Enhancing drug incorporation into tetracycline-loaded chitosan microspheres for periodontal therapy

PURPOSE

To identify optimal formulation parameters for enhancing the incorporation of tetracycline hydrochloride into chitosan microspheres for periodontal therapy.

METHODS

Tetracycline-loaded chitosan microspheres were prepared by ionotropic gelation. Various formulation parameters (salt form of drug, aqueous phase pH, anion structure, inorganic salts and electrolytes, preparation method) were investigated for their influence on drug incorporation efficiency. Microspheres were assessed in terms of drug entrapment and content, microsphere recovery, particle size and morphology.

RESULTS

Although drug incorporation efficiency was increased marginally, the use of a dihydrate form of the drug was not considered feasible due to the lowered microsphere recovery and higher costs. A decrease in the aqueous pH from 9 to 6 enhanced drug incorporation efficiency without an adverse effect on microsphere morphology. The use of inorganic salts/electrolytes and other approaches of microsphere preparation did not significantly enhance drug incorporation efficiency and these approaches also adversely affected microsphere morphology. The ionotropic preparation method in terms of the drug loading technique significantly affected drug incorporation efficiencies.

CONCLUSIONS

This study has shown that formulation variables can be exploited in order to enhance the incorporation of a water soluble drug into chitosan microspheres using the ionotropic gelation technique. Based on a comparison of all results obtained with the different approaches, the modification of the aqueous phase to pH 6 was identified as the most feasible approach.

Fibular allograft and anterior plating for dislocations/fractures of the cervical spine

BACKGROUND

Subaxial cervical spine dislocations are common and often present with neurological deficit. Posterior spinal fusion has been the gold standard in the past. Pain and neck stiffness are often the presenting features and may be due to failure of fixation and extension of fusion mass. Anterior spinal fusion which is relatively atraumatic is thus favored using autogenous grafts and cages with anterior plate fixation. We evaluated fresh frozen fibular allografts and anterior plate fixation for anterior fusion in cervical trauma.

MATERIALS AND METHODS

Sixty consecutive patients with single-level dislocations or fracture dislocations of the subaxial cervical spine were recruited in this prospective study following a motor vehicle accident. There were 38 males and 22 females. The mean age at presentation was 34 years (range 19-67 years). The levels involved were C5/6 (n = 36), C4/5 (n = 15), C6/7 (n = 7) and C3/4 (n = 2). There were 38 unifacet dislocations with nine posterior element fractures and 22 were bifacet dislocations. Twenty-two patients had neurological deficit. Co-morbidities included hypertension (n = 6), non-insulin-dependent diabetes mellitus (n = 2) and asthma (n = 1). All patients were initially managed on skull traction. Following reduction further imaging included Computerized Tomography and Magnetic Resonance Imaging. Patients underwent anterior surgery (discectomy, fibular allograft and plating). All patients were immobilized in a Philadelphia collar for eight weeks (range 7-12 weeks). Eight patients were lost to follow-up within a year. Follow-up clinical and radiological examinations were performed six-weekly for three months and subsequently at three-monthly intervals for 12 months. Pain was analyzed using the visual analogue scale (VAS). The mean follow-up was 19 months (range 14-39 months).

RESULTS

Eight lost to followup, hence 52 patients were considered for final evaluation. The neurological recovery was 1.1 Frankel grades (range 0-3) and two patients with root involvement recovered. At six months bony trabeculae at the graft-vertebrae interface were noted. There were 12 (20 %) cases of graft collapse and one case of angulation which showed no progression. At six months the VAS was 3 (range 0-6). There was no limitation of neck motion at six months in 47 patients.

CONCLUSION

Fresh frozen fibular allografts are suitable and cost-effective for anterior fusion in cervical trauma.

Affinity chromatography using biocompatible and reusable biotinylated membranes

A novel, reusable biotinylated affinity chromatography strategy for the bio-specific binding of bioactive avidin tagged enzymes or polypeptides is reported. Using an avidin coupled peroxidase fusion protein as a test system; non-specific protein shielding and matrix regeneration were also shown. The amphiphilic surfactant Pluronic F108 was used as an affinity linker, by non-covalent binding to membrane chromatographic matrices while the terminal hydroxyl groups of Pluronic were covalently coupled to the biological ligand biotin. Planar nonporous membranes of varying surface chemistry were synthesised to test the matrix dependent affinity binding of biotinylated Pluronic and their respective ability to resist non-specific protein adsorption. Membrane regeneration using sodium dodecyl sulphate (SDS) was capable of displacing both adsorbed proteins and Pluronic. SDS micelles (34 mM) were effective in desorbing membrane bound protein while 5mM SDS removed up to 85% of the bound ligand after 20 h incubation at 20 degrees C. In this study, polyvinylidene membranes had the highest ligand binding capacity of 0.22 mg cm(-2) and specific, competitive affinity binding of avidin-peroxidase was shown in the presence of up to 0.2 mg ml(-1) 'contaminant' proteins. The resultant biocompatible affinity chromatographic system was regenerated and reused with no significant change in performance for up to five cycles.

Histopathology and genotyping in infectious spondylitis of HIV- and HIV+ patients

Approximately 2 million South Africans are HIV/TB coinfected, and many develop skeletal disease. The resurgence of spinal tuberculosis, including atypical forms, is due largely to HIV-associated immune suppression. We investigated the impact of HIV coinfection on the histological features of the disease and the occurrence of atypical opportunistic organisms in infectious spondylitis in an HIV/TB endemic region. We analyzed blood and tissue biopsies from 60 patients with tuberculous spondylitis. Investigations included full blood counts, CD4/CD8 counts, HIV-1 serology and RNA quantification (tissue and plasma), acid-fast bacilli localization and routine TB culture, histopathologic evaluation of biopsies, and bacterial genotyping using the 16S rDNA gene. Twenty-two patients (37%) were HIV positive with a mean age of 29 years (range, 2-65 years). Forty-one (68%) tissue specimens were culture negative for Mycobacterium tuberculosis (Mtb), although nontuberculous mycobacteria (NTM) were identified in three HIV-negative patients. Histopathologic features were characteristic of TB infection in 91.4% of all specimens tested and 100% of the HIV-infected group. Genotyping of 10 culture-positive isolates identified Mtb (3/10), NTMs (2/10), and environmental bacilli (3/10). Our observations suggest HIV-induced immune suppression impacts the histological and clinical features of infectious spondylitis but has no impact on the incidence of NTMs in this setting.

Cervical spine tuberculosis in children

The presentation and outcome of pediatric cervical spine tuberculosis are different from those of adult cervical spine tuberculosis. We retrospectively reviewed the clinical and radiographic outcome of 58 children with cervical spine tuberculosis treated nonoperatively and operatively between 1996 and 2004. The mean age was 3.7 years (range, 1.9-14 years). The cervicodorsal junction was affected in 27 children, the atlantoaxial complex in 19 children, and the mid-cervical spine in 12 children. Multifocal noncontiguous spinal lesions were observed in 21 patients. Surgery was performed in 25 children for: neurologic deficit (14); drainage of retropharyngeal abscesses (four); atlantoaxial fusion for late C1-C2 instability (three); and progressive deformity and pain (four). Neurologic recovery occurred in all patients. Seven patients were lost to followup within 2 years. The minimum followup was 2.4 years (mean, 3.5 years; range, 2.4-10 years). We attributed the improved functional outcome after anti-TB chemotherapy alone to the remodeling potential of the pediatric cervical spine. Surgery was performed only for neurologic deficit, an atlantodental interval greater than 5 mm on flexion/extension view, and progressive deformity. Four patients developed superficial wound infection, two patients had graft repositioning for a slipped graft, and seven children developed a grade 1 pressure sore over the scalp while on traction.

Atypical mycobacterial spondylitis in HIV-negative patients identified by genotyping

Non-tuberculous mycobacterial infections pose a significant diagnostic and therapeutic challenge. We report two cases of such infection of the spine in HIV-negative patients who presented with deformity and neurological deficit. The histopathological features in both specimens were diagnostic of tuberculosis. The isolates were identified as Mycobacterium intracellulare and M. fortuitum by genotyping (MicroSeq 16S rDNA Full Gene assay) and as M. tuberculosis and a mycobacterium other than tuberculosis, respectively, by culture. There is a growing need for molecular diagnostic tools that can differentiate accurately between M. tuberculosis and atypical mycobacteria, especially in regions of the developing world which are experiencing an increase in non-tuberculous mycobacterial infections.

Sacroiliac joint tuberculosis

Infections of the sacroiliac joint are uncommon and the diagnosis is usually delayed. In a retrospective study, 17 patients who had been treated for tuberculosis sacroiliitis between 1994 and 2004 were reviewed. Two patients were excluded due to a short follow-up (less than 2 years). Low back pain and difficulty in walking were the most common presenting features. Two patients presented with a buttock abscess and spondylitis of the lumbar spine was noted in two patients. The Gaenslen's and FABER (flexion, abduction and external rotation) tests were positive in all patients. Radiological changes included loss of cortical margins with erosion of the joints. An open biopsy and curettage was performed in all patients; histology revealed chronic infection and acid-fast bacilli were isolated in nine patients. Antituberculous (TB) medication was administered for 18 months and the follow-up ranged from 3 to 10 years (mean: 5 years). The sacroiliac joint fused spontaneously within 2 years. Although all patients had mild discomfort in the lower back following treatment they had no difficulty in walking. Sacroiliac joint infection must be included in the differential diagnosis of lower back pain and meticulous history and clinical evaluation of the joint are essential.

Antibiotic susceptibility patterns of Neisseria gonorrhoeae isolates in Port Elizabeth

OBJECTIVE

To survey the antibiotic susceptibility of Neisseria gonorrhoeae isolates.

DESIGN

This was a cohort analytical study.

SETTING

Three clinics serving different areas in Port Elizabeth. Outcome measures. Prevalence of antibiotic-resistant N. gonorrhoeae isolates.

RESULTS

Twenty-one of the 35 isolates (60%) were resistant to ciprofloxacin, while 28 (80%) showed resistance to erythromycin, 17 (48.6%) to penicillin, 3 (8.6%) to doxycycline, 11 (31.4%) to spectinomycin and 33 (94.3%) to tetracycline.

CONCLUSION

To ensure effective treatment of gonorrhoea, continued surveillance of antimicrobial susceptibility is necessary.

Optimisation and characterisation of bioadhesive controlled release tetracycline microspheres

A Box-Behnken experimental design was employed to statistically optimise the formulation parameters of a tetracycline microsphere preparation for maximum bioadhesivity and controlled drug release. The quantitative effect of the formulation parameters at different levels on bioadhesion and drug release could be predicted using polynomial equations. A formulation comprising of 3% (w/w) chitosan, 10% (w/w) tetracycline HCl and 9% (w/v) tripolyphosphate was identified for maximising bioadhesivity and obtaining controlled drug release. The optimal microsphere preparation was subsequently characterised in terms of hydration dynamics, release kinetics, antimicrobial activity, thermal properties, morphology and surface pH. Kinetic models revealed that drug release followed Fickian diffusion while textural analysis showed minimal hydration over the test period. Antimicrobial studies showed that the drug concentrations in the in vitro release samples were above the minimum concentration of drug required for inhibition of Staphylococcus aureus growth. Thermal analyses showed a possible interaction between the drug and polymer. Scanning electron microscopy confirmed the integrity of the microspheres and identified the morphological changes following drug release. Surface pH of the microspheres was similar to salivary pH and did not show extremes in changes over the test period.

A robust approach to studying the adsorption of Pluronic F108 on nonporous membranes

A method for poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) desorption from synthetic nonporous polymeric membranes, using hexane:isopropanol treatment and subsequent colorimetric quantification, is described. The polymers polysulfone, poly(vinyldiene fluoride), and poly(ether imide) were used to fabricate solid adsorption matrices. The desorbed Pluronic F108 forms a color complex with ammonium ferrothiocyanate (NH4FeSCN) and is based on partitioning of a chromophore present in NH4FeSCN from an aqueous phase to a chloroform phase in the presence of Pluronic. The protocols for Pluronic desorption and detection are simple, sensitive, inexpensive, rapid, and reproducible over a wide range of Pluronic coating concentrations and membrane surface chemistries. A linear response over the concentration range from 3 to 130 microg ml(-1) is obtained. The adsorption isotherms for flat sheet membranes are also described and the Langmuir equation provides the best fit for the adsorption data obtained within the concentration range studied. The absence of any significant interference from certain proteins, vitamins, carbohydrates, plasma, and halogenated derivatives makes the assay equally suitable for the estimation of Pluronic F108 in the attendant Pluronic conjugates or in biomedical applications. Using nonporous hollow fine fibers and capillary membranes as model curved substrates we were also able to correlate an increase in the radius of curvature with a corresponding increase in the surface interfacial adsorption of Pluronic F108.