SOURCE:

Faculty: Engineering
Department: Mechanical Engineering

CONTRIBUTORS:

Chukwuneke, J. L.
Omenyi, S. N.
Achebe, C. H.

ABSTRACT:

This research work presents the surface thermodynamics approach to mycobacterium tuberculosis (M-TB)/Human Immunodeficiency Virus(HIV)-Macrophage interactions. This involved the use of the Hamaker coefficient concept as a surface energetics tool in determining the interaction processes, with the surface interfacial energies explained using van der Waals concept of particle – particle interactions. Using the previous works that established the role of surface thermodynamics in various processes from the balanced electrostatic repulsion, and the van der waals attraction mechanism, that the concept of attraction or repulsion between the interacting particles were modeled. The Lifshitz derivations for van der Waals forces were applied as an alternative to the contact angle approach which has been widely used in other biological systems. The methodology involved taking sputum samples from twenty infected persons and from twenty uninfected persons for absorbance measurement using a digital Ultraviolet visible Spectrophotometer. The variables required for the computations with the Lifshitz formula were derived from the absorbance data. Matlab software tools were used in the mathematical analysis of the data generated from the experiments (absorbance values). The Hamaker constants and the combined Hamaker coefficients were obtained using the values of the dielectric constant together with the Lifshitz equation. The harmonized Hamaker coefficients A132har and the absolute combined Hamaker coefficients A132abs and A131abs on both infected and uninfected sputum samples were then calculated. The free energies of adhesion calculated were found to be negative with combined Hamaker coefficient positive. The values of A132abs = 0.21631x10-21Joule (for M-TB infected sputum) and Ã132abs = 0.18825x10-21Joule (for M-TB/HIV infected sputum) were obtained. The implication of this result is the positive value of the absolute combined Hamaker coefficient which entails net positive van der waals forces demonstrating an attraction between M-TB and the macrophage. This however, implies that infection is very likely to occur. It was also shown that in the presence of HIV, the interaction energy is reduced by 13% confirming adverse effects observed in HIV patients suffering from tuberculosis. Negative Hamaker coefficient (-0.22669x10-19mJ/m2) indicated that segregation of M-TB is realistic. The desired outcome is that the bacteria do not adhere to the macrophage to avoid bacteria penetrating it, in which case a condition for rendering free energy of adhesion positive and combined Hamaker coefficient negative is required. Thus, condition was sought for repulsion to occur and that condition was based on the value of A33 that would render the absolute combined Hamaker coefficient A131abs negative. Mathematically it was derived as A33≥0.9527x10-21Joule which satisfies this condition for negative A132abs. To achieve the condition of A33 above, possible additive(s) in form of drugs to the sputum should be required.