Old and new uses of surfactant

Surfactant-Triggered Fluorescence Turn "on/off" Behavior of a Polythiophene-graft-Polyampholyte

Polythiophene-graft-polyampholyte (PTP) is synthesized using N,N-dimethylaminoethyl methacrylate and tert-butyl methacrylate monomers by grafting from polythiophene backbone, followed by hydrolysis. The resulting polymer exhibits aqueous solubility via formation of small-sized miceller aggregates with hydrophobic polythiophene at the center and radiating polyionic side chains (cationic or anionic depending on the pH of the medium) at the outer periphery. The critical micelle concentration of PTP in acidic solution (0.025 mg/mL, pH = 2.7) is determined from fluorescence spectroscopy. PTP exhibits reversible fluorescence on and off response in both acidic and basic medium with the sequential addition of differently charged ionic surfactants, repeatedly. The fluorescence intensity of PTP at pH 2.7 increases with the addition of an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS), due to the self-aggregation forming compound micelles. The fluorescence intensity of these solutions again decreases on addition of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), because of assembling of SDBS with CTAB, thus deassembling the PTP-SDBS aggregates. At pH 9.2, these turn on and turn off responses are also shown by PTP with the sequential addition of cationic surfactant (CTAB) and anionic surfactant (SDBS), respectively. This result shows that PTP has potential for surfactant-induced reversible fluorescence turn on and off using ionic surfactant (SDBS and CTAB) through self-assembling and deassembling of the ionic aggregates. The reversible aggregation and disaggregation process of PTP with the surfactants at both acidic and basic pH is supported from dynamic light scattering and Fourier transform infrared spectroscopy. The morphology of the above systems studied by transmission and scanning electron microscopy also supports the above aggregation and disaggregation process.

Therapeutic effects of inhaling aerosolized surfactant alone or with dexamethasone generated by a novel noninvasive apparatus on acute lung injury in rats

BACKGROUND

Pulmonary surfactant (PS) administration has been attempted for the treatment of adults with acute lung injury (ALI)/adult respiratory distress syndrome. Aerosolized surfactants inhaled by spontaneous breathing may be an effective method of surfactant-based therapies. Using a noninvasive apparatus, we evaluated the therapeutic effects of aerosolized PS alone or together with dexamethasone (Dex) on a rat model of ALI.

METHODS

Severe ALI was induced by intravenous injection of 20% oleic acid (0.2 mL/kg) into adult Sprague-Dawley rats. Animals were divided into eight groups: sham (n = 10); model (injury only, n = 10); normal saline (NS) aerosol driven by compressed air (air-NS, n = 13); PS aerosol driven by compressed air (air-PS, n = 13); NS aerosol driven by O2 (O2-NS, n = 13); PS aerosol driven by O2 (O2-PS, n = 13); Dex aerosol driven by O2 (O2-Dex, n = 13); and PS and Dex aerosol driven by O2 (O2-PS-Dex, n = 13). Blood gases, breathing rate, lung index, total protein, and proinflammatory cytokines (tumor necrosis factor-α, interleukin 1β, interleukin 6) in the bronchoalveolar lavage fluid (BALF), and lung histology were examined.

RESULTS

Animals treated with air-PS for 20 minutes had significantly improved lung function, reduced pulmonary edema, decreased concentration of total protein and proinflammatory cytokines in BALF, ameliorated lung injury, and improved animal survival. In the O2-PS group, the breathing rates and lung injury scores were significantly lower than that of the air-PS group. In the O2-PS-Dex group, lung edema, total protein, and inflammatory cytokines in BALF were significantly reduced in comparison with the O2-PS group.

CONCLUSION

Inhalation of aerosolized PS generated by the noninvasive apparatus could significantly reduce lung injury, while using oxygen line available in the clinical wards to generate PS aerosol is more convenient and adds further benefits. This method can also be used to deliver Dex and other therapeutic agents to ameliorate lung injury.

New surfactant with SP-B and C analogs gives survival benefit after inactivation in preterm lambs

BACKGROUND

Respiratory distress syndrome in preterm babies is caused by a pulmonary surfactant deficiency, but also by its inactivation due to various conditions, including plasma protein leakage. Surfactant replacement therapy is well established, but clinical observations and in vitro experiments suggested that its efficacy may be impaired by inactivation. A new synthetic surfactant (CHF 5633), containing synthetic surfactant protein B and C analogs, has shown comparable effects on oxygenation in ventilated preterm rabbits versus Poractant alfa, but superior resistance against inactivation in vitro. We hypothesized that CHF 5633 is also resistant to inactivation by serum albumin in vivo.

METHODOLOGY/PRINCIPAL FINDINGS

Nineteen preterm lambs of 127 days gestational age (term = 150 days) received CHF 5633 or Poractant alfa and were ventilated for 48 hours. Ninety minutes after birth, the animals received albumin with CHF 5633 or Poractant alfa. Animals received additional surfactant if P(a)O(2) dropped below 100 mmHg. A pressure volume curve was done post mortem and markers of pulmonary inflammation, surfactant content and biophysiology, and lung histology were assessed. CHF 5633 treatment resulted in improved arterial pH, oxygenation and ventilation efficiency index. The survival rate was significantly higher after CHF 5633 treatment (5/7) than after Poractant alfa (1/8) after 48 hours of ventilation. Biophysical examination of the surfactant recovered from bronchoalveolar lavages revealed that films formed by CHF 5633-treated animals reached low surface tensions in a wider range of compression rates than films from Poractant alfa-treated animals.

CONCLUSIONS

For the first time a synthetic surfactant containing both surfactant protein B and C analogs showed significant benefit over animal derived surfactant in an in vivo model of surfactant inactivation in premature lambs.