to an increase in professional services, legal fees and consulting fees related to the Business Combination of $17,600. The remaining increase in expenditure was due to increased employee costs associated with increased bonuses and stock based compensation grants.
Sales and marketing
Sales and marketing expense was $2,009 for the Successor period from October 2, 2024 through December 31, 2024, $4,178 for Predecessor period from January 1, 2024 through October 1, 2024 and $3,205 for the Predecessor year ended December 31, 2023. Sales and marketing expense for the combined twelve months ended December 31, 2024 was $6,187, an increase of $2,982, or 93.0%, over the comparable period for the Predecessor year ended December 31, 2023. The increase was primarily due to increased compensation costs as a result of increased headcount across the business and increases in advertising and marketing related events and expenses associated with the commercialization phase of the Technology segment.
Research and development
Research and Development (“R&D”) expense was $5,340 for the Successor period from October 2, 2024 through December 31, 2024, $5,978 for Predecessor period from January 1, 2024 through October 1, 2024 and $4,001 for the Predecessor year ended December 31, 2023. R&D expense for the combined twelve months ended December 31, 2024 was $11,318, an increase of $7,317, or 182.9%, over the comparable period for the Predecessor year ended December 31, 2023. The increase was primarily due to an increase in employee-related costs in the Technology segment and an increase in new product development costs.
Interest expense, net
Interest expense, net was $1,132 for the Successor period from October 2, 2024 through December 31, 2024, $1,300 for Predecessor period from January 1, 2024 through October 1, 2024 and $1,224 for the Predecessor year ended December 31, 2023. Interest expense, net for the combined twelve months ended December 31, 2024 was $2,432, an increase of $1,208, or 98.7%, over the comparable period for the Predecessor year ended December 31, 2023. The increase was primarily due to an increase in facilities and borrowings between the periods as well as the increased cost of borrowing experienced during the Successor period.
Net gain (loss) from investments
Net gain on investments was nil for the Successor period from October 2, 2024 through December 31, 2024, $11,547 for Predecessor period from January 1, 2024 through October 1, 2024 and net loss on investments was $6,448 for the Predecessor year ended December 31, 2023. Net gain on investments for the combined twelve months ended December 31, 2024 was $11,547, an increase of $17,995, or 279.1%, over the comparable period for the Predecessor year ended December 31, 2023. The increase was due to the unrealized gain on investment in PCT owned stock via Class PCTA Units (as defined below) for the year ended December 31, 2024. The PCTA associated assets were not recognized as part of the Business Combination.
Net (loss) gain on investments - due to related parties
Net loss on investments – due to related parties was nil for the Successor period from October 2, 2024 through December 31, 2024, $468 for Predecessor period from January 1, 2024 through October 1, 2024 and net gain on investments was $232 for the Predecessor year ended December 31, 2023. Net loss on investments – due to related parties for the combined twelve months ended December 31, 2024 was $468, a decrease of $700, or 301.7%, over the comparable period for the Predecessor year ended December 31, 2023. The decrease was primarily due to an increase in fair value of liability - PCT stock owed to others. The PCTA associated liabilities were not recognized as part of the Business Combination.
Change in fair value of financial liabilities
The fair value of financial liabilities increased by $20,946 for the Successor period from October 2, 2024 through December 31, 2024, increased by $478 for Predecessor period from January 1, 2024 through October 1, 2024, and decreased by $766 for the Predecessor year ended December 31, 2023. The fair value of financial liabilities for the combined twelve months ended December 31, 2024 increased by $21,424, an increase of