Detection of subclinical infection in significant breast implant capsules

The pathogenesis of fibrous capsular contracture after augmentation mammaplasty is still debated. One hypothesis implicates low-grade bacterial infections as a cause. The presence of a staphylococcal biofilm in a patient with recurrent capsular contracture was previously reported. A comparative, prospective, blinded, clinical study of implants and capsules removed from patients with or without significant capsular contracture was conducted to investigate the association of biofilm contamination, breast implants, and capsular contracture.Capsule and implant samples obtained during explantation were tested by routine microbiological culture, sensitive broth culture (after maceration and sonication), and scanning electron microscopy. Clinical parameters were correlated with microbiological findings. A total of 48 implant and/or capsule samples were obtained from 27 breasts during a 22-month period. Of the 27 breasts, 19 exhibited significant contracture (Baker grade III/IV). The mean duration of implantation was 9.2 years (range, 0.4 to 26.0 years). Routine swab cultures obtained at the time of explantation were negative for bacterial growth for all samples. The sensitive broth culture technique yielded 24 positive samples (50 percent, n = 48). An analysis of capsules demonstrated that 17 of 19 samples obtained from patients with significant contracture were positive, compared with only one of eight samples obtained from patients with minimal or no contracture (p = 0.0006). Fourteen of the 17 positive cultures from significantly contracted breasts yielded coagulase-negative staphylococci, mainly, species of the Staphylococcus epidermidis group. The presence of coagulase-negative staphylococci was also significantly associated with capsular contracture (p = 0.01). There was no significant difference in the frequency of culture positivity for saline versus silicone implants (p = 0.885). Scanning electron microscopy confirmed the presence of extensive biofilm on implants and within capsules.Biofilm, in particular, S. epidermidis biofilm, was detected for a significant proportion of patients with capsular contracture. This implicates biofilm disease in the pathogenesis of contracture, and strategies for its prevention should be explored.     

Measurement of breast volume: comparison of techniques

A system of graduated disks has been previously described as a method to determine breast volume. The accuracy and limitations of this system have not previously been reported. Comparison of these disks with a standardized volumetric method shows this simple system to be accurate. Standard linear correlation analysis was good for the entire group of breasts measured (r = 0.718). Conversion to true volume M is represented by the least-square line M = 20.33 + 1.37G. The correlation is expected to fail at volumes greater than 425 cc (greater than the calibration on the largest Grossman disk). Elimination of volumes greater than 425 cc, however, produced no improvement in correlation coefficient. Firm breasts (i.e., capsular contractures) displace less uniformly into the conical restraint of the disk and cause an overestimation of their volume. Three breasts in this series were evaluated with Baker grade III and IV capsular contractures. Elimination of these values improved the correlation between the two volume analyses (r = 0.853 and M = 1.56G - 4.48). We suggest that when confronted with very large or firm breasts that volumes determined by the Grossman disk be interpreted with care. A formula for calculation of the true breast volume from the Grossman measurement has been derived and presented.     

Design of high-throughput-compatible protocols for microencapsulation, cryopreservation and release of bovine spermatozoa

With a rate exceeding 90% in cattle, artificial insemination (AI) is the prime reproduction technology in stock farming. AI success is expected to increase with extended persistence of sperms in utero. In order to enable controlled sperm release during artificial insemination we have designed two strategies for the automated microencapsulation of bovine spermatozoa in either alginate-Ca2+ or cellulose sulfate (CS)-poly-diallyldimethyl ammonium chloride (pDADMAC) capsules using standard encapsulation hardware. Animal protein- and citric acid-free sperm extenders and encapsulation protocols have been developed to ensure encapsulation compatible with sperm physiology. Bovine spermatozoa have showed high motility rates inside CS-pDADMAC-based capsules, were preserved by standard cryoconservation and rescued with high viability/motility following disintegration of the thawed capsules. CS-pDADMAC-based capsules break up within 72 h after addition of either purified cellulase or cellulase-filled alignate-Ca2+ capsules. The controlled release, associated with the microencapsulation of bovine spermatozoa, may be a promising approach to increase the success rate of artificial insemination.     

Quantitation of breast sensibility following reduction mammaplasty: a comparison of inferior and medial pedicle techniques

The preservation of sensitivity within the nipple-areola complex is of paramount importance to patients presenting for reconstructive and aesthetic breast procedures. Previous attempts to measure sensation in the breast before and after surgery have relied primarily on the Semmes-Weinstein monofilament test, which is an imprecise study that measures the logarithm of force necessary to bend a series of six to 20 filaments. Within the last 10 years, various authors have published normative pressure threshold data for the breast that have varied by a magnitude of greater than 10-fold. Recently, precise anatomic studies have been performed that have elucidated the innervation of the nipple-areola complex medially and laterally from cutaneous branches of the intercostal nerves. Despite this knowledge, no quantitative sensibility studies have yet been performed that compare postoperative sensation when medially versus laterally innervated pedicles have been used in reduction mammaplasty. The present study is the first to use computer-assisted neurosensory testing to generate normal breast sensation data and to compare sensory outcomes between the inferior and the medial pedicle techniques of reduction mammaplasty.A total of 34 patients were divided into four groups and underwent breast sensory testing (67 breasts total) using the Pressure-Specified Sensory Device, a computer-assisted force transducer that measures static and moving one and two-point discrimination. Sensation in the nipple and in the four quadrants of the areola was measured. Groups I and II were composed of 17 unoperated controls with breast sizes ranging from 34A to 36C (group I; 18 breasts) and 36DD to 46EE (group II; 16 breasts) who presented to a general plastic surgery clinic. Groups III and IV were composed of 17 patients who underwent either medial or inferior pedicle reduction mammaplasty between July of 1997 and March of 1999. Pressure thresholds in the most sensitive breasts were as low as 0.3 g/mm2, a marked contrast to data from previous studies using Semmes-Weinstein monofilaments documenting the lowest recordable pressure threshold as greater than 2 g/mm2. Several findings from previous studies using Semmes-Weinstein monofilament testing were confirmed in unoperated controls, including an inverse relationship between sensitivity and breast size, superior nipple sensitivity when compared with the areola, and significant interpatient variability with respect to static and moving two-point discrimination among women matched according to age and breast size. When comparing medial with inferior pedicle reduction mammaplasty patients, it was found that despite significantly greater reductions using the medial pedicle technique (mean of 1.7 kg versus 1.1 kg of breast tissue removed), there were no significant differences in postoperative sensory outcomes in the sample size of 17 patients. Furthermore, within each group of patients undergoing either the medial or inferior pedicle technique, the amount of breast tissue removed did not correlate with postoperative sensory outcomes.Computer-assisted quantitative neurosensory testing is a highly accurate technique for measuring sensibility. The use of this technology demonstrates a 10-fold difference in measurable sensory thresholds in normal patients from preexisting data using Semmes-Weinstein monofilaments. Advances in measurement methods have allowed the authors to compare postoperative sensory outcomes reliably using two popular techniques of reduction mammaplasty.     

Recurrence of subglandular breast implant capsular contracture: anterior versus total capsulectomy

The objective of this study was to determine whether the type of capsulectomy, anterior or total, affects the recurrence of capsular contracture around subglandular silicone-gel breast implants. A retrospective analysis was performed of patients who underwent either anterior or total capsulectomy for Baker grade 3 or 4 subglandular capsular contracture in our unit. All patients were invited to a review clinic where their capsular status was assessed. There were 100 anterior- disc capsulectomies in 60 patients between 1988 and 1997 and 99 total capsulectomies in 60 patients between 1990 and 1998. The follow-up in the former group was a median of 7 years and mean 6.9 years, compared with median 2.5 and mean 3.1 years in the latter group. Eighty-six percent of the implants removed from both groups at capsulectomy were smooth-walled gel-filled implants. Sixty-nine breasts in the anterior group received textured gel implants at capsulectomy; the remaining 31 received polyurethane-coated Meme implants. In the total capsulectomy group, all but two breasts (one patient) received textured gel implants. After review, the capsular status was known in 80 percent of the anterior and 92 percent of the total capsulectomy group. The review clinic found eight new contractures in five patients to have developed in the anterior compared with none in the total group. Recurrent contractures affected 50 percent of patients (46 percent of breasts) in the anterior and 11 percent of patients (10 percent of breasts) in the total capsulectomy group. Kaplan-Meier survival analysis was applied to the data. By including only patients who received textured gel implants at capsulectomy, the Logrank found a statistical difference between the two treatment groups (0.01 < p < 0.5). We believe that this study provides some evidence that total capsulectomy for subglandular silicone breast implant capsular contracture results in a lower capsular recurrence than anterior- disc capsulectomy. The pattern and risk of recurrence after total capsulectomy and exchange for a modern textured prosthesis appear to approach those following primary augmentation.     

A clinical comparison of the tendency to capsular contracture between smooth and textured gel-filled silicone mammary implants.

The aim of this prospective, controlled clinical investigation was to find out if there is a difference in the capsular contracture rate between silicone implants with a smooth or textured surface as the only difference. Twenty-five women with bilateral mammary hypoplasia underwent mammary augmentation. All got a textured implant on one side and a smooth implant on the other. The implants were placed subglandularly. Follow-up examinations were done on six occasions. Three parameters were used for estimation of the tendency to capsular contracture: (1) the patient's opinion on differences in hardness of the breasts, (2) the investigator's classification of capsular contracture, and (3) applanation tonometry. At the end of the follow-up period, after 1 year, all parameters showed with no doubt that the breasts augmented with textured implants had a lower tendency to develop contracting capsules than the breasts augmented with smooth implants.     

Transaxillary subpectoral augmentation mammaplasty: long-term follow-up and refinements

Transaxillary subpectoral augmentation locates the scar in a less visible position in multiple body positions than approaches that locate scars on the aesthetic unit of the breast. In 90 patients, 63 with 2 to 5 years of follow-up, using the surgical technique described, the Baker III/IV capsular contracture rate was 5.6 percent. There was no occurrence of hematoma, periprosthetic space infection, permanent loss of nipple sensation, or significant axillary wound morbidity. Scar results suggest that the axilla is an anatomically favorable location for both high-quality final appearance and minimal visibility. The transaxillary subpectoral approach is an excellent alternative to inframammary and periareolar approaches in all types of breasts requiring augmentation except the ptotic breast or breasts requiring extremely large prostheses.     

Capsular contracture around saline-filled fine textured and smooth mammary implants: a prospective 7.5-year follow-up.

In a previous prospective randomized clinical study comparing in the same patient textured and smooth saline-filled mammary implants (Biocell) with large pore size (300 to 600 microm), we saw no difference in capsular contracture. This study was undertaken in a similar way to compare capsular contracture around smooth and textured saline-filled prostheses with pores of small size. During a period of 7.5 years, the breast hardness was followed up, and at the end of the study patient satisfaction was evaluated.Twenty healthy women with a mean age of 30 years were operated on for breast augmentation. Two surgeons performed all operations in a standardized way. Each patient received subglandularly a Siltex textured saline-filled prosthesis with a pore size of 30 to 70 microm in one breast, and a smooth saline-filled prosthesis in the other. The hardness of the breasts was evaluated after 0.5, 1, and 7.5 years using Baker grading and applanation tonometry. Eighteen patients completed 1-year and 7.5-year follow-up. Two breasts with smooth prostheses were contracted after 6 months (Baker III or IV). After 1 year, four patients with smooth prostheses and one with a textured prosthesis had capsular contracture (p = 0.34). Seven and one-half years after surgery, six patents with smooth and four with textured implants had contracture (p = 0.66). On two patients with smooth prostheses and one patient with a textured prosthesis, the capsule around the implant hardened between 6 and 12 months. Between 1 year and 7.5 years, three breasts with smooth and textured implants contracted and one with a textured implant softened.The patients reported on a Visual Analogue Scale (1 to 10) the impact of the augmentation on their quality of life to be 9 +/- 1. Four patients preferred the breast with the smooth prosthesis, three preferred the breast with the textured prosthesis, and the others found both breasts equal. This study showed no significant difference of contracture with smooth versus fine textured implants. The majority of the patients preferred the smooth implants. The patients reported that the breast augmentation had had an extremely high impact on their quality of life.     

CellMAC: a novel technology for encapsulation of mammalian cells in cellulose sulfate/pDADMAC capsules assembled on a transient alginate/Ca2+ scaffold

Microencapsulation of desired mammalian cell phenotypes in biocompatible polymer matrices represents a powerful technology for cell-based therapies and biopharmaceutical manufacturing of protein therapeutics. We have pioneered a novel jet break-up-compatible process for encapsulation of mammalian cells in cellulose sulfate (CS)/poly-diallyl-dimethyl-ammoniumchloride (pDADMAC) (CellMAC) capsules. CS and pDADMAC polymerize on a transient ad hoc co-assembled Ca2+/alginate scaffold and form homogenous capsules following dissolution of the alginate core by Ca2+ chelating agents. CellMAC capsules exhibited excellent mechanical properties and showed a molecular weight cut-off between 43 and 77kDa. Chinese hamster ovary cells engineered for constitutive production of the glycohormone erythropoietin reached high viable cell densities when grown inside CellMAC capsules, while specific erythropoietin (EPO) productivities matched those of conventional non-encapsulated control cultures. CellMAC-encapsulated EPO-production cell lines induced increased EPO serum levels when implanted intraperitoneally into mice and provided robust glycoprotein production during standard stirred-tank bioreactor operation. We expect the CellMAC technology to foster advances in therapeutic encapsulation of engineered cell lines as well as manufacturing of protein pharmaceuticals.     

Arthropod immune system. III. Septate junctions in the hemocytic capsule of the german cockroach, Blattella germanica

Granulocytes (GRs) and/or plasmatocytes (PLs), the two major immunocytes in arthropods, participate in cellular encapsulation of foreign tissue. Although gap and desmosome junctions have been reported in insect capsules, smooth septate junctions are being reported for the first time by both thin section and freeze-fracture techniques in Blattella germanica. In 7-day-old capsules, the septa are 23 nm thick, faintly 'scalloped' and slightly curved in appearance; the interseptal space has a periodicity of about 5 nm. In freeze-fractured capsules, the septa are associated on both sides with the corresponding intramembranous structures, belonging to the plasma membranes of the two junction-forming GRs. The intercellular space is 27 nm wide. There are 36-40 septa/1 mum junctional length. The junctions show furrows on the extracellular fracture face (E) and the complementary regular rows of intramembranous particles on the cytoplasmic face (P). The septate junctions often occur in the region of the capsule that also shows the presence of gap junctions, but only rarely that of desmosomes. The septate junctions are in close proximity with mitochondria. It is suggested that the function of these junctions is to produce compact capsules.     

A rapid in situ,colorimetric assay for the determination of mammalian cell viability in alginate-immobilized and encapsulated systems

A convenient, rapid colorimetric assay system has been developed in order to determine cell viability of populations of mammalian cells encapsulated using a poly-L-lysine/ alginate encapsulation system. The method is based on the use of 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and involves direct incubation of the capsules with the reagent. This is followed by direct solubilization of the resulting formazan product in dimethyl sulfoxide (DMSO). In order to demonstrate that this assay method may be generally applicable to alginate-based carrier systems, viability of cells immobilized in alginate beads, as distinct from encapsulation in the poly-L-lysine/alginate system, was also determined using the in situ method.     

Polyurethane implants: a 6-year review of 416 patients

The author reviews 6 years of experience and 416 patients in whom polyurethane implants were used for augmentation and reconstruction of the breast. As with many other plastic surgeons, early use was confined to "salvage cases." Owing to the impressive results, use was extended to routine augmentation. Polyurethane implants are now used exclusively for aesthetic breast surgery. Results are evaluated for replacement of gel capsules and simple and radical mastectomy reconstruction. Gel capsules (Baker stages III to IV), in which prostheses were removed and replaced with polyurethane-covered implants, improved in 29 of 32 patients (87 percent). For reconstruction, placement of polyurethane implants in unscarred situations gives far superior results than following repeated procedures. The incidence of infection is no higher than with gel implants. Removal without capsulectomy was not a problem in most instances. However, on two recent occasions capsulectomy was extremely difficult.     

Introduction of a Theoretical Splashing Degree to Assess the Performance of Low-Viscosity Oils in Filling of Capsules

These days an alternative to soft capsules is liquid-filled hard capsules. Their filling technology was investigated earlier with highly viscous formulations, while hardly any academic research focused on low-viscosity systems. Accordingly, this work addressed the filling of such oils that are splashing during the dosing process. It was aimed to first study capsule filling, using middle-chain triglycerides as reference oil, in order to then evaluate the concept of a new theoretical splashing degree for different oils. A laboratory-scale filling machine was used that included capsule sealing. Thus, the liquid encapsulation by microspray technology was employed to seal the dosage form. As a result of the study with reference oil, the filling volume and the temperature were found to be significant for the rate of leaking capsules. The filling volume was also important for weight variability of the capsules. However, most critical for this variability was the diameter of the filling nozzle. We proposed a power law for the coefficient of weight variability as a function of the nozzle diameter and the obtained exponent agreed with the proposed theory. Subsequently, a comparison of different oils revealed that the relative splashing degree shared a correlation with the coefficient of the capsule weight variability (Pearson product moment correlation of r = 0.990). The novel theoretical concept was therefore found to be predictive for weight variability of the filled capsules. Finally, guidance was provided for the process development of liquid-filled capsules using low-viscosity oils.     

Effects of juvenile hormones and precocenes on the immune response of Spodoptera littoralis larvae to supernumerary larvae of the solitary parasitoid,Microplitis rufiventris Kok

The study represents one of the first direct tests of juvenile hormones (JHs) on the cellular immune response of a lepidopteran insect, Spodoptera littoralis (Boisd.), superparasitized by a solitary parasitoid, Microplitis rufiventris Kok. JHII-treated S. littoralis larvae exhibited a significant reduction in encapsulation response to the supernumerary M. rufiventris larvae at different developmental ages (0-4, 10-14 and 24-26 h) of supernumerary M. rufiventris embryos within 48 or 144 h after parasitization than either JHI-treated or control hosts. The reduction in encapsulation response was significantly greater in hosts which received higher JHII dose (5 &mgr;g) than those treated with lower one (1 &mgr;g).The progression of the encapsulation, culminating in melanization in the capsules occurred more frequently in precocene-treated hosts than either JH-treatment or control ones. Application of the anti-juvenile hormones (PI or PII) caused stronger encapsulation reaction to the injured supernumerary parasitoid larvae than JHI or JHII. In PI-treatments, the reaction was rapid and dramatic by lower (25 &mgr;g) dose treatments than higher ones (70 &mgr;g).The capsules formed around the supernumerary larvae of M. rufiventris showed signs of melanization within 48 h in PI-treated hosts. Melanization was more pronounced in either PI- or PII-treated hosts prior emergence of successful parasitoid larvae. Generally, the injured supernumerary larvae were seen within melanin-rich capsules in PI- and PII-treated hosts. Melanization was not observed in most capsules of JHI- and JHII-treated hosts. Additional physiological effects were observed: (1) in some cases, application of JHI to parasitized S. littoralis larvae inhibited subsequent emergence of its wasp, M. rufiventris, and (2) teratocytes (cells of wasp origin) from PI or PII-treated hosts were smaller in size than those observed in the JH-treated or control hosts.Finally, the dramatic increase in encapsulation responses of precocene-treated S. littoralis larvae of the supernumerary of M. rufiventris and definitely opposite reactions in typical hosts but JHII-treated hosts suggested that the cellular defense reaction may be under inhibitory hormonal control.The results of the study have implications for medically important insects such as mosquitoes and their interactions with parasites, as well as having significance for biocontrol and mass rearing programs using parasitoids.     

Thermally induced gelable polymer networks for living cell encapsulation

We report the encapsulation of MIN6 cells, a pancreatic beta-cell line, using thermally induced gelable materials. This strategy uses aqueous solvent and mild temperatures during encapsulation, thereby minimizing adverse effects on cell function and viability. Using a 2:1 mixture of PNIPAAm-PEG-PNIPAAm tri-block copolymer and PNIPAAm homopolymer that exhibit reversible sol-to-gel transition at approximately 30 degrees C, gels were formed that exhibit mechanical integrity, and are stable in H(2)O, PBS and complete DMEM with negligible mass loss at 37 degrees C for 60 days. MTT assays showed undetectable cytotoxicity of the polymers towards MIN6 cells. A simple microencapsulation process was developed using vertical co-extrusion and a 37 degrees C capsule collection bath containing a paraffin layer above DMEM. Spherical capsules with diameters ranging from 500 to 900 microm were formed. SEM images of freeze-dried capsules with PBS as the core solution showed homogenous gel capsule membranes. Confocal microscopy revealed that the encapsulated cells tended to form small aggregates over 5 days, and staining for live and dead cells showed high viability post-encapsulation. A static glucose challenge with day-5 cultured microencapsulated cells exhibited glucose-dependent insulin secretion comparable to controls of free MIN6 cells grown in monolayers. These results demonstrate the potential use of these thermo-responsive polymers as cell encapsulation membranes.     

Dmp1α Inhibits HER2/neu-Induced Mammary Tumorigenesis

Our recent study shows a pivotal role of Dmp1 in quenching hyperproliferative signals from HER2 to the Arf-p53 pathway as a safety mechanism to prevent breast carcinogenesis. To directly demonstrate the role of Dmp1 in preventing HER2/neu-driven oncogenic transformation, we established Flag-Dmp1α transgenic mice (MDTG) under the control of the mouse mammary tumor virus (MMTV) promoter. The mice were viable but exhibited poorly developed mammary glands with markedly reduced milk production; thus more than half of parous females were unable to support the lives of new born pups. The mammary glands of the MDTG mice had very low Ki-67 expression but high levels of Arf, Ink4a, p53, and p21^Cip1, markers of senescence and accelerated aging. In all strains of generated MDTG;neu mice, tumor development was significantly delayed with decreased tumor weight. Tumors from MDTG;neu mice expressed Flag-Dmp1α and Ki-67 in a mutually exclusive fashion indicating that transgenic Dmp1α prevented tumor growth in vivo. Genomic DNA analyses showed that the Dmp1α transgene was partially lost in half of the MDTG;neu tumors, and Western blot analyses showed Dmp1α protein downregulation in 80% of the cases. Our data demonstrate critical roles of Dmp1 in preventing mammary tumorigenesis and raise the possibility of treating breast cancer by restoring Dmp1α expression.     

Breastfeeding in Iran: prevalence, duration and current recommendations

Background

Milk ejection is essential for a successful lactation, however techniques to measure milk ejection in women are often complex and invasive. Recent research has demonstrated that at milk ejection, milk duct diameter increased in the breast (measured by ultrasound) at the same time as milk flow rate increased (measured using a weigh balance). This study aimed to evaluate a purpose-built continuous weigh balance (Showmilk, Medela AG) to measure changes in milk flow rate from the breast to identify milk ejections during milk expression. In addition, the Showmilk was used to determine if milk ejection occurred simultaneously in both breasts during double pumping.

Methods

Increased milk flow rates during single pumping were compared to simultaneous ultrasound measurements of increased milk duct diameters in 14 mothers. In addition, increases in milk flow rate were compared between the left and right breasts of 28 mothers during double pumping for 15 minutes with two separate electric breast pumps attached to two Showmilks to record milk flow rate.

Results

Increased milk flow rates were associated with increased milk duct diameters during single pumping. The mean number of milk ejections was not different between the Showmilk (4.2 ± 2.0) and ultrasound (4.5 ± 1.5) techniques. Overall, 67 milk ejections were measured and of these, 48 (72%) were identified by both techniques. The left and right breasts responded synchronously with 95.5% of the flow rate increases corresponding between the breasts. The mean number of milk ejections identified by an increase in milk flow rate during double pumping was 5.1 ± 1.7 and 5.0 ± 1.7 for the left and right breasts, respectively. In addition, mothers chose the same expression vacuum for the left (-198 ± 31 mmHg) and right (193 ± 33 mmHg) breasts.

Conclusion

The Showmilk can simply and non-invasively record milk ejections by measuring increases in milk flow rate that correspond with increases in milk duct diameter. For the first time measurement of milk flow rate has been used to confirm that milk ejections occur simultaneously in the left and right breasts during double pumping. The use of the Showmilk will facilitate further research into the relationship of milk ejection and milk removal.     

Cell encapsulation with alginate and alpha-phenoxycinnamylidene-acetylated poly(allylamine)

In general, microcapsules prepared from alginate and polycations lack mechanical strength because the interaction between alginate and polycations is ionic instead of covalent, which represents a much stronger bond. To increase the mechanical strength of the capsule, we prepared photosensitive microcapsules that could form covalent bonds between polymers in the capsular membrane by light irradiation. Two types of photosensitive poly(allylamine), with 5% and 10% of amino groups modified by alpha-phenoxycinnamylidene acetylchloride, were synthesized. Both photopolymers exhibited an absorption maximum at 325 nm and were capable of crosslinking upon light exposure. These photosensitive polymers were used for the preparation of microcapsules. The capsules formed from this photosensitive poly(allylamine) and alginate were strengthened significantly by light irradiation. Only 28% of the microcapsules prepared from the 5%-modified photopolymer fractured after 48 h of shaking at 150 rpm. This fracture percentage is much lower when compared with the 60% of capsules fractured when prepared from the untreated poly(allylamine). By using poly(allylamine) at 10% modification, the mechanical strength was improved only slightly, with 26% of capsules fractured. Analysis of the permeability test indicated that the photo-crosslinked capsular membrane was freely permeable to cytochrome c and myoglobin, but less permeable to serum albumin. The encapsulation method was used to entrap and culture IW32 mouse leukemia cells. The cells proliferated to a density of about 1.1 x 10(7) cells/mL in the capsules after 7 days of cultivation. Concurrently, the concentration of erythropoietin in the microcapsules increased to 800 mU/mL. This new encapsulation technique has great potential in the application of a bioindustrial cell-culturing process.     

Incorporation of proteins into polyelectrolyte microcapsules by coprecipitation and adsorption

Microcapsules composed of synthetic (sodium polystyrene sulfonate and polyallylamine hydrochloride) and biodegradable polyelectrolytes (dextran sulfate and polyarginine hydrochloride) deposited on carbonate microparticles have been obtained. The ultrastructural organization of biodegradable microcapsules has been studied by transmission electron microscopy. The shell of biodegradable microcapsules is well formed even after the deposition of six polyelectrolyte layers and has an average thickness of 44 ± 3.0 nm; their inner polyelectrolyte matrix is less branched than that of synthetic microcapsules. By using spectroscopy, the efficiency of the encapsulation of FITC-labeled BSA by adsorption depending on the number of PE layers in the capsule has been estimated. It has been shown that the maximum amount of the protein is incorporated into capsules comprising six and seven polyelectrolyte layers (4 and 2 pg/capsule, respectively). It has been concluded that the adsorption of proteins into preformed polyelectrolyte capsules enables one to avoid protein losses that occur with the method in which biomineral cores obtained by coprecipitation are used for encapsulation.     

Micro-encapsulation of <Emphasis Type="Italic"> Bifidobacterium lactis</Emphasis> for incorporation into soft foods

Summary Micro-encapsulation of the probiotic micro-organism Bifidobacterium lactis isolated from a bio-yoghurt starter culture, was carried out using a mixture of hydrated gellan and xanthan gums. Rheological studies showed that the gum mix was suitable for encapsulation of B. lactis, for incorporation into soft foods/beverages. The gel behaved as a non-Newtonian material, and the flow curve fitted well to the Herschel–Bulkley model. The average yield stress of the gum was 1.515 Pa, indicating gum stability, and the yield stress range was 1 Pa over a temperature range of 35–50 °C. Almost constant minimum gum viscosity occurred between 46 and 61 °C. Oval/round capsules were synthesized manually using a monoaxial gum flow through a 27.5 G bevelled needle, together with a superposed air stream (air knife technique). The diameter of the capsules, measured using laser diffractometry, varied from 20 to 2200μm, with 50% of the capsules having a diameter of ≤637 μm. Numbers of viable B. lactis in the capsules were estimated using high power ultrasound (20 kHz). By using a concentrated inoculum of B. lactis, microcapsules containing log₁₀ 11–12 c.f.u. g−1 were synthesized. Apart from the anaerobic culturing of B. lactis, all other work was done in the presence of atmospheric oxygen. The organism exhibited a high degree of oxygen tolerance. A 21-day survival study of immobilized cells in 1 M sodium phosphate buffer (pH 7) stored at either 4 or 22 °C indicated that B. lactis survived in excess of log₁₀ 11 c.f.u. g−1 microcapsule. This technique represents a suitable means of supplying viable probiotics to the food and/or pharmaceutical industries.