Tuberculosis (TB) is an infectious, wasting disease spread via airborne transmission of droplets of TB bacilli which is responsible for an estimated 10 million new infections and 1.5 million deaths worldwide each year despite being a preventable and treatable disease. Mycobacterium tuberculosis (MTB) is the leading cause of human tuberculosis disease although Mycobacterium bovis can also cause zoonotic TB infections in humans. Conventional methods of TB diagnosis including TB culture, immunological methods and molecular techniques facilitate highly sensitive and specific detection of TB but are either too slow, expensive or procedurally complex for routine diagnosis in low-income, high TB burden regions. These challenges have stimulated research into the development of nanoparticle-based immunoassays and biosensing approaches which offer the potential for more affordable, sensitive, specific, user-friendly and rapid, point-of-care (POC) TB diagnosis and speciation of MTB complex organisms. Differentiation of MTBC spp. is essential to prevent the prevent the development of drug-resistant TB strains, help inform patient treatment strategies and provide more accurate estimates of the scale of TB transmission. The limitations of current approaches for TB diagnosis are highlighted in Chapter 1. At present, there is no immunodiagnostic test available for species-specific diagnosis of TB underlining the urgent requirement for more specific binders for TB. The emergence of nanomaterials including AuNPs, Fe3O4 NPs and composite Au-Fe3O4 NPs which offer advantages of simple synthesis, tunability and unique catalytic, plasmonic and magnetic properties has prompted their application in nanomaterials-based assays and biosensing approaches for TB and this is also detailed in Chapter 1. The production and characterisation of species-specific binders and evaluation of a panel of pre-existing MTBC binders is detailed in Chapter 2. A panel of pathogenic mycobacterial isolates including pathogenic MTB H37Rv and M. bovis (AF2122/97) spp. were cultivated, enumerated and used as targets for novel peptide binder production via phage display pipelines. Two recombinant MTBC-specific antigens, MPT64 and EspC, were used as targets to produce two IgG MAb-producing cell lines, EspC 5E8 and MPT64 6G11. Inactivated mycobacterial spp. were used to characterise the binding specificity of each developed binder which identified three novel phage-display derived peptide binders, with no sequence similarity to existing peptide ligands, EEA6, EEA7 or MPT64 6. All three peptides demonstrate specific detection of MTB when combined with QUBPA-1 antibody in a sandwich ELISA, whilst combining MPT64 6 peptide capture with EspC 5E8 detection antibody enables the selective detection of M. bovis. Two pre-existing antibodies, QUBPA-1 and QUBPA-2 were identified as MTBC-specific and another in-house antibody, QUBMA-1 demonstrated specific detection of M. bovis by indirect ELISA. Two MAbs, EspC 5E8 and GSM237-G8, produced in a collaboration with the research group of Dr. Michael Hust, demonstrated specific detection of MTB by indirect ELISA. With the ultimate objective of developing an immunoassay for TB detection these selected binders were optimised in a sandwich ELISA for TB detection. The results demonstrate that combining either M. bovis-specific QUBMA-1 or MTB-specific GSM237-G8 capture antibodies in combination with either QUBPA-1 or QUBPA-2 detection antibodies facilitates the specific detection of M. bovis and MTB respectively. This finding suggests these antibody pairs could potentially be applied for development of a species-specific immunodiagnostic test for TB.Nanoparticles (NPs) of uniform shape and size are necessary to develop reliable and accurate NP-based immunoassays. Therefore Chapter 3 focuses on the successful synthesis, characterisation and functionalisation of AuNPs, Fe3O4 NPs and composite Au-Fe3O4 NPs of consistent size and shape. Spherical, stable AuNPs were synthesized by citrate reduction within a narrow size distribution (14.05 ± 1.03 nm), whilst co-precipitation of Fe3O4 NPs in TMAOH yielded stable, ferromagnetic, 'multiple-faced' NPs with a size distribution between 5-50 nm, which retain their magnetic capability for long time periods (> 18 months). Bifunctional Au-Fe3O4 NPs were synthesised by surface coating Fe3O4 NPs with Au3+ ions which demonstrate both the magnetic separation capability of iron oxide and the additional plasmonic and catalytic properties of AuNPs. Of particular interest, Au-Fe3O4 NPs demonstrate consistent peroxidase-like catalytic activity with enhanced environmental stability in comparison to conventional HRP. AuNPs were functionalised with antibody binders selected from binder characterisations (Chapter 2) by both passive adsorption and covalent conjugation methods to produce AuNP-antibody bioconjugates which demonstrated specific detection of MTBC spp. by indirect ELISA. AuNP-PEG-GSM237-G8 bioconjugate demonstrates highly specific binding of MTB (OD450 = 1 ± 0.01) without detecting M. bovis, thus indicating its potential for MTB detection in a colorimetric Lateral flow immunoassay (LFIA). Functionalisation of Au-Fe3O4 NPs by attachment of reduced QUBPA-1 to the Au surface yielded stable bioconjugates capable of both specific capture of MTB and M. bovis by indirect ELISA and simultaneous detection via oxidation of TMB substrate in the presence of H2O2. This finding provides the working principle for its use as a signal generation particle in a nanomaterial-based immunoassay. In Chapter 4, a highly sensitive nanoparticle-based immunodiagnostic assay (NPIDA) capable of TB detection was developed by combining either MTB-specific GSM237-G8 capture antibody or M. bovis-specific QUBMA-1 capture antibody with the MTBC-specific Au-Fe3O4 NP-QUBPA-1 bioconjugate produced earlier (Chapter 3). Functionalisation of the Au-Fe3O4 NPs with reduced QUBPA-1 antibody resulted in a minor, 25%, reduction in relative peroxidase activity and QUBPA-1 antibody retained its MTBC binding specificity. In the presence of H2O2, the NPIDA facilitates semi-quantitative, direct sensing of MTB, M. bovis or both MTBC spp. by generation of a blue coloured TMB diimine product measured at 370 nm, thereby removing the requirement for an additional time-consuming antibody incubation step which is required in conventional ELISA. Longer incubation times (> 8 h) were shown to increase the capture of MTBC species and the magnetic capability of the NPIDA facilitates separation of MTBC cells from NTMs offering potential for further sample enrichment to concentrate target cells. The detection limit (LOD50% value) of both MTB and M. bovis NPIDA assays was determined in both assay buffer and TB culture media (Middlebrook 7H9, OADC (10% v/v) PANTA) to be comparable to conventional sandwich ELISA, permitting the detection of either MTBC spp. at (or below) the concentration level of 103 CFU mL-1. As no matrix interference effects were reported the NPIDA represents a cost-effective alternative to either conventional Ziehl-Neelsen staining or molecular identification when a TB BACTECTM MGITTM culture indicates a positive result. Due to the ongoing Covid-19 situation it was not possible to obtain clinical sputum samples necessary to complete extended cross-reactivity studies with the NPIDA. To fully validate the NPIDAs usefulness for POC testing of suspected TB patients, future investigations will aim to complete assessment of the NPIDA with clinical samples, and in addition, assess the developed methodology with alternative binders for other diseases of biological significance. The development of a proof-of-principle, paper-based LFIA for colorimetric detection of TB using selected antibodies and AuNP-antibody bioconjugates produced and evaluated earlier (Chapter 2 and 3 respectively) is described in Chapter 5. Combining AuNP-QUBPA-1 detector bioconjugate with QUBPA-1 capture antibody resulted in the rapid (< 15 min) visual detection of both MTB and M. bovis spp. in a sandwich ELISA format LFIA at concentrations of 105 CFU mL-1 in both assay running buffer and TB culture media (7H9 Middlebrook broth containing 10% (v/v) OADC and PANTA antibiotic mixture). However, significant cross-reactivity was recorded with four other mycobacterial spp. including M. kansasii, M. smegmatis, M. avium subsp. paratuberculosis and M. fortuitum. Due to time constraints towards the end thesis research, it was not possible to generate sufficient quantities of MTB-specific GSM237-G8 or M. bovis-specific QUBMA-1 antibody for optimisation on the LFIA. Therefore, to further develop the LFIA, future research investigations will apply the methodology developed in this research with these species-specific capture antibodies to enable the development of a cost-effective, rapid immunodiagnostic test capable of specific diagnosis of MTB and M. bovis in post-culture TB samples.