 10 and 7 I show the spectra of BSM adsorbed for 24 h on the

1572 1556 3

,wq

1498

1600 Wavenumbers Figure 9 AT&/R spectra of muck adsorbed for 24 h on lathe cut PHEMA surfaces after rinsing in buffer sol&on for I min and 2 h respectively.

2h

1650

l

20

I

40

I 60

t

Adsorption time (h) Figure 8 Adsorbed amounts of mocin on different soft contact lenses: 0, lathe cut PhEMAr X spin cast PHEMA/MA& l, spin cast PHEMA

1600 Wavenumbers Figure 10 AJR-IA spectra of mucin adsorbed for24 h on spin cast PHEMA surfaces after rinsing in buffer solution for 1 min and 2 h respectively.

Biomaterials

1986, Vol 7 January

13

Adsorption on soft contact lenses: E.J. Castillo et al.

1634

0 I

I

1700

1600

30

60

90

120

I

1500

Wavenumbers Figure 11 AT&IR spectra of mucin adsorbed for 24 h on spin cast PHEMA/ MAA surfaces after rinsing in buffer solution for: Bottom, 1 min; Top, 2 h.

different surfaces and subjected to 2 h of desorption with PBS buffer. Spectral changes generally agree with those found for the reversibly adsorbed BSM. The observed broadening and splitting of the amide I and amide II bands are accentuated here. The amide II band maxima shift to even higher frequencies; from the 1548 cm-’ observed in the native spectrum, to 1554 cm-’ for the reversibly adsorbed protein to 1558 cm-’ forthe irreversibly adsorbed BSM indicating a stronger hydrogen bonding between the polymer and the glycoprotein. New peaks are observed at 1592,1572,1530 and 1496 cm-’ and can be assigned to hydrophobic groups (tyrosine, phenylalanine)44and charged groups (aspartic and glutamic acid)45. See Table 3 for a more complete assignment of the spectral bands. More apparent shoulders at 1638 and 1672 cm-’ indicate the increased presence of P-sheet. The spectra of strongly bound BSM on PHEMA/M/U look more distorted. A single peak at 1629 cm -’ is obtained for amide I. This is indicative of an increased random to P-sheet transition. Also an increased involvement of the sugar groups is denoted by a new band at 1380 cm-‘. Figure 12 shows the remaining amounts of BSM on the lenses after longer periods of desorption with static PBS buffer. It is readily observed that all the lenses irreversibly adsorb approx. the same BSM quantities. Apparently, surface finish and chemical composition of the lenses are important factors only for the reversibly adsorbed protein.

Time of desorptron (min) Figure 12 Adsorbed amounts of mucin after different periods of desorption in static buffer for the three contact lens surfaces: 0, lathe cut PHEMA X spin cast PHEMA/Mti l, spin cast PHEMA.

From the above discussion, a three-layer model can be pictured (Figure 73) for the in vitro BSM adsorption on soft contact lens surfaces. The bottom layer of adsorbed BSM is constituted by a high proportion of P-sheet layers interacting strongly with the hydrogel surface by hydrogen bonding; apparently hydrophobic and charged side-chain amino acid residues also interact with hydrophobic areas of the polymer; this layer is rapidly formed as its spectra resemble the short-time adsorption spectra of reversibly adsorbed BSM. The second layer is composed of loosely associated BSM molecules and constitutes most of the weakly bound glycoprotein. The top layer consists of BSM gels and is capable of instantaneous desorption. If we assume that BSM has a molecular weight of 2 X 1 Or’ Daltons23,46 and a radius of gyration of 2000 A23*46 a monolayer of BSM on the lens surface will have a 0.4 j.rg/cm2 density. Accordingly, the first layer of strongly bound BSM will have a 1 O-l 5 monolayer thickness and the middle layer a thickness of 250-500

I

Table 3 Tentative assignments for the spectra of the irreversibly adsorbed bovine serum mucin on different contact lens surfaces SC-PHEMA

LC-PHEMA

1671 (sh) 1651 (s)

1670 1653

1637 1591 1572 1556 1529 1498

1636 (sh) 1591 (m) 1571 (b) 1558 (sh) 1529 (m) 1498 (s)

(sh) (sh) (b) (sh)

(m) (s)

ND

(sh) (s)

ND

SC-PHEMPJMAA ND ND

1629 1592 1571 1558 1533 1498 1348

(s) (m) (sh) (s) (sh) (m) (s)

Assignment B-Sheet (amide I) Random and/or a-helix (amide I) P-sheet (amide I) Tvrosine and phenylalanine Glutamic and aspartic acids Amide II Tryiptophane? Tyrosine and phenylalanine Sugar

sh, Shoulder; s, sharp; m, medium; b, broad: ND, not detected. Frequencies are given in cm-‘.

14

Biomaterials

1986, Vol 7 January

Hydrogel

Figure 13 Suggested model for the bovine submaxillary mucin adsorption on hydmgels. I, Crosslinked mucin; II, reversible adsorbed mucin; IN. irreversible adsorbed mocin.

Adsorption on soft contact lenses: E.J. Castillo et al.

(Grant

ISI-81-1

Center

for Applied

6103)

through

Polymer

of Macromolecular 18

their

cosponsorship

Research

Science,

Case

(CAPRI),

of the

Department

Western

Reserve

Uni-

versity.

NE 8,

REFERENCES 1

Tripathi,

R., Montague,

R. and Tripathl,

B.J., Soh

lens spoilation

in Soft

Contact Lenses; Clinical and Applied Technology, (Ed. M. Ruben), 2

C

3

------I 2

8

6 Time

of desorption

J. Wiley

Et Sons,

Tripathi,

R. and Tripathi,

4 5 6

These

monolayer

are

or bilayer

adsorbed.

higher

thickness

The very slow

the lens surfaces

values

would

for

process

on

LC-PHEMA

desorption

process

lenses.

J.B.

Polymers

D. and Tighe,

problem

Wedler.

of BSM

amount

from

8

F.C.,

slow

to 8-l

of

1983,

Cont. Lens. ,! 1980,

biomatenals

deposited

Fowler,

S.A. and Allansmith,

effect

lenses,

Arch. Opthalmol. 198 1, 99. 1382

Hathaway,

M.R.,

R.A. and Lowther,

in removmg

Allansmlth,

Korb,

in contact

The

G.E., Soft

on

soft

of cleaning

lens cleaners:

D.R.

and

Greiner

contact

soft contact

Their

J.V.,

VIII.

18, 2

effective-

J. Am. Optom. Assoc. 1978,

deposits,

M.R..

p 1 127

lens apphcations.

11, 525

0

Fowler.

S.A..

Gremer,

patients

49,

Giant

259

paptllary

Am. J. Ophthalmol. 1977,83,

lens wearers,

with

Gremer.

J.V.,

M.R..

J.V.

and Allansmlth.

giant

papillary

D.R.,

CovIngton

Korb,

Human

ocular

mucus;

Arch. Ophthalmol. 1982, 10

Dreyer,

V..

chemical

monolayers.

M.H..

Soft

contact

lenses

Am. J. Ophthalmol.

conjunctlvltls,

1056

1979,88,

9

10 h of PBS

of BSM is equivalent

Analysis

Co.,

In contact

J. Biomed. Mater. Res. 1977,

from

in results.

a very

Llppencott

697

process of BSM

Clearly,

B.J.,

of biocompatibillty.

conjunctivltls

irreversibly

is not the case. Even after

rinsing the remaining

7

expected

the divergence

Figure 14 shows the longer time desorption adsorbed

the

a protein

desorption explain

than

p 299

B.J.,

Baker,

ness

monolayers.

1978,

Lens deposits: Classification, appearance Acta XX/W International Congress of Ophthal-

lenses,

Figure 14 Adsorbed amounts of mucin after 24 h of adsorption on lathe cut PHEMA lenses and different periods of desorption.

York,

and mangement, mology, (Ed. P. Henking), The

(h)

New

contact

Jensen,

and

X-ray

lenses

I”

H.I..

Peace,

A scanrung

100,

D.A.

microscopy

study,

1614

and

Prause,

microanalytlcal extended

D.G. and Allansmtth,

electron

J.D.,

Morphological

examination

Act. Ophtht/mo/.

wearing.

hlsto-

of deposits

on soft

1979,

57,

847

CONCLUSIONS 0

11

Solid state BSM presents PBS solution. hydrogen

Its main

bonding

structure from that in

a different difference

Amide

leading to a regularization

of the chain

content

and aspartic hydrogel

surface

and/or

is lightly

probably other

of a thick, weakly

small i.r. spectral

alterations.

associated

thick overlayer bound

instantaneously

with

13

can be correlated

M.A.,

Holly,

I. Factors

the cornea1

Holly,

F.J.

of BSM

increased

amount

for LC-PHEMA that the method

bound

shows

forces

adsorption

On the other

adsorbed

16

Proust.

only

17

salts. A

J.E..

Baszkm.

of the

cornea1

Surface

actuty

determlna-

and normals,

Exp.

M.R.,

Evolutlol

1980,

98,

M.M..

on surface-oxidized 94.

soft

lens

contact

Adsorption

polyethylene

of bovine

1 Co//.

films,

421

J.E. and Boissonade.

mucm

of

95

on silicone

M.NI.,

contact

1984,

5,

Adsorption

lenses

grafted

of bovine

with

poly(vinyi

175

analysis

Formatton

Co..

Boston,

Castlllo. of

and stablllty

J.L.,

protein

Anderson,

of biomedical

transform

E.J., Koenig,

changes

of the teat

1973

Koenig,

tance-Fourier 20

J.M.,

polymers

Biomaterials

mfra-red.

J.L., Anderson,

adsorptlon

on

of adsorbed

soft

human

Kllment.

J.M.

Lo, J.,

total

reflec-

5, 186

1984,

and Lo, R.. Charactenzatlon

contact

serum

C.K. and

by attenuated

lenses.

I.

Conformational

Biomaterials

albumtn.

1984,

5,

319

lenses

Castlllo.

E.J..

between

adsorb 22

23

ACKNOWLEDGEMENTS

Holly,

Koemg,

lysozyme

F.J.

Pigman,

J.L.,

on hydrogels.

and soft contact

Surface

W.

Anderson.

chemistry 49.

J.N.

Il. Reversible

and

and

R..

Protem

interactions

Biomatenals 1 985,

lens surfaces,

of tear

Lo,

rreversible

component

J. Co//.

analogs,

221

and Gottschalk.

A., Submaxillary

gland

glycoprotems

I”

Glycoproteins: Their Composition, Structure and Function, (Ed. A. Gottschalk). 24

from American

‘wetting

Surface

the

of BSM.

acknowledge

C.H.,

A. and Bolssonade.

mucln

lnterf Sci. 1974,

authors

and

tear film

33. 39

E.J.,

Brown

6, 338

The

1970,

in dry eye patients

Allansmith,

Biomaterials

F.J..

BSM.

amounts

precorneal

Castillo.

Holly,

adsorptlon

equivalent

The

19

BSM.

SC-PHEMA

C.H.,

a continuous

film, in The Preocolar F//m and Dry Eye Syndromes, (Eds F.J. Holly and M. A. Lemp). Llttle

21

and

of soft

24, 479

A., Proust,

The chemical composition of the lenses does not appear to play a major rcle in either the weak or strong adsorption of PHEMA’MAA

Wettability

J.T. and Dohlman,

Baszkm,

plrrolidone).

it appears

does not increase

Dolman,

Arch. Ophthalmol

M.A.,

pathololgy

365

18

is

is found

S. and

87,

and maIntainin

tear components

and

submaxillary

and

and

Iwata,

Arch. Ophthalmol.

submaxillary

sites. An

BSM hand,

S.A.

coattngs.

that this BSM

on the strongly

adsorbed

of lens fabrication

of irreversibly

BSM

by gravity

additional

Lemp,

F.J., Patten.

Fowler,

F.J.,

R.. The

1980,

Exp. Eye Res. 197 1, 14, 239

lnterf Sci. 1983,

by the PBS solution.

of reversibly

surfaces.

with the

15

Montague,

In spreadmg surface,

and

tlon of aqueous

molecules.

It is proposed

glycoproteins removed

also interact

BSM

is deposited

Holly,

B.J. and

Ophthalmol.

spoilage.

Eye Res. 1977.

the help of the buffer

Lathe marks may originate

amount

over

of the protein.

acid residues

@ The structure

l

dissolution

Irreversibly adsorbed BSM presents an increased amount of P-sheet structure. Tyrosine, phenylalanine and glutamic

0

Lemp,

tear film.

14

II shift after protein

weakly

R.C.. Tripathi lens

eplthellum,

to the P-sheet 0

12

is due to the profuse

structure. l

Tnpathl. contact

the generous

Hydron and the National

financial

Science

support

Foundation

Plgman, occu:rence maxillary

Elsevier W.,

Publ.

Moschera, of

repetitive

glycoprotein,

Co., J.,

1966, Weiss,

p 434 M.

glycopeptide

ar,d

Eur. J. Biochem. 1973,

Biomatenals

Tettamanti.

sequences

I”

G..

bovine

The sub-

32. 148

1986, Vol 7 January

15

Adsorption on soft contecr lenses: E.J. Cestillo et al.

25

35

Tettamanti, G. and Pigman, W.. Purification and characterization of bovine and ovine submaxillary mucins, Arch. Biochem. Biophys. 1968,124,41 Nisizawa, K. and Pigman, W., The composition and properties of the mucin clot from cattle submaxillary glands, Arch. Ore/ Biol. 1959, 1, 161 DeSalegui. M. and Plonska, l-l., Preparation and properties of porcine submaxillary mucin, Arch. Biochem. Biophys. 1964, 104, 282 Tabak, L.A., Levine, M.J., Mandel, J.D. and Ellison, S.A., Role of salivary mucins in the protection of oral cavity, J. Oral P&ho/. 1982, 11,l Hashimoto. Y., Hashimoto, S. and Pigman W., Purification and properties of porcine submaxillary mucin, Arch. Biochem. Biophys. 1964,104.282 Brodersen. B., Haugard, 8.J.. Jacobsen, C. and Pedersen, A.O., Mainchain sorption of water by serum albumin,Acta Chem. Stand, 1973, 27. 573 Koenig, J.L. and Tabb, D.L., Infrared spectra of globular proteins in aqueous solution, in Analytical Applications of FT-IR to Molecular andBio/ogice/Sys~ems, (Ed. J.R. Durig), D. Reidel Publ. Co., Hingham, M.A., 1980, pp 241-253 Miyazawa T., in Poly-a-amino acids, (Ed. G.D. Fasman). Arnold, London, 1967, p 257 Greenfield, N. and Fasman, G.D., Computed circulardichroism spectra for the evaluation of protein conformation, Biochem. 1969,8, 4108 Shogren, R., Structural Studies of Mucin Glycoprotein in Solution, MS Thesis, Case Western Reserve University, Cleveland, Ohio, 1983 Koening. J.L. Vibrational spectroscopy of carbohydrates, in infrared

16

Biometerials

26

27 28

29

30

31

32 33 34

1986, Vol 7 January

36

37

38 39

40 41 42

43 44 45 46

Reman spectroscopy of Biological Molecules, and (Ed. T.M. Theophanides), D. Reidel Publ. Co., 1978, p 125 Hill, H.D., Reynolds, J.A. and Hill, R.L., Purification, composition, molecular weight and subunit structure of ovine submaxillary mucin, J. Biol. Chem. 1977. 252, 3799 Crowther, R.S., Marriott, C. and James, S.L., Cation induced changes in the rheological properties of purified mucus glycoprotein gels, Eiorheol. 1984, 21, 254 Kwart, H. and Shashona, V.E., The structure and constitution of mucus, Trans. NYAcad. Sci. 1957, 19, 595 Castillo. E.J., Adsorption of proteins on hydrophilic polymers studied by Fourier transform infrared-attenuated total reflectance, Phd Thesis, Case Western Reserve University, Cleveland, Ohio, 1984 Shogren, R., (Unpublished results, 1984). Case Western Reserve University, Cleveland, Ohio Castillo, E.J., Brown, C., Koenig, J.L. and Anderson, J.M., (Unpublished results, 1983) Matas, 8.R.. Spencer, W.H. and Hayes, T.L., Scanning electron microscopy of hydrophilic contact lenses, Arch. Ophthalmol. 1972, 88,287 Coombs, W.F. and Knoll, H.A., Spin casting contact lenses, Optical Eng. 1976, 15. 332 Bendit, E.G., Infrared absorption of tyrosine side chains in proteins, Biopolym. 1967. 5, 525 Timasheff, N.S. and Rupley, J.A., Infrared titration of lysozyme carboxyls, Arch. Biochem. Biophys. 1972, 150, 3 18 Bloomfield, V.A.. Hydrodynamic properties of mucous glycoproteins, Biopolym. 1983, 22, 2 14 1