The development of composite biomaterials constituting both a porous scaffold for filling tissue defects (especially bone tissue) and a carrier of biologically active substances (proteins) is an innovative approach of the presented research. The paper presents the following studies of obtained composites: model protein (bovine serum albumin, BSA) release, changes in microstructure during incubation and bioactive potential in a simulated biological environment (based on scanning electron microscopy with X-ray microanalysis – SEM/EDS – and infrared spectroscopy – FTIR). Three types of composites with a poly(L-lactide) matrix PLLA were investigated. PLA fibres covered with silica-calcium sol, calcium alginate fibres and calcium alginate beads were used as modifiers of the PLA matrix and carriers of protein. Process of releasing albumin proceeded differently depending on the material and form of the carrier. In the case of calcium alginate fibres, almost all protein was released within 14 days. For the remaining materials, this amount was reached after 3 weeks. All tested composites showed bioactive potential connected with apatite precipitation during incubation in a simulated biological environment. However, coating PLA fibres with silica-calcium sol significantly increased this effect. The highest cell viability was observed for a biomaterial modified by calcium alginate beads.