approximately $8,000 decrease in prepaid expenses and other current assets, offset by an approximately $156,000 decrease in operating lease liability.
For the year ended December 31, 2022, net cash used in operating activities was approximately $5,818,000, which consisted of a net loss of approximately $10,246,000 offset by non-cash charges of approximately $2,074,000 which included approximately $1,183,000 related to amortization of internally developed software, approximately $679,000 in stock-based compensation, approximately $107,000 in bad debt expense, approximately $22,000 related to depreciation of property and equipment, approximately $77,000 of amortization of debt issuance costs on the Term Loan, and approximately $6,000 of proceeds from issuance of common stock in exchange for services.
Total changes in assets and liabilities of approximately $2,354,000 were primarily driven by an approximately $1,298,000 decrease in accounts receivable, an approximately $148,000 decrease in operating lease right-of-use asset, an approximately $27,000 decrease in prepaid expenses and other current assets, an approximately $1,626,000 increase in accounts payable, an approximately $521,000 increase in accrued expenses, offset by an approximately $589,000 increase in accounts receivable-unbilled, an approximately $522,000 decrease in deferred revenue, an approximately $147,000 decrease in operating lease liability and an approximately $8,000 decrease in accrued interest.
Investing Activities
During the year ended December 31, 2023, we invested approximately $3.8 million of cash in further developing our iSpecimen Marketplace technology with plans to invest at a lower level in 2024. We intend to continue to use our existing cash to grow our supply network, increase our marketing and sales presence, scale our operations, and for working capital and general corporate purposes.
Net cash used in investing activities was approximately $7,228,000 and $3,191,000 for the years ended December 31, 2023 and 2022, respectively. Net cash used in investing activities for the year ended December 31, 2023 consisted of approximately $13,040,000 of purchases of available-for-sale securities, approximately $3,767,000 of capitalization of internally developed software, approximately $958,000 of capitalization of other intangible assets and approximately $19,000 of purchases of property and equipment, which were offset by $10,556,000 of proceeds from sale and maturities of available-for-sale securities.
Net cash used in investing activities for the year ended December 31, 2022 consisted of approximately $2,976,000 of capitalization of internally developed software and approximately $216,000 for purchase of property and equipment.
Financing Activities
Net cash provided by financing activities was approximately $71,000 for the year ended December 31, 2023, which consisted of approximately $71,000 received from the exercise of stock options.
Net cash used in financing activities was approximately $3,421,000 for the year ended December 31, 2022, which consisted of $3,500,000 for the payoff of the Term Loan, which was offset by approximately $79,000 of proceeds from the exercise of stock options.
Effects of Inflation and Supply Chain Shortages
Our operations are heavily reliant on specimen availability, and as a result, we often receive more requests than we can fulfill. While the Company is subject to these types of supply chain constraints that are specific to the specimen industry, we have not been materially affected by the more common supply chain issues currently affecting the economy, specifically surrounding transportation. Due to the small size of the packages that we ship, our carriers were able to continue making timely deliveries during the year ended December 31, 2023. However, there had been an increase in our shipping costs period over period during the year ended December 31, 2023.
We have experienced negative effects of inflation in certain areas of our business due to the high rates of inflation in the world’s current economy. This inflation is affecting employee salaries, which account for a significant portion of our operating costs. Additionally, the costs of supplies have been affected by inflation; however, these costs are not significant to the Company’s results.
Inflation has not had a significant impact on the cost of specimens due to our long-term contracts maintained with vendors, which include revenue sharing plans.